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Today's increasing demand for aquaculture production is accompanied by various challenges such as diseases, broodstock improvement, domestication, development of suitable pellets and feeding methods, hatchery technology, and water quality management. Thus, probiotic usage has been reported as the ideal alternative to antibiotics, other chemotherapeutics, and additional supplements to other alternative ingredients. The main beneficial roles of probiotics include the enhancement of disease and stress resistance, immunity, promotion of growth and reproduction, improvement of digestion, provide several nutrients, and enhancement of water microbial composition. To guarantee safety, the probiotics provided must be noninvasive and non-pathogenic. The use of probiotics in aquaculture, either directly or in combination with alternative materials such as plant protein diets, vitamins, microalgae, fermented products, and so on, has been shown to improve the health and growth of aquatic animals and offer significant benefits to the sustainability of the industry. There is advocacy for a systematic approach to conducting innovative research to unearth new putative strains, which is substantial in ensuring sustainable probiotic usage and, thus, can help in the continuous development of the aquaculture industry especially in China. Some examples of the probiotics found in China are mainly photosynthetic bacteria (PSB) which are autotroph bacteria capable of photosynthesis, antagonistic bacteria (Pseudoalteromonas sp., Flavobacterium sp., Alteromonas sp., Phaeobacter sp., Bacillus sp., etc.), bacteria that contribute nutrients and enzymes during digestion (lactic acid bacteria, yeasts, etc.), bacteria that improve water quality (nitrifying bacteria, denitrifying bacteria, etc.), Bdellovibrio, and other probiotics. This review also focuses on the potential use of probiotics in aquaculture, especially in China, and probiotics' prospective future role. [ABSTRACT FROM AUTHOR]

Today's increasing demand for aquaculture production is accompanied by various challenges such as diseases, broodstock improvement, domestication, development of suitable pellets and feeding methods, hatchery technology, and water quality management. Thus, probiotic usage has been reported as the ideal alternative to antibiotics, other chemotherapeutics, and additional supplements to other alternative ingredients. The main beneficial roles of probiotics include the enhancement of disease and stress resistance, immunity, promotion of growth and reproduction, improvement of digestion, provide several nutrients, and enhancement of water microbial composition. To guarantee safety, the probiotics provided must be noninvasive and non-pathogenic. The use of probiotics in aquaculture, either directly or in combination with alternative materials such as plant protein diets, vitamins, microalgae, fermented products, and so on, has been shown to improve the health and growth of aquatic animals and offer significant benefits to the sustainability of the industry. There is advocacy for a systematic approach to conducting innovative research to unearth new putative strains, which is substantial in ensuring sustainable probiotic usage and, thus, can help in the continuous development of the aquaculture industry especially in China. Some examples of the probiotics found in China are mainly photosynthetic bacteria (PSB) which are autotroph bacteria capable of photosynthesis, antagonistic bacteria (Pseudoalteromonas sp., Flavobacterium sp., Alteromonas sp., Phaeobacter sp., Bacillus sp., etc.), bacteria that contribute nutrients and enzymes during digestion (lactic acid bacteria, yeasts, etc.), bacteria that improve water quality (nitrifying bacteria, denitrifying bacteria, etc.), Bdellovibrio, and other probiotics. This review also focuses on the potential use of probiotics in aquaculture, especially in China, and probiotics' prospective future role. [ABSTRACT FROM AUTHOR]

Today's increasing demand for aquaculture production is accompanied by various challenges such as diseases, broodstock improvement, domestication, development of suitable pellets and feeding methods, hatchery technology, and water quality management. Thus, probiotic usage has been reported as the ideal alternative to antibiotics, other chemotherapeutics, and additional supplements to other alternative ingredients. The main beneficial roles of probiotics include the enhancement of disease and stress resistance, immunity, promotion of growth and reproduction, improvement of digestion, provide several nutrients, and enhancement of water microbial composition. To guarantee safety, the probiotics provided must be noninvasive and non-pathogenic. The use of probiotics in aquaculture, either directly or in combination with alternative materials such as plant protein diets, vitamins, microalgae, fermented products, and so on, has been shown to improve the health and growth of aquatic animals and offer significant benefits to the sustainability of the industry. There is advocacy for a systematic approach to conducting innovative research to unearth new putative strains, which is substantial in ensuring sustainable probiotic usage and, thus, can help in the continuous development of the aquaculture industry especially in China. Some examples of the probiotics found in China are mainly photosynthetic bacteria (PSB) which are autotroph bacteria capable of photosynthesis, antagonistic bacteria (Pseudoalteromonas sp., Flavobacterium sp., Alteromonas sp., Phaeobacter sp., Bacillus sp., etc.), bacteria that contribute nutrients and enzymes during digestion (lactic acid bacteria, yeasts, etc.), bacteria that improve water quality (nitrifying bacteria, denitrifying bacteria, etc.), Bdellovibrio, and other probiotics. This review also focuses on the potential use of probiotics in aquaculture, especially in China, and probiotics' prospective future role. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Vermicompost contains humic acids, nutrients, earthworm excretions, beneficial microbes, growth hormones, and enzymes, which help plants to tolerate a variety of abiotic stresses. Effective microorganisms (EM) include a wide range of microorganisms' e.g. photosynthetic bacteria, lactic acid bacteria, yeasts, actinomycetes, and fermenting fungi that can stimulate plant growth and improve soil fertility. To our knowledge, no study has yet investigated the possible role of vermicompost and EM dual application in enhancing plant tolerance to water scarcity. Methods: Consequently, the current study investigated the effectiveness of vermicompost and EM in mitigating drought-induced changes in wheat. The experiment followed a completely randomized design with twelve treatments. The treatments included control, as well as individual and combined applications of vermicompost and EM at three different irrigation levels (100%, 70%, and 30% of field capacity). Results: The findings demonstrated that the application of vermicompost and/or EM significantly improved wheat growth and productivity, as well as alleviated drought-induced oxidative damage with decreased the generation of superoxide anion radical and hydrogen peroxide. This was achieved by upregulating the activities of several antioxidant enzymes, including superoxide dismutase, catalase, peroxidase, ascorbate peroxidase, glutathione peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase. Vermicompost and/or EM treatments also enhanced the antioxidant defense system by increasing the content of antioxidant molecules such as ascorbate, glutathione, phenolic compounds, and flavonoids. Additionally, the overproduction of methylglyoxal in water-stressed treated plants was controlled by the enhanced activity of the glyoxalase system enzymes; glyoxalase I and glyoxalase II. The treated plants maintained higher water content related to the higher content of osmotic regulatory substances like soluble sugars, free amino acids, glycinebetaine, and proline. Conclusions: Collectively, we offer the first report that identifies the underlying mechanism by which the dual application of vermicompost and EM confers drought tolerance in wheat by improving osmolyte accumulation and modulating antioxidant defense and glyoxalase systems. [ABSTRACT FROM AUTHOR]

Natural carotenoids (CARs) such as β-carotene, astaxanthin, lutein, norbixin, bixin, capsanthin, lycopene, β-Apo-8-carotenal, canthaxanthin, β-apo-8-carotenal-ester, and zeaxanthin are being explored for possible applications in feed, food, cosmeceuticals, and nutraceuticals. Three primary areas of carotenoid research are emerging: (1) encapsulations for improved chemical and physical properties; (2) natural source carotenoid manufacturing; and (3) preclinical, epidemiological, and clinical studies of carotenoids' potential health benefits. The recent advancements in research on the chemistry and antioxidant activity, marketing strategies, dietary sources, bioavailability, and bioaccessibility, extraction, dietary consumption, encapsulating techniques, and health advantages of carotenoids are all extensively discussed in this review. Carotenoids are pigments found naturally in most fruits and vegetables, algae, plants, and photosynthetic bacteria. Carotenoids cannot be synthesized by humans and must be consumed in the form of food or supplements. There are several roles for carotenoids in human health. Although individual carotenoids may function in different ways, their main action is to act as antioxidants. There are validated techniques for separating and purifying carotenoids, yet, industrial production requires the development of economically viable techniques for larger-scale implementation. Carotenoids have been shown to boost cognitive performance and cardiovascular health, as well as help prevent some types of cancer. Despite evidence for carotenoids' health benefits, major population-based supplementation trials have yielded conflicting outcomes for several carotenoids. This review includes recent developments in carotenoid metabolism and nutritional and health advantages. It also offers an outlook on future directions in these areas. [ABSTRACT FROM AUTHOR]

