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Aerobic anoxygenic phototrophic bacteria (AAPB) are significant bacterial groups in aquatic ecosystems, known for their rapid growth and photoheterotrophic characteristics. However, the distribution and ecological assembly process of AAPB in low irradiation freshwater basins remain unclear, warranting further investigation. In this study, we present the diversity, abundance, spatial variations, ecological process, and community interaction of AAPB in sediment of Three Gorges Reservoir (TGR) under low irradiation. Our findings demonstrate the dominant genera of AAPB community that exist in the TGR area also are appeared in different waters, with some regional preference. Moreover, the concentration of pufM gene, an indicator for AAPB, maintains a consistently high numerical level ranging from (2.21 ± 0.44) × 104 to (9.98 ± 0.30) × 107 gene copies/g. Although solar irradiation is suggested as the major factor affecting AAPB, it remains unclear whether and how AAPB differ between regions due to varying solar irradiation levels. Our results show spatial differences between total bacteria and AAPB communities, with significant differences observed only in AAPB. Geographical and environmental factor contributed less than 10% to the spatial difference of community, with sediment type and environmental factors being the key factors influencing microbial community structure. The stochastic process plays a dominant role in the aggregation and replacement of AAPB communities, among which the most contribution is dispersal limitation. For AAPB network, Yoonia and Gemmobacter are the hubs for modules. Those results valuable insights into the AAPB communities in TGR with low irradiation. [Display omitted] [ABSTRACT FROM AUTHOR]

Anoxygenic phototrophic bacteria (green and purple sulfur bacteria) thrive in anoxic environments where light penetrates a sulfide-containing (euxinic) water column. Genomic data and photosynthetic bacterial carotenoid pigments should provide complementary information on the spatio-temporal dynamics of anoxygenic phototrophs in modern euxinic environments. In turn, these contemporary depositional settings often serve as analogues for ancient counterparts. However, in some modern environments, DNA-informed patterns of phototrophic sulfur bacteria occurrence do not match distributions of their carotenoid inventories. One possible explanation for these seemingly incompatible observations is that the rapid sulfurization of carotenoids and incorporation into macromolecules via multiple carbon–sulfur bonds prevents or confounds their detection by conventional means. Here, to evaluate this conundrum, we revisit some representative contemporary euxinic environments where anoxygenic phototrophic bacteria have mostly been detected based on genomic analyses. Although free intact carotenoids are sporadically detected in surface sediments, their distributions do not reveal a complete picture. Exogenously sourced fossil carotenoids (e.g., paleorenieratane) is an additional complication. Carotenoid inventories obtained by desulfurization with Raney nickel, on the other hand, stand in stark contrast to those present as free lipids. In particular, sulfur-linked carotenoids present in euxinic lake sediments provide a more complete picture of compositions of anoxygenic sulfur bacterial communities and account for discrepancies reported in previous studies. We observe a closer alignment between genomic data and patterns of sulfurized carotenoids and, importantly, our results highlight how sulfurization serves as a pathway for the rapid modification of highly functionalised lipids and their sequestration into the macromolecular component of sediment extracts. [ABSTRACT FROM AUTHOR]

Photosymbiosis evolved recurrently within the tree of life. Oxygen could have provided the primary selection pressure for photosymbiont acquisition. Host recognition and immunity are involved in photosymbiont maintenance. Intracellular pathogens can trigger photosymbiont maintenance. Genetics will open up the analysis of the cellular mechanisms of photosymbiont maintenance. Oxygenic photosynthesis evolved in cyanobacteria around 3.2 giga-annum (Ga) ago and was acquired by eukaryotes starting around 1.8 Ga ago by endosymbiosis. Photosymbiosis results either from integration of a photosynthetic bacteria by heterotrophic eukaryotes (primary photosymbiosis) or by successive integration of photosymbiotic eukaryotes by heterotrophic eukaryotes (secondary photosymbiosis). Primary endosymbiosis is thought to have been a rare event, whereas secondary and higher-order photosymbiosis evolved multiple times independently in different taxa. Despite its recurrent evolution, the molecular and cellular mechanisms underlying photosymbiosis are unknown. In this opinion, we discuss the primary events leading to the establishment of photosymbiosis, and we present recent research suggesting that, in some cases, domestication occurred instead of symbiosis, and how oxygen and host immunity can be involved in symbiont maintenance. [ABSTRACT FROM AUTHOR]

Growing concerns over greenhouse gas emissions and energy insecurity caused by the depletion of conventional fuels have led to a search for sustainable fuel alternatives. As an alternative energy carrier, hydrogen (H 2) is particularly attractive as only water is released during combustion. The process of H 2 production from genetically engineered phototrophic microorganisms through biophotolysis leads the way to solve energy shortages. Genetically engineered cyanobacteria species are potential candidates due to their superior properties for reducing greenhouse gases and using solar energy as an energy source. The review discusses the mechanisms and enzymes involved in H 2 production by cyanobacteria and applications of genetic engineering. A critical analysis of the fundamental issues attributed to the technical advancement of photobiological cyanobacteria-based H 2 production is provided, as well as the perspectives for future research to reduce carbon dioxide emissions through the creation of waste-free technology. • Genetic engineering findings of cyanobacterial nitrogenase enzyme are described. • Recent genetic engineering methods to obtain hydrogenase mutants are discussed. • Engineering photosynthetic H 2 production is shown as an efficient method. • Development of a non-waste H 2 production technology is explained. [ABSTRACT FROM AUTHOR]

Among multiple alternative clean and renewable energy sources, hydrogen is the most promising green fuel because of its high conversion efficiency, energy potentiality, and sustainability. In this review, green biohydrogen production by anoxygenic photosynthetic bacteria (APB) is summarized with the aim to enhance the present understanding of the underlying mechanisms and to gain a definite presentation of the current state of biohydrogen production. Mechanisms of biohydrogen derived from APB are briefly summarized, including the transformation of light energy into adenosine triphosphate, the metabolism of organic matter producing hydrogen ions, and photosynthetic bacteria coupled with reducing substances. In addition, factors affecting biohydrogen production by APB, including internal factors and external factors, are systematically described and discussed. Moreover, current methods for improving the hydrogen production efficiency from APB are presented. Promising applications ingratiating sustainable development goals are summarized, and both economic viability and environmental sustainability are reviewed. [Display omitted] • Anoxygenic photosynthetic bacteria (APB) do not evolve O 2 in hydrogen production. • APB consume organic substrates and produce hydrogen at high rates. • ATP serving as co-factor participate in nitrogenase-catalyzed hydrogen evolution. • APB can yield carotenoid as by-products during the process of hydrogen production. • More high-quality life cycle assessment studies should be performed in the future. [ABSTRACT FROM AUTHOR]

The photosynthetic reaction center−light-harvesting 1 (RC−LH1) complex is a membrane-protein core supercomplex that plays a crucial role in the primary reactions of anoxygenic photosynthesis. Recent developments of structural biology techniques have greatly promoted the structural characterization of various RC−LH1 complexes. The structural analysis provides insight into the assembly principles and functionality of RC−LH1 supercomplexes. The studies highlight the structural variations and modularity of RC−LH1 complexes among different phototrophic bacteria in an evolutionary and adaptive context. Advanced understanding of natural photosynthetic RC−LH1 structure and function could aid in the design and engineering of efficient artificial photosynthetic systems. Bacterial photosynthesis is essential for sustaining life on Earth as it aids in carbon assimilation, atmospheric composition, and ecosystem maintenance. Many bacteria utilize anoxygenic photosynthesis to convert sunlight into chemical energy while producing organic matter. The core machinery of anoxygenic photosynthesis performed by purple photosynthetic bacteria and Chloroflexales is the reaction center−light-harvesting 1 (RC−LH1) pigment–protein supercomplex. In this review, we discuss recent structural studies of RC−LH1 core complexes based on the advancement in structural biology techniques. These studies have provided fundamental insights into the assembly mechanisms, structural variations, and modularity of RC−LH1 complexes across different bacterial species, highlighting their functional adaptability. Understanding the natural architectures of RC−LH1 complexes will facilitate the design and engineering of artificial photosynthetic systems, which can enhance photosynthetic efficiency and potentially find applications in sustainable energy production and carbon capture. [ABSTRACT FROM AUTHOR]

