Photosynthetic Sulfur Bacteria Research Articles

The diversity of indigenous and potential bacteria as bioremediator of palm oil mill secondary effluent (POMSE) by metagenomics assessment

Abstract. Karno R, Arisoesilaningsih E, Mustafa I, Siswanto D. 2024. The diversity of indigenous and potential bacteria as bioremediator of palm oil mill secondary effluent (POMSE) by metagenomics assessment. Biodiversitas 25: 1194-1200. This study aimed to identify the indigenous bacteria for potential bioremediation agents of palm oil mill secondary effluent (POMSE). Samples were obtained from the secondary pond of palm oil mill treatment. The bacterial diversity on the POMSE water samples was revealed by Next Generation Sequencing (NGS) of 16S rRNA gene amplicons. The results showed that the high abundance of bacteria phylum was Pseudomonadota or Proteobacteria (50%), Bacillota (31%), Bacteroidota (5%), and Thermotogae (3%). A photosynthetic sulfur bacterium, Allochromatium humboldtianum, was the most abundant species detected in the POMSE, with more than 8% of the total Operational Taxonomic Unit (OTU) detected. It was followed by Allochromatium phaeobacterium (6%), Allochromatium sp. (6%), and Macromonas bipunctata (6%). Meanwhile, the level of physicochemical parameters in POMSE were relatively high for several main parameters of the quality standard of palm oil industry waste, such as Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD). In contrast, oil and fat are low and meet the quality standards. The value of POMSE physicochemical parameters, including COD, BOD, and oil and fat, were 2,492.46, 852.96, and 6.20 mg/L, respectively. Metagenomic analysis showed that the bacterial community at POMSE was highly diverse. Nine dominant and codominant species found are Allochromatium humboldtianum, Allochromatium phaeobacterium, Allochromatium sp., Allochromatium vinosum, Macromonas bipunctata, Tepidibaculum saccharolyticum, Rhodocyclus purpureus, Comamonas nitrativorans, and Fervidobacterium riparium. Several indigenous bacterial species found in this research were bacteria that have potential as bioremediation agents for palm oil wastewater.

The potential extent of Early Triassic Kockatea Shale equivalent source rocks in the Northern Carnarvon and Perth Basins, Western Australia

In the northern Perth Basin (Western Australia), the Early Triassic Kockatea Shale is the primary petroleum source rock. Possible source rocks in the Northern Carnarvon Basin are more varied and include the Upper Jurassic Dingo Claystone as well as the Early Triassic Locker Shale. Biomarker analyses were conducted on petroleum samples from these basins to understand the nature of the petroleum systems. Many of the analysed petroleum samples contain carotenoids (okenane, chlorobactane and isorenieratane) derived from photosynthetic sulfur bacteria, suggesting that their source rocks were deposited under conditions of photic zone euxinia (PZE) and/or derived from microbialites. In the northern Perth Basin, the major lithofacies contributing to the source rock are dark coloured mudstones deposited under PZE conditions and/or derived from microbialites. In the southern Perth Basin, the potential source rock is either Permian, Jurassic or Cretaceous in age as indicated by the low concentrations or absence of carotenoids and the Triassic biomarker n -C 33 alkylcyclohexane. There is also a possibility that the Lower Triassic Locker Shale is the source rock of petroleum in the Tubridgi field on the Peedamullah Shelf of the Northern Carnarvon Basin, based on the similarity of biomarkers to Perth Basin petroleum sourced from the Kockatea Shale. However, the possibility of charge from the Upper Jurassic Dingo Claystone cannot be entirely excluded. Supplementary material: biomarker dataset is available at https://doi.org/10.6084/m9.figshare.c.6452153

Bacterial Proliferation Reduces Sulphur Toxicity in Stabilization Ponds: Safer Water Resources by Photosynthesis

