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.     

Pelodictyon phaeoclathratiforme sp. nov., a new brown-colored member of the Chlorobiaceae forming net-like colonies

A new strain of the green sulfur bacteria was isolated from the monimolimnion of Buchensee (near Radolfzell, Lake Constance region, FRG). Single cells were rod-shaped, nonmotile and contained gas vacuoles. Typical net-like colonies were formed by ternary fission of the cells. As photosynthetic pigments bacteriochlorophylls a, e, isorenieratene and -isorenieratene were present. Sulfide, sulfur and thiosulfate were used as electron donors during anaerobic phototrophic growth. Besides carbon dioxide, acetate and propionate could serve as carbon sources under mixotrophic conditions in the light. Like all other members of the green sulfur bacteria, the new bacterium is strictly anaerobic and obligately phototrophic. The possession of gas vacuoles and the formation of net-like colonies and the guanine plus cytosine content of the DNA (47.9 mol% G+C) are typical characteristics of the genus Pelodictyon. Because of its photosynthetic pigments which differ from those of Pelodictyon clathratiforme, strain BU 1 represents a new species, P. Phaeoclathratiforme sp. nov.     

Isolation and characteristics of Thiopedia rosea (neotype)

Four new strains of Thiopedia rosea were isolated in pure culture from blooms of platelet-forming purple sulfur bacteria in the top layers of the anoxic hypolimnia of two freshwater lakes. Individual cells of the new strains as well as of T. rosea strain 4211 were spherical to oval, nonmotile and contained gas vesicles in the central part. The predominant photosynthetic pigments were bacteriochlorophyll a and okenone. All strains were strictly anaerobic and obligately phototrophic. Optimal growth occurred at low light intensities of 100 E · m^-2 s^-1 (tungsten lamp); intensities above 150 E · m^-2 s^-1 inhibited growth completely. Photoautotrophic growth was possible at sulfide concentrations up to 0.6 mM; higher concentrations were inhibitory. Acetate, butyrate and valerate supported photoorganotrophic growth in the presence of bicarbonate and sulfide concentrations below 1 mM. Sulfide was required as a source of cellular sulfur because assimilatory sulfate reduction is lacking. All strains were assigned to the species Thiopedia rosea with strain 4211 as a neotype.Dedicated to Prof. Dr. H. G. Schlegel on the occasion of his 66th birthday     

Effect of winter conditions on distributions of anoxic phototrophic bacteria in two meromictic lakes in Siberia,Russia

The year-to-year variations of vertical distribution and biomass of anoxic phototrophic bacteria were studied during ice periods 2003–2005 and 2007–2008 in meromictic lakes Shira and Shunet (Southern Siberia, Russian Federation). The bacterial layers in chemocline of both lakes were sampled with a thin-layer hydraulic multi-syringe sampler. In winter, biomass of purple sulphur bacteria varied considerably depending on the amount of light penetrating into the chemocline through the ice and snow cover. In relatively weakly stratified, brackish Shira Lake, the depth of chemocline varied between winters, so that light intensity for purple sulphur bacteria inhabiting this zone differed. In Shira Lake, increased transparency of mixolimnion in winter, high chemocline position and absence of snow resulted in light intensity and biomass of purple sulphur bacteria exceeding the summer values in the chemocline of the lake. We could monitor snow cover at the lake surface using remote sensing and therefore estimate dynamics and amount of light under ice and its availability for phototrophic organisms. In Shunet Lake, the light intensities in the chemocline and biomasses of purple sulphur bacteria were always lower in winter than in summer, but the biomasses of green sulphur bacteria were similar.     