Rhodobacter sphaeroides is a facultative phototrophic bacterium that performs aerobic respiration when oxygen is available. Only when oxygen is present at low concentrations or absent are pigment–protein complexes formed, and anoxygenic photosynthesis generates ATP. The regulation of photosynthesis genes in response to oxygen and light has been investigated for decades, with a focus on the regulation of transcription. However, many studies have also revealed the importance of regulated mRNA processing. This study analyzes the phenotypes of wild type and mutant strains and compares global RNA-seq datasets to elucidate the impact of ribonucleases and the small non-coding RNA StsR on photosynthesis gene expression in Rhodobacter. Most importantly, the results demonstrate that, in particular, the role of ribonuclease E in photosynthesis gene expression is strongly dependent on growth phase. [ABSTRACT FROM AUTHOR]

Diel cycle is of enormous biological importance as it imposes daily oscillation in environmental conditions, which temporally structures most ecosystems. Organisms developed biological time-keeping mechanisms – circadian clocks – that provide a significant fitness advantage over competitors by optimising the synchronisation of their biological activities. While circadian clocks are ubiquitous in Eukaryotes, they are so far only characterised in Cyanobacteria within Prokaryotes. However, growing evidence suggests that circadian clocks are widespread in the bacterial and archaeal domains. As Prokaryotes are at the heart of crucial environmental processes and are essential to human health, unravelling their time-keeping systems provides numerous applications in medical research, environmental sciences, and biotechnology. In this review, we elaborate on how novel circadian clocks in Prokaryotes offer research and development perspectives. We compare and contrast the different circadian systems in Cyanobacteria and discuss about their evolution and taxonomic distribution. We necessarily provide an updated phylogenetic analysis of bacterial and archaeal species that harbour homologs of the main cyanobacterial clock components. Finally, we elaborate on new potential clock-controlled microorganisms that represent opportunities of ecological and industrial relevance in prokaryotic groups such as anoxygenic photosynthetic bacteria, methanogenic archaea, methanotrophs or sulphate-reducing bacteria. [ABSTRACT FROM AUTHOR]

The bacterial light-dependent energy metabolism can be divided into two types: oxygenic and anoxygenic photosynthesis. Bacterial oxygenic photosynthesis is similar to plants and is characteristic for cyanobacteria. Bacterial anoxygenic photosynthesis is performed by anoxygenic phototrophs, especially green sulfur bacteria (GSB; family Chlorobiaceae) and purple sulfur bacteria (PSB; family Chromatiaceae). In anoxygenic photosynthesis, hydrogen sulfide ( H2S) is used as the main electron donor, which differs from plants or cyanobacteria where water is the main source of electrons. This review mainly focuses on the microbiology of GSB, which may be found in water or soil ecosystems where H2S is abundant. GSB oxidize H2S to elemental sulfur. GSB possess special structures—chlorosomes—wherein photosynthetic pigments are located. Chlorosomes are vesicles that are surrounded by a lipid monolayer that serve as light-collecting antennas. The carbon source of GSB is carbon dioxide, which is assimilated through the reverse tricarboxylic acid cycle. Our review provides a thorough introduction to the comparative eco-physiology of GSB and discusses selected application possibilities of anoxygenic phototrophs in the fields of environmental management, bioremediation, and biotechnology. [ABSTRACT FROM AUTHOR]

The gas vesicle (GV) is like a hollow nanoparticle consisting of an internal gas and a protein shell, which mainly consists of hydrophobic gas vesicle protein A (GvpA) and GvpC attached to the surface. GVs, first discovered in cyanobacteria, are mainly produced by photosynthetic bacteria (PSB) and halophilic archaea. After being modified and engineered, GVs can be utilized as contrast agents, delivery carriers, and immunological boosters for disease prevention, diagnosis, and treatment with good results due to their tiny size, strong stability and non-toxicity advantages. Many diagnostic and therapeutic approaches based on GV are currently under development. In this review, we discuss the source, function, physical and chemical properties of GV, focus on the current application progress of GV, and put forward the possible application prospect and development direction of GV in the future. [ABSTRACT FROM AUTHOR]

Therapeutic mRNA vaccines have become powerful therapeutic tools for severe diseases, including infectious diseases and malignant neoplasms. mRNA vaccines encoding tumor‐associated antigens provide unprecedented hope for many immunotherapies that have hit the bottleneck. However, the application of mRNA vaccines is limited because of biological instability, innate immunogenicity, and ineffective delivery in vivo. This study aims to construct a novel mRNA vaccine delivery nanosystem to successfully co‐deliver a tumor‐associated antigen (TAA) encoded by the Wilms' tumor 1 (WT1) mRNA. In this system, named PSB@Nb1.33C/mRNA, photosynthetic bacteria (PSB) efficiently delivers the iMXene‐WT1 mRNA to the core tumor region using photo‐driven and hypoxia‐driven properties. The excellent photothermal therapeutic (PTT) properties of PSB and 2D iMxene (Nb1.33C) trigger tumor immunogenic cell death, which boosts the release of the WT1 mRNA. The released WT1 mRNA is translated, presenting the TAA and amplifying immune effect in vivo. The designed therapeutic strategy demonstrates an excellent ability to inhibit distant tumors and counteract postsurgical lung metastasis. Thus, this study provides an innovative and effective paradigm for tumor immunotherapy, i.e., photo‐immunogene cancer therapy, and establishes an efficient delivery platform for mRNA vaccines, thereby opening a new path for the wide application of mRNA vaccines. [ABSTRACT FROM AUTHOR]

Vallisneria spinulosa Yan (V.spinulosa Yan) with good ability of water purification is often used for ecological restoration of polluted water bodies. However, it is difficult to survive in turbid water bodies due to the low lighting condition. This study explored the feasibility of introducing artificial underwater light source into water bodies with high turbidity to strengthen the water restoration by V.spinulosa Yan. Addition of underwater light source promoted the clonal reproduction ability of V.spinulosa Yan, thus enhancing the removal loads of total nitrogen (TN), total phosphorus (TP), and nitrate nitrogen ( NO 3 − - N ) by 1.60–3.43 × 10−2, 1.49–3.49 × 10−3, and 0.80–2.06 × 10−2 g m−2 d−1, respectively. Underwater light source significantly reduced the abundance of microbial community on V.spinulosa Yan leaves, as well as most nitrifying bacteria (Nitrosomonadaceae) and denitrifying bacteria (Nitrospira, Comamonadaceae, and Rhodocyclaceae) in the system. But the attachment of some Cyanophyta (Chloroplast and Cyanobacteria) and Photosynthetic bacteria (Rhodobacter) onto the leaves and the growth of Methyloligellaceae in water and sediments were promoted. Nitrogen and phosphorus removal by the growth system of V.spinulosa Yan without underwater light source mainly depended on the biological processes by functional bacteria, while the absorption and co-assimilation effect of V.spinulosa Yan with underwater light source. [ABSTRACT FROM AUTHOR]