Background: Studies suggest that sulfur may react with plants or monocellular organisms, such as fungi, to produce toxic agents. It has been theorized that sulfur enters cells and affects their respiration. This study reports on a phototroph development that leads to the diminution and/or production of sulfur and release of hydrogen sulfide from public ponds. Methods: This study was conducted in anoxic stabilization ponds at a dimension of 1×0.25×1 (m), with a hydraulic retention time of 6 days. The ponds’ water was tested during the dark and light cycles. The experiments were carried out by factorial design and measured three variables: volumetric organic loading, sulphate concentrations and temperature. Results: Cyanobacteria and Rhodobacter species were the most abundant phototroph cellular organisms. The mean value of total sulfur and un-ionized hydrogen sulfide concentration were 74 mg/L and 21 mg/L, respectively, at the volumetric organic loading of 100 g BOD5/m3 per day. The efficiencies of biochemical and chemical oxygen removal were 71.9% and 59.1%, respectively. The mean proliferation rate of photosynthetic sulfur bacteria was 3.4×106 cells/ml. Conclusion: photosynthetic sulfur bacteria significantly reduced the sulfur concentration generated in the ponds. The illumination of bright light enhanced the sulfur reduction by the photosynthetic sulfur bacteria in the wastewater of the anoxic stabilization ponds.

The Eastern Nebraska Salt Marsh Microbiome Is Well Adapted to an Alkaline and Extreme Saline Environment.

The Eastern Nebraska Salt Marshes contain a unique, alkaline, and saline wetland area that is a remnant of prehistoric oceans that once covered this area. The microbial composition of these salt marshes, identified by metagenomic sequencing, appears to be different from well-studied coastal salt marshes as it contains bacterial genera that have only been found in cold-adapted, alkaline, saline environments. For example, Rubribacterium was only isolated before from an Eastern Siberian soda lake, but appears to be one of the most abundant bacteria present at the time of sampling of the Eastern Nebraska Salt Marshes. Further enrichment, followed by genome sequencing and metagenomic binning, revealed the presence of several halophilic, alkalophilic bacteria that play important roles in sulfur and carbon cycling, as well as in nitrogen fixation within this ecosystem. Photosynthetic sulfur bacteria, belonging to Prosthecochloris and Marichromatium, and chemotrophic sulfur bacteria of the genera Sulfurimonas, Arcobacter, and Thiomicrospira produce valuable oxidized sulfur compounds for algal and plant growth, while alkaliphilic, sulfur-reducing bacteria belonging to Sulfurospirillum help balance the sulfur cycle. This metagenome-based study provides a baseline to understand the complex, but balanced, syntrophic microbial interactions that occur in this unique inland salt marsh environment.

Nitrite oxidation by phototrophic bacteria of Chlorobium, Thiocapsa and Lamprocystis genera under the influence of inorganic pollutants

