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Tumor oxygenation level has been regarded as an attractive target to elevate the efficiency of photodynamic therapy (PDT). Cyanobacterial photosynthesis-mediated reversal of tumor hypoxia could enable an oxygen-boosted PDT, but is limited by scant penetration depth and efficiency of external light. Herein, aiming at the dual purposes of reducing biological toxicity induced by long-term light irradiation and alleviating hypoxia, we here introduce a novel-designed CaAl2O4:Eu,Nd blue persistent luminescence material (PLM) as the in vivo light source after pre-excited in vitro. The ingenious construction of blue-emitting PLM with “optical battery” characteristics activates cyanobacterial cells and verteporfin simultaneously, which performs the successive oxygen supply and singlet oxygen generation without the long-term external excitation, resulting in the modulated tumor hypoxic microenvironment and enhanced photodynamic tumor proliferation inhibition efficiency. Both in vitro cellular assessment and in vivo tumor evaluation results affirm the advantages of self-produced oxygen PDT system and evidence the notable antineoplastic outcome. This work develops an irradiation-free photosynthetic bacteria-based PDT platform for the optimization of both oxygen production capacity and light utilization efficiency in cancer treatment, which is expected to promote the clinical progress of microbial-based photonic therapy., Graphical abstract A distinct exogenous “irradiation-free” cyanobacteria-based PDT platform is rationally engineered for ameliorating the tumor hypoxic microenvironment and achieving the successive singlet oxygen (1O2) generation without the need of exogenous light excitation, which provides a specific paradigm of microbial-based nanotherapy with the assistance of rational design, engineering and integration of persistent luminescence phosphors as the desirable light irradiation source.Image 1, Highlights • Construction of CaAl2O4:Eu,Nd PLM to generate 1O2 without the aid of exogenous light excitation. • Cyanobacteria with light-triggered oxygenation effect were employed for the normalization of tumor microenvironment. • A distinct exogenous “irradiation-free” cyanobacteria-based PDT platform was rationally engineered.

Summary Photo-generation of a proton gradient over a lipid bilayer is of interest due to its essential role in photosynthetic bacteria. Membrane asymmetry is key to the proton gradient generation via directional proton transport. Here, we report a light-driven proton pump based on two-dimensional, porphyrin-based Janus metal-organic layers (Janus-MOLs). The Janus-MOL, functionalized with carboxyquinone on one side and Acitretin on the other via a microemulsion-based method, was attached to liposome surface. Upon photoexcitation, the porphyrins initiate electron and hole transfers to carboxyquinone and Acitretin, respectively, which undergo redox reactions with freely diffusing quinone (Q)/hydrosemiquinone (HQ·) in the lipid bilayer to produce a concentration gradient of quinone-based species. Owing to different pKa values of HQ+ and HQ·, these redox reactions trigger proton transport across the membrane to create a pH gradient, which drives ATP production by CFoF1-ATP synthase in a similar fashion as photosynthetic bacteria.

This study investigated the use of effective microorganisms (EM) to enhance cost-effective biogas purification at household-level application. It involved experimental setups for biogas purification in two different runs: 4 L activated EM and 1 L dormant EM by bubbling biogas through EM purification units. Biogas composition was analyzed using an industry-standard biogas analyzer. The results indicated that EM has the potential for biogas purification through a biological process, to remove H2S and CO2 by involving photosynthetic bacteria (Rhodopseudomonas palustris) in the presence of light. The raw biogas average composition was 62.2% CH4, 37.4% CO2 and 1359.3 ppm H2S. The 4L activated EM batch solution purified the raw biogas to 80.2% CH4, 19.5% CO2 and 786.1 ppm H2S. The corresponding purification efficiencies are 60% for CO2 and 49% for H2S. Purified biogas could be used by the household to cook for 1.82 h (85%) while raw biogas could cover only 55%. The designed biogas purification system can cost only Tshs 91,010/= and purify about 15,000 L of biogas at EM cost of Tshs 9,100/month. Key words: Biogas composition, photosynthetic bacteria, anaerobic digestion, biochemical processes, Rhodopseudomonas palustris, biological desulphurization.

Zooxanthellae of corals, soft corals, and molluscs are endosymbiont dinoflagellates. Free-living dinoflagellates are also common in aquatic environments. Although aqueous 90% acetone and 100% acetone are excellent spectroscopic solvents, they are frequently unsatisfactory for quantitative solvent extraction of chlorophylls. In other studies, our laboratory has shown that dimethyl sulfoxamine (DMSO) is an excellent extractant for chlorophylls and bacteriochlorophylls from cyanobacteria (Chl a), chlorophytes (Chl a + b), diatoms (Chl a + c1c2), Acaryochloris (Chl d + a), and anoxygenic photosynthetic bacteria (Rhodopseudomonas) and have published algorithms for DMSO solvent. However, most endosymbiont dinoflagellates contain Chl a + c2. The soft coral, Sarcophyton sp., grown in an aquaculture outdoor aquarium and field material was used as source material. Here, we present DMSO Chl a + c2 spectrophotometric algorithms, describe their development for Chl a + c2, and calibrate them against the standard 90% acetone algorithms. The DMSO algorithms correlate very well (r > 0.989) with Chl assays based on 90% acetone. The soft coral had a Chl c2/a ratio of ≈ 0.3 to 0.6 but the zooxanthellae that actually grew in culture had a Chl c2/a ratio of ≈ 0.18; however, this difference had no significant effect on the chlorophyll algorithms.

