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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.

This paper is a tribute to a great scientist and an authentic “honest man” that was Jean Lavorel (1928–2021). He was a pioneer in research on the primary events of photosynthesis in algae, plants, and photosynthetic bacteria. He focused his attention on chlorophyll fluorescence and luminescence, and also on oxygen evolution, both experimentally (with laboratory-built refined apparatus) and theoretically. Many of his results are classical now. Besides a survey of his main achievements, most of them obtained by him alone, different reminiscences on the researcher and the person he was illustrate the rich personality of Jean Lavorel.

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.

Desert soils harbour diverse communities of aerobic bacteria despite lacking substantial organic carbon inputs from vegetation. A major question is therefore how these communities maintain their biodiversity and biomass in these resource-limiting ecosystems. Here, we investigated desert topsoils and biological soil crusts collected along an aridity gradient traversing four climatic regions (sub-humid, semi-arid, arid, and hyper-arid). Metagenomic analysis indicated these communities vary in their capacity to use sunlight, organic compounds, and inorganic compounds as energy sources. Thermoleophilia, Actinobacteria, and Acidimicrobiia were the most abundant and prevalent bacterial classes across the aridity gradient in both topsoils and biocrusts. Contrary to the classical view that these taxa are obligate organoheterotrophs, genome-resolved analysis suggested they are metabolically flexible, with the capacity to also use atmospheric H2 to support aerobic respiration and often carbon fixation. In contrast, Cyanobacteria were patchily distributed and only abundant in certain biocrusts. Activity measurements profiled how aerobic H2 oxidation, chemosynthetic CO2 fixation, and photosynthesis varied with aridity. Cell-specific rates of atmospheric H2 consumption increased 143-fold along the aridity gradient, correlating with increased abundance of high-affinity hydrogenases. Photosynthetic and chemosynthetic primary production co-occurred throughout the gradient, with photosynthesis dominant in biocrusts and chemosynthesis dominant in arid and hyper-arid soils. Altogether, these findings suggest that the major bacterial lineages inhabiting hot deserts use different strategies for energy and carbon acquisition depending on resource availability. Moreover, they highlight the previously overlooked roles of Actinobacteriota as abundant primary producers and trace gases as critical energy sources supporting productivity and resilience of desert ecosystems.

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.

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.

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.

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.

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.

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.

Oil pollution in marine environment caused by oil spillage has been a main threat to the ecosystem including the ocean life and to the human being. In this research, three indigenous purple photosynthetic strains Rhodopseudomonas sp. DD4, DQ41, and FO2 were isolated from oil-contaminated coastal zones in Vietnam. The cells of these strains were immobilized on different carriers including cinder beads (CB), coconut fiber (CF), and polyurethane foam (PUF) for diesel oil removal from artificial seawater. The mixed biofilm formed by using CB, CF, and PUF as immobilization supports degraded 90, 91, and 95% of diesel oil (DO) with the initial concentration of 17.2 g/L, respectively, after 14 days of incubation. The adsorption of DO on different systems was accountable for the removal of 12-16% hydrocarbons for different carriers. To the best of our knowledge, this is the first report on diesel oil degradation by purple photosynthetic bacterial biofilms on different carriers. Moreover, using carriers attaching purple photosynthetic bacteria to remove diesel oil in large scale is considered as an essential method for the improvement of a cost-effective and efficient bioremediation manner. This study can be a promising approach to eliminate DO from oil-contaminated seawater.

Aquaculture faces substantial challenges in mitigating the detrimental environmental impacts of intensive farming. Traditional methods have given rise to serious concerns, leading to the search for alternative approaches using probiotics. An indigenously isolated photosynthetic purple bacterium, Rhodovulum sulfidophilum, was introduced into a marine integrated multitrophic aquaculture system cultivating Chanos chanos in southwestern Taiwan. The effects of R. sulfidophilum on water quality parameters, the relative levels of nitrogenase-encoding nifH and nitrous oxide reductase-encoding nosZ genes, the occurrence of sulfonamide resistance, the presence of sulfonamide resistance genes, and microbial community structure were determined. Supplementation with R. sulfidophilum decreased the chemical oxygen demand, the nitrate levels, and the occurrence of sulfonamide-resistant bacteria in the fishpond water compared with that of the control after rearing. The level of the sulfonamide resistance gene sul2 decreased in R. sulfidophilum-supplemented water samples, while the control exhibited an elevated level of sul2 after rearing. Supplementation with R. sulfidophilum also maintained the integrity of the bacterial community structure. In conclusion, our results suggest that R. sulfidophilum is an attractive supplement for enhanced disease emergence control, microbial biodiversity maintenance, and sustainable marine aquaculture practice.