Pollutants of inorganic nature (acids, alkalis, mineral salts of different composition, metals) change the course of biological processes of environmental purification, but their influence on the physiological properties of phototrophic sulfur bacteria has not been studied enough. The usage of nitrite ions as an electron donor of anoxygenic photosynthesis by cells of phototrophic green and purple sulfur bacteria Chlorobium limicola IMV K-8, Thiocapsa sp. Ya-2003 and Lamprocystis sp. Ya-2003, isolated from Yavorivske Lake, under the influence of the most widespread inorganic pollutants – hydro- and dihydrophosphates, sulfates, chlorides and chlorates, has been studied. It is shown that KH2PO4, K2HPO4, Na2SO4, NaCl and KClO3, present in the van Niel medium with 4.2 mM NaNO2 at concentrations that are 0.5, 1.0, 2.0, 3.0, 4.0 times different from the maximum permissible concentrations (MPC), influenced the biomass accumulation and nitrite ions oxidation by phototrophic green and purple sulfur bacteria. In media with hydro- and dihydrophosphate ions at concentrations 4.0 times higher than the MPC, inhibition of bacterial growth was up to 1.7 times lower than in the control. The biomass accumulation by bacteria in media with chloride and chlorate ions at concentrations 3.0–4.0 times higher than MPC was 2.0–2.8 times lower compared to the control. In the medium with Na2SO4 at concentrations 2.0–4.0 times higher than MPC, the biomass was 2.0–4.0 times lower than in the control. Nitrites’ oxidation by all strains in the media with the studied pollutants was slowed down. The residual content of nitrite ions in media with hydro- and dihydrophosphate, chloride and chlorate ions at their concentrations 4.0 times higher than MPC, exceeded the NO2– content in the control variants up to 1.7 times. If in the medium without pollutants the cells of C. limicola IMV K-8, Thiocapsa sp. Ya-2003 and Lamprocystis sp. Ya-2003 strains oxidized 72.7%, 72.2% and 71.4%, respectively, of nitrite ions present in the medium, then in the medium with sulfate ions at concentration 4.0 times higher than the MPC, bacteria oxidized nitrite ions only at 39.6%, 34.4% and 27.0%, respectively. Oxidation of a lower quantity of nitrites by phototrophic bacteria in the media with inorganic pollutants led to the production by them of a lower quantity of nitrates. The content of NO3– in the media with hydro-, dihydrophosphate and chlorate ions at all concentrations was up to 1.9 times lower than in the control. In media with sulfate ions at concentrations 2.0–4.0 times higher than MPC and chloride at concentration 4.0 times higher than MPC, the content of nitrate ions was 2.1–4.3 and 2.0 times, respectively, lower than in the control variants. Inorganic pollutants stimulated the synthesis of intracellular carbohydrates in C. limicola IMV K-8. If the content of intracellular glucose in cells grown in the medium without pollutants was 10.3 mg/g dry cell weight, then in cells grown in media with K2HPO4, KH2PO4, Na2SO4, NaCl and KClO3 at concentrations 4.0 times higher than MPC, its content increased by 12.2%, 10.7%, 51.6%, 17.1% and 35.9%, respectively. The glycogen content in the cells grown in the medium without pollutants was 45.1 mg/g dry cell weight. Hydro- and dihydrophosphate, chloride and chlorate ions at concentrations 4.0 times higher than MPC stimulated glycogen synthesis in cells by 47.5%, 57.6%, 67.4% and 74.6%, respectively. The glycogen content in cells grown in the medium with Na2SO4 at concentrations 3.0 and 4.0 times higher than MPC increased by 102.9% and 107.5%, respectively. Therefore, it is established that pollutants of inorganic nature affect the physiological properties of photosynthetic sulfur bacteria and thus change the course of biological processes of environment purification, in particular, from nitrite ions.

Biomarkers of photosynthetic sulfur bacteria in Lower Cretaceous crude oils, East Brazilian marginal basin

Diagenetic aromatic carotenoids and degradation products, which are derived from the carotenoids of photosynthetic sulfur bacteria, were characterized in the aromatic fraction of Brazilian Cretaceous crude oils (NE Brazil, Sergipe-Alagoas Basin) by high-temperature comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (HT-GC × GC–TOFMS). Unresolved complex mixtures (UCM), coeluting compounds, and limited mass spectrometric identification were noted by traditional one-dimensional (1D) GC–MS screening of aromatic compounds. Group-type separation on a two-dimensional chromatographic plane, first- and second-dimension retention times (1tR and 2tR, respectively), and mass spectra enabled the assignment of alkylated mono-, di-, tri-, and tetra-aryl hydrocarbons with confidence. A series of diagenetic C40 carotenoids and degraded products, which are likely indicators for green-brown sulfur bacteria, were detected. This finding corroborates previous results, and isorenieratane was relatively more abundant than 2,3,6-trimethylaryl isoprenoids. Moreover, atropisomeric biphenyls (m/z 237), which coeluted using 1D GC–MS analyses, were resolved by GC × GC and identified by mass spectrometry. The identification of minor abundances of chlorobactane, diagenetic biphenyl chlorobactane, and related compounds, for the first time in these Brazilian Cretaceous oils, may indicate a contribution of green sulfur bacteria (Chlorobiaceae) and photic zone euxinia in shallow waters.