To develop an efficient photofermentative process capable of higher rate biohydrogen production using carbon components of lignocellulosic hydrolysate, a desired carbon substrate by mixing xylose with glucose was formulated. Effects of crucial process parameters affecting cellular biochemical reaction of hydrogen by photosynthetic bacteria (PSB), i.e., variation in initial concentration of total carbon, glucose content in initial carbon substrate, and light intensity, were experimentally investigated using response surface methodology (RSM) with a Box-Behnken design (BBD). Hydrogen production rate (HPR) in the maximum value of 30.6 mL h−1 L−1 was attained under conditions of 39 mM initial concentration of total carbon, 59% (mol/mol) glucose content in initial carbon substrate, and 12.6 W m−2 light intensity at light wavelength of 590 nm. Synergic effects of metabolizing such a well-formulated carbon substrate for sustaining the active microbial synthesis to sufficiently accumulate biomass in bioreactor, as well as stimulating enzyme activity of nitrogenase for the higher rate biohydrogen production, were attributed to this carbon substrate that can enable PSB to maintain the relatively consistent microenvironment in suitable culture pH condition during the optimized photofermentative process.

Background: Chlorophyll is a green color pigment in plants, algae and photosynthetic bacteria. The chlorophyll contained in the leaves has a function as an antioxidant, anti-inflammatory, and antibacterial. This study aims to determine the ability of chlorophyll from several types of vegetables to inhibit Escherichia coli and Staphylococcus aureus and determine the differences in the diameter of the inhibition zone between them. Methods: This study was a laboratory experimental study using a completely randomized design (CRD) divided into 4 treatments, namely aquadest (P0), cassava leaf chlorophyll (P1), kale leaf chlorophyll (P2), and spinach leaf chlorophyll (P3). 6 repetitions each. Microbiological tests were carried out using the well diffusion method. Results: Anova test showed that the chlorophyll extracts of cassava, kale and spinach were very influential (P = 0.000) in inhibiting the growth of Escherichia coli and Staphylococcus aureus. Duncan's further test showed that the largest average inhibition zone diameter for Escherichia coli was formed by cassava leaf chlorophyll (17.66 mm) and was significantly different from kale leaf chlorophyll (7 mm) and spinach leaves (6.16 mm). Similar to Staphylococcus aureus, the largest average inhibition zone diameter was also formed by cassava leaf chlorophyll, which was 18.16 mm and significantly different from kale leaf chlorophyll (6.75 mm) and spinach leaves (6.08 mm). Conclusion: The chlorophyll extract of cassava leaves, kale and spinach can inhibit the growth of Escherichia coli and Staphylococcus aureus with the largest inhibition zone diameter formed by the chlorophyll extract of cassava leaves.

Martin Kamen was a giant of twentieth century science. Trained as a physical chemist, he was the co-discoverer of radioactive Carbon 14, which has transformed many areas of science as a tracer and as a way to date artifacts. He later switched to the study of metabolism and biochemistry and made important contributions to the understanding of nitrogen fixation and photosynthesis. Finally, he studied cytochromes, primarily from anoxygenic photosynthetic bacteria.

Abstract Cyanobacteria are characterized by a very high tolerance to environmental factors. They are found in salt water, fresh water, thermal springs, and Antarctic waters. The wide spectrum of habitats suitable for those microorganisms is related to their particularly effective metabolism; resistance to extreme environmental conditions; and the need for only limited environmental resources such as water, carbon dioxide, simple inorganic salts, and light. These metabolic characteristics have led to cyanobacterial blooms and the production of cyanotoxins, justifying research into effective ways to counteract the excessive proliferation of these microorganisms. A new and interesting idea for the immediate reduction of cyanobacterial abundance is to use natural substances with broad-spectrum biological activity to restore phytoplankton diversity. This study describes the effects of selected monoterpenoid derivatives on the development of cyanobacterial cultures. In the course of the study, some compounds ((±)-citronellal, (+)-α-pinene) showed the ability to inhibit the colonization of the tested photosynthetic bacteria, while others (eugenol, eucalyptol) stimulated the growth of these microorganisms. By analyzing the results of these experiments, information was obtained on the mutual relations of cyanobacteria and the tested monoterpenes, which are present in the aquatic environment. Key points • Monoterpenoids significantly inhibit the growth of single cyanobacterial strains. • Monoterpenoids can inhibit the growth of cyanobacterial consortia. • Natural substances can control the growth of freshwater cyanobacteria.

The Changjiang River Estuary (CRE) in the East China Sea suffers from seasonal hypoxia in summer. The vertical distributions and seasonal changes of microbial communities in the CRE were well documented. However, little is known about the diurnal changes of bacterial communities in the hypoxic zone of the CRE. Here, 16S rRNA gene analysis was used to explore the changes of bacterial communities in the oxic surface and hypoxic middle seawater layers during 24 h in the CRE. Significant differences between the hypoxic and oxic layers were observed: the phyla Cyanobacteria, Bacteroidetes and Acidimicrobiia were enriched in the oxic layer, whereas the phylum SAR406 and the class Deltaproteobacteria were more abundant in the hypoxic layer. In addition, some subtle diurnal variations of the bacterial relative abundance were found in both two layers. The relative abundance of Synechococcus increased at night, and this change was more obvious in the hypoxic layer. The similar trend was also found in some phototrophic and several heterotrophic bacteria, such as Rhodobacteraceae, OM60 and Flavobacteriaceae. Their relative abundances peaked at 16:00 in the oxic layer, while the relative abundances peaked at around 7:00 and decreased until 13:00 in the hypoxic layer. Together, the results of the present study suggest that some photosynthetic bacteria and several heterotrophic bacteria have similar diurnal variations implying the light and physicochemical heterogeneity in the course of a day are important for bacterial diurnal changes in the CRE.