Purple non-sulfur photosynthetic bacteria such as Rhodobacter sphaeroides and Rhodopseudomonas palustris produce hydrogen gas (H2) via proton reduction, which is catalyzed by nitrogenase. Although the expression of nitrogenase is usually repressed under nitrogen-sufficient conditions, a partial deletion of nifA, which encodes a transcriptional activator of nitrogen-fixation genes, has been reported to enable the constitutive expression of nitrogenase in R. palustris. In this study, we evaluated the effects of a similar mutation (nifA* mutation) on H2 production during the photoheterotrophic growth of R. sphaeroides, based on the notion that H2 production by nitrogenase compensates for the loss of CO2 fixation via the Calvin cycle, thereby restoring the redox balance. The chromosomal nifA* mutation resulted in the slight restoration of the photoheterotrophic growth of a mutant strain lacking ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO), the key enzyme of the Calvin cycle, when the strain was cultured in van Niel's yeast medium. In addition, the strain with the nifA* mutation produced detectable levels of H2 during photoheterotrophic growth with acetate and ammonium; however, the H2 production was considerably lower than that observed during the photoheterotrophic growth of the strain with acetate and L-glutamate, where L-glutamate serves as a poor nitrogen source, thereby causing nitrogenase derepression. On the other hand, introduction of a multicopy plasmid harboring nifA* markedly restored the photoheterotrophic growth of the RubisCO-deletion mutant in van Niel's yeast medium and resulted in efficient H2 production during the photoheterotrophic growth with acetate and ammonium.

We provide here an edited version of the “Farewell discussion” by the late Aleksandr (Alex) Yuryevich (Yu) Borisov (1930–2019) on several aspects related to the excitation energy transfer in photosynthetic bacteria. It is preceded by a prolog giving the events that led to our decision to publish it. Further, we include here a few photographs to give a personal glimpse of this unique biophysicist of our time. In addition, we provide here a reminiscence, by Andrei B. Rubin, on the scientific beginnings of Borisov. This article follows a Tribute to Borisov by Semenov et al. (2019, Photosynthesis Research, this issue).

Cyanobacteria acclimate and adapt to changing light conditions by controlling the energy transfer between photosystem I (PSI) and II (PSII) and pigment composition. Photosynthesis is driven by balancing the excitation between PSI and PSII. To predict the detailed electron transfer flux of cyanobacteria, we refined the photosynthesis-related reactions in our previously reconstructed genome-scale model. Two photosynthetic bacteria, Arthrospira and Synechocystis, were used as models. They were grown under various spectral light conditions and flux balance analysis (FBA) was performed using photon uptake fluxes into PSI and PSII, which were converted from each light spectrum by considering the photoacclimation of pigments and the distribution ratio of phycobilisome to PSI and PSII. In Arthrospira, the FBA was verified with experimental data using six types of light-emitting diodes (White, Blue, Green, Yellow, Red1, and Red2). FBA predicted the cell growth of Synechocystis for the LEDs, excepting Red2. In an FBA simulation, cells used respiratory terminal oxidases and two NADH dehydrogenases (NDH-1 and NDH-2) to balance the PSI and PSII excitations depending on the light conditions. FBA simulation with our refined model functionally implicated NDH-1 and NDH-2 as a component of cyclic electron transport in the varied light environments.

Carotenoids are tetraterpene pigments that are distributed in photosynthetic bacteria, some species of archaea and fungi, algae, plants, and animals. About 850 naturally occurring carotenoids had been reported up until 2018. Photosynthetic bacteria, fungi, algae, and plants can synthesize carotenoids de novo. Carotenoids are essential pigments in photosynthetic organs along with chlorophylls. Carotenoids also act as photo-protectors, antioxidants, color attractants, and precursors of plant hormones in non-photosynthetic organs of plants. Animals cannot synthesize carotenoids de novo, and so those found in animals are either directly accumulated from food or partly modified through metabolic reactions. So, animal carotenoids show structural diversity. Carotenoids in animals play important roles such precursors of vitamin A, photo-protectors, antioxidants, enhancers of immunity, and contributors to reproduction. In the present review, I describe the structural diversity, function, biosyntheses, and metabolism of natural carotenoids.

Background Pinene is a monoterpene, that is used in the manufacture of fragrances, insecticide, fine chemicals, and renewable fuels. Production of pinene by metabolic-engineered microorganisms is a sustainable method. Purple non-sulfur photosynthetic bacteria belong to photosynthetic chassis that are widely used to synthesize natural chemicals. To date, researches on the synthesis of pinene by purple non-sulfur photosynthetic bacteria has not been reported, leaving the potential of purple non-sulfur photosynthetic bacteria synthesizing pinene unexplored. Results Rhodobacter sphaeroides strain was applied as a model and engineered to express the fusion protein of heterologous geranyl diphosphate synthase (GPPS) and pinene synthase (PS), hence achieving pinene production. The reaction condition of pinene production was optimized and 97.51 μg/L of pinene was yielded. Then, genes of 1-deoxy-d-xylulose 5-phosphate synthase, 1-deoxy-d-xylulose 5-phosphate reductoisomerase and isopentenyl diphosphate isomerase were overexpressed, and the ribosome binding site of GPPS-PS mRNA was optimized, improving pinene titer to 539.84 μg/L. Conclusions In this paper, through heterologous expression of GPPS-PS, pinene was successfully produced in R. sphaeroides, and pinene production was greatly improved by optimizing the expression of key enzymes. This is the first report on pinene produce by purple non-sulfur photosynthetic bacteria, which expands the availability of photosynthetic chassis for pinene production.