Strategy to improve single-stage photofermentative hydrogen productivity of photosynthetic bacteria (PSB) by efficient use a formulated lignocellulosic substrate through suitable supplement of iron and molybdenum as enhancers of microbial activity of R. palustris was proposed. The maximum hydrogen production rate of 48.1 ml h−1 L−1 was obtained using response surface methodology as the result of accelerated bioreaction of proton reduction under inoculum density of 118.1 mg L−1, Fe2+ of 13.2 mg L−1 and Mo6+ of 2.65 μg L−1. Biokinetic analysis revealed the enhanced microbial activities in biomass synthesis and H 2 production. Suitable metal addition enabled PSB to act in whole as biocatalyst to facilitate assimilation of the formulated electron-rich carbon source from wheat straw through the efficient electron transfer needed for both cell growth and enzyme function of nitrogenase. Therefore, higher kinetic values of k c in 0.146 h−1 and R m in 59.4 ml h−1 L−1, accompanied with improved performances of H 2 yield in 1.56 mol mol−1 carbon and substrate degradation in 93.6% were attained. [Display omitted] • Enhancement strategy of lignocellulosic photofermentation was developed. • A higher production rate of 48.1 ml H 2 h−1 l−1 from wheat straw was attained by R. palustris. • Synergistic effect of metal Fe and Mo addition stimulated nitrogenase-catalyzed H 2 reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fish sludge solubilization and phototrophic bioconversion is tested in aquaponics. • Anaerobic solubilization is superior to aerobic one in providing volatile fatty acids. • Phototrophic bioconversion is conducted using purple phototrophic bacteria. • Light-anaerobic condition achieves the desired biomass and mineral nutrients. • A novel multiloop aquaponics is proposed for the reuse of phototrophic nutrients. Nutrient recovery from fish sludge in aquaponics is crucial to improve the economic output of a system sustainably and hygienically. Currently, fish sludge is treated using conventional anaerobic and aerobic mineralization, which does not allow the recovery of valuable nutrients in fish wastes. In this study, a two-stage approach (named as solubilization process and phototrophic bioconversion) is proposed to convert fish sludge into mineral nutrients and biomass nutrients using purple phototrophic bacteria (PPB), thereby promoting the growth of plants and fish simultaneously in aquaponics. Anaerobic and aerobic solubilization methods are tested to pretreat the fish sludge, generating substrates for PPB. Anaerobic solubilization yields 2.1 times more soluble chemical oxygen demand (SCOD) and 3.7 times more total volatile fatty acid (t-VFA) from fish sludge compared with aerobic solubilization. The anaerobic solubilization effluent indicates a COD t-VFA /SCOD of 60% and a VFA comprising 13.3% acetate and 49.0% propionate for PPB. The phototrophic bioconversion using anaerobic solubilization effluent under the light-anaerobic condition results in the highest biomass yield (0.94 g COD biomass /g COD removed) and the highest PPB dominance (Ectothiorhodospira , 58.7%). The anaerobic solubilization and light-anaerobic phototrophic bioconversion achieves 54.1% of carbon recovery efficiency (CRE) (in terms of COD), as well as 44.8% and 91.3% of nutrient recovery efficiency (NRE) for N and P. A novel multiloop aquaponic system combined with PPB-based nutrient recovery is proposed for the reuse of mineral nutrients and PPB biomass generated from fish sludge. [ABSTRACT FROM AUTHOR]

NifA is the primary activator of nitrogenase, and the N-terminal domain of nifA is sensitive to ammonium concentration. In this work, a mutant Rhodobacter capsulatus ZX01 with a genetically engineered deletion in the N-terminal region of nifA1 was constructed by employing overlap extension PCR to mitigate the inhibition of ammonium on nitrogenase expression in photosynthetic bacteria. The effects of different ammonium ion concentrations on the growth and photo-fermentative hydrogen production performance of wild-type strain R. capsulatus SB1003 and mutant ZX01 with glucose and volatile fatty acids as the carbon sources were studied, respectively. When the ratio of NH 4 +-N was 20% and 30%, the hydrogen yield of the mutant ZX01 was enhanced by 14.8% and 20.9% compared with that of R. capsulatus SB1003 using 25 mM acetic acid and 34 mM butyric acid as the carbon source, respectively. In comparison, using 30 mM glucose as the carbon source, the hydrogen yield of ZX01 was increased by 17.7% and 22.2% compared with that of R. capsulatus SB1003 when the ratio of NH 4 +-N was 20% and 30%, and the nitrogenase activity of ZX01 was also enhanced by 38.0% and 47.6%, respectively. When using 10 mM NH 4 + as a single nitrogen source, ZX01 showed a 2.6-fold increase in H 2 production. These results indicated that ZX01 demonstrated higher ammonium tolerance and better hydrogen production performance than the wild-type. The deletion in the N-terminal region of nifA1 could partially de-repress the nitrogenase activity inhibited by ammonium. [Display omitted] • The mutant with a deletion in the N-terminal region of nifA1 was constructed by overlap extension PCR. • The deletion in the N-terminal of nifA1 appeared to partially derepress the NH 4 + inhibition on nitrogenase activity. • The H 2 yield of ZX01 was increased by up to 22.3% compared with that of wild-type in the presence of ammonium. [ABSTRACT FROM AUTHOR]

Photo-fermentative hydrogen production rate improving has been a key limiting link in the field of biological hydrogen production by photosynthetic bacterium (PSB) in recent years. In our previous study, apparent hydrogen production enhancement was observed in R. sphaeroides HY01 with tetA expressed under tetracycline (Tc), which attracted our interests. It was found that Tc-resistant strains always presented stable hydrogen production promotion on the maximum hydrogen production rate (R m), which was approximately 30% with Tc addition. Figuring out the underlying connections between Tc resistance and hydrogen production of R. sphaeroides may provide new methods for obtaining engineered PSB with high hydrogen production performance. In this study, basing on experimental tests, hydrogen promotion of resistant strain was found to be Tc dose-dependent. Some relevant gene expression differences on hydrogen production of Rodobacter sphaeroides induced by the expression of TetA and the addition of Tc were also tested and discussed. [Display omitted] • Apparent H 2 production enhancement was observed in tetA expressing mutants under Tc. • The promotion on H 2 production was found to be Tc concentration dependent. • Significant gene expression differences of resistant strains presented under Tc. • Synergistic promoting effects may exist between Tc transport and H 2 production. [ABSTRACT FROM AUTHOR]

Cardiovascular disease, primarily caused by coronary artery disease, is the leading cause of death in the United States. While standard clinical interventions have improved patient outcomes, mortality rates associated with eventual heart failure still represent a clinical challenge. Macrorevascularization techniques inadequately address the microvascular perfusion deficits that persist beyond primary and secondary interventions. In this work, we investigate a photosynthetic oxygen delivery system that rescues the myocardium following acute ischemia. Using a simple microfluidic system, we encapsulated Synechococcus elongatus into alginate hydrogel microparticles (HMPs), which photosynthetically deliver oxygen to ischemic tissue in the absence of blood flow. We demonstrate that HMPs improve the viability of S. elongatus during the injection process and allow for simple oxygen diffusion. Adult male Wistar rats (n = 45) underwent sham surgery, acute ischemia reperfusion surgery, or a chronic ischemia reperfusion surgery, followed by injection of phosphate buffered saline (PBS), S. elongatus suspended in PBS, HMPs, or S. elongatus encapsulated in HMPs. Treatment with S. elongatus -HMPs mitigated cellular apoptosis and improved left ventricular function. Thus, delivery of S. elongatus encapsulated in HMPs improves clinical translation by utilizing a minimally invasive delivery platform that improves S. elongatus viability and enhances the therapeutic benefit of a novel photosynthetic system for the treatment of myocardial ischemia. [ABSTRACT FROM AUTHOR]

Homologs of the protein Get3 have been identified in all domains yet remain to be fully characterized. In the eukaryotic cytoplasm, Get3 delivers tail-anchored (TA) integral membrane proteins, defined by a single transmembrane helix at their C terminus, to the endoplasmic reticulum. While most eukaryotes have a single Get3 gene, plants are notable for having multiple Get3 paralogs. Get3d is conserved across land plants and photosynthetic bacteria and includes a distinctive C-terminal a-crystallin domain. After tracing the evolutionary origin of Get3d, we solve the Arabidopsis thaliana Get3d crystal structure, identify its localization to the chloroplast, and provide evidence for a role in TA protein binding. The structure is identical to that of a cyanobacterial Get3 homolog, which is further refined here. Distinct features of Get3d include an incomplete active site, a "closed" conformation in the apostate, and a hydrophobic chamber. Both homologs have ATPase activity and are capable of binding TA proteins, supporting a potential role in TA protein targeting. Get3d is first found with the development of photosynthesis and conserved across 1.2 billion years into the chloroplasts of higher plants across the evolution of photosynthesis suggesting a role in the homeostasis of photosynthetic machinery. [ABSTRACT FROM AUTHOR]

Phosphorus (P) and nitrogen (N) are the major nutrients that constrain plant and algal growth in nature. Recent advances in understanding nutrient signalling mechanisms of these organisms have revealed molecular attributes to optimise N and P acquisition. This has illuminated the importance of interplay between N and P regulatory networks, highlighting a need to study synergistic interactions rather than single-nutrient effects. Emerging insights of nutrient signalling in polyphyletic model plants and algae hint that, although core P-starvation signalling components are conserved, distinct mechanisms for P (and N) sensing have arisen. Here, the N and P signalling mechanisms of diverse photosynthetic eukaryotes are examined, drawing parallels and differences between taxa. Future directions to understand their molecular basis, evolution, and ecology are proposed. The expansion of sequencing resources and the development of advanced plant and algal model systems provide a new framework to examine the distribution and evolution of N and P signalling mechanisms in photosynthetic eukaryotes. This has revealed that, although core P-starvation signalling components are conserved, distinct mechanisms for P (and N) sensing may have arisen. Ca2+ signalling is emerging as an important player in N and P sensing in photosynthetic eukaryotes, albeit that distinct roles have evolved in different lineages. Sophisticated mechanisms to integrate N and P signalling networks and maximise nutrient acquisition are employed by diverse photosynthetic eukaryotes. Integration of plant and algal research will expedite advances in our understanding of N and P signalling, and inform strategies to engineer improved N and P use efficiency in crops. [ABSTRACT FROM AUTHOR]