Recent cyanobacteria abundance in a large sub-tropical reservoir inferred from analysis of sediment cores

Salto Grande is a large South American reservoir on the border between Uruguay and Argentina that was impounded in 1979 and experiences recurrent, massive cyanobacteria blooms. A water-monitoring program was initiated 20 years after the dam was built, hence the causes and onset of cyanobacteria blooms remain poorly known. We collected two sediment cores from the old river channel in the reservoir (z = 17 m) and used physical, chemical and biological variables in the sediments, along with existing limnological data, to explore the history of cyanobacteria in the sub-tropical water body. Cyanobacteria fossil pigments were present at low concentrations during the first 24 years after impoundment, but more than doubled thereafter. Phytoplankton abundance tracked shifts in cyanobacteria pigment concentration, indicating an overall increase in all primary producers. Several sediment variables indicate a decline in water quality after 2003, such as increases in the number of photosynthetic sulfur bacteria and a reduction in sediment magnetic susceptibility. Akinetes (dormant cyanobacteria cells, Order Nostocales) in recent reservoir deposits were abundant and five species germinated under laboratory conditions, underscoring the ability of akinetes to initiate cyanobacteria blooms. The germinated assemblage reflected closely the composition of cyanobacteria blooms in the reservoir. Recorded increases in air temperature and decreases in wind speed, together with other variables (e.g. nutrients), can promote the large, recurrent cyanobacteria blooms. Invasion of the bivalve Limnoperna fortunei apparently promoted cyanobacteria blooms by preferential feeding on other phytoplankton taxa, and perhaps by altering nutrient concentrations and ratios. This work highlights the potential for using multiple variables in sediment cores from large reservoirs to better understand the responses of biota to multiple environmental stressors.

Microbial life in the nascent Chicxulub crater

Abstract The Chicxulub crater was formed by an asteroid impact at ca. 66 Ma. The impact is considered to have contributed to the end-Cretaceous mass extinction and reduced productivity in the world’s oceans due to a transient cessation of photosynthesis. Here, biomarker profiles extracted from crater core material reveal exceptional insights into the post-impact upheaval and rapid recovery of microbial life. In the immediate hours to days after the impact, ocean resurge flooded the crater and a subsequent tsunami delivered debris from the surrounding carbonate ramp. Deposited material, including biomarkers diagnostic for land plants, cyanobacteria, and photosynthetic sulfur bacteria, appears to have been mobilized by wave energy from coastal microbial mats. As that energy subsided, days to months later, blooms of unicellular cyanobacteria were fueled by terrigenous nutrients. Approximately 200 k.y. later, the nutrient supply waned and the basin returned to oligotrophic conditions, as evident from N2-fixing cyanobacteria biomarkers. At 1 m.y. after impact, the abundance of photosynthetic sulfur bacteria supported the development of water-column photic zone euxinia within the crater.

Sedimentation of ballasted cells-free EPS in meromictic Fayetteville Green Lake.

Fayetteville Green Lake (FGL) is a recognized, extensively studied present-day model of the stratified Proterozoic ocean. Nonetheless, biomass sedimentation in FGL remains hard to explain: while virtually all sediment pigments belong to photosynthetic sulfur bacteria from a chemocline, the isotopic carbon signature of the bulk organic matter suggests its epilimnetic phytoplankton origin. To explain the epilimnetic origin of sedimented carbon, we studied the dominant Synechococci, isolated from FGL. Here, we present experimental evidence that FGL Synechococci produce copious extracellular polysaccharides (EPS) especially when availability of inorganic carbon (Ci ) is high relative to availability of other macronutrients, for example phosphorus. The accumulating EPS become impregnated with calcium, magnesium, and sodium cations and are released to the environment as ballasted cell coverings. Sedimentation of these cell-free EPS can constitute the bulk of pigment-free organic material in FGL sediment. Because increased availability of Ci specifically stimulates production of EPS and the accumulated EPS adsorb cations and become ballasted, we propose the universal role of cyanobacterial EPS in biomass sedimentation in the high-Ci Paleoproterozoic ocean as well as in modern aquatic systems like FGL.