Introduction: Several fluorescent proteins (FPs) and chromoproteins (CPs) are present in anthozoans and play possible roles in photoprotection. Coral tissues in massive corals often display discoloration accompanied by inflammation. Incidences of the pink pigmentation response (PPR) in massive Porites, described as inflammatory pink lesions of different shapes and sizes, has recently increased worldwide. FPs are reported to be present in PPR lesions, wherein a red fluorescent protein (RFP) appears to play a role in reducing reactive oxygen species. However, to date, the biochemical characterization and possible roles of the pigments involved are poorly understood. The present study aimed to identify and characterize the proteins responsible for pink discoloration in massive Porites colonies displaying PPRs, as well as to assess the differential distribution of pigments and the antioxidant properties of pigmented areas. Method: CPs were extracted from PPR lesions using gel-filtration chromatography and identified via genetic analysis using liquid chromatography-tandem mass spectrometry. The coexistence of CPs and RFP in coral tissues was assessed using microscopic observation. Photosynthetic antivity and hydrogen peroxide-scavenging activitiy were measured to assess coral stress conditions. Results: The present study revealed that the same CP (plut2.m8.16902.m1) isolated from massive Porites was present in both the pink spot and patch morphologies of the PPR. CPs were also found to coexist with RFP in coral tissues that manifested a PPR, with a differential distribution (coenosarc or tip of polyps’ tentacles). High hydrogen peroxide-scavenging rates were found in tissues affected by PPR. Discussion and Conclusion: The coexistence of CPs and RFP suggests their possible differential role in coral immunity. CPs, which are specifically expressed in PPR lesions, may serve as an antioxidant in the affected coral tissue. Overall, this study provides new knowledge to our understanding of the role of CPs in coral immunity. [ABSTRACT FROM AUTHOR]

FtsH proteases (FtsHs) belong to intramembrane ATP-dependent metalloproteases which are widely distributed in eubacteria, mitochondria and chloroplasts. The best-studied roles of FtsH in Escherichia coli include quality control of membrane proteins, regulation of response to heat shock, superoxide stress and viral infection, and control of lipopolysaccharide biosynthesis. While heterotrophic bacteria mostly contain a single indispensable FtsH complex, photosynthetic cyanobacteria usually contain three FtsH complexes: two heterocomplexes and one homocomplex. The essential cytoplasmic FtsH1/3 most probably fulfills a role similar to other bacterial FtsHs, whereas the thylakoid FtsH2/3 heterocomplex and FtsH4 homocomplex appear to maintain the photosynthetic apparatus of cyanobacteria and optimize its functionality. Moreover, recent studies suggest the involvement of all FtsH proteases in a complex response to nutrient stresses. In this review, we aim to comprehensively evaluate the functions of the cyanobacterial FtsHs specifically under stress conditions with emphasis on nutrient deficiency and high irradiance. We also point to various unresolved issues concerning FtsH functions, which deserve further attention. [ABSTRACT FROM AUTHOR]

In the monitoring the discharge of ballast water, the count of living algal cells is of utmost significant. Variable fluorescence, denoted as Fv, stands as an optimal parameter for photosynthetic fluorescence, efficiently charactering the living algal cells count, unaffected by the ballast waters' complex background fluorescence environment. This study deeply investigates the quantitative relationship between Fv and the count of living algal cells. Observations indicate that single cell fluorescence yield (abbreviated as SCF) varies significantly across different algae species, leading to considerable errors in quantifying living algal cell count in ballast water with unknown components using the calibration relationship between Fv and the cell count. Thus, correcting SCF prior to calibration becomes necessary. The paper proposes an innovative SCF correction method based on cell cross-sectional area and an eμ factor (where μ is the expected value of the functional absorption cross-section of PSII) This method mitigates the influence of cell size and species differences on quantifying the living algal cell count. Correction operation trials revealed that dividing the SCF measurement by cell cross-sectional area and multiplying by eμ enhanced the correction effect. Comparative experiments demonstrated marked improvement: Relative errors (REs) for Chlorella pyrenoidosa and Chlorella marine, both belonging to the Chlorophyta group, fell from 92.1% and 90.6% to 37.2% and 9.5% respectively post-correction. Similarly, REs for Thalassiosira weissflogii and Nitzschia closterium minutissima, from the Bacillariophyta group, decreased from 74.7% and 68.1% to 14.3% and 19.1% respectively. The RE of Peridinium from the Pyrrophyta group dropped from 28.4% to 12.1%. The results underscore the effectiveness of cell cross-sectional area and eμ in correcting SCF, thus offering a novel correction method for swift and precise measurement of living algal cell count in ballast water, based on variable fluorescence. [ABSTRACT FROM AUTHOR]

Aerobic anoxygenic phototrophic (AAP) bacteria are an important component of freshwater bacterioplankton. They can support their heterotrophic metabolism with energy from light, enhancing their growth efficiency. Based on results from cultures, it was hypothesized that photoheterotrophy provides an advantage under carbon limitation and facilitates access to recalcitrant or low-energy carbon sources. However, verification of these hypotheses for natural AAP communities has been lacking. Here, we conducted whole community manipulation experiments and compared the growth of AAP bacteria under carbon limited and with recalcitrant or low-energy carbon sources under dark and light (near-infrared light, λ > 800 nm) conditions to elucidate how they profit from photoheterotrophy. We found that AAP bacteria induce photoheterotrophic metabolism under carbon limitation, but they overcompete heterotrophic bacteria when carbon is available. This effect seems to be driven by physiological responses rather than changes at the community level. Interestingly, recalcitrant (lignin) or low-energy (acetate) carbon sources inhibited the growth of AAP bacteria, especially in light. This unexpected observation may have ecosystem-level consequences as lake browning continues. In general, our findings contribute to the understanding of the dynamics of AAP bacteria in pelagic environments. [ABSTRACT FROM AUTHOR]

The whole-cell inorganic-biohybrid systems show special functions and wide potential in biomedical application owing to the exceptional interactions between microbes and inorganic materials. However, the hybrid systems are still in stage of proof of concept. Here, we report a whole-cell inorganic-biohybrid system composed of Spirulina platensis and gold nanoclusters (SP-Au), which can enhance the cancer radiotherapy through multiple pathways, including cascade photocatalysis. Such systems can first produce oxygen under light irradiation, then convert some of the oxygen to superoxide anion (•O2−), and further oxidize the glutathione (GSH) in tumor cells. With the combination of hypoxic regulation, •O2− production, GSH oxidation, and the radiotherapy sensitization of gold nanoclusters, the final radiation is effectively enhanced, which show the best antitumor efficacy than other groups in both 4T1 and A549 tumor models. Moreover, in vivo distribution experiments show that the SP-Au can accumulate in the tumor and be rapidly metabolized through biodegradation, further indicating its application potential as a new multiway enhanced radiotherapy sensitizer. [ABSTRACT FROM AUTHOR]

The photosynthetic amoeba, Paulinella provides a recent (ca. 120 Mya) example of primary plastid endosymbiosis. Given the extensive data demonstrating host lineage‐driven endosymbiont integration, we analysed nuclear genome and transcriptome data to investigate mechanisms that may have evolved in Paulinella micropora KR01 (hereinafter, KR01) to maintain photosynthetic function in the novel organelle, the chromatophore. The chromatophore is of α‐cyanobacterial provenance and has undergone massive gene loss due to Muller's ratchet, but still retains genes that encode the ancestral α‐carboxysome and the shell carbonic anhydrase, two critical components of the biophysical CO2 concentrating mechanism (CCM) in cyanobacteria. We identified KR01 nuclear genes potentially involved in the CCM that arose via duplication and divergence and are upregulated in response to high light and downregulated under elevated CO2. We speculate that these genes may comprise a novel CO2 delivery system (i.e., a biochemical CCM) to promote the turnover of the RuBisCO carboxylation reaction and counteract photorespiration. We posit that KR01 has an inefficient photorespiratory system that cannot fully recycle the C2 product of RuBisCO oxygenation back to the Calvin‐Benson cycle. Nonetheless, both these systems appear to be sufficient to allow Paulinella to persist in environments dominated by faster‐growing phototrophs. [ABSTRACT FROM AUTHOR]

