Sedimentary photosynthetic pigments of algae and phototrophic bacteria in Lake Hamana,Japan: temporal changes of anoxia in its five basins

We analyzed photosynthetic pigments of algae and bacteria (phototrophic sulfur bacteria: Chromatium and brown Chlorobium) in sediment cores and water samples obtained from five basins of Lake Hamana, a brackish, eutrophic, holomictic lake in Japan, and discussed our findings in relation to the distribution of the phototrophs. The four outer basins are connected to the central basin by narrow inlets. The prevalence of anoxia in Lake Hamana was demonstrated by the widespread presence of bacterial pigments in each core. The construction of training walls in 1954–1956 to direct tidal currents into the lake via Imagire-guchi Channel, the sole inlet for seawater, increased the lake water circulation, suppressed the development of anoxia, and caused Chromatium to disappear. Strong correlations (r ² 0.7) between total algal carotenoid (TAC) and total bacterial carotenoid (TBC) contents in each core were found in four basins. We ascribe this to the induction of anoxia by water stratification and algal proliferation, which precede the growth of phototrophic sulfur bacteria in the deeper layers of the water column. The slopes of the TBC–TAC correlations in the sediment cores, indicating the extent and stability of anoxia at each site, differed among basins (0.23–0.67) and were inversely related to the exchange rate of water by seawater intrusion in each basin.     

Acclimation of the photosynthetic response of Chromatium vinosum to light-limiting conditions

The photosynthetic response of the purple sulfur bacterium Chromatium vinosum DSM 185 to different degrees of illumination was analyzed. The microorganism was grown in continuous culture, and samples were taken from the effluent of the culture and incubated at different irradiances to determine the specific rate of sulfur oxidation as a measure of the photosynthetic activity of the organism. The activities obtained were plotted as a function of the specific rate of light uptake, and for each set of data a photosynthesis equation was fitted, which allowed the estimation of P_max (photosynthetic capacity), q_k (the threshold irradiance for light limitation), and m (maintenance coefficient). The results indicated that cells grown under light limitation are able to achieve higher photosynthetic activities than cells grown under light saturation. The photosynthetic capacity (P_max) remained constant under all the conditions of illumination tested, while the maintenance expenses (m) were higher under light limitation. The parameter q_k, on the contrary, decreased considerably at limiting irradiances. Received: 16 January 1998 / Accepted: 7 September 1998     

Abundance and diversity of aerobic anoxygenic phototrophic bacteria in saline lakes on the Tibetan plateau

Aerobic anoxygenic phototrophic (AAP) bacteria are heterotrophic prokaryotes that are capable of utilizing light as an energy source but are not capable of producing molecular oxygen. Recently, multiple studies have found that AAP bacteria are widely distributed in oceans and estuaries and may play an important role in carbon cycling. However, AAP bacteria in inland lake ecosystems have not been investigated in depth. In this study, the abundance and diversity of the pufL-M genes, encoding photosynthetic reaction centers of AAP bacteria, were determined in the oxic water column and anoxic sediments of saline lakes (Qinghai, Erhai, and Gahai Lakes) on the Tibetan Plateau, China. Our results indicated that AAP bacteria were abundant in inland lakes, with the proportion of AAP bacteria (in total bacteria) comparable to those in the oceans, but with a lower diversity. Salinity and pH were found to be potential factors controlling the AAP bacterial diversity and community composition. Our data have implications for a better understanding of the potential role of AAP bacteria in carbon cycling in inland lake ecosystems.     

Convenient method to prepare neutral sulfide solution for cultivation of phototrophic sulfur bacteria

A device is described for the preparation and storage of sterile neutral sulfide solution which is required for the repeated addition of this substrate to growing cultures of phototrophic sulfur bacteria.     

Interactions between phototrophic bacteria in sediment ecosystems

The environmental conditions in laminated microbial sediment ecosystems on the island of Schiermonnikoog (The Netherlands) were monitoredin situ over 24-hour periods by using micro-electrodes. In the layer of purple sulfur bacteria dramatic diel aerobic/anaerobic shifts occurred, whereas the top layer of cyanobacteria was occasionally confronted with sulfide. Pure cultures of the dominant organisms, being the cyanobacteriumMicrocoleus chthonoplastes and the purple sulfur bacteriumThiocapsa roseopersicina, were subjected to regimes mimicking the natural circumstances. It was demonstrated that both organisms are physiologically very well adapted to the fluctuating environmental conditions. The organisms interact by releasing metabolic end-products, the removal of toxic compounds and by competition for common substrates. It was demonstrated that positive interactions between both organisms are more important than negative interactions.     