Aerobic respiration evolved by bricolage, with modules cobbled together as microbial biochemistry coevolved with Earth's geochemistry. The mitochondrial electron transport chain represents a patchwork of respiratory modules inherited from microbial methanogenesis, iron oxidation, anoxygenic photosynthesis, and denitrification pathways, and preserves a biochemical record of Earth's redox environment over its four-billion-year history. Imprints of the anoxic early Earth are recognizable in Complex I's numerous iron-sulfur cofactors and vestigial binding sites for ferredoxin, nickel-iron, and molybdopterin, whereas the more recent advent of oxygen as a terminal electron acceptor necessitated use of heme and copper cofactors by Complex IV. Bricolage of respiratory complexes resulted in supercomplexes for improved electron transfer efficiency in some bacteria and archaea, and in many eukaryotes. Accessory subunits evolved to wrap mitochondrial supercomplexes for improved assembly and stability. Environmental microbes with 'fossil' proteins that are similar to ancestral forms of the respiratory complexes deserve further scrutiny and may reveal new insights on the evolution of aerobic respiration. The mitochondrial electron transport chain is derived from modular enzyme complexes assembled from microbial pathways, including methanogenesis, iron oxidation, anoxygenic photosynthesis, and denitrification. The vestiges of ancient anaerobic respiratory complexes are especially evident in Complex I, which represents a bricolage of modules, each of which originated with a function different from that which they have today. Ancestral Complex II likely ran in the opposite direction for anaerobic respiration and was later co-opted to provide additional reducing power for aerobic respiration. Complex III likely originated in anaerobic anoxygenic photosynthetic bacteria. Ancestral Complex IV was likely involved in denitrification, and iron-oxidizing bacteria may have contributed to adaptation of Complex IV to higher oxygen levels. [ABSTRACT FROM AUTHOR]

The biohydrogen production is promising for the alternative green hydrogen. The two-stage of the dark and photo-fermentation system increases the hydrogen production yield. In this study, the experiments carried out the cell immobilizations on dark and photo bacteria; and liquid suspended photo bacteria for those two-stage batch systems. The optimized parameters obtained, such as materials for immobilized cells, different substrates, and the substrate concentrations for hydrogen fermentation. The experiment results showed pure substrate glucose could produce a higher amount of hydrogen in the photo immobilized cells, the hydrogen concentration was up to about 40%, the utilization rate of glucose was as high as 99.41%, the accumulated hydrogen volume was 169.13 mL, and the hydrogen yield, HY, was 0.63 mol H 2 /mol glucose. In addition, the activated immobilized cells are used for two-stage fermentation to generate hydrogen, HY 1.75 mol H 2 /mol substrate. The two-stage batch fermentations for producing hydrogen, used the Gompertz equation model to obtain the cumulative hydrogen volume and hydrogen production rate (HPR). When the ratio of dark immobilized cells (DIMC) to photo suspended liquids (PSL) is 1.0:5.0, the hydrogen production shows well performance. Moreover, an advanced molecular biological technique, next-generation sequencing (NGS) with ultra-high-throughput DNA output, was applied to perform microbial communities in a different stage of hydrogen fermentation. The NGS help to understand the detailed microbial community change in such fermentation processes and provide better biological efficacy via clarifying the role of microorganisms and their interactions. After the experiments, the Clostridia increased to 28%, and the Enterobacter also increased to 15%, therefore the Rhodobacter and Bosea were reduced from 55% to 17%. Understand the detailed composition of microbial populations in stages of such bio-system will provide the useful information via clarify the biological role of microorganisms and its interactions. [Display omitted] • The study successfully made the immobilized cells of photosynthetic bacteria in batch reactors. • Photo-immobilized cells obtained the best hydrogen production of 169.13 mL H 2 /100 mL. • The microbial community of photo-immobilized cells changed significantly before and after the experiments. • The next-generation sequencing technique provides the relations of microbial and H 2 production. • Immobilized cells applied to two-stage of dark/photo H 2 productions obtained good outcomes. [ABSTRACT FROM AUTHOR]

The vision to replace coal with hydrogen goes back to Jules Verne in 1874. However, sustainable hydrogen production remains challenging. The most elegant approach is to utilize photosynthesis for water splitting and to subsequently save solar energy as hydrogen. Cyanobacteria and green algae are unicellular photosynthetic organisms that contain hydrogenases and thereby possess the enzymatic equipment for photosynthetic hydrogen production. These features of cyanobacteria and algae have inspired artificial and semi-artificial in vitro techniques, that connect photoexcited materials or enzymes with hydrogenases or mimics of these for hydrogen production. These in vitro methods have on their part been models for the fusion of cyanobacterial and algal hydrogenases to photosynthetic photosystem I (PSI) in vivo , which recently succeeded as proofs of principle. Biotechnological solar hydrogen production has the aim to utilize electrons from the light reactions of photosynthesis. Recently, cyanobacterial and algal H 2 ases, the enzymes that catalyze production of H 2 , were successfully fused to PSI. They intercept electrons from the photosynthetic electron transport chain. Both engineered strains produce photosynthetic hydrogen for prolonged periods. They maintained their ability to grow photoautotrophically. The processes do not exclusively rely upon water oxidation as desired, which is mostly due to the fact that the H 2 ases are sensitive to oxygen. [ABSTRACT FROM AUTHOR]

Towards improving the knowledge of possible paleo-microorganisms interaction with trace metals (micro-nutrients and toxicants), we studied adsorption of Mn, Zn, Sr, Cd, and Pb onto modern Chloroflexus aurantiacus , thermophilic anoxygenic phototrophic bacterium which could be highly abundant in the Precambiran aquatic environments. Acid-base surface titrations allowed quantifying the number of proton-active surface groups, whereas non-electrostatic linear programming method (LPM) was used to assess the surface site concentrations and adsorption reaction constants between divalent cations (Zn, Mb, Sr, Cd, Pb) and bacterial surface, based on results of pH-dependent adsorption edge and constant-pH 'langmuirian' adsorption experiments. The total proton/hydroxyl binding site number of Chl. aurantiacus surfaces was sizably lower than that of other phototrophic anaerobic bacteria studied previously using similar experimental and modeling approach. Divalent metals exhibited a decreasing order of adsorption affinity (Pb > Cd ≥ Zn ≥ Mn > Sr), which reflected the order of cation hydrolysis and was similar to adsorption order on other phototrophic bacteria. At the same time, adsorption of Zn increased with increasing of temperature, from 4 °C to 60 °C and was stronger under light compared to the darkness. This suggested some active metabolic control involved in this metal interaction with bacterial surfaces. Overall, Chl. aurantiacus exhibited trace metal adsorption parameters (site number and binding constants) which were lower compared to other anoxygenic phototrophic bacteria (Rhodopseudomonas palustris ; Rhodobacter blasticus) and cyanobacteria. This may reflect different bioavailability of trace metals in the paleo-ocean, given that thermophilic Chl. aurantiacus are among the oldest phototrophs on the planet. [Display omitted] • Adsorption of Mn, Sr, Cd, Pb and Zn onto Chl. Aurantiacus. • Surface complexation modeling of adsorption reaction. • Increase of adsorption at higher temperature and under light. • Biotic versus physico-chemical control on metal interaction with bacterium. • Evolutionary consequences for trace metal bioavailability in the paleo-ocean. [ABSTRACT FROM AUTHOR]

Non-classical correlations generated within a quantum probe system when it interacts with a large, macroscopic system can signal the presence of quantum features in the latter. Theoretical models have considered how entanglement generated in photosynthetic bacteria can be probed using light that interacts with them. More recently, a tardigrade was entangled to a transmon qubit. We consider a detailed model including noise for such systems wherein a small quantum probe interacts with a large system in order to delineate the regimes with respect to coupling strengths and noise levels in which such signatures of quantumness in macroscopic systems can realistically be detected. • Quantum features present in a macroscopic system can be sensed using a quantum probe. • We model biological systems like bacteria and Tardigrades interrogated with quantum state of light. • We find detectable signatures of 'quantumness' in the macroscopic system, surviving under moderate levels of noise. [ABSTRACT FROM AUTHOR]

[Display omitted] • 5% MP DFMs decreased soil BD, MWD and CEC, but increased soil pH, DOC and TOC. • Alpha diversity in bacterial and fungal communities remained unchanged with MP DFMs. • Structure of bacterial and fungal communities was changed by 5% MP DFMs. • 5 % MP DFMs affect C transformation, NH 4 + accumulation, and SO 4 2- consumption. Improper disposal of disposable face masks (DFMs), which are used as a fundamental measure to limit the spread of pandemics, can lead to the release of microplastics (MPs) into the soil. However, limited data exist regarding their impacts on soil physicochemical properties, as well as the composition and structure of microbial communities. In this study, we conducted a 92-day soil microcosm experiment with added MP DFMs to investigate the effects of these additions on the physicochemical properties and microbial communities of agricultural soils. Our findings demonstrated that a 5 % addition of MP DFMs decreased the bulk density (BD), mean weight diameter (MWD), and cation exchange capacity (CEC) while increasing pH, dissolved organic carbon (DOC), and total organic carbon (TOC) content. No significant changes were detected in the alpha diversity of the bacterial or fungal communities. However, at the 5 % MP DFM addition level, there was an increase in the abundance of Gp6 , Rhabdothermincola , and Metacordyceps bacteria, in addition to a decrease in Sphingomonas abundance. Furthermore, an increase in the abundance of phototrophic bacteria, as well as ammonification- and sulfate-respiring bacteria, at the 5 % MP DFM addition level may accelerate carbon transformation processes, NH 4 + accumulation, and SO 4 2- consumption within the soil. These results provide valuable insights into the impact of MP DFMs on soil health while also offering a scientific foundation for effective DFM management. [ABSTRACT FROM AUTHOR]