Marine biogeochemical cycles are built on interactions between surface ocean microbes, particularly those connecting phytoplankton primary producers to heterotrophic bacteria. Details of these associations are not well understood, especially in the case of direct influences of bacteria on phytoplankton physiology. Here we catalogue how the presence of three marine bacteria (Ruegeria pomeroyi DSS‐3, Stenotrophomonas sp. SKA14 and Polaribacter dokdonensis MED152) individually and uniquely impact gene expression of the picoeukaryotic alga Micromonas commoda RCC 299. We find a dramatic transcriptomic remodelling by M. commoda after 8 h in co‐culture, followed by an increase in cell numbers by 56 h compared with the axenic cultures. Some aspects of the algal transcriptomic response are conserved across all three bacterial co‐cultures, including an unexpected reduction in relative expression of photosynthesis and carbon fixation pathways. Expression differences restricted to a single bacterium are also observed, with the Flavobacteriia P. dokdonensis uniquely eliciting changes in relative expression of algal genes involved in biotin biosynthesis and the acquisition and assimilation of nitrogen. This study reveals that M. commoda has rapid and extensive responses to heterotrophic bacteria in ways that are generalizable, as well as in a taxon specific manner, with implications for the diversity of phytoplankton‐bacteria interactions ongoing in the surface ocean. [ABSTRACT FROM AUTHOR]

Ecological health surveys are crucial for evaluating the well-being of ecosystems, as they provide essential insights through surrogate indicators, enabling informed decision-making for sustainable environmental management and conservation. This study conducted an ecosystem health survey in Miagao, Iloilo, Philippines, with specific objectives including the evaluation of physico-chemical parameters, identification of plankton at the family level, microbiological analysis, and detection of photosynthetic bacteria in selected sites. Four sites were chosen, and physico-chemical parameters in sites 1 and 4 were almost identical. Plankton presence was observed, but quantification was not conducted. Microbiological analysis in Site 1 indicated that the total plate count was 105 CFU mL-1. Growth of photosynthetic bacteria was observed in samples with sediment after 14 days. Despite limitations in site coverage and real-time insight, the study highlights the presence of bioindicators, offering valuable groundwork for future research and the need for comprehensive analysis across all sites. [ABSTRACT FROM AUTHOR]

The addition of specific ions has a significant effect on the characteristics and kinetics of hydrogen production by photofermentation (PFHP). In this article, a new basic research investigated by us find that adjusting the addition ratio of Zn2+ and Mn2+ ions in the R. sphaeroides HY01 system can effectively improve their biohydrogen production from xylose. The largest biohydrogen yield can be obtained as high as 219.2 mL/g xylose at concentration levels of 12 mg/L Zn2+ and 8 mg/L Mn2+. The shortest lag time is 5.76 h, along with most of the organic energy in the substrate transferred to H2. To evaluate the effect of Zn2+ and Mn2+, the Gompertz model with appropriately modification is applied on the photosynthetic bacteria R. sphaeroides HY01, and the corresponding constants are obtained by fitting the model, which is of great guiding significance for the optimization of fermentation conditions. [ABSTRACT FROM AUTHOR]

Environmental conditions at different water depths on tropical atolls are substantially different, but few studies have investigated the depth distribution and adaptation in the microbiomes of juvenile and adult corals. We collected samples of juvenile and adult Pocillopora verrucosa from different depths on an atoll in the central South China Sea and analyzed their communities of symbiotic Symbiodiniaceae and associated bacteria. Results showed that the Symbiodiniaceae communities were significantly different at different depths in both juvenile and adult P. verrucosa. Symbiodiniaceae community changed with increasing depth and was dominated by Durusdinium and Cladocopium at 1-m and 20-m depth, respectively. Furthermore, the composition and diversity of Symbiodiniaceae in juvenile and adult corals were different at the same depths. The compositions of associated bacterial communities at different depths also differed significantly between juvenile and adult P. verrucosa. The relative abundance of Endozoicomonas in juvenile and adult P. verrucosa increased with increasing depth, while the Thermus decreased. Our study suggests that juvenile and adult P. verrucosa corals in shallow-water regions associate with high abundances of thermotolerant Symbiodiniaceae and bacteria in the shallow reef flats with high temperature and intense solar radiation, but associate with Symbiodiniaceae and associated bacteria with high photosynthetic efficiency at greater depths. [ABSTRACT FROM AUTHOR]

At present, the application of sewage treatment technologies is restricted by high sulfate concentrations. In the present work, the sulfate removal was biologically treated using an upflow anaerobic sludge blanket (UASB) in the absence/presence of light. First, the start-up of UASB for the sulfate removal was studied in terms of COD degradation, sulfate removal, and effluent pH. Second, the impacts of different operation parameters (i.e., COD/SO42− ratio, temperature and illumination time) on the UASB performance were explored. Third, the properties of sludge derived from the UASB at different time were analyzed. Results show that after 28 days of start-up, the COD removal efficiencies in both the photoreactor and non-photoreactor could reach a range of 85–90% while such reactors could achieve > 90% of sulfate being removed. Besides, higher illumination time could facilitate the removal of pollutants in the photoreactor. To sum up, the present study can provide technical support for the clean removal of sulfate from wastewater using photoreactors. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

DPA membranes from Allochromatium vinosum cells, in which carotenoid biosynthesis was inhibited using diphenylamine (DPA) were obtained, into which rhodopin was incorporated. The LH2 complex with rhodopin content of 85% was isolated. Using a test for the thermal stability of LH2 complexes (DPA and with incorporated rhodopin), it was established that carotenoids of the early stages of biosynthesis (≤1 molecules per complex) did not interfere with rhodopin incorporation. It was found that when the LH2 complex with incorporated rhodopin was irradiated with light at the wavelength of 502 nm, BChl850 was photobleached at a rate close to that in the control LH2 complex. This indicates that rhodopin, after being incorporated into the DPA LH2 complex, is capable of generating singlet oxygen under illumination. Previously obtained data on heterogeneity of the carotenoid composition in DPA LH2 complexes (variation in the number of individual carotenoids molecules per complex in the general population) and our earlier suggestion about the structural role of carotenoids, namely, their ability to stabilize the LH2 complexes, were confirmed. Based on analysis of our results, as well as of the literature data, the interaction of singlet oxygen and carotenoids is discussed. [ABSTRACT FROM AUTHOR]

The relic Lake Mogilnoe, separated from the Barents Sea by a sand and pebble dam, is located in the high Arctic on the Kildin island (Murmansk region). This lake is a classic example of a meromictic basin of marine origin. The data obtained during the 2018 expedition showed changes in the hydrochemical regime of the lake that have occurred over the past 20 years. Sulfide concentration in the monimolimnion of the lake was as high as 140 mg/L. A tendency for salinization of the surface waters to 7 g/L has been noted. The Lake Mogilnoe is characterized by a discrepancy between the halocline and thermocline levels. The chemocline zone in the lake is below the halocline level. In a narrow oxygen-containing layer between 3 and 7.5 m, aerobic microflora of the marine type and marine fauna were present. The bacterial plate was formed at the boundary of the sulfide layer at ~8 m and mainly consisted of green sulfur bacteria (GSB). Brown-colored GSB species containing bacteriochlorophyll e were predominant. The previously formed concept of anaerobic phototrophic bacteria (APB) biodiversity based on morphological characteristics was modified using metagenomic data obtained by analyzing DNA from two samples of lake water in the chemocline zone, and was also supplemented by identifying new GSB species. Molecular diagnostic data confirmed the absolute dominance of the brackish species of GSB Chlorobium phaeovibrioides. This is the first isolation and identification of brown- and green-colored Prosthecochloris aestuarii morphotypes from Lake Mogilnoe, as well as of bacteriochlorophyll c-containing Prosthecochloris sp. The taxonomic position of Pelodyction phaem, which was constantly present in the Lake Mogilnoe, is discussed in detail. Despite the partial isolation of the ecosystem of Lake Mogilnoe from the Barents Sea, the main properties of the dominant GSB species and Prosthecochlori aestuarii turned out to be similar to those of the phylotypes living in lakes on the White Sea coast. [ABSTRACT FROM AUTHOR]