Draft Whole-Genome Sequence of the Green Sulfur Photosynthetic Bacterium Chlorobaculum sp. Strain 24CR, Isolated from the Carmel River.

Green sulfur bacteria are in the family Chlorobiaceae, which is composed of four distinct genera, namely, Chlorobaculum, Chlorobium, Prosthecochloris, and Chloroherpeton, with Chlorobium species being the most commonly represented in genome studies. We have now sequenced only the fourth species of Chlorobaculum, which established Chlorobaculum sp. 24CR as a separate species and should help characterize the genus.

Quenchers Protect BChl850 from Action of Singlet Oxygen in the Membranes of a Sulfur Photosynthetic Bacterium Allochromatium vinosum Strain MSU

The effect of singlet oxygen was studied in the system of Allochromatium (Alc.) vinosum MSU membranes, rose bengal, and light (547−600nm) with and without a quencher. In the system without a quencher, bleaching of the BChl850 band of the LH2 light-harvesting complex was observed and an absorption peak emerged at 698 nm, which belonged to the oxidized product, 3-acetyl-chlorophyll. The efficiency of five quenchers of singlet oxygen for neutralization of the effect of singlet oxygen on bacteriochlorophyll in the light-harvesting complexes of the membranes Alc. vinosum MSU was studied: sodium ascorbate, histidine, imidazole, trolox, and sodium azide. All of them, with the exception of sodium azide, neutralized successively the effect of singlet oxygen.

Controlling Photosynthetic Excitons by Selective Pigment Photooxidation.

As a basis of photosynthesis, photoinduced oxidation of (bacterio)chlorophyll molecules in the special reaction center complexes has been a subject of extensive research. In contrast, the generally harmful photooxidation of antenna chromoproteins has received much less attention. Here, we have established the permanent structural changes in the LH2 antenna bacteriochlorophyll-protein complex from a sulfur photosynthetic purple bacterium Ectothiorhodospira haloalkaliphila taking place at physiological conditions upon intense optical irradiation. To this end, a crystal structure of the LH2 complex from E. haloalkaliphila was first resolved by X-ray diffraction to 3.7 Å, verifying a great similarity with the earlier structure from Phaesporillum molischianum. Analysis of the various steady-state and picosecond time-resolved optical spectroscopy data and related model simulations then confirmed that the major spectral effects observed-bleaching and blue-shifting of the B850 exciton band and correlated emergence of a higher-energy C700 exciton band-are associated with photooxidation of increasing numbers of B850 bacteriochlorophylls into 3-acetyl-chlorophylls, with no noticeable damage to the pigment-binding protein scaffold. A prospective noninvasive method for an in situ optical control of excitons by selective photooxidation of pigment chromophores was thus revealed and demonstrated in a structurally well-defined native system.

Properties and structure of a low-potential, penta-heme cytochrome c552 from a thermophilic purple sulfur photosynthetic bacterium Thermochromatium tepidum.

The thermophilic purple sulfur bacterium Thermochromatium tepidum possesses four main water-soluble redox proteins involved in the electron transfer behavior. Crystal structures have been reported for three of them: a high potential iron-sulfur protein, cytochrome c', and one of two low-potential cytochrome c552 (which is a flavocytochrome c) have been determined. In this study, we purified another low-potential cytochrome c552 (LPC), determined its N-terminal amino acid sequence and the whole gene sequence, characterized it with absorption and electron paramagnetic spectroscopy, and solved its high-resolution crystal structure. This novel cytochrome was found to contain five c-type hemes. The overall fold of LPC consists of two distinct domains, one is the five heme-containing domain and the other one is an Ig-like domain. This provides a representative example for the structures of multiheme cytochromes containing an odd number of hemes, although the structures of multiheme cytochromes with an even number of hemes are frequently seen in the PDB database. Comparison of the sequence and structure of LPC with other proteins in the databases revealed several characteristic features which may be important for its functioning. Based on the results obtained, we discuss the possible intracellular function of this LPC in Tch. tepidum.