Light-harvesting adaptations of planktonic phototrophic micro-organisms to different light quality conditions

The effects of light spectral distribution on the composition of phototrophic microbial communities were analyzed in three metalimnetic levels (relative depth positions) of 41 lakes. Principal Component Analysis was used to compare light quality conditions reaching the populations of phototrophic micro-organisms containing different photosynthetic pigments. Results allowed to identify the optimal light quality conditions for the selection of each microbial group at their respective levels. Two general light-harvesting adaptations were defined, according to the wavebands that could be related to the selection of these microbial groups. The micro-organisms adapted to use red and near-infrared light – eukaryotic phytoplankton, Chloronema spp. and green-coloured Chlorobiaceae – predominated at shallow depths (specially in waters containing high gilvin contents) using their respective Q_y absorption bands. The micro-organisms adapted to green-yellow light – phycoerythrin-containing cyanobacteria, Chromatiaceae and brown-coloured Chlorobiaceae – were dominant in deep metalimnetic communities. Laboratory experiments with cultures of Chlorobium limicola and C. phaeobacteroides growing under different light quality conditions showed that the green-coloured species had higher photosynthetic activity under red light, while the brown-coloured species was more active under green light. These results demonstrated that physiological differences between micro-organisms with different light-harvesting adaptations are responsible of their selection under different light quality conditions. This selection is experimented by Chlorobiaceae (as it was previously indicated by other investigators) at the deepest positions of the metalimnetic communities (level 3), but also by Chromatiaceae and Chloronema spp. at level 2 and by the eukaryotic phytoplankton and cyanobacteria at level 1.     

The effect of the pH level on the communities of anoxygenic phototrophic bacteria of soda lakes of the southeastern Transbaikal Region

The effect of pH on the structure of the communities of anoxygenic phototrophic bacteria (APB) was studied under laboratory conditions. Samples of natural APB communities were inoculated into media that differed in pH values, which were 7, 9.5, or 10.5. The structure of the APB communities in the obtained enrichment cultures at all pH values depended also on the mineralization levels of the media, which were the same as in the lakes from which samples were taken. The same dependence of the community structure on salinity was observed as in the case of the natural communities that had been described previously. APB were most diverse in the enrichment cultures grown at pH 9.5. The shift of the pH to either neutral or extremely alkaline values restricted the species diversity within the APB community, resulting in marked predominance of the most adapted forms. It was shown that the status of Ectothiorhodospira species within the community could serve not only as an indicator of salinity but also as an indicator of pH in soda lakes with a water mineralization of higher than 5 g/l. The statuses of various APB groups in the community as dependent on pH and salinity are discussed, as well as possible changes in these statuses due to changes in the water level and other environmental parameters in the studied lakes.     

Microbial ecology of planktonic filamentous phototrophic bacteria in holomictic freshwater lakes

The microbial ecology of the filamentous phototrophic bacterium, Chloronema giganteum, has been studied in the water column of three central European lakes (Schlein, Buchen and Vechten). In these lakes an anoxic layer, termed the transition zone, was located between the oxycline and the redoxcline. The migration capacity of Chloronema through this zone appears to be responsible for the natural preponderance of either straight or spiral forms. When the transition zone is less than 1 m thick the straight form is dominant, but when this transition zone is wider than 2 m the spiral form is enriched. The intermediate situations favour both filamentous forms.     

Influences of light and oxygen conditions on photosynthetic bacteria macromolecule degradation: different metabolic pathways

Direct degradation of macromolecules by photosynthetic bacteria (PSB) is important for the industrial application of PSB wastewater treatment. Light and oxygen are the most important parameters in PSB growth. This paper studied the PSB macromolecule degradation process under three different light and oxygen conditions: light-anaerobic, natural light-microaerobic and dark-aerobic. The results showed that under three different light-oxygen conditions, PSB degradation of macromolecules was higher than 90%; the removal ratios of COD, TN, TP, total sugar and protein were also high; and the biomass yield reached nearly 0.5 mg-biomass/mg-COD-removal. Light and oxygen significantly influenced the efficiency. Macromolecules and pollutants removals were higher under oxygen condition than those under light-anaerobic condition. Theoretical analysis showed that under aerobic condition, PSB carried out oxidative phosphorylation, in which pollutants were sufficiently utilized with high mineralization degree. Under light-anaerobic condition, PSB carried out photophosphorylation and fermentation, which led to low pollutants removal efficiency.     