Malonyl-CoA reductase utilizes two equivalents of NADPH to catalyze the reduction of malonyl-CoA to 3-hydroxypropionic acid (3HP). This reaction is part of the carbon fixation pathway in the phototrophic bacterium Chloroflexus aurantiacus. The enzyme is composed of two domains. The C-terminal domain catalyzes the reduction of malonyl-CoA to malonic semialdehyde, while the N-terminal domain catalyzes the reduction of the aldehyde to 3HP. The two domains can be produced independently and retain their enzymatic activity. This report focuses on the kinetic characterization of the C-terminal domain. Initial velocity patterns and inhibition studies showed the kinetic mechanism is ordered with NADPH binding first followed by malonyl-CoA. Malonic semialdehyde is released first, while CoA and NADP+ are released randomly. Analogs of malonyl-CoA showed that the thioester carbon is reduced, while the carboxyl group is needed for proper positioning. The enzyme transfers the pro- S hydrogen of NADPH to malonyl-CoA and pH rate profiles revealed that a residue with a pK a value of about 8.8 must be protonated for activity. Kinetic isotope effects indicated that NADPH is not sticky (that is, NADPH dissociates from the enzyme faster than the rate of product formation) and product release is partially rate-limiting. Moreover, the mechanism is stepwise with the pH dependent step occurring before or after hydride transfer. The findings from this study will aid in the development of an eco-friendly biosynthesis of 3HP which is an industrial chemical used in the production of plastics and adhesives. • MCR-C binds substrates in an orderly fashion, with NADPH binding first. • MSA is released first, followed by the random release of CoA and NADP+. • MCR-C transfers the pro- S hydrogen of NADPH to malonyl-CoA. • MCR-C has a stepwise mechanism. • pH dependent step can occur before or after hydride transfer. [ABSTRACT FROM AUTHOR]

This study investigates the microbiologically influenced corrosion (MIC) of X80 steel accelerated by the phototrophic bacterium Rhodopseudomonas palustris TIE-1. The photorespiration plays a key role in promoting extracellular electron transfer (EET)-induced MIC. In the early corrosion stage, unstable localized corrosion dominated in the dark, while intense diffusion-controlled corrosion occurs in light. Compared to the sterile anaerobic medium, R. palustris TIE-1 accelerated corrosion of X80 steel, with a significantly higher corrosion rate under light conditions, approximately three times that of dark conditions. Inhibition of photosynthetic electron transfer or cessation of photostimulation resulted in pronounced reduction in the corrosion rate. • MIC of X80 steel by R. palustris TIE-1 can be accelerated by light-driven EET. • The R. palustris TIE-1 induced predominant localized corrosion under light but uniform corrosion in the dark. • Inhibition of photorespiration or cessation of light significantly reduced MIC. [ABSTRACT FROM AUTHOR]

Purple phototrophic bacteria possess light-harvesting 1 and reaction center (LH1-RC) core complexes that play a key role in converting solar energy to chemical energy. High-resolution structures of LH1-RC and RC complexes have been intensively studied and have yielded critical insight into the architecture and interactions of their proteins, pigments, and cofactors. Nevertheless, a detailed picture of the structure and assembly of LH1-only complexes is lacking due to the intimate association between LH1 and the RC. To study the intrinsic properties and structure of an LH1-only complex, a genetic system was constructed to express the Thermochromatium (Tch.) tepidum LH1 complex heterologously in a modified Rhodospirillum rubrum mutant strain. The heterologously expressed Tch. tepidum LH1 complex was isolated in a pure form free of the RC and exhibited the characteristic absorption properties of Tch. tepidum. Cryo-EM structures of the LH1-only complexes revealed a closed circular ring consisting of either 14 or 15 αβ-subunits, making it the smallest completely closed LH1 complex discovered thus far. Surprisingly, the Tch. tepidum LH1-only complex displayed even higher thermostability than that of the native LH1-RC complex. These results reveal previously unsuspected plasticity of the LH1 complex, provide new insights into the structure and assembly of the LH1-RC complex, and show how molecular genetics can be exploited to study membrane proteins from phototrophic organisms whose genetic manipulation is not yet possible. • Thermochromatium tepidum LH1-only complex was heterologously expressed in a modified Rhodospirillum rubrum mutant strain. • The LH1-only complex was a closed circular ring consisting of either 14 or 15 αβ-subunits and its structure was resolved using cryo-EM. • LH1-only complex displayed even higher thermostability than that of the native LH1-RC complex. [ABSTRACT FROM AUTHOR]

The rates, yields, mechanisms and directionality of electron transfer (ET) are explored in twelve pairs of Rhodobacter (R.) sphaeroides and R. capsulatus mutant RCs designed to defeat ET from the excited primary donor (P*) to the A-side cofactors and re-direct ET to the normally inactive mirror-image B-side cofactors. In general, the R. sphaeroides variants have larger P+H B − yields (up to ∼90%) than their R. capsulatus analogs (up to ∼60%), where H B is the B-side bacteriopheophytin. Substitution of Tyr for Phe at L-polypeptide position L181 near B B primarily increases the contribution of fast P* → P+B B − → P+H B − two-step ET, where B B is the "bridging" B-side bacteriochlorophyll. The second step (∼6–8 ps) is slower than the first (∼3–4 ps), unlike A-side two-step ET (P* → P+B A − → P+H A −) where the second step (∼1 ps) is faster than the first (∼3–4 ps) in the native RC. Substitutions near H B , at L185 (Leu, Trp or Arg) and at M-polypeptide site M133/131 (Thr, Val or Glu), strongly affect the contribution of slower (20–50 ps) P* → P+H B − one-step superexchange ET. Both ET mechanisms are effective in directing electrons "the wrong way" to H B and both compete with internal conversion of P* to the ground state (∼200 ps) and ET to the A-side cofactors. Collectively, the work demonstrates cooperative amino-acid control of rates, yields and mechanisms of ET in bacterial RCs and how A- vs. B-side charge separation can be tuned in both species. [Display omitted] • Cooperative amino-acid control of electron transfer mechanisms in proteins. • Constructed twelve pairs of R. sphaeroides and R. capsulatus mutant reaction centers. • Ultrafast studies of rates, yields, mechanisms & directionality of electron transfer. • Higher yield of wrong way electron transfer to H B in R. sphaeroides vs. R. capsulatus. • Both one- and two-step electron transfer are effective in reducing H B in both species. [ABSTRACT FROM AUTHOR]

Light-induced electron flow between reaction center and cytochrome bc 1 complexes is mediated by quinones and electron donors in purple photosynthetic bacteria. Upon high-intensity excitation, the contribution of the cytochrome bc 1 complex is limited kinetically and the electron supply should be provided by the pool of reduced electron donors. The kinetic limitation of electron shuttle between reaction center and cytochrome bc 1 complex and its consequences on the photocycle were studied by tracking the redox changes of the primary electron donor (BChl dimer) via absorption change and the opening of the closed reaction center via relaxation of the bacteriochlorophyll fluorescence in intact cells of wild type and pufC mutant strains of Rubrivivax gelatinosus. The results were simulated by a minimum model of reversible binding of different ligands (internal and external electron donors and inhibitors) to donor and acceptor sides of the reaction center. The calculated binding and kinetic parameters revealed that control of the rate of the photocycle is primarily due to 1) the light intensity, 2) the size and redox state of the donor pool, and 3) the unbinding rates of the oxidized donor and inhibitor from the reaction center. The similar kinetics of strains WT and pufC lacking the tetraheme cytochrome subunit attached to the reaction center raise the issue of the physiological importance of this subunit discussed from different points of view. A crucial factor for the efficacy of electron donors in photosynthetic photocycle is not just the substantial size of the pool and large binding affinity (small dissociation constant K D = k off / k on) to the RC, but also the mean residence time (k off)−1 in the binding pocket. This is an important parameter that regulates the time of re-activation of the RC during multiple turnovers. The determination of k off has proven challenging and was performed by simulation of widespread experimental data on the kinetics of P+ and relaxation of fluorescence. This work is a step towards better understanding the complex pathways of electron transfer in proteins and simulation-based design of more effective electron transfer components in natural and artificial systems. • Cooperative redox control of electron transfer mechanisms in proteins. • Continuous and strong illumination drives the photocycle without cyt bc 1 complex. • The rate of photocycle depends on the size and redox poise of the periplasmic donor pool. • The natural electron donors have similar binding affinities to the tetraheme cytochrome and to the reaction center. • Ligands to both sides of the reaction center limit the rate of the photocycle. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zinc 31-demethyl-bacteriochlorophylls- d with pinacol boronate on B-ring were prepared. • The synthetic analogs self-aggregated in aqueous micelles similar to chlorosome. • The chlorosome-like aggregates exhibited red-shifted and broadened Qy bands. • Exciton-coupled circular dichroism couplets were observed in the red-shifted regions. • The J-aggregation suppressed with an increase in the size of the boron substituents. Zinc 3-hydroxymethyl-131-oxo-bacteriochlorins possessing a variety of pinacol boronates on the B-ring were prepared from chemical modification of naturally occurring chlorophyll- a. The synthetic bacteriochlorophyll- d analogs were dissolved into an aqueous Triton X-100 solution to exhibit red-shifted and broadened electronic absorption bands with reversed S-shape circular dichroism bands, compared with their monomeric bands. The behaviors indicated that most synthetic models possessing a bacteriochlorin π-system self-aggregated inside the aqueous micelles to give similar oligomers as the J-aggregates of bacteriochlorophyll- d bearing a chlorin π-skeleton in major light-harvesting antennas of green photosynthetic bacteria, chlorosomes. The methylboronate self-aggregated more largely than the phenylboroante, and the self-aggregation was suppressed by ortho -substitution on the phenyl ring: phenyl > 1-naphthyl ≫ 9-anthryl and phenyl > 2,6-dimethylphenyl. Along with an increase in the size of the substituents on the boron atom of their boronates, the formation of the chlorosome-like self-aggregates decreased substantially. [ABSTRACT FROM AUTHOR]

