[Poly- β -Hydroxybutyrate Accumulation by Rhodobacter sphaeroides Phase Variants].

The Rand M variants of a purple photosynthetic bacterium Rhodobacter sphaeroides 2R grown on a medium with acetate accumulate poly- β-hydroxybutyrate (PHB). Accumulation of this polymer occurs in the cells grown either anaerobically on the light or aerobically in the dark. On the medium with C/N imbalance (C/N = 4), PHB content during the stationary growth phase under aerobic conditions in the dark was 40 and 70% of the dry biomass of the R and M variant, respectively.

[metabolism of the phase variants of the phototrophic bacterium Rhodobacter sphaeroides].

Growth, bacteriochlorophyll a content, electron transport chain (ETC), and activities of the tricarboxylic acid (TCA) cycle enzymes were studied in R and M phase variants of Rhodobactersphaeroides cells grown anaerobically in the light and aerobically in the dark. Under all cultivation conditions tested, bacteriochlorophyll a content was 2-3 times lower in the cells of the M. variant compared to the R variant, which therefore was predominant in the cultures grown in the light.

[Use of genes of carbon metabolism enzymes as molecular markers of Chlorobi Phylum representatives].

This work examined the feasibility of using certain genes of carbon metabolism enzymes as molecular markers adequate for studying phylogeny and ecology of green sulfur bacteria (GSB) of the Chlorobi phylum. Primers designed to amplify the genes of ATP citrate lyase (aclB) and citrate synthase (gltA) revealed the respective genes in the genomes of all of the newly studied GSB strains. The phylogenetic trees constructed based on nucleotide sequences of these genes and amino acid sequences of the conceptually translated proteins were on the whole congruent with the 16S rRNA gene tree, with the single exception of GltA of Chloroherpeton thalassium, which formed a separate branch beyond the cluster comprised by other representatives of the Chlorobi phylum.

[Comparative study of metabolism of the purple photosynthetic bacteria grown in the light and in the dark under anaerobic and aerobic conditions].

For three species of anoxygenic phototrophic alphaproteobacteria differing in their reaction to oxygen and light, physiological characteristics (capacity for acetate assimilation, activity of the tricarboxylic acid (TCA) cycle enzymes, respiration, and the properties of the oxidase systems) were studied. Nonsulfur purple bacteria Rhodobacter sphaeroides, Rhodobaca bogoriensis, and aerobic anoxygenic phototrophic bacteria Roseinatronobacter thiooxidans were the subjects of investigation. All these organisms were able to grow under aerobic conditions in the dark using the respiratory system with cytochrome aa3 as the terminal oxidase.

[Enzymes of the citramalate cycle in Rhodospirillum rubrum].

Rhodospirillum rubrum is among the bacteria that can assimilate acetate in the absence of isocitrate lyase, the key enzyme of glyoxylate shunt. Previously we have suggested the functioning of a new anaplerotic cycle of acetate assimilation in this bacterium: citramalate cycle, where acetyl-CoA is oxidized to glyoxylate. This work has demonstrated the presence of all the key enzymes of this cycle in R.

[Ecophysiology and polymorphism of the unicellular extremely natronophilic cyanobacterium Euhalothece sp. Z-M001 from Lake Magadi].

Strain Z-M001 of a unicellular cyanobacterium, assigned by analysis of the 16S rRNA gene sequence to the phylogenetic group of the generic level Euhalothece, was isolated from soda Lake Magadi. It was shown that strain Z-M001, unlike all other known cultured and uncultured organisms of the Euhalothece group, is extremely natronophilic, and it was named accordingly "Euhalothece natronophila". In its ecophysiological characteristics, it is comparable to extremely alkaliphilic organotrophic natronobacteria, which is essential for soda ecosystems, because cyanobacteria belong to primary producers.

[Transport systems for carbonate in the extremely natronophilic cyanobacterium Euhalothece sp].