Cryptophyte algae are an evolutionarily distinct and ecologically important group of photosynthetic unicellular eukaryotes. Photosystem II (PSII) of cryptophyte algae associates with alloxanthin chlorophyll a/c-binding proteins (ACPs) to act as the peripheral light-harvesting system, whose supramolecular organization is unknown. Here, we purify the PSII-ACPII supercomplex from a cryptophyte alga Chroomonas placoidea (C. placoidea), and analyze its structure at a resolution of 2.47 Å using cryo-electron microscopy. This structure reveals a dimeric organization of PSII-ACPII containing two PSII core monomers flanked by six symmetrically arranged ACPII subunits. The PSII core is conserved whereas the organization of ACPII subunits exhibits a distinct pattern, different from those observed so far in PSII of other algae and higher plants. Furthermore, we find a Chl a-binding antenna subunit, CCPII-S, which mediates interaction of ACPII with the PSII core. These results provide a structural basis for the assembly of antennas within the supercomplex and possible excitation energy transfer pathways in cryptophyte algal PSII, shedding light on the diversity of supramolecular organization of photosynthetic machinery. The authors report structure of PSII-ACPII from a cryptophyte alga Chroomonas placoidea, providing insights into a distinct supramolecular organization and assembly of antennas in the supercomplex and possible excitation energy transfer pathways. [ABSTRACT FROM AUTHOR]

A variety of costly research-grade imaging devices are available for the detection of spectroscopic features. Here we present an affordable, open-source and versatile device, suitable for a range of applications. We provide the files to print the imaging chamber with commonly available 3D printers and instructions to assemble it with easily available hardware. The imager is suitable for rapid sample screening in research, as well as for educational purposes. We provide details and results for an already proven set-up which suits the needs of a research group and students interested in UV-induced near-infrared fluorescence detection of microbial colonies grown on Petri dishes. The fluorescence signal confirms the presence of bacteriochlorophyll a in aerobic anoxygenic phototrophic bacteria (AAPB). The imager allows for the rapid detection and subsequent isolation of AAPB colonies on Petri dishes with diverse environmental samples. To this date, 15 devices have been build and more than 7000 Petri dishes have been analyzed for AAPB, leading to over 1000 new AAPB isolates. Parts can be modified depending on needs and budget. The latest version with automated switches and double band pass filters costs around 350€ in materials and resolves bacterial colonies with diameters of 0.5 mm and larger. The low cost and modular build allow for the integration in high school classes to educate students on light properties, fluorescence and microbiology. Computer-aided design of 3D-printed parts and programming of the employed Raspberry Pi computer could be incorporated in computer sciences classes. Students have been also inspired to do agar art with microbes. The device is currently used in seven different high schools in Finland. Additionally, a science education network of Finnish universities has incorporated it in its program for high school students. Video guides have been produced to facilitate easy operation and accessibility of the device. [ABSTRACT FROM AUTHOR]

Cyanobacteria are photosynthetic bacteria whose gene expression patterns are globally regulated by their circadian (daily) clocks. Due to their ability to use sunlight as their energy source, they are also attractive hosts for "green" production of pharmaceuticals, renewable fuels, and chemicals. However, despite the application of traditional genetic tools such as the identification of strong promoters to enhance the expression of heterologous genes, cyanobacteria have lagged behind other microorganisms such as Escherichia coli and yeast as economically efficient cell factories. The previous approaches have ignored large-scale constraints within cyanobacterial metabolic networks on transcription, predominantly the pervasive control of gene expression by the circadian (daily) clock. Here, we show that reprogramming gene expression by releasing circadian repressor elements in the transcriptional regulatory pathways coupled with inactivation of the central oscillating mechanism enables a dramatic enhancement of expression in cyanobacteria of heterologous genes encoding both catalytically active enzymes and polypeptides of biomedical significance. [ABSTRACT FROM AUTHOR]

Exchange of B800 bacteriochlorophyll (BChl) a in light-harvesting complex 2 (LH2) is promising for a better understanding of the mechanism on intracomplex excitation energy transfer of this protein. Structural and spectroscopic properties of LH2 lacking B800 BChl a (B800-depleted LH2), which is an important intermediate protein in the B800 exchange, will be useful to tackle the energy transfer mechanism in LH2 by the B800 exchange strategy. In this study, we report a unique spectral change of B800-depleted LH2, in which the Qy absorption band of B800 BChl a is automatically recovered under neutral pH conditions. This spectral change was facilitated by factors for destabilization of LH2, namely, a detergent, lauryl dimethylamine N-oxide, and an increase in temperature. Spectral analyses in the preparation of an LH2 variant denoted as B800-recovered LH2 indicated that most BChl a that was released by decomposition of part of B800-depleted LH2 was a source of the production of B800-recovered LH2. Characterization of purified B800-recovered LH2 demonstrated that its spectroscopic and structural features was quite similar to those of native LH2. The current results indicate that the recovery of the B800 Qy band of B800-depleted LH2 originates from the combination of decomposition of part of B800-depleted LH2 and in situ reconstitution of BChl a into the B800 binding pockets of residual B800-depleted LH2, resulting in the formation of stable B800-recovered LH2. [ABSTRACT FROM AUTHOR]

Hydrogen gas is attractive as a clean fuel source if it can be produced efficiently without relying on fossil fuels. Biohydrogen production using photosynthetic bacteria may enable environmentally friendly hydrogen production but is currently limited by factors such as low oxygen tolerance. In this study, we isolate a new strain of bacteria that can produce hydrogen under aerial-phase conditions compared with those under liquid-phase conditions in a nitrogen gas or an argon gas atmosphere. Bacterial strains were cultured from scrapings taken from a steel signboard. Investigation of the hydrogen production of the strains under aerial- and liquid-phase conditions and subsequent DNA sequencing led to identification of the bacterium Cereibacter sp. KGU-NF001. Aerial-phase conditions were achieved by filter membranes with the bacterial strains and placing the membranes on medium-soaked cotton wool. The gas atmosphere affected the behavior of the isolated bacterial strains under both aerial- and liquid-phase conditions. Cereibacter sp. KGU-NF001 showed promising oxygen tolerance and was able to maintain hydrogen production of 1.33 mL/mg/d even when the atmosphere contained 12% oxygen. Our findings illustrate that biohydrogen production may be achieved by photosynthetic bacteria under oxygen-containing aerial-phase conditions, indicating a possible pathway to help lower our reliance on fossil fuels. [ABSTRACT FROM AUTHOR]

Marshes are an important ecosystem, acting as a biodiversity hotspot, a carbon sink and a bioremediation site, breaking down anthropogenic waste such as antibiotics, metals and fertilizers. Due to their participation in these metabolic activities and their capability to contribute to primary productivity, the microorganisms in such habitats have become of interest to investigate. Since Proteobacteria were previously found to be abundant and the waters are well aerated and organic-rich, this study on the presence of anoxygenic phototrophic bacteria, purple non-sulfur bacteria and aerobic anoxygenic phototrophs in marshes was initiated. One sample was collected at each of the seven Manitoban sites, and anoxygenic phototrophs were cultivated and enumerated. A group of 14 strains, which represented the phylogenetic diversity of the isolates, was physiologically investigated further. Aerobic anoxygenic phototrophs and purple non-sulfur bacteria were present at each location, and they belonged to the α- and β-Proteobacteria subphyla. Some were closely related to known heavy metal reducers (Brevundimonas) and xenobiotic decomposers (Novosphingobium and Sphingomonas). All were able to synthesize the photosynthetic complexes aerobically. This research highlights the diversity of and the potential contributions that anoxygenic phototrophs make to the essential functions taking place in wetlands. [ABSTRACT FROM AUTHOR]