Palm liquid sewage is organic waste that contains complex compounds such as water, oil, and organic solids. The organic content of palm liquid sewages is an indication of the abundance of microorganisms. This study aims to obtain anoxygenic photosynthetic bacteria (BFA) that produce carotenoid pigments from palm liquid sewages. Therefore, We isolated and screened of BFA from three palm liquid sewage disposal sites in Jambi Province. This research was conducted by an experimental method using a modified mineral medium. BFA isolates that growth and produced carotenoid pigments are visible because of the distribution of reddish-yellow pigments on the culture media. Screening results obtained 11 isolates of BFA sequentially Bg1K201, Bg1K202, Bg2k201, Bg3k201, Mr1k201, Mr1k202, Sl1k201, Sl1k202, Sl2k201, Sl2k202 and Sl3k202. The results of morphological and physiological characterization based on the Bergeys Manual of Determinative Bacteriology show that there are two types of BFA genera that have carotenoid pigments, respectively, the genus Rhodobacter (Bg1k201, Bg1k202, Bg3k201, Sl1k201, Sl1k202, and Sl1k202, and Sl2k202, and Sl1k202, and Sl2k202, and Sl1k202 and Sl2k202, and Sl2k202, and Sl2k202. Sl2k202, and) the genus Rhodopseudomonas (Bg2k201, Mr1k201 and Mr1k202)

Control of the spectral overlap between energy donors and acceptors provides insight into excitation energy transfer (EET) mechanisms in photosynthetic light-harvesting proteins. Substitution of energy-donating B800 bacteriochlorophyll (BChl) a with other pigments in the light-harvesting complex 2 (LH2) of purple photosynthetic bacteria has been extensively performed; however, most studies on the B800 substitution have focused on the decrease in the spectral overlap integral with energy-accepting B850 BChl a by reconstitution of chlorophylls into the B800 site. Here, we reconstitute BChl b into the B800 site of the LH2 protein from Rhodoblastus acidophilus to increase the spectral overlap with B850 BChl a. BChl b in the B800 site had essentially the same hydrogen-bonding pattern as B800 BChl a, whereas it showed a red-shifted Qy absorption band at 831 nm. The EET rate from BChl b to B850 BChl a in the reconstituted LH2 was similar to that of native LH2 despite the red shift of the Qy band of the energy donor. These results demonstrate the importance of the contribution of the density of excitation states of the B850 circular assembly, which incorporates higher lying optically forbidden states, to intracomplex EET in LH2.

Cultivation of high-lipid microalgae using municipal sewage can both treat polluted water and gain biodiesel. Rapid cultivation of microalgae is crucial for the entire process. In this study, four stimulants (phytohormone 2,4-d; Fe3+; photosynthetic bacteria—Rhodopseudomonas palustris; CO2) were firstly chosen to investigate their effects on microalgae Chlorella pyrenoidosa cultivation in municipal sewage. Meanwhile, orthogonal experiments were designed to compare the enhancing effects on the growth of microalgae C. pyrenoidosa and lipid accumulation by different combinations of stimulants, which were also conducted for outdoor culture. The optimum stimulant combination was 1.0 mg/L 2,4-d; 10−7 mol/L Fe3+; 4.5 mL (109 cells/mL) photosynthetic bacteria; and 8% CO2. Among the four kinds of stimulants, phytohormone 2,4-d and photosynthetic bacteria played more important roles on the microalgae growth and lipid accumulation. The optimum combination of stimulants could also promote the microalgae biomass and lipid yield during outdoor cultivation. The maximum OD681 of microalgae was 37.9% higher than that of the control group without addition of stimulants. The obtained microalgae dry weight and lipid production were 0.3 and 0.13 g /L, which were 80.0% and 85.7% higher than that of the control group, respectively. The promotion of microalgae photosynthetic rate was the main reason for the stimulant-enhanced microalgae cultivation. This study exerts positive effects on the development of microalgae biodiesel.

Utilizing solar energy for hydrogen production by combining light-activated materials and biocatalysts has become a promising alternative to fossil fuels. Herein, a feasible and simple bio-hybrid complex based on water-soluble oligofluorene (OF), polythiophene (PTP) and Rhodopseudomonas palustris (R. palustris), one kind of photosynthetic bacteria, was constructed for enhancing photocatalytic hydrogen production. Under the irradiation of visible light, there was fluorescence resonance energy transfer (FRET) between OF and PTP, which amplified photoelectron signals and transferred electrons via PTP to methyl viologen (MV2+), an electron mediator that established electron transfer pathways between organic materials and R. palustris. Hydrogen production involving R. palustris was catalyzed by nitrogenase. It is noteworthy that MV2+ was reduced to MV+˙ and transferred electrons to nitrogenase in R. palustris, converting protons and electrons to molecular hydrogen. Besides, triethanolamine (TEOA) was added as an electron donor to provide electrons to PTP. The proposed OF/PTP/MV2+/TEOA/R. palustris system provided a feasible strategy for photocatalytic hydrogen production with low-cost and easily implemented techniques.

Chlorosomes in green photosynthetic bacteria are the largest and most efficient light-harvesting antenna systems of all phototrophs. The core part of chlorosomes consists of bacteriochlorophyll c, d, or e molecules. In their biosynthetic pathway, a BciC enzyme catalyzes the removal of the C132-methoxycarbonyl group of chlorophyllide a. In this study, the in vitro enzymatic reactions of chlorophyllide a analogues, C132-methylene- and ethylene-inserted zinc complexes, were examined using a BciC protein from Chlorobaculum tepidum. As the products, their hydrolyzed free carboxylic acids were observed without the corresponding demethoxycarbonylated compounds. The results showed that the in vivo demethoxycarbonylation of chlorophyllide a by an action of the BciC enzyme would occur via two steps: (1) an enzymatic hydrolysis of a methyl ester at the C132-position, followed by (2) a spontaneous (nonenzymatic) decarboxylation in the resulting carboxylic acid.