A novel enzyme of type VI sulfide:quinone oxidoreductases in purple sulfur photosynthetic bacteria.

Sulfide detoxification can be catalyzed by ancient membrane-bound flavoproteins, sulfide:quinone oxidoreductases (Sqr), which have important roles in sulfide homeostasis and sulfide-dependent energy conservation processes by transferring electrons from sulfide to respiratory or photosynthetic membrane electron flow. Sqr enzymes have been categorized into six groups. Several members of the groups I, II, III, and V are well-known, but type IV and VI Sqrs are, as yet, uncharacterized or hardly characterized at all. Here, we report detailed characterization of a type VI sulfide:quinone oxidoreductase (TrSqrF) from a purple sulfur bacterium, Thiocapsa roseopersicina. Phylogenetic analysis classified this enzyme in a special group composed of SqrFs of endosymbionts, while a weaker relationship could be observed with SqrF of Chlorobaculum tepidum which is the only type VI enzyme characterized so far. Directed mutagenesis experiments showed that TrSqrF contributed substantially to the sulfide:quinone oxidoreductase activity of the membranes. Expression of the sqrF gene could be induced by sulfide. Homologous recombinant TrSqrF protein was expressed and purified from the membranes of a SqrF-deleted T. roseopersicina strain. The purified protein contains redox-active covalently bound FAD cofactor. The recombinant TrSqrF enzyme catalyzes sulfur-dependent quinone reduction and prefers ubiquinone-type quinone compounds. Kinetic parameters of TrSqrF show that the affinity of the enzyme is similar to duroquinone and decylubiquinone, but the reaction has substantially lower activation energy with decylubiquinone, indicating that the quinone structure has an effect on the catalytic process. TrSqrF enzyme affinity for sulfide is low, therefore, in agreement with the gene expressional analyis, SqrF could play a role in energy-conserving sulfide oxidation at high sulfide concentrations. TrSqrF is a good model enzyme for the subgroup of type VI Sqrs of endosymbionts and its characterization might provide deeper insight into the molecular details of the ancient, anoxic, energy-gaining processes using sulfide as an electron donor.

Dynamic cellular complexity of anoxygenic phototrophic sulfur bacteria in the chemocline of meromictic Lake Cadagno.

The meromictic Lake Cadagno is characterized by a compact chemocline with high concentrations of anoxygenic phototrophic purple sulfur bacteria (PSB) and green sulfur bacteria (GSB). The co-occurrence of phylogenetically distant bacterial groups such as PSB and GSB in the same ecological niche, makes the chemocline of Lake Cadagno an ideal system for studying the conditions and consequences of coexistence of photosynthetic bacteria populations. In this study, we applied flow cytometry (FCM) as a fast tool to identify metabolic changes due to the production and consumption of inclusion bodies such as sulfur globules (SGBs), and follow population dynamics of closely related anoxygenic photosynthetic sulfur bacteria in their natural environment. Large-celled PSB Chromatium okenii and GSB Chlorobium populations were reliably separated and identified due to differences in auto-fluorescence and cell size. Moreover, we showed that these dominant taxa share the same ecological niche over seasonal periods. Taking advantage of FCM detection of dynamic cellular complexity variation during phases of photosynthetic activity, we identified an unexpected alternation in PSB versus GSB metabolic activity, indicating dynamic interspecific interactions between these two populations.