The effect of light quality on the growth and development of in vitro cultured Doritaenopsis plants

The influence of light quality on growth and development of in vitro grown Doritaenopsis hort. (Orchidaceae) plants was investigated. Growth parameters like leaf and root fresh/dry mass and leaf area were highest with plants grown under red plus blue light emitting diodes (LEDs). Leaf length was greater with the plants grown under red LED. Carbohydrate (starch, sucrose, glucose and fructose) and leaf pigment (chlorophylls and carotenoids) biosynthesis of the plants was significantly increased in plants grown under red plus blue LEDs compared to red or blue LED and fluorescent light treatments. This study suggests that the production of quality Doritaenopsis plants is possible by culturing the plants in vitro under a mixture of blue plus red light sources.     

Excitation energy transfer kinetics and efficiency in phototrophic green sulfur bacteria

A series of spectroscopic measurements were performed on membrane fractions and detergent-solubilized complexes from the green sulfur bacterium (GSB) Chlorobaculum (Cba.) tepidum. The excitation migration through the entire GSB photosynthetic apparatus cannot be observed upon excitation of membranes in the chlorosome region at 77?K. In order to observe energy transfer from the Fenna-Matthews-Olson (FMO) protein to the reaction center (RC), FMO was directly excited at ~800?nm in transient absorption experiments. However, interpretation of the results is complicated by the spectral overlap between FMO and the RC. The availability of the Y16F FMO mutant, whose absorption spectrum is drastically different from that of the WT, has enabled the selection of spectral regions where either only FMO or the RC contributes. The application of a directed kinetic modeling approach, or target analysis, revealed the various decay and energy transfer pathways within the pigment-protein complexes. The calculated FMO-to-RC excitation energy transfer efficiencies are approximately 25% and 48% for the Y16F and WT samples, respectively.     

The sulfide affinity of phototrophic bacteria in relation to the location of elemental sulfur

Seventeen strains of phototrophic bacteria (4 strains of Chromatium spp., 2 strains of Thiocapsa sp., 4 strains of Ectothiorhodospira spp., 2 strains of Rhodopseudomonas sp., and 5 strains of Chlorobium spp.) have been grown in sulfide-limited continuous cultures to assess the affinity for sulfide. It was found that the affinity (calculated as the initial slope of the specific growth rate versus the concentration of sulfide) is higher in those phototrophic bacteria that deposit elemental sulfur outside the cells, than in those bacteria that store the sulfur inside the cells. A hypothesis is presented to explain this correlation.Dedicated to Prof. Dr. Hans G. Schlegel on the occasion of his 60th birthday     

Identification of phototrophic sulfur bacteria through the analysis of lmwRNA band patterns

Several phototrophic sulfur bacteria were identified preliminarily through the analysis of the low-molecular-weight RNA fraction (lmwRNA) of bacterial cells. This fraction includes the ribosomal 5S RNA and several transfer RNAs. These molecules were separated by high-resolution electrophoresis in polyacrylamide gels, and the resulting band patterns were used as fingerprints for the identification of the organisms. We examined a large number of well-characterized reference strains together with a broad range of purple sulfur bacterial isolates from freshwater and marine environments. A cluster analysis was run using the similarity matrix calculated from the band patterns. Despite the shortcomings of the method, close relatives were clustered together yielding a number of groups consistent with the phylogenetic arrangement established through the analyses of a few available 16S rRNA gene sequences. Thus, the classification obtained gives further support to rearrangement of the group as the analyses of 16S rRNA gene sequences had previously suggested. We conclude that the analysis of lmwRNA band patterns is a rapid and simple tool for grouping and preliminarily identifying new isolates of phototrophic sulfur bacteria. Received: 5 February 1998 / Accepted: 15 June 1998     

Quinones of phototrophic purple bacteria

Abstract The quinone composition of the recognized species of the phototrophic purple nonsulfur bacteria, the Ectothiorhodospiraceae, and some Chromatiaceae species has been determined. Altogether more than 50 strains of 33 species have been investigated. Some of the purple nonsulfur bacteria have Q-10 as sole quinone component, while others have Q-10, Q-9, or Q-8, respectively, together with menaquinones of the same isoprenoid chain length as the major components. Rhodoquinone is present in Rhodospirillum rubrum and Rhodospirillum photometricum . The Ectothiorhodospira species have either Q-8 and MK-8, like the Chromatiaceae species, or Q-7 and MK-7 as the major components.     