Hypoxia can increase the resistance of tumor cells to radiotherapy and chemotherapy. However, the dense extracellular matrix, high interstitial fluid pressure, and irregular blood supply often serve as physical barriers to inhibit penetration of drugs or nanodrugs across tumor blood microvessels into hypoxic regions. Therefore, it is of great significance and highly desirable to improve the efficiency of hypoxia-targeted therapy. In this work, living photosynthetic bacteria (PSB) are utilized as hypoxia-targeted carriers for hypoxic tumor therapy due to their near-infrared (NIR) chemotaxis and their physiological characteristics as facultative aerobes. More interestingly, we discovered that PSB can serve as a kind of photothermal agent to generate heat through nonradiative relaxation pathways due to their strong photoabsorption in the NIR region. Therefore, PSB integrate the properties of hypoxia targeting and photothermal therapeutic agents in an "all-in-one" manner, and no postmodification is needed to achieve hypoxia-targeted cancer therapy. Moreover, as natural bacteria, noncytotoxic PSB were found to enhance immune response that induced the infiltration of cytotoxicity T lymphocyte. Our results indicate PSB specifically accumulate in hypoxic tumor regions, and they show a high efficiency in the elimination of cancer cells. This proof of concept may provide a smart therapeutic system in the field of hypoxia-targeted photothermal therapeutic platforms.

Cyanobacteria are photosynthetic bacteria that can directly convert CO2 into several bio-products for industrial use, such as alcohols and diols, terpenes, acids, and sugars. However, some of these compounds are either produced in low amounts or are absent in cyanobacteria, and thus strain development is required to achieve optimal production of these bio-products for industrial applications. Metabolic engineering has been applied to modify cyanobacteria for enhanced production of value-added compounds. In this review, we have elucidated metabolic engineering of various pathways with the yield and productivity of the desired products. We have also described recent overall strategies in advanced metabolic engineering.

To supply the sustainable calorie-free sweetener stevioside, synthetic photosynthetic bacteria were developed to produce ent-kaurenoic acid as a precursor of stevioside directly from CO2. By the use of a combinatorial and modular approach for gene expression, including a cytochrome P450 and the corresponding reductase, engineered Synechoccous elongatus PCC 7942 as a model cyanobacterium enabled the biosynthesis of ent-kaurenoic acid at 2.9 ± 0.01 mg L-1 from CO2. We found that the order of genes for expression was critical, producing ent-kaurenoic acid by balancing gene expressions and accumulation of the toxic intermediate in a cell. The engineered bacteria allowed the complete biosynthesis of ent-kaurenoic acid, and it will be used for stevioside biosynthesis from CO2 as a controlled fermentation.

The mechanism of excitation energy transfer in photoexcited bacteriochlorophyll (BChl) aggregates poses intriguing questions, which have important implications for the observed efficiency of photosynthesis. We investigate this process through fully quantum mechanical calculations of exciton-vibration dynamics in chains and rings of BChl a molecules, with parameters characterizing the B850 ring of the LH2 complex of photosynthetic bacteria. The calculations are performed using the modular path integral methodology, which allows the exact treatment of 50 intramolecular vibrations on each pigment using parameters obtained from spectroscopic Huang-Rhys factors with computational effort that scales linearly with aggregate length. Our results indicate that the interplay between electronic and vibrational time scales leads to the rapid suppression but not the overdamping of electronic coherence, which facilitates the spreading of excitation energy throughout the aggregate.

By coating photosynthetic bacteria of Rhodopseudomonas palustris with conjugated polymers nanoparticles modified with positively charged peptide TAT (CPNs-TAT), a bio-optical hybrid composite of R....

Scanning spectrophotometers equipped with integrating spheres were once highly specialized spectrophotometric equipment but are now more readily available commercially. They are particularly useful for objectively assessing the spectral absorption and reflectance of algal cell suspensions. Ordinary dual-beam spectrometers do not give valid measurements of the spectral properties of cells due to light scattering. Spectra of unicellular algae using integrating sphere spectroscopy can measure the absorbance (Abs), transmissions (%T) and reflectance (%R) and hence the actual absorptance (%Abt) of turbid cell suspensions and hence the in vivo pigment absorption properties of photosynthetic organisms. These results were compared with those obtained using conventional dual-beam spectrophotometry scans on turbid cell suspensions and the in solvent spectra of photosynthetic pigments. The common unicellular green alga, Chlorella sp., is used as an example of an oxygenic photo-organism with chlorophyll a as the primary photosynthetic pigment and comparisons made to other unicellular algae such as a cyanobacterium (Synechococcus), Acaryochloris and a diatom (Chaetoceros). Photosynthetic bacteria, such as Rhodopseudomonas palustris, are photosynthetic but do not produce oxygen, and their photosynthesis is usually based on bacteriochlorophyll a. Comparisons are made of integrating sphere vs. dual-beam transmission spectroscopy of BChl a and BChl b organisms in solvent and in vivo of anoxygenic photosynthetic bacteria (Afifella & Thermochromatium [BChl a], Blastochloris [BChl b]) and with oxygenic organisms.

Metabolomics based on LC-MS was used for the analysis of the fermentation of Proteiniphilum acetatigenes PSB-W treated by different culture time and different light intensity. 26 putative metabolites were detected in samples treated by different culture time. Most of the components were produced in the metabolic activity in order to participate in the whole life process of bacteria. Compared with samples treated with light intensity, a total of 37 metabolites were detected and analyzed. Only 10 compounds were detected in 1000 Lux group, which is significantly less than 1500 Lux group. The metabolite data of light groups were passed through principal component analysis (PCA) and differential metabolites were screened for each comparison group by using the Volcano Plot model. The differential metabolites were annotated by the Kyoto Encyclopedia of Genes and Genomes (KEGG) database and 7 differential metabolites related to the carotenoid synthesis enrichment pathway were screened. The results showed that carotenoids synthesis may occur during the stationary phase of bacterial growth. The precursor of carotenoid synthesis of photosynthetic bacteria is isopentenyl diphosphate (IPP) synthesized by acetyl coenzyme A under the catalysis of HMG CoA reductase. It is preliminarily clarified that it is the accumulation mechanism of bacterial carotenoid biosynthesis and provides a new clue for the comprehensive study of the synthesis and regulation mechanism of carotenoids. Key words: Carotenoids, metabolomics analysis, Proteiniphilum acetatigenes PSB-W.