Amphiphilic zinc bacteriochlorophyll a derivatives that function as artificial energy acceptors in photosynthetic antenna complexes chlorosomes of the green sulfur photosynthetic bacterium Chlorobaculum limnaeum

Abstract Green photosynthetic bacteria have extramembranous light-harvesting complexes called chlorosomes. Light-energy captured by bacteriochlorophyll (BChl) self-aggregates inside chlorosomes is transferred to BChl a -peptide complexes called baseplates on the chlorosome surface. We substitute the baseplate complex in chlorosomes from a green sulfur photosynthetic bacterium Chlorobaculum limnaeum with amphiphilic Zn BChl a derivatives. Zn BChl a derivatives 1 – 3 , which were esterified with polyethylene glycol (PEG) 600, PEG400, and diethylene glycol, respectively, were successfully hybridized with chlorosomes without baseplates. These derivatives in the hybridized chlorosomes emitted by predominant excitation of BChl e self-aggregates at 460 nm, indicating that they were able to accept the excitation energy from BChl e aggregates inside chlorosomes. Zn BChl a derivatives 1 and 2 emitted at 787 nm by the excitation energy transfer. In contrast, fluorescence from 3 esterified with a short hydrophilic chain, diethylene glycol, was broadened around 785 and 820 nm. The broad emission bands would consist of at least two bands, which were ascribable to the monomeric and aggregated forms. These results indicate that PEG600 and PEG400 provide appropriate amphiphilicity to Zn BChl a derivatives for dispersion in the membranous region of chlorosomes. The present study will be helpful for not only elucidation of the energy transfer mechanism in chlorosomes but also development of artificial photofunctional supramolecular complexes by hybridization of natural photosynthetic systems with synthetic molecules.

Modeling the biogeochemical role of photosynthetic sulfur bacteria in phosphorus cycling in a managed eutrophic lake

Vertical distributions of total dissolved phosphorus (TDP), sulfide, chlorophyll, and primary production produced by photosynthetic sulfur bacteria (PSB) were studied in a small stratified, highly productive, and dimictic lake, Linsley Pond, CT, USA. The goal was to understand and model the role of PSB in a lake undergoing trophic transformation as a result of lake management involving reduced phosphorus loading. High levels of sulfide developed in the anoxic hypolimnion, though a decrease was observed compared to earlier years, possibly as a result of lake management under a Total Maximum Daily Load (TMDL) process. A deep chlorophyll maximum was observed, and absorption spectra confirmed that it was the result of photosynthetic sulfur bacteria. The summer chlorophyll maximum occurred at an interface marked by high amounts of sulfide and low, but adequate, levels of light. Primary production by PSB was found at a depth of 7m in July 2008, and thereafter extended slowly to 9m until late fall overturn. PSB only contributed a minor portion of total primary production in Linsley Pond that year, but a straightforward biogeochemical phosphorus model reveals that the existence of PSB serves as a significant biological barrier for phosphorus being transported back into the upper mixing zone. A large amount of TDP was trapped in the hypolimnion, and upward transport of TDP from the upper boundary of the hypolimnion to the mixing zone was about 30% of external phosphorus loading from the only tributary during the summer stratification period. By comparison, the amount of TDP assimilated by PSB and settling back to the hypolimnion was comparable to external phosphorus loading to the lake from its tributary. As lake management reduces external P loading and productivity, bottom sulfide is likely to decrease, suppressing PSB activity and having the undesired effect of allowing more TDP to be transported upward to the epilimnion as this biological barrier is suppressed.

Effect of pH on optimization of photofermentative hydrogen production by co-culture of Rhodobacter sphaeroides-NMBL-02 and Bacillus firmus-NMBL-03.