Seasonal changes in the structure of the anoxygenic photosynthetic bacterial community in Lake Shunet,Khakassia

Seasonal studies of the anoxygenic phototrophic bacterial community of the water column of the saline eutrophic meromictic Lake Shunet (Khakassia) were performed in 2002 (June) and 2003 (February–March and August). From the redox zone down, the lake water was of dark green color. Green sulfur bacteria predominated in every season. The maximum number of green sulfur bacteria was 10⁷ cells/ml in summer and 10⁶ cells/ml in winter. A multi-syringe stratification sampler was applied for the study of the fine vertical distribution of phototrophs in August 2003; the sampling was performed every 5 cm. A 5-cm-thick pink-colored water layer inhabited by purple sulfur bacteria was shown to be located above the layer of green bacteria. The species composition and ratio of purple bacterial species depended on the sampling depth and on the season. In summer, the number of purple sulfur bacteria in the layer of pink water was 1.6 × 10⁸ cells/ml. Their number in winter was 3 × 10⁵ cells/ml. In the upper oxygen-containing layer of the chemocline the cells of purple nonsulfur bacteria were detected in summer. The maximum number of nonsulfur purple bacteria, 5 × 10² cells/ml, was recorded in August 2003. According to the results of the phylogenetic analysis of pure cultures of the isolated phototrophic bacteria, which were based on 16S rDNA sequencing, green sulfur bacteria were close to Prosthecochloris vibrioformis, purple sulfur bacteria, to Thiocapsa and Halochromatium species, and purple nonsulfur bacteria, to Rhodovulum euryhalinum and Pinkicyclus mahoneyensis.     

Seeing green bacteria in a new light: genomics-enabled studies of the photosynthetic apparatus in green sulfur bacteria and filamentous anoxygenic phototrophic bacteria

Based upon their photosynthetic nature and the presence of a unique light-harvesting antenna structure, the chlorosome, the photosynthetic green bacteria are defined as a distinctive group in the Bacteria. However, members of the two taxa that comprise this group, the green sulfur bacteria (Chlorobi) and the filamentous anoxygenic phototrophic bacteria (Chloroflexales), are otherwise quite different, both physiologically and phylogenetically. This review summarizes how genome sequence information facilitated studies of the biosynthesis and function of the photosynthetic apparatus and the oxidation of inorganic sulfur compounds in two model organisms that represent these taxa, Chlorobium tepidum and Chloroflexus aurantiacus. The genes involved in bacteriochlorophyll (BChl) c and carotenoid biosynthesis in these two organisms were identified by sequence homology with known BChl a and carotenoid biosynthesis enzymes, gene cluster analysis in Cfx. aurantiacus, and gene inactivation studies in Chl. tepidum. Based on these results, BChl a and BChl c biosynthesis is similar in the two organisms, whereas carotenoid biosynthesis differs significantly. In agreement with its facultative anaerobic nature, Cfx. aurantiacus in some cases apparently produces structurally different enzymes for heme and BChl biosynthesis, in which one enzyme functions under anoxic conditions and the other performs the same reaction under oxic conditions. The Chl. tepidum mutants produced with modified BChl c and carotenoid species also allow the functions of these pigments to be studied in vivo.     

Ectothiorhodospira halochloris sp. nov., a new extremely halophilic phototrophic bacterium containing bacteriochlorophyll b

A new bacteriochlorophyll b containing phototrophic bacterium was isolated from extremely saline and alkaline soda lakes in Egypt. Enrichment and isolation were performed using a synthetic medium with high contents of sodium carbonate, sodium sulfate and sodium chloride. Photoautotrophic growth occurred with hydrogen sulfide as photosynthetic electron donor. During oxidation of sulfide to sulfate extracellular elemental sulfur globules appeared in the medium. Cells were also capable to grow under photoheterotrophic conditions with acetate, propionate, pyruvate, succinate, fumarate or malate as carbon sources and electron donors. Under these conditions sulfate was assimilated. Optimal growth under the applied experimental conditions occurred at a total salinity of 14–27%, a pH-range between 8.1 and 9.1 and a temperature between 47°C and 50°C. The cells were 0.5–0.6 m wide and, depending on cultural conditions, 2.5–8.0 m long; they were spiral shaped, multiplied by binary fission and were motile by means of bipolar flagella. Intercytoplasmic photosynthetic membranes were present as stacks. Bacteriochlorophyll b was the main photosynthetic pigment; small amounts of carotenoids were mainly present as glucosides of rhodopin and its methoxy derivative. The new organism is described as Ectothiorhodospira halochloris.Dedicated to Professor C. B. van Niel on the occasion of his 80th birthday     

Carotenoids from plankton and photosynthetic bacteria in sediments as indicators of trophic changes in Lake Lobsigen during the last 14000 years