In marine and freshwater oxygen-deficient zones, the remineralization of sinking organic matter from the photic zone is central to driving nitrogen loss. Deep blooms of photosynthetic bacteria, which form the suboxic/anoxic chlorophyll maximum (ACM), widespread in aquatic ecosystems, may also contribute to the local input of organic matter. Yet, the influence of the ACM on nitrogen and carbon cycling remains poorly understood. Using a suite of stable isotope tracer experiments, we examined the transformation of nitrogen and carbon under an ACM (comprising of Chlorobiaceae and Synechococcales) and a non-ACM scenario in the anoxic zone of Lake Tanganyika. We find that the ACM hosts a tight coupling of photo/litho-autotrophic and heterotrophic processes. In particular, the ACM was a hotspot of organic matter remineralization that controlled an important supply of ammonium driving a nitrification-anammox coupling, and thereby played a key role in regulating nitrogen loss in the oxygen-deficient zone., Nature Communications, 12 (1), ISSN:2041-1723

Effective microbes (EM) are the coexisting naturally occurring useful microbes applied as inoculant to enhance the beneficial microflora of the soil ecosystem to facilitate agricultural production. The participating microbial consortium includes lactic acid and photosynthetic bacteria, actinomycetes, fermenting fungi, and yeast, among others. These microbes are physiologically well-matched and coexist in a provided medium. EM formulation could be applied to a target crop in the most appropriate manner and form, and is easy to handle. It could be applied in several manners, as soil application, foliar application and as seed treatment. Microbial formulation in agricultural practices for enhancing productivity is sustainable and eco-friendly approach. When applied, EM formulations reportedly have positive effect on several crop growth parameters. It enhances the productivity, biomass accumulation, photosynthetic efficiency, and antioxidative response to abiotic stress in rice. EM formulations reportedly augment the trace elements contents, root and shoot weight, nodulation and pod yield in rajmah, while it boosts the root and shoot weight, nodulation and seed yields in bean, and drought and virus tolerance, shoot weight, pod number and biomass in soybean. Reportedly, formulated EM perks up the chlorophyll, N, P, carbohydrate and protein contents in sunflower, whereas it stimulates the root and shoot growth, leaf number, fungal disease resistance in groundnut. It could lead to an improved root growth, plant height, chlorophyll content, pod yield, fungal disease resistance, Cr-resistance and pest resistance in okra. This review compiles and provides critical insight to the effects of EM formulations on various crops, particularly the cereals (rice), pulses (rajmah, bean and soybean), oilseeds (sunflower and groundnut) and vegetable (okra).

Agro-industrial based industries have produced large amounts of residues. The recycling of agro-industrial wastes to produce value-added products is a promising aspect. The photosynthetic bacterium Rhodopseudomonas faecalis PA2 is an attractive source for carotenoid production because of its high carotenoid productivity. However, carotenoid composition of this bacterium remains unclear. In this study, agro-industrial wastes including soybean meal, coconut meal and cassava meal were optimised as sole substrate to produce carotenoids. Biomass and carotenoid productions were highest in soybean meal medium containing 50% soybean meal. The optimal condition was used to produce this bacterium in a photo-bioreactor and investigate carotenoid composition by using a high performance liquid chromatography (HPLC) and absorption spectral characteristics. The saponified extract consisted of lycopene, 1,2-dihydrolycopene, cis-1,2-dihydrolycopene and 1,2-dihydro-3,4-didehydrolycopene. To our knowledge this is the first study to investigate carotenoid composition of R. faecalis and the bioactive compounds produced by photosynthetic bacteria grown in soybean meal without additional nutrients was proposed. The utilization of this bacterium as a lycopene source with cost competitiveness will be further studied.

We demonstrated in our recent Communications Biology paper how marine photosynthetic bacteria, Prochlorococcus, are adversely affected by leachates from commonly used plastics. This study was one of the first to consider how substances leaching from plastics may affect marine primary producers and demonstrated that plastic pollution has the potential to negatively impact a wider range of organisms than previously appreciated. We outline here key outstanding questions regarding how ocean plastic pollution may impact small, but essential, marine microbes and discuss how these can be addressed., Following up on their recent study in Communications Biology Sasha Tetu et al discuss how plastic pollution of the oceans may affect marine microbes as well as strategies to identify the substances responsible for leachate toxicity and to further understand their impact.

Saline wastewater generation has increased in recent years, and saline-tolerant bacteria are very important for the treatment of saline wastewater. In this study, a haloduric photosynthetic bacterium Ectothiorhodospira shaposhnikovii P2 was isolated, and its cell biomass, pigments accumulation, and pollutants removal capacity were analyzed during salinity wastewater treatment process. The results showed that the optimal pH for obtaining maximum cell biomass (1.161 ± 0.021 g/L) and COD (95.83 ± 0.32%) and NH4+–N (87.72 ± 0.88%) removal was 8.0, whereas that for achieving high carotenoids (17.3 ± 0.2 mg/L) and bacteriochlorophylls (52.2 ± 2.3 mg/L) yields was 8.5. Thus, wastewater treatment processes using photosynthetic bacteria have the advantage of accumulating valuable biomass together with pollutant removal.