Anoxygenic phototrophic bacteria is a promising catalyst for constructing bioanode, but the mixed culture with non-photosynthetic bacteria is inevitable in an open environment application. In this study, a Rhodopseudomonas -dominated mixed culture with other electrogenic bacteria was investigated for deciphering the differentiated performance on electricity generation in light or dark conditions. The kinetic study showed that reaction rate of OM degradation was 9 times higher than that under dark condition, demonstrating that OM degradation was enhanced by photosynthesis. However, CE under light condition was lower. It indicated that part of OM was used to provide hydrogen donors for the fixation of CO 2 or hydrogen production in photosynthesis, decreasing the OM used for electron transfer. In addition, higher COD concentration was not conducive to electricity generation. EIS analysis demonstrated that higher OM concentration would increase Rct to hinder the transfer of electrons from bacteria to the electrode. Indirect and direct electron transfer were revealed by CV analysis for light and dark biofilm, respectively, and nanowires were also observed by SEM graphs, further revealing the differentiate performance. Microbial community analysis demonstrated Rhodopseudomonas was dominated in light and decreased in dark, but Geobacter increased apparently from light to dark, resulting in different power generation performance. The findings revealed the differentiated performance on electricity generation and pollutant removal by mixed culture of phototrophic bacteria in light or dark, which will improve the power generation from photo-microbial fuel cells. In this study, a simple air-cathode MFC dominated by purple non-sulfur bacteria (PNSB) was constructed to investigate the effect of light, COD concentration and microbial community on its electricity generation and OM degradation, which can provide a theoretical guidance for the long-term stability of application of PNSB-MFC. [Display omitted] • Indirect/direct electron transport is revealed under light and dark, respectively. • Light condition is beneficial to OM degradation rather than electricity generation. • Dark condition can increase the diversity of electrogenic bacteria. • PNBS-MFC has better power generation performance in low COD concentration. [ABSTRACT FROM AUTHOR]

Despite solid, growing genomic evidence for bacteria practicing bacteriochlorophyll and rhodopsin-based dual phototrophy, direct physiological proof has been lacking for over a decade until Kopejtka et al. recently solved the puzzle in an Alpine psychrophilic bacterium. Here, I highlight conceptual developments and address an overlooked, ecologically important phototrophic byproduct – heat. [ABSTRACT FROM AUTHOR]

The mildly thermophilic purple phototrophic bacterium Allochromatium tepidum provides a unique model for investigating various intermediate phenotypes observed between those of thermophilic and mesophilic counterparts. The core light-harvesting (LH1) complex from A. tepidum exhibits an absorption maximum at 890 nm and mildly enhanced thermostability, both of which are Ca2+-dependent. However, it is unknown what structural determinants might contribute to these properties. Here, we present a cryo-EM structure of the reaction center–associated LH1 complex at 2.81 Å resolution, in which we identify multiple pigment-binding α- and β-polypeptides within an LH1 ring. Of the 16 α-polypeptides, we show that six (α1) bind Ca2+ along with β1- or β3-polypeptides to form the Ca2+-binding sites. This structure differs from that of fully Ca2+-bound LH1 from Thermochromatium tepidum, enabling determination of the minimum structural requirements for Ca2+-binding. We also identified three amino acids (Trp44, Asp47, and Ile49) in the C-terminal region of the A. tepidum α1-polypeptide that ligate each Ca ion, forming a Ca2+-binding WxxDxI motif that is conserved in all Ca2+- bound LH1 α-polypeptides from other species with reported structures. The partial Ca2+-bound structure further explains the unusual phenotypic properties observed for this bacterium in terms of its Ca2+-requirements for thermostability, spectroscopy, and phototrophic growth, and supports the hypothesis that A. tepidum may represent a “transitional” species between mesophilic and thermophilic purple sulfur bacteria. The characteristic arrangement of multiple αβ-polypeptides also suggests a mechanism of molecular recognition in the expression and/or assembly of the LH1 complex that could be regulated through interactions with reaction center subunits. [ABSTRACT FROM AUTHOR]

• External potential enhanced MNZ removal by C. vulgaris - R. Palustris co-culture. • 0 V led to the highest photosynthetic current intensity and fastest MNZ removal. • MNZ removal rate was positively related to photosynthetic current intensity. • Photosynthetic electron extraction enhanced C. vulgaris - R. Palustris synergism. • Accumulation of tryptophan, tyrosine and humic acid accelerated MNZ removal. High efficient removal of antibiotics during nutriments recovery for biomass production poses a major technical challenge for photosynthetic microbial biofilm-based wastewater treatment since antibiotics are always co-exist with nutriments in wastewater and resist biodegradation due to their strong biotoxicity and recalcitrance. In this study, we make a first attempt to enhance metronidazole (MNZ) removal from wastewater using electrochemistry-activated binary-species photosynthetic biofilm of Rhodopseudomonas Palustris (R. Palustris) and Chlorella vulgaris (C. vulgaris) by cultivating them under different applied potentials. The results showed that application of external potentials of -0.3, 0 and 0.2 V led to 11, 33 and 26-fold acceleration in MNZ removal, respectively, as compared to that of potential free. The extent of enhancement in MNZ removal was positively correlated to the intensities of photosynthetic current produced under different externally applied potentials. The binary-species photoelectrogenic biofilm exhibited 18 and 6-fold higher MNZ removal rate than that of single-species of C. vulgaris and R. Palustris , respectively, due to the enhanced metabolic interaction between them. Application of an external potential of 0V significantly promoted the accumulation of tryptophan and tyrosine-like compounds as well as humic acid in extracellular polymeric substance, whose concentrations were 7.4, 7.1 and 2.0-fold higher than those produced at potential free, contributing to accelerated adsorption and reductive and photosensitive degradation of MNZ. [Display omitted] [ABSTRACT FROM AUTHOR]

The production of hydrogen using microorganisms is an environment-friendly and less energy-intensive way of producing hydrogen. Rhodoplanes piscinae is a photosynthetic bacterium with the ability of hydrogen production under photosynthetic conditions. In this study, a new strain 51ATA was isolated from Lake Akkaya, Nigde, Turkey that is exposed to some industrial effluent charges. The new strain was identified as R. piscinae by phylogenetic analysis of the 16S ribosomal DNA (rDNA) sequence. The quality of molasses as a substrate for hydrogen production was evaluated by comparing it with other substrates, such as glucose and acetate. Five different culture media of various concentrations (1.0 g/L, 2.0 g/L, 5.0 g/L, 10 g/L, and 20 g/L) for each substrate were used. Results have shown that molasses was the best substrate for the biohydrogen production. The highest amount of biohydrogen obtained from each (20 g/L) substrate was (1.27 L H 2 /L from molasses-containing culture), (0.72 L H 2 /L from glucose-containing culture), and acetate-containing culture (0.21 L H 2 /L) respectively. From these results, we could conclude that R.piscinae 51ATA strain is as good as the other bacterial species used for hydrogen production and may be considered as a high potential strain for hydrogen production when used in combination with molasses under phototrophic conditions. • A new photosynthetic bacterial strain 51ATA of Rhodoplanes piscinae was observed hydrogen production. • Molasses was determined the best co-substrate for R.piscinae compared to acetate and glucose in hydrogen production. • As a co substrate, acetate promoted biomass production not hydrogen production. [ABSTRACT FROM AUTHOR]

Spectral variations of light-harvesting (LH) proteins of purple photosynthetic bacteria provide insight into the molecular mechanisms underlying spectral tuning of circular bacteriochlorophyll (BChl) arrays, which play crucial roles in photoenergy conversion in these organisms. Here we investigate spectral changes of the Q y band of B850 BChl a in LH2 protein from purple sulfur bacterium Thermochromatium tepidum (tepidum -LH2) by detergents and Ca2+. The tepidum -LH2 solubilized with lauryl dimethylamine N -oxide and n -octyl-β-D-glucoside (LH2 LDAO and LH2 OG , respectively) exhibited blue-shift of the B850 Q y band with hypochromism compared with the tepidum -LH2 solubilized with n -dodecyl-β-D-maltoside (LH2 DDM), resulting in the LH3-like spectral features. Resonance Raman spectroscopy indicated that this blue-shift was ascribable to the loss of hydrogen-bonding between the C3-acetyl group in B850 BChl a and the LH2 polypeptides. Ca2+ produced red-shift of the B850 Q y band in LH2 LDAO by forming hydrogen-bond for the C3-acetyl group in B850 BChl a , probably due to a change in the microenvironmental structure around B850. Ca2+-induced red-shift was also observed in LH2 OG although the B850 acetyl group is still free from hydrogen-bonding. Therefore, the Ca2+-induced B850 red-shift in LH2 OG would originate from an electrostatic effect of Ca2+. The current results suggest that the B850 Q y band in tepidum -LH2 is primarily tuned by two mechanisms, namely the hydrogen-bonding of the B850 acetyl group and the electrostatic effect. • Tepidum -LH2 solubilized with LDAO and OG exhibited blue-shift of the B850 Q y band. • The Q y blue-shift was due to the loss of hydrogen-bond of the B850 acetyl group. • The B850 Q y band is primarily tuned by hydrogen-bonding and the electrostatic effect. [ABSTRACT FROM AUTHOR]