Blue green algae are microscopic photosynthetic bacteria, naturally in ponds, rivers, lakes and streams. Tetra pyrroles can be classified based on the presence, position and substituents of a chelated metal in the pyrrole ring. Heme and chlorophyll, which are the most common tetra pyrolle in nature, are synthesized by blue green algae. Heme is an essential cofactor for virtually all forms of life and the last step of heme biosynthesis is catalyzed by ferrochelatase enzyme. In this study, blue green algae, photosynthetic bacteria, isolated from Yeşilırmak were used. Eight morphologically different isolates were obtained. The highest specific activity belongs to isolate 8 as 0.217 Umg-1.

Biosynthesis of chlorophyll involves several enzymatic reactions of which many are shared with the heme biosynthesis pathway. Magnesium chelatase is the first specific enzyme in the chlorophyll pathway. It catalyzes the formation of Mg-protoporphyrin IX from the insertion of Mg2+ into protoporphyrin IX. The enzyme consists of three subunits encoded by three genes. The three genes are named Xantha-h, Xantha-g and Xantha-f in barley (Hordeum vulgare L.). The products of the genes have a molecular weight of 38, 78 and 148 kDa, respectively, as mature proteins in the chloroplast. Most studies on magnesium chelatase enzymes have been performed using recombinant proteins of Rhodobacter capsulatus, Synechocystis sp. PCC6803 and Thermosynechococcus elongatus, which are photosynthetic bacteria. In the present study we established a recombinant expression system for barley magnesium chelatase with the long-term goal to obtain structural information of this enigmatic enzyme complex from a higher plant. The genes Xantha-h, -g and -f were cloned in plasmid pET15b, which allowed the production of the three subunits as His-tagged proteins in Escherichia coli BL21(DE3)pLysS. The purified subunits stimulated magnesium chelatase activity of barley plastid extracts and produced activity in assays with only recombinant proteins. In preparation for future structural analyses of the barley magnesium chelatase, stability tests were performed on the subunits and activity assays were screened to find an optimal buffer system and pH.

Oxygenic photosynthesis can be measured easily using O2 or CO2 gas exchange, oxygen electrodes, Winkler titration, 14CO2-fixation and by PAM (pulse amplitude modulation) fluorometry. PAM estimates the photosynthetic electron transport rate (ETR) by measuring the variable fluorescence of chlorophyll (Chl) a (> 695 nm) induced by absorption of blue or red light. Anoxygenic photosynthetic bacteria (APB) do not use water as an electron source and are typically photoheterotrophic rather than photoautotrophic and so 14CO2 fixation is a misleading estimate of photosynthetic electron transport in APB photosynthesis. In vivo bacteriochlorophyll a (BChl a) absorbs blue light similar to Chl a but its characteristic longer-wavelength absorption is in the infrared and fluorescence is at > 800 nm. Blue light-induced PAM fluorescence can be used to measure the ETR in purple non-sulphur anoxygenic photobacteria and purple sulphur photobacteria because their RC-2 type BChl a complexes fluoresce similarly to PSII but at longer wavelengths than Chl a. Conventional PAM fluorometers using blue light cannot readily distinguish between oxygenic and RC-2 type anoxygenic photosynthesis because they use a simple > 700 nm highpass filter in front of the detector diode. We modified one fluorometer to use a 695–750-nm bandpass filter to measure Chl a fluorescence from PS-II, representing oxygenic photosynthesis. Similarly, we modified another fluorometer to use a highpass filter (> 830 nm) to measure BChl a fluorescence, representing anoxygenic photosynthesis. However, the fluorescence bands of Chl a and BChl a were found to be too wide to unambiguously distinguish between oxygenic and anoxygenic photosynthesis purely by fluorometry. Treatment with the specific PS-II inhibitor DCMU (Diuron) did enable discrimination of the two types of photosynthesis in a mixture of oxygenic and anoxygenic organisms. Ecological niches made up of both oxygenic and anoxygenic organisms such as microbial mats and hypereutrophic environments such as sewage ponds, wastewater ponds and prawn farm ponds are much more common than often realized. Anoxygenic photosynthesis in such systems is significant yet largely unquantified.

Cyanobacteria, as photosynthetic bacteria, can generate energy and carbon sources directly from sunlight and atmospheric carbon dioxide. With the aid of genetic engineering, heterologous enzymes and/or pathways have been introduced into cyanobacteria, enabling the production of various biofuels and biochemicals. By utilizing cyanobacteria as production hosts, biofuels and biochemicals can be produced directly from carbon dioxide, and ultimately carbon dioxide fixation by cyanobacteria can help reduce atmospheric carbon dioxide concentration, alleviating global warming and air pollution. In this review, we introduce various biofuels and biochemicals produced, particularly from acetyl-CoA by cyanobacteria, and summarize research strategies that have been made to improve their production. This review will provide comprehensive information and valuable insights into strategies for enhancing cyanobacterial biofuels/chemicals production.

All purple photosynthetic bacteria contain RC–LH1 ‘Core’ complexes. The structure of this complex from Rhodobacter sphaeroides, Rhodopseudomonas palustris and Thermochromatium tepidum has been solved using X-ray crystallography. Recently, the application of single particle cryo-EM has revolutionised structural biology and the structure of the RC–LH1 ‘Core’ complex from Blastochloris viridis has been solved using this technique, as well as the complex from the non-purple Chloroflexi species, Roseiflexus castenholzii. It is apparent that these structures are variations on a theme, although with a greater degree of structural diversity within them than previously thought. Furthermore, it has recently been discovered that the only phototrophic representative from the phylum Gemmatimonadetes, Gemmatimonas phototrophica, also contains a RC–LH1 ‘Core’ complex. At present only a low-resolution EM-projection map exists but this shows that the Gemmatimonas phototrophica complex contains a double LH1 ring. This short review compares these different structures and looks at the functional significance of these variations from two main standpoints: energy transfer and quinone exchange.