The photosynthetic bacterium Rhodopseudomonas faecalis PA2 could be used as a carotenoid producer with significant amounts of nutritional profile, particularly fatty acid composition. This strain produces a large yield of biomass and cultivation can be done with ease making it a great choice for commercial carotenoid source. The mass production intended to be used for fortified food and nutraceuticals is limited because of the high cost of chemically synthetic medium. In this study, we present a molasses-based medium based on inexpensive locally available material. In its composition, glutamic acid, malic acid, vitamins and trace elements have been omitted. The newly formulated medium contained 0.25 g/L molasses, 6.4 g/L yeast extract, 0.5 g/L K2HPO4, 0.5 g/L KH2PO4, 0.8 g/L (NH4)2HPO4, 0.2 g/L MgSO4 and 0.053 g/L CaCl2·2H2O. Carotenoid productivity in molasses-based medium was comparable with that in the chemical medium but the medium cost was reduced to 90.88%. Palmitic acid (16:0) was the major constituent accounting for 55.35% of total fatty acids and the biomass contained both omega-3 (alpha-linolenic acid [18:3, n-3]) and omega-6 fatty acids (linoleic acid [18:2, n-6] and dihomo-gamma-linolenic acid [20:3, n-6]). The proposed medium could be used as a medium for carotenoids and fatty acid production for commercial uses.

We provide a tribute to George Feher, one of the founding scientists in the use of biophysical techniques to probe photosynthetic complexes, especially the bacterial reaction center. His early life is briefly reviewed followed by a description of the impact of his 30 years of photosynthesis research. We describe his pioneering work in bacterial photosynthesis that helped to provide a detailed picture of the molecular events responsible for light energy capture and the subsequent electron and proton transfer events in photosynthetic organisms. These studies had a profound and lasting impact on our understanding of the molecular mechanisms of photosynthesis. We also include some personal comments from his former students and colleagues.

Leachate sewage ponds at Phuket Integrated Waste Management (Phuket, Thailand) are typical hypereutrophic red-water ponds found at sewage treatment plants and piggery, feedlot and poultry waste ponds with mixed communities of anoxygenic purple photosynthetic bacteria (PPB) (Bacteriochlorophyll a) and Chlorella-type green algae (Chl a + b). In vivo integrating sphere spectrometer scans (Model AE PPB, Eopt = 386 ± 15 μmol quanta m−2 s−1, ETRmax = 316 ± 7.3 μmol e− g−1 BChl a s−1 but in a mixture of Chlorella and PPB only the oxygenic photosynthesis could be detected. In sewage pond samples, PAM rapid light curves in the presence and absence of DCMU allowed separate estimates of oxygen and anoxygenic photosynthesis to be made only if the Chl a content was very low (Chl a ≈ 0.26 μg mL−1; BChl a ≈ 1.4 μg mL−1). If substantial amounts of Chl a were present, fluorescence from PSII overwhelmed the signal from RC-2 of PPB, preventing the detection of anoxygenic photosynthesis. New PAM technology to measure Chl a and BChl a fluorescence separately is needed.

Sewage lagoons and wastewater ponds from industrialised swine and poultry farms are typically hypereutrophic, auxinic and dominated by purple non-sulphur bacteria and unicellular green algae both typically growing photoheterotrophically. To manage such ponds, it is essential to know the balance between oxygenic and anoxygenic photosynthesis. Typical spectrophotometric algorithms to estimate chlorophyll use 750 nm as a zero (A750 nm) but a 750 nm zero protocol is unsuitable where substantial amounts of bacteriochlorophylls are present. Algorithms were developed to estimate chlorophylls a and b (Chl a and Chl b) and bacteriochlorophyll a (BChl a) in solvent in ethanol, 7:2 acetone/ethanol and 90% acetone. The algorithms use an 850-nm absorbance zero (A850 nm) well outside the absorbance ranges of both chlorophylls and bacteriochlorophylls in solvent. There are many habitats where the presence of anoxygenic photosynthetic bacteria is unsuspected and so using a routine A750 nm zero effectively masks their presence and leads to underestimations of Chl a and Chl b. The in-solvent red peak of bacteriochlorophyll c is too close to that of Chl a for BChl c and Chl a to be resolved spectroscopically, but its presence can be easily identified from in vivo scans. The spectroscopic advantage of 90% acetone is negated by its poor quantitative extraction of pigments. Acetone/ethanol (7:2) is an excellent solvent spectroscopically and as an extractant.

Aquatic ecosystems depend on photosynthetic bacteria that use various strategies of adaptation to light quantity and quality; the qualitative strategies include far-red/near infrared (> 700 nm) light adaptations. The usage of > 700 nm light as energy source is disadvantageous for photosynthesis (long-wavelength quanta are poorer in energy than short-wavelength quanta, and such light is largely screened out by water). Nevertheless, some bacteria produce long-wavelength absorbing “red-shifted” chlorophylls (Chls) that extend the range of photosynthetically active radiation to the infrared region. The majority of cyanobacteria use 400–700 nm light, with excited state being ultimately entrapped by Chl a at a long-wavelength maximal absorbance of ~ 700 nm. This photoadaptation to far-red light was unknown until the discovery of strains producing Chls d and f in 1996 and 2010, respectively. Today, there is much data on cyanobacteria utilizing Chl d as their main pigment and many studies on accessory Chls d and/or f produced under exposure to far-red light. Further analysis of the photosynthetic apparatuses of cyanobacteria that produce red-shifted Chls will contribute to a better understanding of primary productivity in aquatic communities. In this review, we report on the diversity, distribution, physiological ecology, taxonomy and evolution of aquatic cyanobacteria producing red-shifted Chls.