[Display omitted] • Antheraxanthin is a natural carotenoid with diverse applications. • External stimuli significantly affect the synthesis of antheraxanthin. • Processing methods impact bioaccessibility and retention of antheraxanthin. • Antheraxanthin shows excellent pharmacological and nutritional potential. Antheraxanthin (C 40 H 56 O 3) is one of fat-soluble carotenoids belonging to natural pigments. Its chemical structure is based on the unsaturated polyene chain skeleton, with a hydroxy-β-ionone ring and an epoxy-β-ionone ring on each side of the skeleton. It is found in a wide range of plants and photosynthetic bacteria, and external stimuli (high temperature, drought, ozone treatment, etc.) can significantly affect its synthesis. It also, like other carotenoids, exhibits a diverse potential pharmacological profile as well as nutraceutical values. However, it is worth noting that various food processing methods (extrusion, puffing, baking, etc.) and storage conditions for fruits and vegetables have distinct impacts on the bioaccessibility and retention of antheraxanthin. This compilation of antheraxanthin includes sources, biosynthesis, chemical analysis, and processing effects. [ABSTRACT FROM AUTHOR]

The late Famennian Dasberg event is described as a series of global hypoxic and transgressive events associated with global faunal turnover. The event, recorded on a deep shelf of the Rhenohercynian basin from southern Euramerica, was investigated in the Holy Cross Mountains of Poland using integrated high-resolution geochemical, mineralogical, and palynological studies. The data revealed the progressive restriction of the intrashelf basin resulting from intense regional block tectonics likely connected with the Late Devonian Variscan tectonic activity. This led to weak chemocline ventilation, the development of anoxic conditions, and the deposition of two organic-rich Dasberg black shale (DBS) horizons. The DBS was deposited in an environment characterized by the constant contribution of detrital components from a common source area. A slight change in terrestrial input may have been driven by modest bathymetric changes associated with the tectonics and stronger winds delivering charcoal and terrestrial components (i.e., miospores and phytoclasts). A supply of nutrients from land and delivery of crucial biolimiting elements (i.e., nitrogen and phosphorus) from deeper waters stimulated primary productivity, as recorded in phytoplankton blooms. The δ13C organic values in the DBS reflect the incorporation of primary biomass from mainly marine photoautotrophs into sedimentary organic matter. Episodic delivery of toxic sulphides to the photic zone was detected by small-sized framboids and biomarkers, which record the appearance of green sulphur bacteria that photosynthesized in euxinic water column. The activity of phototrophic sulphide-oxidizing bacteria could have led to hyper-enrichment of Zn (715–1002 ppm) in the Lower DBS. The diachronous appearance of the DBS horizons in Euramerica and Gondwana, and regionally marked extinction of benthic fauna, suggest that anoxia developed in restricted Black Sea–like basins formed by intensive tectonic activity and continental plate convergence. • Progressive restriction led to development of anoxia and deposition of the late Famennian Dasberg black shale (DBS) • Geochemical and palynological proxies indicate amplified primary productivity during the DBS deposition • Deposition of the DBS took place in an environment with a constant contribution of detrital component • Episodically euxinic conditions reached the photic zone during the Dasberg event • Regional block tectonic connected with Variscan tectonic activity may have led to the periodic isolation of the basin [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems have been used to enhance the carbon sequestration of photosynthetic bacteria (PSB), but it is unclear whether the electrical stimulation affects the structure of membrane proteins involved in photochemical activity. In this study, the rate of CO 2 fixation in the photosynthetic bacteria R. palustris increased with electrical stimulation, and the enhancement partly remained even after the power off. The CO 2 fixation rate in electrical-stimulated PSB was 10% higher than in non-stimulated PSB, and the activity of the CO 2 fixation enzyme Rubisco was 16% higher. This resulted from the improved light utilization efficiency of the photosynthetic units in R. palustris after electrical stimulation, particularly due to the enhancement of the primary reaction mediated by the light capture protein RC-LH1. The molar extinction coefficient of the light capture protein RC-LH1 increased from 3301 cm−1 mM−1 to 3733 cm−1 mM−1, and the maximum rate of the primary reaction increased from 6.88 × 10−3 e−RC−1s−1 to 8.66 × 10−3 e−RC−1s−1. Circular dichroism spectroscopy and Fourier transform infrared spectroscopy indicated that the electrical stimulation increased the dipole moment of the α-helix in RC-LH1 to facilitate the quinone transport in the primary reaction. Nuclear magnetic resonance spectroscopy revealed that the electrical stimulation increased the formation of hydrogen bonds in bacteriochlorophyll a for electron transition. This study investigated the response of photosynthetic bacteria to electrical stimulation, providing a distinct outlook on the electrochemical regulation of photosynthesis for carbon capture. [Display omitted] • Photosynthetic bacteria fixed CO 2 more efficiently even under power off. • Photochemical activity of RC-LH1 in photosynthetic units was improved. • Electrical stimulation changed the structure of RC-LH1 in photosynthetic unit. • Up-regulated protein W expression benefits the quinone transport in RC-LH1. • Increased hydrogen bond formation accelerated the electron transition in BChl a. [ABSTRACT FROM AUTHOR]

• Reducing power allocation varies with different ammonia loading. • Under ammonia limited conditions, PHA and H 2 production compete for reducing power. • After PHA accumulation reached saturation, H 2 generation dominated. • Under ammonia limited conditions, TCA cycle was more active. • In N-limited cases, PHA, H 2 production and CO 2 fixation genes were highly activated. The global energy crisis has intensified the search for sustainable and clean alternatives, with biohydrogen emerging as a promising solution to address environmental challenges. Leveraging photo fermentation (PF) process, purple phototrophic bacteria (PPB) can harness reducing power derived from organic substrates to facilitate hydrogen production. However, existing studies report much lower H 2 yields than theoretical value when using acetate as carbon source and ammonia as nitrogen source, primarily attributed to the widely employed pulse-feeding mode which suffers from ammonia inhibition effect on nitrogenase. To address this issue, a continuous feeding mode was applied to avoid ammonia accumulation in this study. On the other hand, other pathways like carbon fixation and polyhydroxyalkanoate (PHA) formation could compete reducing power with H 2 production. However, the reducing power allocation under continuous feeding mode is not yet clear. In this study, the reducing power allocation and hydrogen production performance were evaluated under various ammonia loading, using acetate as carbon source and infrared LED at around 50 W·m−2 as light source. The results show that (a) The absence of ammonia resulted in the best performance for hydrogen production, with 44 % of the reducing power distributed to H 2 and the highest H 2 volumetric productivity, while the allocation of reducing power to hydrogen production stopped when ammonia loading was above 7.6 mg NH 4 -N·L−1·d−1; (b) when PPB required to eliminate reducing power under ammonia limited conditions, PHA production was the preferred pathway followed by the hydrogen production pathway, but once PHA accumulation reached saturation, hydrogen generation pathway dominated; (c) under ammonia limited conditions, the TCA cycle was more activated rendering higher NADH (i.e. reducing power) production compared with that under ammonia sufficient conditions which was verified by metagenomics analysis, and all the hydrogen production, PHA accumulation and carbon fixation pathways were highly active to dissipate reducing power. This work provides the insight of reducing power distribution and PPB biohydrogen production variated by ammonia loading under continuous feeding mode. [Display omitted] [ABSTRACT FROM AUTHOR]

• Systematically metabolic engineering of R. sphaeroides for improving H 2 production. • Photosynthesis was enhanced by eliminating pucBA with integrating pufQ and spbA. • Electron transfer chain was boosted by deleting qxtBA with integrating cycY. • Modified transposon with the integration of nifHDK-atpXF resulted in a mutant YH27. • An optimal H 2 titer of 17630.4 mL/L was reached by YH27 under fed-batch conditions. The photo-fermentative hydrogen production by purple non-sulfur photosynthetic bacteria (PNSB) is regarded as a promising approach for sustainable hydrogen production. In PNSB, biohydrogen synthesis is catalyzed by nitrogenase which requires two essential cofactors of adenosine triphosphate (ATP) and electron. To avoid the insufficient ATP supply that limits the nitrogenase activity for hydrogen production, we systematically engineered Rhodobacter sphaeroides to improve the hydrogen production by manipulating the light harvesting (LH) complexes, the electron transfer chain (ETC), the adenosine diphosphate (ADP) synthetic pathway, the F 0 F 1 -ATPase expression, and the nitrogenase expression. To improve the photosynthetic efficiency, we engineered the LH complexes by eliminating pucBA and overexpressing pufQ and spbA. Then, the ETC was boosted by deleting qxt -type oxidase and integrating the electron carrier cytochrome c y at the site of cyt cbb 3 oxidase. In addition, we increased the supply of precursor ADP by overexpressing adk , and the abundance of F 0 F 1 -ATPase was efficiently enhanced through overexpressing atpXF. Further transposon engineering with the integration of nifHDK and atpXF resulted in a mutant YH27 with a substantial improvement of performance over the base strain, and its nitrogenase activity and hydrogen production were enhanced by 404 % and 93 %, respectively. Taken together, the multidimensional strategies enabled the engineered R. sphaeroides with a hydrogen productivity of 61.2 mL/(Lh) and a yield of 3.0 mol/mol acetate under the fed-batch condition, which represents one of the most efficient biohydrogen-producing strains. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pumice and smectite are robust carriers for cell immobilization recycling. • Bacteria-pumice and bacteria-smectite nanocomposites are efficient for recycling. • Continuous production of microbial products from wastes was achieved. • Secondary treatment is unneeded in treating waste using the proposed nanocomposites. Recycling waste into commercial products is a profitable strategy but the lifetime of immobilized cells for long-term waste treatment remains a problem. This study presents alternative cell immobilization methods for valorizing food waste (FW) and oily food waste (OFW) to microbial carotenoids and proteins. Carriers (pumice or smectite), magnetite nanoparticles, and isolated photosynthetic bacteria were integrated to obtain magnetically recoverable bacteria-pumice and bacteria-smectite nanocomposites. After recycling five batches (50 d), chemical oxygen demand removal from FW reached 76% and 78% with the bacteria-pumice and bacteria-smectite nanocomposite treatments, respectively, and oil degradation in OFW reached 71% and 62%, respectively. Destructive changes did not occur, suggesting the durability of nanocomposites. The used nanocomposites had no impact on the lifespan of Moina macrocopa or water quality as assessed by toxicity analysis. Bacteria-pumice and bacteria-smectite nanocomposites are efficient for food waste recycling and do not require secondary treatment before being discharged into the environment. [ABSTRACT FROM AUTHOR]