Aphanizomenon flos-aquae (AFA) is the dominant filamentous cyanobacterium that develops into blooms in Upper Klamath Lake, Oregon, each year. During AFA bloom and collapse, ecosystem conditions for endangered Lost River and shortnose suckers deteriorate, thus motivating the need to identify processes that limit AFA abundance and decline. Here, we investigate the relations between AFA and other members of the microbial community (photosynthetic and nonphotosynthetic bacteria and archaea), how those relations impact abundance and collapse of AFA, and the types of microbial conditions that suppress AFA. We found significant spatial variation in AFA relative abundance during the 2016 bloom period using 16S rRNA sequencing. The Pelican Marina site had the lowest AFA relative abundance, and this was coincident with increased relative abundance of Candidatus Sericytochromatia, Flavobacterium , and Rheinheimera , some of which are known AFA antagonists. The AFA collapse coincided with phosphorus limitation relative to nitrogen and the increased relative abundance of Cyanobium and Candidatus Sericytochromatia, which outcompete AFA when dissolved inorganic nitrogen is available. The data collected in this study indicate the importance of dissolved inorganic nitrogen combined with microbial community structure in suppressing AFA abundance. [ABSTRACT FROM AUTHOR]

Endocrine disruption compounds can be found in various daily products, like pesticides, along with cosmetic and pharmaceutical commodities. Moreover, occurrence of EDCs in the wastewater alarms the urgency for their removal before discharge owing to the harmful effect for the environment and human health. Compared to implementation of physical and chemical strategies, cultivation of photosynthetic microorganisms has been acknowledged for their high efficiency and eco-friendly process in EDCs removal along with accumulation of valuable byproducts. During the process, photosynthetic microorganisms remove EDCs via photodegradation, bio-adsorption, -accumulation, and -degradation. Regarding their high tolerance in extreme environment, photosynthetic microorganisms have high feasibility for implementation in wastewater treatment plant. However, several considerations are critical for their scaling up process. This review discussed the potency of EDCs removal by photosynthetic microorganisms and focused on the efficiency, mechanism, challenge, along with the prospect. Details on the mechanism's pathway, accumulation of valuable byproducts, and recent progress in scaling up and application in real wastewater were also projected in this review. [ABSTRACT FROM AUTHOR]

Rhodopseudomonas palustris, is a purple non-sulphur bacterium with properties of extraordinary metabolic versatility, carbon source diversity and metabolite diversity. Due to its biodetoxification and biodegradation properties, R. palustris has been traditionally applied in wastewater treatment and bioremediation, and also in agriculture. This study aimed to isolate and identify R. palustris from waste dump site in Minna, Nigeria, using conventional and molecular techniques. Soil samples were collected at 3 cm depth from different points at waste dump sites in Minna, Niger State, Nigeria. Inoculation was made on Nutrient agar plates and incubated at 30 °C under 60 W incandescent light for 7days. The suspected bacterial isolate, based on cultural and morphological characteristics as well as biochemical reactions was subjected to molecular ribotyping. A PCR product of approximately 789 bp DNA maker was detected by agarose gel electrophoresis using 1500 bp Lamda maker. The DNA fragments of the isolates were obtained from DNA sequencing and were deposited in the NCBI-GenBank database. Based BLASTn search in GenBank using the fragments as the query, showed that the 16S rDNA of EG-4 share 99% sequence identity with Rhodopseudomonas palustris. Results of this study indicate the presence of R. palustris in waste dump site in Minna. [ABSTRACT FROM AUTHOR]

Annually, the food industry generates large amounts of waste and by-products, causing serious problems in their management and final disposal. In particular, by-products are mainly recovered as livestock feed. A most appealing strategy to valorize them has herein been investigated, through polyhydroxyalkanoate (PHA) production. In this view, a stream rich in volatile fatty acids deriving from the acidogenic fermentation of reground pasta (RP), a farinaceous food-industry by-product, was used as a carbon source for PHA production with a phototrophic purple bacteria (PPB) consortium. PPB are very versatile organisms that present a unique metabolism allowing them to adapt to a variety of environmental conditions. The PPB-PHA enrichment phase was performed in a lab-scale semi-continuous photo-bioreactor under a permanent carbon feast regime, with organic loading rate (OLR) increments from 14 to 19 mmolC/Ld. The results showed that the fermented RP solution composition (with 23.4% of HV precursors on a COD basis) was suitable for the PHBHV copolymer production, with the PPB consortium being capable of reaching a very high content in the hydroxyvalerate (HV) monomer, with a maximum of 60% (gHV/gPHA). Regarding the PHA accumulation stage where the light intensity was increased up to 20.2 W/L, a further increase in the culture PHA content by 76% after 12 h was obtained. Overall, these results open the possibility of valorizing food-industry by-products through the development of a biocatalytic process for PHA production with PPB, thus making the overall approach more sustainable from a green perspective. [ABSTRACT FROM AUTHOR]

In purple bacteria, photosynthesis is performed by densely packed pigmentprotein complexes, including the light-harvesting complexes known as RC-LH1 and LH2, with carotenoids to assist in the functioning of photosynthesis. Most photosynthetic bacteria are exposed to various abiotic stresses such as light, temperature, alkalinity-acidity, and salinity. Rhodobacter (R.) alkalitolerans was discovered from the alkaline pond; here, we report the comparative study of the photosynthetic apparatus of R. alkalitolerans in various light intensities in relation to its high pH tolerance ability. With increased light intensity, the stability of photosystem complexes decreased in normal pH (npH pH 6.80 ± 0.05) conditions, whereas in high pH (hpH pH 8.60 ± 0.05), acclimation was observed to high light. The content of bacteriochlorophyll a, absorbance spectra, and circular dichroism data shows that the integrity of photosystem complexes is less affected in hpH compared with npH conditions. Large pore blue native polyacrylamide gel electrophoresis of photosystem protein complexes and sucrose density gradient of n-dodecyl ß-D-maltoside solubilized intracytoplasmic membranes show that LH2 is more affected in npH than in hpH, whereas RCLH1 monomer or dimer has shown interplay between monomer and dimer in hpH, although the dimer and monomer both increased in npH. Increased content and expression level of ATPase protein complex and subunit--"c" of ATPase, fast relaxation kinetics of p515, and relatively higher membrane lipid content in hpH along with less photooxidative stress and subsequently lesser superoxide dismutase activity exemplify photoprotection in hpH. Furthermore, the increased expression levels of antiporter NhaD in hpH signify its role in the maintenance of homeostatic balance in hpH. [ABSTRACT FROM AUTHOR]