Mercuric contamination of aqueous cultures results in impairment of viability of photosynthetic bacteria primarily by inhibition of the photochemistry of the reaction center (RC) protein. Isolated reaction centers (RCs) from Rhodobacter sphaeroides were exposed to Hg2+ ions up to saturation concentration (~ 103 [Hg2+]/[RC]) and the gradual time- and concentration-dependent loss of the photochemical activity was monitored. The vast majority of Hg2+ ions (about 500 [Hg2+]/[RC]) had low affinity for the RC [binding constant Kb ~ 5 mM−1] and only a few (~ 1 [Hg2+]/[RC]) exhibited strong binding (Kb ~ 50 μM−1). Neither type of binding site had specific and harmful effects on the photochemistry of the RC. The primary charge separation was preserved even at saturation mercury(II) concentration, but essential further steps of stabilization and utilization were blocked already in the 5 < [Hg2+]/[RC]

Biological method has been recognized as a low-cost and ecofriendly approach for removing heavy metals from aqueous wastes. In this study, the ability of five photosynthetic bacteria isolates (strains labeled SC01, HN02, SC05, JS01, and YN01) was examined for their ability to remove Cr from Cr-containing solutions. Furthermore, the possible removal mechanisms were elucidated by comparing chromium removal rates, antioxidant reaction, and accumulation of reactive oxygen species (ROS). Among the five bacteria, strains SC01 and SC05 presented the highest removal rates of chromium ions and the activity of cysteine desulfhydrase under Cr stress. They also showed lower levels of ROS and cell death than the other three bacteria strains under Cr stress. In addition, total bacteriochlorophyll content and activities of six antioxidant enzymes in SC01 were highest among these selected strains. On the contrary, strain HN02 presented the lowest level of Cr removal and the lowest activities of antioxidant enzymes. It also exhibited the highest level of ROS under Cr(VI) stress. Overall, these results show that the strains SC01 and SC05 have good Cr removal ability and could be used for removal of Cr in industrial effluents.

Upon high light excitation in photosynthetic bacteria, various triplet states of pigments can accumulate leading to harmful effects. Here, the generation and lifetime of flash-induced carotenoid triplets (3Car) have been studied by observation of the quenching of bacteriochlorophyll (BChl) fluorescence in different strains of photosynthetic bacteria including Rvx. gelatinosus (anaerobic and semianaerobic), Rsp. rubrum, Thio. roseopersicina, Rba. sphaeroides 2.4.1 and carotenoid- and cytochrome-deficient mutants Rba. sphaeroides Ga, R-26, and cycA, respectively. The following results were obtained: (1) 3Car quenching is observed during and not exclusively after the photochemical rise of the fluorescence yield of BChl indicating that the charge separation in the reaction center (RC) and the carotenoid triplet formation are not consecutive but parallel processes. (2) The photoprotective function of 3Car is not limited to the RC only and can be described by a model in which the carotenoids are distributed in the lake of the BChl pigments. (3) The observed lifetime of 3Car in intact cells is the weighted average of the lifetimes of the carotenoids with various numbers of conjugated double bonds in the bacterial strain. (4) The lifetime of 3Car measured in the light is significantly shorter (1–2 μs) than that measured in the dark (2–10 μs). The difference reveals the importance of the dynamics of 3Car before relaxation. The results will be discussed not only in terms of energy levels of the 3Car but also in terms of the kinetics of transitions among different sublevels in the excited triplet state of the carotenoid.

A chlorosome is a large and efficient light-harvesting antenna system found in some photosynthetic bacteria. This system comprises self-aggregates of bacteriochlorophyll (BChl) c, d, or e possessing a chiral 1-hydroxyethyl group at the 3-position, which plays a key role in the formation of the supramolecule. Biosynthesis of chlorosomal pigments involves stereoselective conversion of 3-vinyl group to 3-(1-hydroxyethyl) group facilitated by a 3-vinyl hydratase. This 3-vinyl hydration also occurs in BChl a biosynthesis, followed by oxidation that introduces an acetyl group at the 3-position. Herein, we present in vitro enzymatic assays of paralogous 3-vinyl hydratases derived from green sulfur bacteria, Chlorobaculum tepidum and Chlorobaculum limnaeum, the filamentous anoxygenic phototroph Chloroflexus aurantiacus, and the chloracidobacterium Chloracidobacterium thermophilum. All the hydratases showed hydration activities. The biosynthetic pathway of BChl a and other chlorosomal pigments is discussed considering the substrate specificity and stereoselectivity of the present hydratases.