Rhodobacter sphaeroides NMBL-02, photosynthetic purple non sulfur (PNS) bacteria and associated Bacillus firmus NMBL-03 were isolated from water sample collected from 15-20 inches beneath the surface of ponds from Northern region of India in modified Sistrom's media (120 ml) containing 3 g/L malate and 1.2 g/L ammonium sulfate. The isolation was done in air tight serum bottles (120 ml) under tungsten bulb (1.8 kLux light intensity) at 30 oC ± 2 oC. The PNS and heterotrophic bacteria associated with the culture was purified by clonal selection method and characterized by 16S rDNA sequencing. The PNS isolate was identified as Rhodobacter sphaeroides NMBL-02 (ID: 1467407, Accession BANKIT: JN256030) and associated heterotroph as Bacillus firmus NMBL-03 (Gene Bank Accession no.: JN 256029). The effect of initial medium pH on optimization of hydrogen production was investigated in batch process. The maximum hydrogen potential and hydrogen production rate was 2310 ± 55 ml/L and 4.75 ml/L culture/h respectively using glutamate (1.7 mmol/L) as nitrogen source and malate (22.38 mmol/L) as carbon source with 76.39% malate conversion efficiency at initial medium pH 5.0. This co-culture has the ability to produce significant amount of hydrogen in the pH range of 5.0 to 10.0 with 76.39% to 35.71% malate conversion respectively.

Effects of exogenous isoprenoid diphosphates on in vivo attachment to bacteriochlorophyllide c in the green sulfur photosynthetic bacterium Chlorobaculum tepidum

Metabolic substitution of the esterifying chain in bacteriochlorophyll (BChl) c in green photosynthetic bacteria grown by supplementation of exogenous alcohols has attracted attentions to study supramolecular structures and biogenesis of major antenna complexes chlorosomes in these bacteria as well as BChl pigment biosynthesis. Actual substrates in the enzymatic attachment of the esterifying moieties to the precursor of BChl c, namely bacteriochlorophyllide (BChlide) c, in these bacteria are believed to be diphosphate esters of alcoholic substrates, although only intact alcohols have so far been supplemented in the bacterial cultures. We report herein BChl c compositions in the green sulfur photosynthetic bacterium Chlorobaculum tepidum by supplementation with geranyl and geranylgeranyl diphosphates. The supplementation of these diphosphates hardly produced BChl c derivatives esterified with geraniol and geranylgeraniol in Cba. tepidum, whereas these BChl c derivatives were accumulated by supplementation of intact geraniol and geranylgeraniol. The sharp contrast of the incorporation efficiency of the supplemental isoprenoid moieties in BChl c using the isoprenoid diphosphates to that by the isoprenoid alcohols was mainly ascribable to less penetration abilities of the diphosphate substrates into Cba. tepidum cells because of their anionic and polar diphosphate moiety.

Biosynthesis of unnatural glycolipids possessing diyne moiety in the acyl chain in the green sulfur photosynthetic bacterium Chlorobaculum tepidum grown by supplementation of 10,12-heptadecadiynic acid

Unnatural glycolipids possessing the diyne moiety in their acyl groups were successfully biosynthesized in the green sulfur photosynthetic bacterium Chlorobaculum (Cba.) tepidum by cultivation with supplementation of 10,12-heptadecadiynic acid. Monogalactosyldiacylglycerol (MGDG) and rhamnosylgalactosyldiacylglycerol (RGDG) esterified with one 10,12-heptadecadiynic acid were primarily formed in the cells, and small amounts of glycolipids esterified with the two unnatural fatty acids can also be detected. The relative ratio of these unnatural glycolipids occupied in the total glycolipids was estimated to be 49% based on HPLC analysis using a evaporative light scattering detector. These results indicate that the acyl groups in glycolipids, which play important roles in the formation of extramembranous antenna complexes called chlorosomes, can be modified in vivo by cultivation of green sulfur photosynthetic bacteria with exogenous synthetic fatty acids. Visible absorption and circular dichroism spectra of Cba. tepidum containing the unnatural glycolipids demonstrated the formation of chlorosomes, indicating that the unnatural glycolipids in this study did not interfere with the biogenesis of chlorosomes.