Previous examination of drilling cores showed that the majority of the carotenes and carotenoids originally present in the various planktonic organisms and phototrophic bacteria are preserved in sediments. The indicator pigments for algae phyla are: Lutein for Chlorophyta, Myxoxanthophylls and their derivatives for Cyanophyta, Fucoxanthin for Chrysophyta, and Alloxanthin for Cryptophyta.The pigments in the deepest sediment sample (late glacial time, clay, 12.83 m) consists primarily of Alloxanthin, secondly of Lutein and -carotene and thirdly of traces of Okenone, Speroidenone and other such bacterial carotenoids. The first plankton organisms were thus Cryptophyta and some Chlorophyta. The presence of the phototrophic bacteria pigments indicates that at the time of sediment formation, anaerobic conditions prevailed at the lake bottom.The Holocene era commences at a depth of 8.55 m and is characterized by the first occurrence of Myxoxanthophyll and Echinenone from Cyanophyta, as well as by a rapid increase of -carotene, Lutein and Alloxanthin. The pronounced occurrence of Oscillatoria rubescens (blood of the Burgundies), characterized by Oscillaxanthin at 8.21 m must be considered for Swiss lakes as a very surprising discovery.The intensive plankton production again lead to stringent anaerobic conditions. Predominant among phototrophic bacteria pigments were Okenone, Spheroidene and Rhodopin.     

Seasonal Changes in the Structure of the Anoxygenic Phototrophic Bacterial Community in Lake Mogilnoe,a Relict Lake on Kil'din Island in the Barents Sea

An anaerobic phototrophic bacterial community in Lake Mogilnoe, a relict lake on Kil'din Island in the Barents Sea, was studied in June 1999 and September 2001. Irrespective of the season, the upper layer of the anaerobic zone of this lake had a specific species composition of sulfur phototrophic bacteria, which were dominated by the brown-colored green sulfur bacterium Chlorobium phaeovibrioides. The maximum number of sulfur phototrophic bacteria was observed in June 1999 at a depth of 9 m, which corresponded to a concentration of bacteriochlorophyll (Bchl) e equal to 4.6 mg/l. In September 2001, the maximum concentration of this pigment (3.4 mg/l) was found at a depth of 10 m. In both seasons, the concentration of Bchl a did not exceed 3 μg/l. Purple sulfur bacteria were low in number, which can be explained by their poor adaptation to the hydrochemical and optical conditions of the Lake Mogilnoe water. In June 1999, the water contained a considerable number of Pelodictyon phaeum microcolonies and Prosthecochloris phaeoasteroides cell chains, which was not the case in September 2001. A 16S rDNA-based phylogenetic analysis of pure cultures of phototrophic bacteria isolated from the lake water confirmed that the bacterial community is dominated by Chl. phaeovibrioides and showed the presence of three minor species, Thiocystis gelatinosa, Thiocapsa sp., and Thiorhodococcus sp., the last of which is specific to Lake Mogilnoe.     

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     

Induction of the Synthesis of Endo-1,4-β-xylanase and β-Galactosidase in Original and Recombinant Strains of the Fungus Penicillium canescens

The induction of synthesis of the secreted enzymes endo-1,4--xylanase (EC 3.2.1.8) and -galactosidase (EC 3.2.1.23) in original and recombinant Penicillium canescens strains has been studied. In all producer strains, the synthesis of these enzymes was induced by arabinose and its metabolite arabitol. The two enzymes differed in the concentration of arabinose required for induction: the synthesis of -galactosidase was most pronounced at 1 mM, whereas maximum synthesis of endo-1,4--xylanase was observed at 5–10 mM. An increase in the number of endo-1,4--xylanase copies in the high-copy-number strain of the fungus suppressed the synthesis of -galactosidase; the synthesis of endo-1,4--xylanase in the high-copy-number recombinant producing -galactosidase was affected to a lesser extent. The amount of enzymes synthesized did not depend on the saccharide used as the sole source of carbon for growing the mycelium prior to its transfer to the inducer-containing medium.     