In recent years, the photosynthetic bacteria have been used widely in agriculture, but the effects of different agricultural applications on crop rhizosphere microorganism and crops are lack. In this study, we provide new insights into the structure and composition of the rice root-associated microbiomes as well as the effect on crop of the Rhodopseudomonas palustris(R. palustris) PSB06 and CGA009 at the rice seedling stage with seed immersion and root irrigation. Compare with CK group, the length of stem, the peroxidase (POD), and superoxide dismutase (SOD) activities in PSB06 treatment group was significantly higher, while the length of stem in CGA009 treatment group was significantly higher. The POD and SOD activities in CGA009 treatment groups only were higher slightly than the CK group. In the study, the dominant phyla were Proteobacteria (51.95–61.66%), Bacteroidetes (5.40–9.39%), Acidobacteria (4.50–10.52%), Actinobacteria (5.06–8.14%), Planctomycetes (2.90–4.48%), Chloroflexi (2.23–5.06%) and Firmicutes (2.38–7.30%), accounted for 87% bacterial sequences. The principal coordinate analysis (pCoA) and mantel results showed the two application actions of R. palustris CGA009 and PSB06 had significant effects on rice rhizosphere bacterial communities (p R. palustris CGA009 has no significant effect on rice. Dissimilarity test and canonical correspondence analysis (CCA) results showed that the TN and pH were the key factors affecting rice rhizosphere bacterial community in the seedling stage. This study will provide some guidance advices for the study of the microecological regulation of photosynthetic bacteria on crops.

Development of a genetic tool for visualization of photosynthetic bacteria (PSB) is essential for understanding microbial function during their interaction with plant and microflora. In this study, Rhodopseudomonas palustris GJ-22-gfp harboring the vector pBBR1-pckAPT-gfp was constructed using an electroporation transformation method and was used for dynamic tracing of bacteria in plants. The results showed that strain GJ-22-gfp was stable and did not affect the biocontrol function, and the Confocal Laser Scanning Microscopy (CLSM) results indicated it could successfully colonised on the surface of leaf and root of tobacco and rice. In tobacco leaves, cells formed aggregates on the mesophyll epidermal cells. While in rice, no aggregate was found. Instead, the fluorescent cells colonise the longitudinal intercellular spaces between epidermal cells. In addition, the results of strain GJ-22 on the growth promotion and disease resistance of tobacco and rice indicated that the different colonization patterns might be related to the bacteria could induce systemic resistance in tobacco.

In this study, agar immobilization technique was employed for biological hydrogen production using Rhodobacter capsulatus DSM 1710 (wild type) and YO3 (hup-mutant) strains in sequential batch process. Different agar and glutamate concentrations were tested with defined nutrient medium. Agar concentration 4% (w/v) and 4 mM glutamate were selected for bacterial immobilization in terms of rate and longevity of hydrogen production. Acetate concentration was increased from 40 to 60-100 and 60 mM gave best results with both bacterial strains immobilized in 4% (w/v) agar. Cell concentration was increased from 2.5 to 5 mg dcw mL-1 agar and it was found that increasing cell concentration of wild-type strain caused decrease in yield and productivity while these parameters improved by increasing cell concentration of mutant strain. Also, the hydrogen production time has extended from 17 days up to 60 days according to the process conditions and parameters. Hydrogen production by immobilized photosynthetic bacteria is a convenient technology for hydrogen production as it enables to produce hydrogen with high organic acid concentrations comparing to suspended cultures. Besides, immobilization increases the stability of the system and allowed sequential batch operation for long-term application.

Apprehension over exhaustion of fossil fuels and global warming, due to increasing amounts of CO2, has generated a lot of attention for the subject of renewable energy. Renewable energy has an intermittency problem and its output fluctuates depending on natural conditions. Biohydrogen is one of the promising renewable energy sources. Hydrogen produced by photosynthetic bacteria depends on the intensity of light irradiation and also fluctuates with the daily variation of sunlight. The co-culture system of dark-fermentative and photosynthetic bacteria is one solution for reducing the dependency of hydrogen production on light intensity. Because these two strains of bacteria have different processes of hydrogen production, it is possible to combine different outputs so far as the co-culture system works well. This study performed hydrogen production by the co-culture system composed of agar gels embedded with both dark-fermentative bacteria, Clostridium butyricum MIYAIRI, and photosynthetic bacteria, Rhodobacter sphaeroides RV, under a fluctuating light-irradiation. The time-course of hydrogen production was determined for the different conditions of co-culture in the mixing ratios of the two bacterial strains and light-irradiation patterns. As a result, the co-culture system succeeded in producing hydrogen exceeding that in the case of a single culture system and improved its stability against light fluctuation. Hydrogen production by the co-culture system would be applicable to the reduction of intermittency in renewable energies.

Renewable energy is regarded as a clean energy source but has some problems, one of which is intermittency. To reduce this, the time-delay of hydrogen production by photosynthetic bacteria can be effective. In this study, we qualitatively evaluated the time-delay of hydrogen production by photosynthetic bacteria under various irradiation conditions, and we also quantitatively evaluated it by fitting the experimental data and the hydrogen production model with a genetic algorithm. As a result of model fitting, we found that the relationship between the lengths of the optimized time-delay of hydrogen production by photosynthetic bacteria and the amount of light irradiation is linear. And we also found that the time-delay of hydrogen production by photosynthetic bacteria had an upper limit under low light intensity. We have suggested the existence of an energy store mechanism in photosynthetic bacteria.