High potential iron–sulfur proteins (HiPIPs) are a class of small proteins (50–100 aa residues), containing a 4Fe–4S iron–sulfur cluster. The 4Fe–4S cluster shuttles between the oxidation states [Fe4S4]3+/2+, with a positive redox potential in the range (500–50 mV) throughout the different known HiPIPs. Both oxidation states are paramagnetic at room temperature. HiPIPs are electron transfer proteins, isolated from photosynthetic bacteria and usually provide electrons to the photosynthetic reaction-center. PioC, the HIPIP isolated from Rhodopseudomonas palustris TIE-1, is the smallest among all known HiPIPs. Despite their small dimensions, an extensive NMR assignment is only available for two of them, because paramagnetism prevents the straightforward assignment of all resonances. We report here the complete NMR assignment of 1H, 13C and 15N signals for the reduced [Fe4S4]2+ state of the protein. A set of double and triple resonance experiments performed with standardized parameters/datasets provided the assignment of about 72% of the residues. The almost complete resonance assignment (99.5% of backbone and ca. 90% of side chain resonances) was achieved by combining the above information with those obtained using a second set of NMR experiments, in which acquisition and processing parameters, as well as pulse sequences design, were optimized to account for the peculiar features of this paramagnetic protein.

Generation of ion electrochemical potential differences by primary active transport can involve energy inputs from light, from exergonic redox reactions and from exergonic ATP hydrolysis. These electrochemical potential differences are important for homoeostasis, for signalling, and for energizing nutrient influx. The three main ions involved are H+, Na+(efflux) and Cl−(influx). In prokaryotes, fluxes of all three of these ions are energized by ion-pumping rhodopsins, with one archaeal rhodopsin pumping H+intothe cells; among eukaryotes there is also an H+influx rhodopsin inAcetabulariaand (probably) H+efflux in diatoms. Bacteriochlorophyll-based photoreactions export H+from the cytosol in some anoxygenic photosynthetic bacteria, but chlorophyll-based photoreactions in marine cyanobacteria do not lead to export of H+. Exergonic redox reactions export H+and Na+in photosynthetic bacteria, and possibly H+in eukaryotic algae. P-type H+- and/or Na+-ATPases occur in almost all of the photosynthetic marine organisms examined. P-type H+-efflux ATPases occur in charophycean marine algae and flowering plants whereas P-type Na+-ATPases predominate in other marine green algae and non-green algae, possibly with H+-ATPases in some cases. An F-type Cl−-ATPase is known to occur inAcetabularia. Some assignments, on the basis of genomic evidence, of P-type ATPases to H+or Na+as the pumped ion are inconclusive.

Photosynthetic bacteria, Rhodobacter spharoides, can grow using carbon dioxide as a carbon source and produce physiologically active compounds. This study was carried out to investigate the impact of R. sphaeroides extract on the growth and quality of lettuce(Lactuca sativa L.) in the LED-plant factory. The concentrations of R. sphaeroides extracts(0, 4, 8 and 12 mg/L) were supplemented in medium on one day and 14 days after transplanting, respectively. The growth of lettuce as affected by extract amount was evaluated at 14, 28 and 35 days after transplanting and the contents of minerals and chlorogenic acid were analyzed at 35 days after transplanting. As a result, higher growth was obtained in the treatment with R. sphaeroides extract than the control. The extract of R. sphaeroides showed the best growth at 4 mg/L concentration(leaf width- 120%, leaf length- 109%, number of leaves- 113%, total leaf area- 144%, fresh weight- top: 153%, root: 142%, dry weight- top: 137%, root: 120%) and the highest effect at the early stage of growth on 14 days after transplanting(leaf width- 115%, leaf length- 123%, number of leaves- 124%, total leaf area- 158%, fresh weight- top: 139%, root: 120%, dry weight- top: 130%, root: 139%). In addition, the extract of 4 mg/L concentration improved the content of minerals and chlorogenic acid contained in lettuce. Therefore, R. sphaeroides extract suggested the possibility of producing high-value crops through promotion of growth and quality improvement of lettuce.

Continuous exposure of 395 nm light increases the fluorescence emission intensity of photosynthetic purple non-sulphur bacteria, Rhodobacter capsulatus (SB1003). We show that such an increase in fluorescence emission of extracellular pigment complexes (PC) from these photosynthetic bacteria depends on the concentration of the pigment and temperature and can also be modulated by the static magnetic field. The time-dependent enhanced emission disappears either at or below 300 K or below a threshold sample concentration (0.1 mg/ml). The enhanced emission reappears at this condition (T 0). At PC concentration higher than a threshold, k becomes negative if the temperature is lowered. But, surprisingly, at low temperature, a static magnetic field reverts the k value to positive. We explain the logical nature of k-switching and photo-dynamics of the aforesaid microbial fluorescence emission by aggregation of protoporphyrin rings present in the PC. While the simultaneous presence of decay in fluorescence and susceptibility to static magnetic field suggests the dominance of triplet states at low temperatures, the process is reversed by SMF-induced removal of spin degeneracy. At higher temperatures, the optical excitability and lack of magnetic response suggest the dominance of singlet states. We propose that the restructuring of the singlet-triplet distribution by intersystem crossing may be the basis of this logical behaviour. In context with microbial function, time-dependent enhancement of fluorescence also implies relay of red photons to the neighbouring microbes not directly exposed to the incident radiation, thus serving as an indirect photosynthetic regulator. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s10867-020-09545-6) contains supplementary material, which is available to authorized users.