The large-scale cultivation of photosynthetic bacteria requires significant quantities of fresh water. Screening strains that can thrive in brackish water or seawater is a solution to mitigate the dwindling availability of freshwater. Through phylogenetic analysis based on 16S rDNA sequences, this study identified a strain Rubrivivax gelatinosus MBE isolated from seawater. The effects of several key factors, including carbon sources, pH, NH 4 + and NaCl concentration on hydrogen production performance were investigated. Rubrivivax gelatinosus MBE showed a preference for glucose, but not organic acids for hydrogen production. It also exhibited alkalinity, achieving its peak hydrogen yield of 4626.82 ± 155.65 mL⋅L−1 at pH 8. Interestingly, Rubrivivax gelatinosus MBE could exploit ammonium nitrogen for hydrogen synthesis, thriving even in specific ammonium and salt concentrations. Its resilience was further highlighted by a maximum hydrogen production yield of 4741.41 ± 167.01 mL⋅L−1 and a hydrogen production rate of 37.59 ± 3.37 mL⋅L−1⋅h−1 with 10 g⋅L−1 NaCl, underscoring its significant salt tolerance. These results suggested that Rubrivivax gelatinosus MBE could be a promising candidate for biofuel production, and it is significant to take sustainability study on the application of MBE to deal with alkali wastewater from paper making, pharmacy and printing and high salinity wastewater in the future. • A newly halotolerant Rubrivivax gelatinosus MBE for photo fermentation hydrogen production was isolated. • The strain possessed the characteristics of thriving even in the presence of 10 mM NH 4 + and 15 g L−1 NaCl. • A maximum hydrogen yield of 4741.41 ± 167.01 mL L−1 with 10 g L−1 NaCl was obtained. [ABSTRACT FROM AUTHOR]

Cultural heritage worldwide is threatened by microbial biodeterioration. However, we know very little about the global biogeography, ecology, and driving forces of these microbiomes. Here, we provide the first global ecological perspective on the microbiomes of cultural heritage by meta-analyzing ∼1000 microbiomes from contrasting environmental conditions. The results show that the bacterial communities of cultural heritage are mainly influenced by global climate (especially by precipitation patterns), while those fungal communities, dominated by saprotrophs, are largely explained by local habitat conditions. Amongst, phototrophic bacteria (e.g., Alpha-proteobacteria, and Cyanobacteria) and some saprotrophic fungi (e.g., Sordariomycetes, and Dothideomycetes) construct the backbone of the cultural heritage microbiome. In this regard, the biodeterioration of cultural heritage could be pre-estimated and predicted by the ecological calculation on the big data of global environmental conditions and microbiome. In summary, the ecological perspective of the microbiomes on global cultural heritage can help to safeguard the long-term sustainable conservation for future generations. • Global biogeographic patterns of heritage microbiome are traceable. • They can be predicted by multi-environmental factors. • Heritage-deteriorating bacteria are driven by global climate patterns. • Heritage-deteriorating fungi are determined by local habitat conditions. • Ecological perspective can build the cornerstone for sustainable conservation. [ABSTRACT FROM AUTHOR]

Chlorosomes of green photosynthetic bacteria are large light-harvesting complexes enabling these organisms to survive at extremely low-light conditions. Bacteriochlorophylls found in chlorosomes self-organize and are ideal candidates for use in biomimetic light-harvesting in artificial photosynthesis and other applications for solar energy utilization. Here we report on the construction and characterization of an artificial antenna consisting of bacteriochlorophyll c co-aggregated with β-carotene, which is used to extend the light-harvesting spectral range, and bacteriochlorophyll a , which acts as a final acceptor for excitation energy. Efficient energy transfer between all three components was observed by means of fluorescence spectroscopy. The efficiency varies with the β-carotene content, which increases the average distance between the donor and acceptor in both energy transfer steps. The efficiency ranges from 89 to 37% for the transfer from β-carotene to bacteriochlorophyll c , and from 93 to 69% for the bacteriochlorophyll c to bacteriochlorophyll a step. A significant part of this study was dedicated to a development of methods for determination of energy transfer efficiency. These methods may be applied also for study of chlorosomes and other pigment complexes. • A three-component self-assembling artificial light-harvesting antenna was prepared. • The antenna is based on bacteriochlorophyll aggregates from chlorosomes. • β-carotene was used to extend the spectral coverage of the aggregates. • Bacteriochlorophyll a was used as the final acceptor of the excitation. • Methods for determination of energy transfer efficiency in the antenna were developed. [ABSTRACT FROM AUTHOR]

Recovering resources from wastewater to alleviate the energy crisis has become the prevailing trend of technological development. Purple phototrophic bacteria (PPB), a group of fast-growing microbes, have been widely noticed for their potential in producing value-added products from waste streams. However, saline contents in these waste streams, such as food processing wastewater pose a big challenge, which not only restrain the pollutant removal efficiency, but also hinder the growth of functional microbes. To overcome this, a photo anaerobic membrane bioreactor cultivating PPB (PPB-MBR) was constructed and its performance upon long-term salinity stress was investigated. PPB-MBR achieved desirable pollutants removal performance with the average COD and NH 4 + removal efficiency being 87% (±8%, n = 87) and 89% (±10%, n = 87), respectively during long-term exposure to salinity stress of 1–80 g NaCl L−1. PPB were predominant during the entire operation period of 87 days (60%–80%), obtaining maximum biomass yield of 0.67 g biomass g−1 COD removed and protein productivity of 0.18 g L−1 d−1 at the salinity level of 20 g NaCl L−1 and 60 g NaCl L−1, respectively. The sum of value-added products in proportion to the biomass reached 58% at maximum at the salinity level of 60 g NaCl L−1 with protein, pigments and trehalose contributing to 44%, 8.7%, and 5%, respectively. Based on economic analysis, the most cost-saving scenario treating food processing wastewater was revealed at salinity level of around 20 g NaCl L−1. However, more optimization tools are needed to boost the production efficiency so that the profit from value-added products can outweigh the additional cost by excess salinity in the future implication. [Display omitted] • A PPB-MBR was constructed to remove 87% COD and 89% NH 4 + from high-salt wastewater. • The PPB-MBR achieved desirable biomass and protein productivity upon salinity stress. • Salinity stress enhances the protein by 83% and the pigments by 82%. • An economic analysis was performed to assess the most cost-saving scenario. [ABSTRACT FROM AUTHOR]

[Display omitted] • Removal and valorization of cooking oil by photosynthetic bacteria is feasible. • Fe 3 O 4 nanoparticles (NPs) could act as a catalyst in photosynthetic bacteria. • Supplementation with Fe 3 O 4 NPs enhanced biomass, protein, and carotenoid production. • Fe 3 O 4 NPs increased microbial tolerance to toxicity of heavy metals. Waste cooking oil discharge causes environmental pollution in receiving waters, particularly when associated with heavy metals that can lead to formation of hazardous organometallic compounds. This study combined iron oxide nanomaterial and the anoxygenic photosynthetic bacterium Rhodopseudomonas faecalis PA2 for removal of cooking oil in the presence of heavy metals. R. faecalis PA2, with known capability to generate beneficial substances from several wastes, was capable of cooking oil removal with production of valuable products. Oil removal, biomass, protein, and carotenoid production were 82.38%, 1.48 g/L, 1,600.19 mg/L, and 1,046.33 mg/L, respectively, under optimal conditions (cooking oil as carbon source and 30% inoculum density). Iron (Fe) stimulates growth of R. faecalis ; in this study, Fe 3 O 4 nanoparticles were synthesized and used as a catalyst to facilitate interaction and high reactivity between Fe and R. faecalis PA2. Size measurement by transmission electron microscopy (17.44 nm), X-ray diffraction peaks, and magnetic susceptibility confirmed that the synthesized nanoparticles were magnetite Fe 3 O 4. Biomass, protein, and carotenoid production of the Fe 3 O 4 supplemented experiment increased by 61.56%, 70.78%, and 57.2%, respectively, when compared with the control. When different concentrations of heavy metals (Pb, Ni, Co, and Zn) were supplemented in the media containing cooking oil, Fe 3 O 4 addition increased heavy metal tolerance, improved bacterial growth, and enhanced valuable products when compared with the non-supplemented group. This study reports the positive impact of nanoparticle application as a catalyst for valorization of cooking oil waste with heavy metal co-contamination by the photosynthetic bacterium R. faecalis PA2. [ABSTRACT FROM AUTHOR]