In recent years, world climate change and global warming have been big issues. One of the solutions is to use renewable energies; however, renewable energies have an intermittent nature. In the case of photovoltaic arrays, the intermittency is mainly caused by fluctuating irradiation from sunlight due to clouds. In this study, biohydrogen production from photosynthetic bacteria was focused for the use of fluctuating sunlight irradiation. Previous researches have revealed some characteristics of biohydrogen production, and these results enable one to expect that photosynthetic bacteria have fluctuating light tolerance of biohydrogen production, in which the bacteria are able to produce biohydrogen continuously under fluctuating light irradiation. There have been quite a few studies to evaluate time-course changes of biohydrogen production under fluctuating irradiation, and therefore time-course evaluations have been performed. A 10-min light/dark illumination pattern was set for the fluctuating irradiation and the magnitude of the fluctuation was used to evaluate the fluctuation of the hydrogen production rate and irradiation light. The results indicated that the fluctuation was 0.22 times smaller through the photosynthetic bacteria. The results of this study indicate that photosynthetic bacteria have fluctuating light tolerance. Biohydrogen production, having fluctuating light tolerance, would be useful for realistic use of sunlight energy as renewable energy.

The molar extinction coefficients of light-harvesting complex 2 (LH2) have been ambiguous in spite of its fame and wide utilization. Herein we determine the molar extinction coefficients of the LH2 proteins derived from the three purple photosynthetic bacteria Rhodoblastus acidophilus, Rhodobacter sphaeroides and Phaeospirillum molischianum at 298 K by direct extraction of bacteriochlorophyll (BChl) a from the lyophilized proteins, followed by estimation of BChl a amounts from their electronic absorption spectra.

We investigated seasonal and spatial patterns of phytoplankton variability in the East China Sea in order to understand biomass and compositional responses to environmental factors in the contemporary ocean. We used satellite imagery from 2002 to 2013 to define the mean seasonal climatology of sea surface temperature and chlorophyll a. Phytoplankton and environmental measurements were synthesized for the study region and four seasons from 11 cruises conducted from 2006 to 2012. The results of CHEMTAX analyses on group-specific phytoplankton composition were consistent with those of microscopy and flow cytometry observations, revealing three patterns of seasonal variability. Canonical correspondence analysis and generalized additive models (GAMs) were used to resolve the spatiotemporal variations of major phytoplankton groups and their relationships to month, temperature, salinity, nutrients, mixed layer depth, and bottom depth. Monsoon forcing drove the distributional patterns of environmental factors and was critical to explaining phytoplankton dynamics at the seasonal scale. Compared to autumn and winter, significantly higher chlorophyll a concentrations were observed during spring and summer, associated with the spring bloom and the Changjiang (Yangtze) River plume, respectively. Diatoms dominated biomass over the East China Sea, especially during the summer months influenced by the Changjiang (Yangtze) River plume, whereas dinoflagellates were especially important during spring blooms. GAMs analysis showed the differences in their responses to environmental variability, with a clear mid-range salinity optimum (~31) and a more pronounced temperature effect for dinoflagellates. The photosynthetic bacteria, Prochlorococcus and Synechococcus, both increased strongly with warming, but Prochlorococcus showed stronger sensitivity to variations in physical environmental parameters, whereas Synechococcus was more responsive to chemical (nutrient) variability, with broader tolerance of low-salinity conditions.

Use of photosynthetic bacteria to produce carotenoids has increased considerably in recent decades; however, few studies have been conducted to identify additional carotenoid producers. In this study, Rhodopseudomonas faecalis PA2 was shown to be capable of carotenoid production, and factors influencing this production were identified. The maximum carotenoid content was observed at an initial pH of 7 in the presence of 0.8% malic acid, 0.4% yeast extract, and 0.05% Fe3+ under light at 4,000 lux. Fe3+ significantly enhanced carotenogenesis, resulting in a production rate of 2.5 mg/g/day and a reduction in time to maximum production from 12 to 8 days. The carotenoid content and carotenoid yield under modified conditions were 413 mg/L and 13 mg/g (mg total carotenoids per gram of dry cells), respectively, representing an increase of 117% relative to the original condition. The biomass and carotenoid productivity reached 4 g/L/day and 51.6 mg/L/day, respectively. To the best of our knowledge, this is the first study of carotenoid production by Rps. faecalis PA2. The results indicated that the productivity of this organism under the aforementioned conditions was comparable to that of previously described purple photosynthetic bacterial species.

Colin Allen Wraight (1945-2014) was a well-known biophysicist and biochemist of our times-formerly Professor of Biochemistry, Biophysics and Plant Biology, and Head of the Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA. (See a detailed Tribute to him by Govindjee et al., Photosynth Res, 2015.) During the latter part of his life, Colin had (1) given an excellent lecture in 2008 on the overall topic of the molecular mechanisms in biological energy conversion, focusing on how an ubiquinone is reduced to ubiquinol at the so-called "two electron gate", and (2) presented a review poster on the design features of long distance proton transport in biological systems, with focus on photosynthetic bacteria (a pdf file of the original is available from one of us, Govindjee). We present here for historical purpose, a complete transcript of his 2008 lecture and his 2013 poster, which have been annotated and expanded by the authors of this paper. The major theme is: electron and proton transfer in biological systems, with emphasis on bacterial reaction centers. The figures, some of which were prepared by us, are presented in sequence for both the lecture and the poster. A common bibliography is provided at the end of the paper, which is divided into two parts: (I) The Lecture; and (II) The Poster.