Photosynthetic bacteria (PSB) technology is a promising method for biomass, protein, pigments, and other value-added substances generation from wastewater. However, the above bioresources production efficiency is relatively low. In this work, a static magnetic field (SMF) was used to promote bioresources production. Results showed that SMF had positive effects on value-added substances production. With 0.35 Tesla (T) SMF, the PSB biomass, protein, carotenoids, and bacteriochlorophyll concentration were promoted by 31.1%, 22.6%, 56.7%, and 73.1% compared with the control group, respectively. Biomass yield finally reached 0.58 g biomass/g COD removal, which was promoted by 37.1%. The doubling time was shortened by 37.9% in 0.35 T group, showing that SMF can promote cell growth. With 0.35 T SMF, the intracellular NADH dehydrogenase and ATP synthase activities concentration increased by 23.4% and 29.1%, respectively, thus increased the ATP content by 38.0%. Succinic dehydrogenase activity concentration greatly increased by 609.0% at 48 hr, which potentially accelerated the tricarboxylic acid cycle and COD degradation as well as enhanced biomass production. PRACTITIONER POINTS: SMF promoted PSB bioresource production during wastewater treatment processing. Biomass, protein, carotenoids, and Bchl concentration were promoted by 31.1%, 22.6%, 56.7%, and 73.1%, respectively. PSB yield of 0.35 T group was promoted by 37.1% compared with the control group. SDH concentration of 0.35 T was promoted by 609.0% compared with the control group. Increased NADH and ATP synthase activity concentration by SMF enhanced energy metabolism.

The aim of this research was to find out the effect of substrate concentrations (COD) of vinasse and the length of fermentation time to bio-hydrogen gas production using agent fermentation of photosynthetic bacteria, Rhodobium marinum. The production of bio-hydrogen was examined by varying COD of vinasse (10,000; 20,000; 30,000; 40,000; 50,000 mg COD/L) at certain fermentation time in the third, sixth and ninth day. The highest Hydrogen gas was obtained at ninth day of fermentation (82.66±18.6 mL). The highest Hydrogen Production Rate (HPR) and COD removal rate were obtained at concentration 50,000 mg COD/L, namely 109.98 mL H2/L/d and 1437.66 mg COD/L/d, respectively. Thus it can be concluded, the concentration of substrates (COD) from vinasse and the length of fermentation time have an effect on production of bio-hydrogen gas using Rhodobium marinum

The possibility of singlet oxygen generation in five species of photosynthetic bacteria under irradiation with light was studied using the Singlet Oxygen Sensor Green (SOSG) dye that, when singlet oxygen is bound, is transformed into a fluorescent endoperoxide form. Irradiation was carried out using light of different spectral composition: red (absorption of bacteriochlorophyll, BChl) and white (absorption of BChl and carotenoids). No singlet oxygen generation was detected under red light irradiation, which indicated that BChl was not involved in this process. Under white light, as the irradiation time increased, an increase in SOSG fluorescence was recorded in the membranes of four bacterial species: Allochromatium vinosum MSU, Rhodobacter sphaeroides G1C, Rba. blasticus K-1 and Rhodopseudomonas faecalis. In Rba. sphaeroides, no increase in SOSG fluorescence was observed. It is assumed that in the white light this process occurs due to the pigments that absorb in the blue-green region of the spectrum, i.e. carotenoids with 8‒11 conjugated double bonds (neurosporene, spheroidene, lycopene, and rhodopin). Similar to Trolox, SOSG may slow down the bleaching process of BChl850 in the membranes of Alc. vinosum strain MSU and may therefore effectively perform the role of a singlet oxygen trap.

Bacteriochlorophyll c molecules self-aggregate to form large oligomers in the core part of chlorosomes, which are the main light-harvesting antenna systems of green photosynthetic bacteria. In the biosynthetic pathway of bacteriochlorophyll c, a BciC enzyme catalyzes the removal of the C132 -methoxycarbonyl group of chlorophyllide a, which possesses a free propionate residue at the C17-position and a magnesium ion as the central metal. The in vitro C132 -demethoxycarbonylations of chlorophyll a derivatives with various alkyl propionate residues and central metals were examined by using the BciC enzyme derived from one green sulfur bacteria species, Chlorobaculum tepidum. The BciC enzymatic reactions of zinc pheophorbide a alkyl esters were gradually suppressed with an increase of the alkyl chain length in the C17-propionate residue (from methyl to pentyl esters) and finally the hexyl ester became inactive for the BciC reaction. Although not only the zinc but also nickel and copper complexes were demethoxycarbonylated by the BciC enzyme, the reactions were largely dependent on the coordination ability of the central metals: Zn>Ni>Cu. The above substrate specificity indicates that the BciC enzyme would not bind directly to the carboxy group of chlorophyllide a, but would bind to its central magnesium to form the stereospecific complex of BciC with chlorophyllide a, giving pyrochlorophyllide a, which lacks the (132 R)-methoxycarbonyl group.

As a member of photosynthetic bacteria, Rhodopseudomonas palustris, which has extraordinary metabolic versatility, has been applied as one of potential probiotics in feed industry. To explore whether R. palustris can increase rumen microbial viability and thus improve microbial fermentation, a 2×5 factorial experiment was conducted to evaluate the effect of R. palustris at dose rates of 0, 1.3, 2.6, 3.9, 5.2×106 cfu/ml on ruminal fermentation of two representative total mixed rations (HY, a ration for high-yield (>32 kg/d) lactating cows; LY, a ration for low-yield (48) and total volatile fatty acids (VFA, P48 (P2 proportion in headspace of fermentation system was linearly reduced by 46.1% in LY and 32.9% in HY group, respectively (P

Living supramolecular polymerization is a breakthrough system to control the size of supramolecular aggregates. Multidimensional (2D or 3D) self-aggregates of chiral and unsymmetric molecules are observed in nature. For instance, a chlorosome, which is the main light-harvesting antenna in green photosynthetic bacteria, possesses tubular structures of chlorophyll pigments with J-type slipped cofacial and circular arrangements. Here, we report size-controllable construction of chlorosome-like aggregates by photoactivated supramolecular assembly of “caged chlorophyll”. The caged chlorophylls, which were nonassembling (inert) species, were illuminated with UV-light to give the active species one by one, and then the resulting active monomers spontaneously assembled to construct tubular self-aggregates. The length of such chlorosome-like aggregate tubes was dependent on the UV-irradiation duration and intensity of UV-light. The photoactivated supramolecular assembly system would be useful for application of (o...