Why some fruits are green when they are ripe: carbon balance in fleshy fruits

Summary Fruits that are green upon ripening (green-ripe) tend to be dispersed by a limited range of frugivores, whereas those that are brightly colored (bright-ripe) are dispersed by a wide range of birds and mammals. Because green fruits are probably less conspicuous than other colors of fruits, their pigmentation cannot be attributed to the attraction of seed dispersers. Instead, we hypothesize that a major benefit of green pigmentation is the ability to photosynthesize when ripe. Photosynthesis by fruits may lower their costs of production, and could result in fruits with greater nutrient reward. We present data on physical, chemical, and photosynthetic characteristics of ripe fleshy fruit of variable colors for 28 plant species at the La Selva Biological Station, Costa Rica. In addition to color and morphological characteristics of pulp and seeds, we report soluble solids content (refractive index), and photosynthetic/respiratory carbon-dioxide balance of ripe fruits. Carbon balance was much more dependent upon ambient light levels in green-ripe fruits than in bright-ripe fruit. In particular, data from light response curves indicated that green-ripe fruits may go into positive carbon balance at high light levels (above 300 mol/m²/s). Rather than finding a positive relationship between soluble solids content and green fruit, as we predicted based on photosynthetic capacity, our data indicate that greater respiration rates of green-ripe fruits may result in carbon losses at low light levels. Our results were consistent with previously described morphological differences between the two color classes, with green-ripe fruits displaying significantly greater wet pulp mass, wet seed mass, and total fruit mass. Our data suggest that photosynthesis due to the retention of chlorophyll in ripe fleshy fruit may offset respiratory costs for plants with large or otherwise costly fruit, but this advantage should be evident only under high-light conditions.     

Two new motile phototrophic consortia: “Chlorochromatium lunatum” and “Pelochromatium selenoides”

Two new phototrophic consortia, “Chlorochromatium lunatum” and “Pelochromatium selenoides”, were observed and collected in the hypolimnion of several dimictic lakes in Wisconsin and Michigan (USA). The two consortia had the same morphology but different pigment composition. The cells of the photosynthetic components of the consortia were half-moon-shaped. This morphology was used to differentiate them from the previously described motile phototrophic consortia “Chlorochromatium aggregatum” and “Pelochromatium roseum”. These phototrophic cells did not resemble any described unicellular green sulfur bacteria. The predominant pigments detected were bacteriochlorophyll d and chlorobactene for the green-colored “Clc. lunatum”, and bacteriochlorophyll e and isorenieratene for the brown-colored “Plc. selenoides”. Their pigment compositions and the presence of chlorosomes attached to the inner face of the cytoplasmic membrane in both kinds of photosynthetic cells confirmed this new half-moon-shaped morphotype as a green sulfur bacterium. Both consortia were found thriving in lakes with low concentrations of sulfide (< 60 μM), below the layers of “Clc. aggregatum” and “Plc. roseum”. The green consortia were observed in lakes where the oxic-anoxic interface was located at shallow depths (2–7 m), while the brown consortia were found at greater depths (8–16 m). The two newly described consortia were never detected together at the same depth in any lake. Received: 30 April 1997 / Accepted: 17 January 1998     

Anoxygenic phototrophic bacteria from gypsum karst lakes of Lithuania

The spatial distribution and composition of anoxygenic phototrophic bacteria in the enriched bacterial communities from different depths of karst lakes Kirkilai and Ramunelis was studied using spectrophotometric analysis, as well as microbiological and molecular methods. In Lake Kirkilai, the highest bacterial abundance was measured in the metalimnion and near the bottom (up to 10.7 × 10⁶ cell/mL); in Lake Ramunelis it was in the anoxic hypolimnion (up to 22.4 × 10⁶ cell/mL). Increased water mineralization (0.5–1.2 g/L) with the domination of SO ₄ ^2? and Ca²⁺ ions created favorable conditions for the development of sulfate-reducing bacteria; hydrogen sulfide produced as a result of their life activity facilitated the development of sulfur-oxidizing bacteria. The pigment analysis of phototrophic green and purple sulfur bacteria showed the domination of green sulfur bacteria in the enrichment culture. The results of phylogenetic analysis showed that Chlorobium limicola dominated in the enrichment culture for the green sulfur bacteria, whereas purple nonsulfur bacteria of the genus Rhodopseudomonas dominated in the enrichment culture for the purple sulfur bacteria.     