The McMurdo Dry Valleys of Antarctica support extensive yet cryptic microbial communities but little evidence for ‘top-down’ herbivory control. A question therefore arises as to how standing microbial biomass is regulated. Here, we present results from a survey of soil and rock microbial community metagenomes using the GeoChip microarray that demonstrate antibiotic resistance and phage infection are widespread. We interrogated a range of dry valley locations from maritime to extreme inland sites. Antibiotic resistance genes were identified in three categories: beta-lactamases, tetracycline and vanomycin plus a range of transporter genes. Frequency of recovery generally reflected microbial diversity, with greatest abundance among Halobacteria, Proteobacteria and the photosynthetic bacteria (Chlorobi, Chloroflexi and Cyanobacteria). However, no clear differences between locations and soil/rock communities were apparent. Phage signals were also recovered from all locations in soil and rock communities. The Leviviridae, Myoviridae, Podoviridae and Siphoviridae were ubiquitous . The Corticoviridae occurred only in moisture-sufficient hyporheic soils, the Microviridae occurred only in maritime and hyporheic sites and an unidentified group within the order Caudovirales occurred only at dry inland sites. We postulate that widespread antibiotic resistance indicates potential inter-specific interaction and that phage signals indicate possible ‘bottom-up’ trophic regulation in the dry valleys.

Cyanobacteria are a widely distributed, diverse group of photosynthetic bacteria that exhibit phototaxis, or motion in response to light. Cyanobacteria such asSynechocystissp. secrete a mixture of complex polysaccharides that facilitate cell motion, while their type 4 pili allow them to physically attach to each other. Even though cells can respond individually to light, colonies of such bacteria are observed to move collectively towards the light source in dense finger-like projections. Agent-based models are especially useful in connecting individual cell behaviour with the emergent collective phenomena that arise out of their interactions. We present an agent-based model for cyanobacterial phototaxis that accounts for slime deposition as well as for direct physical links between bacteria, mediated through their type 4 pili. We reproduce the experimentally observed aggregation of cells at the colony boundary as a precursor to finger formation. Our model also describes the changes in colony morphology that occur when the location of the light source is abruptly changed. We find that the overall motion of cells toward light remains relatively unimpaired even if a fraction of them do not sense light, allowing heterogeneous populations to continue to mount a robust collective response to stimuli. Our work suggests that in addition to bio-chemical signalling via diffusible molecules in the context of bacterial quorum-sensing, short-ranged physical interactions may also contribute to collective effects in bacterial motility.

The lattice Boltzmann method is adopted to simulate hydrodynamics and mass transfer accompanying with biochemical reaction in a channel with cylinder bundle, which is the scenario of biohydrogen production by photosynthetic bacteria in the biofilm attached on the surface of cylinder bundle in photobioreactor. The effects of cylinder spacing, Reynolds number and cylinder arrangement are investigated. The numerical results reveal that highest glucose concentration and the lowest hydrogen concentration are obtained at the front of the first row cylinders for all cases. The staggered arrangement leads to an increment in average drag coefficient, Sherwood number and consumption efficiency of substrate under a given condition, and the increment in Sherwood number reaches up to 30 %, while that in drag coefficient is around 1 %, moreover, the increment in consumption efficiency reaches the maximum value of 12 %. The results indicate that the staggered arrangement is beneficial to the mass transfer and biochemical reaction.

Appropriate experimental platforms are required to clarify the structure–function relationships of membrane protein assemblies. In photosynthetic bacteria, light-harvesting complex 2 and light-harvesting/reaction center core complex play key roles in capturing and transferring light energy and facilitating subsequent charge separation. These photosynthetic apparatuses form a supramolecular assembly in the photosynthetic membrane. However, the mechanism through which this assembly influences the efficiency of energy conversion remains to be clarified. We review our recent studies that were conducted to evaluate the structure–function relationship of the supramolecular assembly of photosynthetic antenna complexes in various lipid bilayer systems, as well as the construction of novel systems of planar lipid membranes for use as experimental platforms.

Environmental management is crucial for sustainable growth and development. The use of microorganisms to clean up contaminated environment provides cheap alternative method to the conventional treatment methods. But the choice of easily grown, viable and effective natural occurring microorganism to do the cleaning is a major challenge. In this article we presented and reviewed the application of photosynthetic bacteria in bioremediation due to their utilisation of various kinds of pollutants, minimum nutrients requirement and the possibility of generating valuable products concomitantly cleaning the contaminated environment. Pollutants such as pesticides, heavy metals, dyes, crude oil and odour with the specific photosynthetic bacteria capable of degrading the pollutants were identified and discussed in this article. The possible value added products to be generated as well as the mechanism of degradation are also highlighted and discussed in the article. The utilisation of carbon dioxide and the generation of value added products while cleaning up polluted environment are the major advantages of using these bacteria in bioremediation and have both environmental and economic benefits.

A biofilm photobioreactor under unsaturated flow condition (BFPBR-U) is proposed using a polished optical fiber as the internal light source for photo-H2 production in continuous culture. The main chamber was filled with spherical glass beads to create the reaction bed and the cells were immobilized to form a biofilm under unsaturated flow condition obtained by pumping substrate solution over a packing bed at a rate to create a thin fluid film and injecting the argon to maintain the gas phase space. The effects of operational conditions, including flow rate and influent substrate concentration, on the photo-H2 production performance were investigated. The unsaturated flow conditions eliminated the inhibition caused by high organic loading rate and enhanced light transmission efficiency, leading to an improvement in the photo-H2 production performance.