A Type I reaction center (RC) (Fe-S type, ferredoxin reducing) is found in several phyla containing anoxygenic phototrophic bacteria. These include the heliobacteria (HB), the green sulfur bacteria (GSB), and the chloracidobacteria (CB), for which high-resolution homodimeric RC-photosystem (PS) structures have recently appeared. The 2.2-Å X-ray structure of the RC-PS of Heliomicrobium modesticaldum revealed that the core PshA apoprotein (PshA-1 and PshA-2 homodimeric pair) exhibits a structurally conserved PSI arrangement comprising five C-terminal transmembrane α-helices (TMHs) forming the RC domain and six N-terminal TMHs coordinating the light-harvesting (LH) pigments. The Hmi. modesticaldum structure lacked quinone molecules, indicating that electrons were transferred directly from the A0 (81-OH-chlorophyll (Chl) a) acceptor to the FX [4Fe-4S] component, serving as the terminal RC acceptor. A pair of additional TMHs designated as Psh X were also found that function as a low-energy antenna. The 2.5-Å resolution cryo-electron microscopy (cryo-EM) structure for the RC-PS of the green sulfur bacterium Chlorobaculum tepidum included a pair of Fenna–Matthews–Olson protein (FMO) antennae, which transfer excitations from the chlorosomes to the RC-PS (PscA-1 and PscA-2) core. A pair of cytochromes cZ (PscC) molecules was also revealed, acting as electron donors to the RC bacteriochlorophyll (BChl) a' special pair, as well as PscB, housing the [4Fe-4S] cluster FA and FB, and the associated PscD protein. While the FMO components were missing from the 2.6-Å cryo-EM structure of the Zn- (BChl) a' special pair containing RC-PS of Chloracidobacterium thermophilum, a unique architecture was revealed that besides the (PscA)2 core, consisted of seven additional subunits including PscZ in place of PscD, the PscX and PscY cytochrome c serial electron donors and four low mol. wt. subunits of unknown function. Overall, these diverse structures have revealed that (i) the HB RC-PS is the simplest light–energy transducing complex yet isolated and represents the closest known homolog to a common homodimeric RC-PS ancestor; (ii) the symmetrically localized Ca2+-binding sites found in each of the Type I homodimeric RC-PS structures likely gave rise to the analogously positioned Mn4CaO5 cluster of the PSII RC and the TyrZ RC donor site; (iii) a close relationship between the GSB RC-PS and the PSII Chl proteins (CP)43 and CP47 was demonstrated by their strongly conserved LH-(B)Chl localizations; (iv) LH-BChls of the GSB-RC-PS are also localized in the conserved RC-associated positions of the PSII ChlZ-D1 and ChlZ-D2 sites; (v) glycosylated carotenoids of the GSB RC-PS are located in the homologous carotenoid-containing positions of PSII, reflecting an O2-tolerance mechanism capable of sustaining early stages in the evolution of oxygenic photosynthesis. In addition to the close relationships found between the homodimeric RC-PS and PSII, duplication of the gene encoding the ancestral Type I RC apoprotein, followed by genetic divergence, may well account for the appearance of the heterodimeric Type I and Type II RCs of the extant oxygenic phototrophs. Accordingly, the long-held view that PSII arose from the anoxygenic Type II RC is now found to be contrary to the new evidence provided by Type I RC-PS homodimer structures, indicating that the evolutionary origins of anoxygenic Type II RCs, along with their distinct antenna rings are likely to have been preceded by the events that gave rise to their oxygenic counterparts. [ABSTRACT FROM AUTHOR]

Copyright of Biomass Chemical Engineering is the property of Editorial Office of Biomass Chemical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Calcium ions play a dual role in expanding the spectral diversity and structural stability of photocomplexes from several Ca2+-requiring purple sulfur phototrophic bacteria. Here, metal-sensitive structural changes in the isotopically labeled light-harvesting 1 reaction center (LH1-RC) complexes from the thermophilic purple sulfur bacterium Thermochromatium (Tch.) tepidum were investigated by perfusion-induced attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. The ATR-FTIR difference spectra induced by exchanges between native Ca2+ and exogenous Ba2+ exhibited interconvertible structural and/or conformational changes in the metal binding sites at the LH1 C-terminal region. Most of the characteristic Ba2+/Ca2+ difference bands were detected even when only Ca ions were removed from the LH1-RC complexes, strongly indicating the pivotal roles of Ca2+ in maintaining the LH1-RC structure of Tch. tepidum. Upon 15N-, 13C- or 2H-labeling, the LH1-RC complexes exhibited characteristic 15N/14N-, 13C/12C-, or 2H/1H-isotopic shifts for the Ba2+/Ca2+ difference bands. Some of the 15N/14N or 13C/12C bands were also sensitive to further 2H-labelings. Given the band frequencies and their isotopic shifts along with the structural information of the Tch. tepidum LH1-RC complexes, metal-sensitive FTIR bands were tentatively identified to the vibrational modes of the polypeptide main chains and side chains comprising the metal binding sites. Furthermore, important new IR marker bands highly sensitive to the LH1 BChl a conformation in the Ca2+-bound states were revealed based on both ATR-FTIR and near-infrared Raman analyses. The present approach provides valuable insights concerning the dynamic equilibrium between the Ca2+- and Ba2+-bound states statically resolved by x-ray crystallography. [ABSTRACT FROM AUTHOR]

Electronic Energy Transfer (EET) between chromophores is fundamental in many natural light-harvesting complexes, serving as a critical step for solar energy funneling in photosynthetic plants and bacteria. The complicated role of the environment in mediating this process in natural architectures has been addressed by recent scanning tunneling microscope experiments involving EET between two molecules supported on a solid substrate. These measurements demonstrated that EET in such conditions has peculiar features, such as a steep dependence on the donor-acceptor distance, reminiscent of a short-range mechanism more than of a Förster-like process. By using state of the art hybrid ab initio/electromagnetic modeling, here we provide a comprehensive theoretical analysis of tip-enhanced EET. In particular, we show that this process can be understood as a complex interplay of electromagnetic-based molecular plasmonic processes, whose result may effectively mimic short range effects. Therefore, the established identification of an exponential decay with Dexter-like effects does not hold for tip-enhanced EET, and accurate electromagnetic modeling is needed to identify the EET mechanism. Electronic energy transfer (EET) between chromophores is a critical process for solar energy funneling, and recent studies using scanning tunneling microscopy have shown that chromophores deposited on solid substrates in such conditions display peculiar EET features. Here, hybrid ab initio and electromagnetic modeling provide a comprehensive theoretical analysis of tip-enhanced EET. [ABSTRACT FROM AUTHOR]

The mesophilic purple sulfur phototrophic bacterium Allochromatium (Alc.) vinosum (bacterial family Chromatiaceae) has been a favored model for studies of bacterial photosynthesis and sulfur metabolism, and its core light-harvesting (LH1) complex has been a focus of numerous studies of photosynthetic light reactions. However, despite intense efforts, no high-resolution structure and thorough biochemical analysis of the Alc. vinosum LH1 complex have been reported. Here we present cryo-EM structures of the Alc. vinosum LH1 complex associated with reaction center (RC) at 2.24 Å resolution. The overall structure of the Alc. vinosum LH1 resembles that of its moderately thermophilic relative Alc. tepidum in that it contains multiple pigment-binding α- and β-polypeptides. Unexpectedly, however, six Ca ions were identified in the Alc. vinosum LH1 bound to certain α1/β1- or α1/β3-polypeptides through a different Ca2+-binding motif from that seen in Alc. tepidum and other Chromatiaceae that contain Ca2+-bound LH1 complexes. Two water molecules were identified as additional Ca2+-coordinating ligands. Based on these results, we reexamined biochemical and spectroscopic properties of the Alc. vinosum LH1–RC. While modest but distinct effects of Ca2+ were detected in the absorption spectrum of the Alc. vinosum LH1 complex, a marked decrease in thermostability of its LH1–RC complex was observed upon removal of Ca2+. The presence of Ca2+ in the photocomplex of Alc. vinosum suggests that Ca2+-binding to LH1 complexes may be a common adaptation in species of Chromatiaceae for conferring spectral and thermal flexibility on this key component of their photosynthetic machinery. The cryo-EM structure of the partially Ca2 + -bound light-harvesting 1–reaction center (LH1–RC) complex from Alc. vinosum, the best-studied model purple sulfur bacterium, is presented, characterized and compared to other photosynthetic bacteria. [ABSTRACT FROM AUTHOR]

Recent advances in coupling light-harvesting microorganisms with electronic components have led to a new generation of biohybrid devices based on microbial photocatalysts. These devices are limited by the poorly conductive interface between phototrophs and synthetic materials that inhibit charge transfer. This study focuses on overcoming this bottleneck through the metabolically-driven encapsulation of photosynthetic cells with a bio-inspired conductive polymer. Cells of the purple non sulfur bacterium Rhodobacter sphaeroides were coated with a polydopamine (PDA) nanoparticle layer via the self-polymerization of dopamine under anaerobic conditions. The treated cells show preserved light absorption of the photosynthetic pigments in the presence of dopamine concentrations ranging between 0.05–3.5 mM. The thickness and nanoparticle formation of the membrane-associated PDA matrix were further shown to vary with the dopamine concentrations in this range. Compared to uncoated cells, the encapsulated cells show up to a 20-fold enhancement in transient photocurrent measurements under mediatorless conditions. The biologically synthesized PDA can thus act as a matrix for electronically coupling the light-harvesting metabolisms of cells with conductive surfaces. [ABSTRACT FROM AUTHOR]