Treating wounds with multidrug-resistant bacterial infections remains a huge and arduous challenge. In this work, we prepared a "live-drug"-encapsulated hydrogel dressing for the treatment of multidrug-resistant bacterial infections and full-thickness skin incision repair. Our live dressing was comprised of photosynthetic bacteria (PSB) and extracellular matrix (ECM) gel with photothermal, antibacterial and antioxidant properties, as well as good cytocompatibility and blood compatibility. More interestingly, live PSB could be regarded as not only photothermal agents but also as anti-inflammatory agents to promote wound healing owing to their antioxidant metabolites. In vitro and in vivo studies showed that the PSB hydrogel not only had a high killing rate against methicillin-resistant Staphylococcus aureus (MRSA) but it also accelerated collagen deposition and granulation tissue formation by promoting cell proliferation and migration, which significantly promoted skin tissue regeneration and wound healing. We believe that the large-scale production of PSB Gel-based therapeutic dressings has the advantages of easy use and promising clinical applications. Rapid wound healing and the treatment of bacterial infections have always been the two biggest challenges in the field of wound care. We prepared a "live drug" dressing by encapsulating photosynthetic bacteria into an extracellular matrix hydrogel to sterilize the wound and promote wound healing. First, photosynthetic bacteria are not only a photothermal agent for photothermal wound sterilization, but also possess the anti-inflammatory capacity to enhance wound healing due to their antioxidant metabolites. Second, the extracellular matrix hydrogel is rich in a variety of growth factors and nutrients to promote cell migration and accelerate wound healing. Third, photosynthetic bacteria are not only green and non-toxic, but also can be obtained on a large scale, which facilitates manufacturing and clinical transformation. [Display omitted] [ABSTRACT FROM AUTHOR]

Photo fermentation is an emerging approach of biohydrogen production as it is energy saving and environmentally friendly. Understanding mechanisms of controlling the bacteria growth and biohydrogen production is critical for effective improvements in energy harvest and waste treatment in photo fermentative bioreactors. In this study a comprehensive three-dimensional numerical platform of photo fermentation was developed, based on lattice Boltzmann method coupled with cellular automata. The model accounts for photosynthetic bacteria growth, illumination energy conversion by photosynthetic bacteria, and light transfer under biofilm growth. The results showed a threshold of illumination intensity. Below this threshold, the bioreactor performance increased as the illumination intensity increased. Above the threshold, the performance declined if the illumination intensity rose. The normalized average biohydrogen production at the illumination intensity of 6000lx, increased about 66.31%, 13.82% and 13.12%, respectively, compared to ones at 4000lx, 5000lx and 7000lx. An increase in inlet glucose concentration could increase biohydrogen concentration and extraction but dwindled biohydrogen yield. It was found that a lower inlet velocity had higher biohydrogen production rate and concentration but lower biohydrogen extraction and yield. The results demonstrate that the present LBM-CA platform can be a tool to study and enhance the photo fermentative production of biohydrogen. • Present a refined model of biohydrogen production during photo fermentation. • Evaluate the effects of illumination, geometry and velocity on photo fermentation. • Accounts for photosynthetic bacteria growth and illumination energy conversion. • Provide an integrated modeling tool to improve design of photo microbioreactors. [ABSTRACT FROM AUTHOR]

Developing kinetic models to simulate Rhodopseudomonas palustris biohydrogen production within different configurations of photobioreactors (PBRs) poses a significant challenge. In this study, two types of PBRs: schott bottle-based and vertical tubular-based, were investigated, and three original contributions are presented. Firstly, a mechanistic model was constructed to simulate effects of light intensity, light attenuation and temperature on biomass growth and biohydrogen synthesis, previously not unified for photosynthetic bacteria. Secondly, perturbation analysis was exploited to identify critical parameters influencing the accuracy of the model. Thirdly, two parameters: effective light coefficient and biohydrogen enhancement coefficient , both linked to the PBR's transport phenomena were proposed for process scale-up prediction. By comparing against experimental data, the model's accuracy was confirmed to be high. Moreover, the enhancement of biohydrogen production rate by improved culture mixing and gas removal was also described mechanistically. This provides important advances for future efficient design of PBRs and process online optimisation. [Display omitted] • Modelling biomass growth and biohydrogen production of Rhodopseudomonas palustris. • Unified influences of light intensity, light attenuation and temperature. • Perturbation analysis for evaluating model accuracy and reliability. • Acceptable extrapolations for two different Photobioreactor (PBR) scales and sizes. • Embedding light/dark cycles and biohydrogen partial pressure onto PBR performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • R. capsulatus is suitable for recombinant biosynthesis of di-, tri and tetraterpenes. • Co-expression of precursor biosynthetic genes increased casbene and β-carotene levels. • Modular precursor engineering can optimize the synthesis of diverse terpene classes. • M. capsulatus squalene synthase enabled highest product levels of 90 mg/L squalene. Terpenes constitute one of the largest groups of secondary metabolites that are used, for example, as food-additives, fragrances or pharmaceuticals. Due to the formation of an intracytoplasmic membrane system and an efficient intrinsic tetraterpene pathway, the phototrophic α-proteobacterium Rhodobacter capsulatus offers favorable properties for the production of hydrophobic terpenes. However, research efforts have largely focused on sesquiterpene production. Recently, we have developed modular tools allowing to engineer the biosynthesis of terpene precursors. These tools were now applied to boost the biosynthesis of the diterpene casbene, the triterpene squalene and the tetraterpene β-carotene in R. capsulatus SB1003. Selected enzymes of the intrinsic isoprenoid pathway and the heterologous mevalonate (MVA) pathway were co-expressed together with the respective terpene synthases in various combinations. Remarkably, co-expression of genes ispA , idi and dxs enhanced the synthesis of casbene and β-carotene. In contrast, co-expression of precursor biosynthetic genes with the squalene synthase from Arabidopsis thaliana reduced squalene titers. Therefore, we further employed four alternative pro- and eukaryotic squalene synthases. Here, the synthase from Methylococcus capsulatus enabled highest product levels of 90 mg/L squalene upon co-expression with ispA. In summary, we demonstrate the applicability of R. capsulatus for the heterologous production of diverse terpene classes and provide relevant insights for further development of such platforms. [ABSTRACT FROM AUTHOR]

Thymidylate kinase (TMK/TMPK) is an important enzyme in DNA biosynthesis and catalyses the conversion of dTMP to dTDP. Due to its therapeutic potential, the focus has been on characterizing the TMK proteins of pathogens and human origin, with very little information available on the TMK proteins of photosynthetic organisms and agriculturally important nitrogen-fixing organisms. In this work we report the characterisation of TMK in an evolutionarily ancient organism, cyanobacteria. The TMK protein of the photosynthetic, nitrogen-fixing cyanobacterium Nostoc PCC7120 (AnTMK) was found to have low conformational stability, which related to its low Tm of ~46 °C confirmed by D ifferential S canning F luorimetry (DSF) and D ifferential S canning C alorimetry (DSC) techniques. The AnTMK protein exhibited substrate specificity for dTMP and ATP with K m of 20.74 ± 1.47 μM and 20.17 ± 2.96 μM respectively. The enzyme kinetics data and the positive co-operativity observed between dTMP and ATP binding correlated well with the data obtained from I sothermal T itration C alorimetry (ITC). Homology model of the enzyme suggested that the binding mode of substrate nucleotides to the enzyme is conserved. When overexpressed constitutively in Nostoc PCC7120 (An tmk +), it supported faster growth measured in terms of chlorophyll a content under normal growth conditions, but exhibited lower photosynthetic efficiency. Compared to the vector control recombinant Nostoc AnpAM, the An tmk + cells exhibited higher photoinhibition at higher light irradiance with more open reaction centres and lower dissipation of heat, indicative of damage to photosynthetic machinery. This indicated that the TMK is likely to have a significant role in photosynthetic organisms. • Thymidylate kinase of the cyanobacterium Nostoc PCC7120 (AnTMK) exhibits low conformational stability in vitro. • Dimeric AnTMK exhibits high substrate specificity for its two substrates dTMP and ATP and cooperative binding. • Overexpression of AnTMK in Nostoc decreases its photosynthetic efficiency. • First complete characterisation of TMK in a photosynthetic organism demonstrates its importance in photosynthesis. [ABSTRACT FROM AUTHOR]

Meeting energy demands necessitates the initial focus on hydrogen generation, followed by prioritizing hydrogen storage and transportation. Hydrogen generation can be categorized into on-site and off-site methods. Opting for on-site hydrogen generation is preferable when powering fuel cells for electricity generation, as it eliminates the costs associated with storage and transportation. Nevertheless, certain off-site hydrogen production techniques coupled with storage and transportation are more cost-effective than some on-site generation approaches. In this review paper, diverse hydrogen production methods (both on-site and off-site) are explored, involving a range of chemical compounds such as composite materials, various photosynthetic bacteria, different electrolysis approaches for water, aluminum-assisted hydrolysis, and steam reforming of methane and methanol. The paper offers a thorough examination of the hydrogen generation method within its peer group, leading to conclusions that are drawn from their potential exergo-economic implications. Furthermore, the viability of different methods for generating hydrogen, particularly in the context of fuel cell applications, is indicated. [Display omitted] [ABSTRACT FROM AUTHOR]