Anoxygenic phototrophic bacteria of the high-altitude meromictic Lake Gek-Gel,Azerbaijan

The anoxygenic phototrophic bacterial community of the high-altitude meromictic Lake Gek-Gel (Azerbaijan) was investigated in September 2003. The highest concentration of bacteriochlorophyll e (48 μg/l) was detected at a depth of 30 m; the peak of bacteriochlorophyll a (4.5 μg/l) occurred at 29 m. Phylogenetic analysis revealed that brown-colored green sulfur bacteria Chlorobium phaeobacteroides predominated in the lake. Nonsulfur purple bacteria phylogenetically close to Blastochloris sulfoviridis were found in insignificant amounts; these organisms have not been previously reported in Lake Gek-Gel.     

Distribution of dissolved organic carbon in lakes of different trophic types

The distributions of dissolved organic carbon (DOC) in the warm season were elucidated in ten lakes of different trophic types in Japan, Russia, and China. DOC showed similar vertical distributions in all the lakes in summer when thermal stratification occurred. DOC in the epilimnion was higher than the value of 0.8mgCl^–1 found in the hypolimnion. In three Japanese lakes, hypolimnion DOC was negatively correlated with apparent oxygen utilization (AOU), reflecting the net oxidation of DOC using the dissolved oxygen in lake water. The DOC:O₂ ratios (0.115–0.179), calculated by the slopes of the regression lines of DOC versus AOU in hypolimnion water, were as low as those of deep-sea water, which indicates low bioavailability of lake water DOC for heterotrophic bacteria. DOC and conductivity did not correlate well except in two Japanese lakes: one showed a positive correlation and the other a negative correlation, indicating DOC loading from the inflowing rivers. Eutrophic lakes tended to have higher DOC values than meso- and oligotrophic lakes, and DOC values in the surface water negatively correlated with Secchi depths.     

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.     

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.     

Development of gene transfer methods forRubrivivax gelatinosus S1: construction, characterization and complementation of apuf operon deletion strain

Gene transfer systems were developed inRubrivivax (Rx.) gelatinosus S1. First, a system for conjugative transfer of mobilizable plasmids fromEscherichia coli toRx. gelatinosus S1 was established. Secondly, optimal conditions for the transformation ofRx. gelatinosus S1 by electroporation were determined. A puf strain was constructed. Complementation with thepuf operon from a wild-type strain cloned in a replicative plasmid restored photosynthetic growth. Two insertion strains were also selected. All the strains constructed were green, due to a change in carotenoid content. Characterization of these strains provides genetic evidence for a superoperon organization in this bacterium.     

A novel cilia-based feature within the food grooves of the ctenophore Mnemiopsis mccradyi Mayer

We describe a novel compound ciliary structure (g-cilium) from the food groove of the lobate ctenophore Mnemiopsis mccradyi. G-cilia are small, flat compound ciliary organelles that are oriented with their tips pointing toward the mouth. Typically three to four rows of g-cilia line the inner surface of the tentacular groove, which together with the transport groove, make up the food groove. G-cilium cells are 11.4 m long and 4.2 m wide at the g-cilium base. The g-cilium itself is 3.4 m long and tapers to a flat, sharp tip. G-cilia are not motile but are surrounded by many hundreds of smaller, actively motile cilia that beat with orally-directed effective strokes. G-cilia contain 50 conventional `9+2' cilia embedded in a fibrous core that arises from the cell body. In addition, g-cilia contain mitochondria, thousands of small membrane-bounded vesicles and rod bacteria. G-cilia basal bodies are anchored by large, strongly-banded rootlets that extend approximately the entire length of the cell. G-cilia may have organizational, sensory and/or secretory function within the feeding apparatus. Their placement strongly suggests that they play critical roles in feeding. They may enhance the efficiency of prey capture and so contribute to M. mccradyi's well-known voracious appetite. By enhancing prey capture they probably play a critical role in the capacity of this organism to follow prey dynamics, so contributing to dense blooms in mid-late summer in coastal regions.