The structure of phototrophic communities of soda lakes of the southeastern Transbaikal Region

The structure of benthic phototrophic communities of 24 soda lakes of the southeastern Transbaikal Region was studied. The physicochemical properties of the lakes were determined. The results of enumeration of anoxygenic phototrophic bacteria (APB) belonging to various groups are presented. The influence of salinity on the structure of APB communities was investigated. The APB reaction to environmental conditions was determined. Massive development of phototrophic microorganisms in the form of mats and films was observed in the majority of the investigated lakes. The APB communities were characterized by a wide diversity and evenness of species composition. Purple sulfur bacteria of the families Ectothiorhodospiraceae and Chromatiaceae were predominant. Purple nonsulfur bacteria of the family Rhodobacteraceae, green filamentous bacteria Oscillochloris sp., and heliobacteria were also detected. According to preliminary data, no less than 15 species of APB occur in the studied lakes. Among them, three novel genera and four species have already been described. Identification of other isolates is still in progress. The lakes make an almost continuous series of fresh, brackish, and saline water bodies, varying in their degree of mineralization. It was demonstrated that the structure of APB communities was unaffected by changes in salinity from 5 to 40 g/l. At salt concentrations of lower than 5 g/l, the level of water mineralization became a limiting factor. Experiments with the isolated cultures showed that the APB were obligately dependent on the presence of carbonate ions in the medium. They were haloalkalitolerant or haloalkaliphilic. Thus, they are well adapted to the conditions of soda lakes with a low of moderate mineralization. It was demonstrated that soda lakes of the southeastern Transbaikal Region represent a special type of habitat which harbors a peculiar autochthonous microflora and differs from both highly mineralized soda lakes and shallow saline water bodies of the sea origin.     

The occurrence of gas-vacuolate bacteria in lakes

In order to assess the importance of gas vacuoles in planktonic bacteria we carried out a survey of 35 lakes of different types. At least 39 morphologically distinct species of gas-vacuolate bacteria were encountered. All of the freshwater lakes, and one of two seawater-flooded quarries, which became thermally stratified in summer, contained gas-vacuolate bacteria in their anaerobic hypolimnia; however, with one exception, none was found in isothermally mixed lakes. This pattern of distribution supports the idea that gas vacuoles are important in providing buoyancy, a function which is relevant only in non-turbulent aquatic systems.     

Organic nitrogen metabolism of phototrophic bacteria

Recent reviews dealing with phototrophic bacteria are concerned with bioenergetics, nitrogen fixation and hydrogen metabolism, synthesis of the photosynthetic apparatus and phylogeny/taxonomy. The organic N-metabolism of these phylogenetically diverse bacteria has last been reviewed in 1978. However, amino acid utilization and biosynthesis, ammonia assimilation, purine and pyrimidine metabolism and biosynthesis of -aminolevulinic acid as precursor of bacteriochlorophylls and hemes are topics of vital importance. This review focusses on utilization of amino acids as N- and C/N-sources, the pathways of purine and pyrimidine degradation, novel aspects of amino acid biosynthesis (with emphasis on branched-chain amino acids and -aminole-vulinic acid) and some aspects of ammonia assimilation and glutamate synthesis by purple bacteria, green sulfur bacteria and Chloroflexus aurantiacus.Abbreviations R Rhodospirillum - Rhb Rhodobacter - Rc Rhodocyclus - Rp Rhodopila - Rps Rhodopseudomonas     

A modified method for the cultivation of phototrophic bacteria

Simplified anaerobic media and a convenient method for the cultivation of Rhodospirillaceae, Chlorobiaceae, Chloroflexaceae and Chromatiaceae are described. The modified conditions assure almost complete anaerobiosis for media, growth and maintenance.Strains representing several species of Rhodospirillaceae, Chlorobiaceae and Chromatiaceae were successfully grown within relatively short times with full pigmentation, indicating that the new media and cultivation conditions were most suited for photoautotrophic growth.     

A comparison of phototrophic bacteria in two adjacent saline meromictic lakes

Two adjacent saline, meromictic lakes in Saskatchewan host different populations of phototrophic bacteria. Deadmoose Lake hosts a population of Lamprocystis roseopersicina (Chromatiaceae) while in Waldsea Lake a population of a Chlorobium species (Chlorobiaceae) is dominant. Differences in light quantity, light quality, temperature, pH and Lamprocystis' capacity for photoorganoheterotrophic growth explain why different genera of phototrophic bacteria are found within the two lakes. These phototrophic bacteria make a significant contribution to total photosynthetic productivity, fixing 14.3 and 32 g C m^-2 year ^-1 in Deadmoose and Waldsea Lake respectively.