Photolithotrophic sulfur bacteria are involved in biota functioning and have a biotechnological potential for bioremediation of contaminated environment, but the mechanisms of xenobiotics, in particular of heavy metal ions damaging action and the pathways of photolithotrophic bacteria adaptation under these conditions have not been established. In this work, the biochemical indicators of green photosynthetic bacteria Chlorobium limicola response to Cu ions were studied. C. limicola cells were incubated during one hour in buffer containing copper (II) sulfate in 0.05–0.5 mM concentrations and grown for 8 days in GSB medium. The content of Cu2+ in cells was estimated by atomic absorption spectroscopy. The activity of enzymes of antioxidant defense, photosynthetic pigments and glutathione content, indexes of lipids unsaturation and membrane viscosity as markers of membrane fluidity were estimated. It was shown that the response of green photosynthetic bacteria C. limicola to Cu2+ action varied depending on cations concentration. Under the influence of metal salt at 0.05 mM concentration, the activity of antioxidant enzymes, GSH/GSSG ratio, the content of photosynthetic pigments and membrane fluidity indexes were higher as compared with control. Under the increase of copper (II) sulfate concentration to 0.25 mM, the activity of antioxidant enzymes was lower compared to the response of the cells under the influence of 0.05 mM copper (II) and the GSSG content was increased. Under the influence of 0.5 mM copper (II) the indexes of membrane fluidity did not differ from the control, but superoxide dismutase and peroxidase activity inhibition and the further decrease of GSH/GSSG ratio were observed followed by the highest Cu2+ cations accumulation in cells and significant decrease of bacteria biomass growth.

An artificial photosynthetic assembly (APA) of a hollow-rod structure was successfully constructed by using synthetic building blocks to mimic the structure and function of natural photosynthetic bacteria. The APA was formed by the incorporation of carbon nanoparticles as light harvesters into an enzyme-like polymer, PEI-Co, containing cobalt complexes as redox catalytic centres. The APA features a bacteria-like shape of ca. 2–3 μm length rods and a hollow structure positioning photosynthetic components at the surface. The APA integrates key components, the light harvester, redox catalyst, and proton relay group, of photosynthetic systems in assemblies formed from a polymeric framework. The APA system in aqueous solution converts protons to H2 under visible light irradiation with obvious advantages. It exhibits a 50-fold improvement in hydrogen production activity and has a broader pH response of photocatalytic H2 production compared with a non-assembled system.

The main aim of this study was to investigate the effects of the initial pH values of the buffer on photo-fermentation biohydrogen production. Hydrogen production and the kinetics of it under different initial pH values were analyzed. Effects of initial pH values on reducing sugar consumption, hydrogen production rate, and byproduct production were evaluated at initial pH values of 5–7. The results showed that initial pH values of phosphate buffer had a significant effect on biohydrogen production via photo-fermentation. With the initial pH value of phosphate buffer at 6.0, the cumulative hydrogen production reached its maximum, 569.6 mL. The maximum hydrogen production rate was 23.96 mL/h at the initial pH value of 6.5. With the initial pH values at 5.0 and 7.5, the maximum hydrogen production rates were becoming lower, only 5.59 mL/h and 5.42 mL/h, respectively. And with the increase in pH values, the peak period of hydrogen production was gradually delayed, indicating that the alkaline environment had a negative effect on the ability of photosynthetic bacteria. This study revealed the influence of phosphate buffer initial pH values on the biohydrogen production via photo-fermentation and aimed to provide a scientific reference for further improving the theory and technology for biohydrogen production from biomass., Graphical Abstract

The encapsulation of living cells in the transformation of contaminants into green energy has great potential for solving energy and environmental pollution problems. However, some unresolved challenges related to the maintenance of the capsules' mechanical stability, biomass harvesting without leaking and necessary high activities hinder its practicability. Here, we develop a novel “interior division-external capsulation” dual-immobilization method to anchor photosynthetic bacteria into self-assembled fiber macrospheres and coating with polymer layers by phase inversion. The functional sites (C–N, C–OH and N–H) of the modified macrospheres cause more cells to adhere in the cage and its large void volume provides sufficient space for cell harvesting. Micro/nanoporous polymer shells can not only facilitate the rapid diffusion of substrates into the cavity, but also effectively reduce cell leakage. This strategy provides a facile method to significantly enhance the chemical/physical stability of the host and quickly achieve much higher activity of the encapsulated cells in the degradation of organics and H2 production as compared to free cells. Importantly, the core–shell confined encapsulation concept enables the cells to have considerable salt tolerance as high as 80 g L−1 and wide pH stability. The long-term reusability of the self-assembled macrospheres provides extensive application prospects for cell encapsulation as a clean and sustainable alternative in broader fields.

Photosynthetic bacteria (PSB) wastewater treatment is a new method with great resource recovery potential. In order to improve the biomass and valuable resources of bacteria in the wastewater treatment of photosynthetic bacteria, the effects of different light conditions on the efficiency of Proteiniphilum acetatigenes PSB-W in the treatment of sugar wastewater and the production of bacteria and carotenoids in the wastewater were analyzed from three aspects of light source, light intensity and light period. Under the principle of priority of pollutant removal efficiency, the red LED light was selected with the light intensity of 4000 Lux, 16L (light):8D (dark) for light cycle, and the best efficiency of wastewater removal and bacterial yield were obtained when the culture time was 3d, Chemical oxygen demand (COD) removal rate was 80.9%, bacterial OD600 was 0.907 ± 0.023, carotenoid yield was 7.83 ± 0.27 mg/L, respectively. These results show that PSB-W strains can provide more biomass and valuable substances in suitable environment. It provides a theoretical basis for the realization of wastewater recycling.