Living photovoltaics are microbial electrochemical devices that use whole cell–electrode interactions to convert solar energy to electricity. The bottleneck in these technologies is the limited electron transfer between the microbe and the electrode surface. This study focuses on enhancing this transfer by engineering a polydopamine (PDA) coating on the outer membrane of the photosynthetic microbe Synechocystis sp. PCC6803. This coating provides a conductive nanoparticle shell to increase electrode adhesion and improve microbial charge extraction. A combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis absorption, and Raman spectroscopy measurements were used to characterize the nanoparticle shell under various synthesis conditions. The cell viability and activity were further assessed through oxygen evolution, growth curve, and confocal fluorescence microscopy measurements. The results show sustained cell growth and detectable PDA surface coverage under slightly alkaline conditions (pH 7.5) and at low initial dopamine (DA) concentrations (1 mM). The exoelectrogenicity of the cells prepared under these conditions was also characterized through cyclic voltammetry (CV) and chronoamperometry (CA). The measurements show a three-fold enhancement in the photocurrent at an applied bias of 0.3 V (vs. Ag/AgCl [3 M KCl]) compared to non-coated cells. This study thus lays the framework for engineering the next generation of living photovoltaics with improved performances using biosynthetic electrodes. [ABSTRACT FROM AUTHOR]

Improving the efficiency of photosynthesis has important theoretical and practical value, and the application of pulsed light is an effective strategy for this goal. This study explored the theoretical temporal model of photosynthesis. In the experiment, the mean rate of oxygen evolution was measured under different photosynthetic photon flux densities and cycle durations with incremental pulse width modulation. The results revealed that the instantaneous oxygen evolution rate calculated using the differential method is an exponential curve, and a mathematical model was fitted. A photosynthetic capacitance model was proposed by referencing the capacitor charge circuit. The model suggests that a particular substance, which is stored in the photosynthetic capacitor, is consumed during the light period and accumulated during the dark period. This model could be used to explain the impact of the pulse parameters on the photosynthetic rate and provide new avenues for the study of photosynthesis under pulsed light to increase the photosynthetic rate. Oxygen evolution rate was measured using a new differential method. Temporal curve of photosynthetic rate was achieved by calculation. A capacitance model was proposed for photosynthesis under pulsed light. [ABSTRACT FROM AUTHOR]

Introduction: Cyanobacteria appeared in the anoxic Archean Earth, evolving for the first time oxygenic photosynthesis and deeply changing the atmosphere by introducing oxygen. Starting possibly from UV-protected environments, characterized by low visible and far-red enriched light spectra, cyanobacteria spread everywhere on Earth thanks to their adaptation capabilities in light harvesting. In the last decade, few cyanobacteria species which can acclimate to far-red light through Far-Red Light Photoacclimation (FaRLiP) have been isolated. FaRLiP cyanobacteria were thus proposed as model organisms to study the origin of oxygenic photosynthesis as well as its possible functionality around stars with high far-red emission, the M-dwarfs. These stars are astrobiological targets, as their longevity could sustain life evolution and they demonstrated to host rocky terrestrial-like exoplanets within their Habitable Zone. Methods: We studied the acclimation responses of the FaRLiP strain Chlorogloeopsis fritschii sp. PCC6912 and the non-FaRLiP strain Synechocystis sp. PCC6803 to the combination of three simulated light spectra (M-dwarf, solar and far-red) and two atmospheric compositions (oxic, anoxic). We first checked their growth, O2 production and pigment composition, then we studied their transcriptional responses by RNA sequencing under each combination of light spectrum and atmosphere conditions. Results and discussion: PCC6803 did not show relevant differences in gene expression when comparing the responses to M-dwarf and solar-simulated lights, while far-red caused a variation in the transcriptional level of many genes. PCC6912 showed, on the contrary, different transcriptional responses to each light condition and activated the FaRLiP response under the M-dwarf simulated light. Surprisingly, the anoxic atmosphere did not impact the transcriptional profile of the 2 strains significantly. Results show that both cyanobacteria seem inherently prepared for anoxia and to harvest the photons emitted by a simulated M-dwarf star, whether they are only visible (PCC6803) or also far-red photons (PCC6912). They also show that visible photons in the simulated M-dwarf are sufficient to keep a similar metabolism with respect to solar-simulated light. Conclusion: Results prove the adaptability of the cyanobacterial metabolism and enhance the plausibility of finding oxygenic biospheres on exoplanets orbiting Mdwarf stars. [ABSTRACT FROM AUTHOR]

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Background: Plant-microbe associations play central roles in ecosystem functioning, with some critical microbes significantly influencing the growth and health of plants. Additionally, some microbes are highly associated with other microbes in either competitive or cooperative microbe-microbe associations. Here, we aimed to determine whether there is overlap between critical microbes in plant-microbe and microbe-microbe associations by using guayule (a rubber-producing crop) as a model plant. Methods: Using marker gene amplicon sequencing, we characterized the bacterial/archaeal and fungal communities in soil samples collected from a guayule agroecosystem at six time points that represent changes in guayule productivity and growth stage. The critical microbes in guayule-microbe associations were phylotypes whose relative abundances were positively (positive taxa) or negatively (negative taxa) associated with guayule productivity. Network analysis was used to identify the critical microbes in microbe-microbe associations. Results: Some positive taxa in guayule-microbe associations were ammonia-oxidizing archaea (AOA) and bacteria (AOB) and arbuscular mycorrhizal fungi (AMF), and negative taxa included some microbes resistant to aridity. Some of the critical microbes in microbe-microbe associations were fungal plant pathogens. There were 9 phylotypes representing the overlap between critical microbes in guayule-microbe and microbe-microbe associations. This overlap group included AOB, phototrophic bacteria, AMF, and saprotrophic fungi, along with unique taxa of unknown function. Conclusions: Our study highlighted the association of the soil microbiome with the growth and health of guayule. Our systematic approach narrowed down the immense number of microbial taxa to a 'most wanted' list that we define as critical to the entire guayule agroecosystem. [ABSTRACT FROM AUTHOR]

Cyanobacteria utilize CO2 and HCO3− as inorganic carbon (Ci) sources. In low Ci, like in ambient air, cyanobacteria efficiently collect Ci using a carbon concentrating mechanism (CCM). The CCM includes bicarbonate transporters SbtA, BicA and BCT1; the specialized NDH complexes NDH‐13 and NDH‐14, which convert CO2 to HCO3− in the cytoplasm; and carboxysomes that are protein shell encapsulated ribulose‐1,5‐bisphosphate carboxylase/oxygenase (RuBisCo) and carbonic anhydrase containing bodies in which the first reaction of carbon fixation occurs. Ci‐dependent regulation of bicarbonate transporters and specialized NDH complexes, especially the regulation of the SbtA transporter, are well understood. CcmR (also called NdhR), CyAbrB2, CmpR and RbcR act as transcription factors regulating CCM genes. Ci signalling molecules detecting the metabolic status of the cells include 2‐oxoglutarate, which accumulates when the Ci/nitrogen ratio of the cell is high, and 2‐phosphoglycolate, the first intermediate of the photorespiration pathway, whose accumulation indicates low Ci. These signalling molecules act as corepressors and coactivators of the CcmR repressor protein, whereas 2‐phosphoglycolate and ribulose‐1,5‐bisphosphate activate transcription activator CmpR. In addition, bicarbonate or CO2 activates the adenylyl cyclase that produces cAMP, and ATP/ADP/AMP provide information about the energy status of the cell. Less is known about the molecular mechanisms regulating carboxysome dynamics or how production, activity and degradation of photosynthetic complexes are regulated by prevailing Ci conditions or which mechanisms adjust cell division according to Ci. This minireview summarizes the present knowledge about molecular mechanisms regulating cyanobacterial acclimation to prevailing Ci. [ABSTRACT FROM AUTHOR]