The effect of carbonate concentration, pH of the medium, and illumination intensity on the major physiological characteristics (growth rate and the intensities of CO2 assimilation and oxygen photoproduction) of the natronophilic cyanobacterium Euhalothece sp. Z-M001 have been studied. It was established that the investigated microorganism has at least two transport systems (TS) for CO2, which differ in both the pH optimum and substrate affinity: TS I has a pH, 9.

[Chlorobaculum macestae sp. nov., a new green sulfur bacterium].

The investigated green sulfur bacterium, strain M, was isolated from a sulfidic spring on the Black Sea Coast of the Caucasus. The cells of strain M are straight or curved rods 0.6-0.

[Phylogeny of anoxygenic filamentous phototrophic bacteria of the family Oscillochloridaceae as inferred from comparative analyses of the rrs, cbbL, and nifH genes].

Phylogeny of anoxygenic filamentous phototrophic bacteria (AFPB) of the family Oscillochloridaceae (Oscillochloris trichoides DG6T and the recently isolated strains Oscillochloris sp. R and C6) was studied based on comparative analyses of the genes coding for 16S rRNA (rrs), ribulose- 1,5-bisphosphate carboxylase/oxygenase (cbbL), and nitrogenase (nifH). The sequences of the genes studied proved to be identical in the three strains, which is in agreement with data obtained earlier that showed lack of differentiating phenotypic distinctions between these strains; therefore, it is proposed that the new strains should be identified as representatives of the species O.

[The mechanism of acetate assimilation in purple nonsulfur bacteria lacking the glyoxylate pathway: enzymes of the citramalate cycle in Rhodobacter sphaeroides].

The mechanism of acetate assimilation by the purple nonsulfur bacterium Rhodobacter sphaeroides, which lacks the glyoxylate shortcut, has been studied. In a previous work, proceeding from data on acetate assimilation by Rba. sphaeroides cell suspensions, a suggestion was made regarding the operation, in this bacterium, of the citramalate cycle.

[The mechanism of acetate assimilation in purple nonsulfur bacteria lacking the glyoxylate pathway: acetate assimilation in Rhodobacter sphaeroides cells].

The mechanism of acetate assimilation in the purple nonsulfur bacterium Rhodobacter sphaeroides, which lacks the glyoxylate pathway, is studied. It is found that the growth of this bacterium in batch and continuous cultures and the assimilation of acetate in cell suspensions are not stimulated by bicarbonate. The consumption of acetate is accompanied by the excretion of glyoxylate and pyruvate into the medium, stimulated by glyoxylate and pyruvate, and inhibited by citramalate.

[Carbon metabolism of filamentous anoxygenic phototrophic bacteria of the family Oscillochloridaceae].

The carbon metabolism of representatives of the family Oscillochloridaceae (Oscillochloris trichoides DG6 and the recent isolates Oscillochloris sp. R, KR, and BM) has been studied. Based on data from an inhibitory analysis of autotrophic CO2 assimilation and measurements of the activities of the enzymes involved in this process, it is concluded that, in all Oscillochloris strains, CO2 fixation occurs via the operation of the Calvin cycle.

[An oligonucleotide primer system for amplification of the ribulose-1,5-bisphosphate carboxylase/oxygenase genes of bacteria of various taxonomic groups].

Based on the analysis of GenBank nucleotide sequences of the cbbL and cbbM genes, coding for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC), the key enzyme of the Calvin cycle, a primer system was designed that allows about 800-bp-long fragments of these genes to be PCR-ampliflied in various photo- and chemotrophic bacteria. The efficiency of the designed primer system in detection of RuBPC genes was demonstrated in PCR with DNA of taxonomically diverse bacteria possessing RuBPC genes with a known primary structure. Nucleotide sequences of RuBPC gene fragments of bacteria belonging to the genera Acidithiobacillus.

[A comparative study of the isocitrate dehydrogenases of Chlorobium limicola forma Chlorobium thiosulfatophilum and Rhodopseudomonas palustris].

The carboxylation of 2-oxoglutarate in the reductive tricarboxylic acid cycle in the obligate photolithotroph Chlorobium limicola forma thiosulfatophilum and the oxidation of isocitrate in the tricarboxylic acid cycle in the photoheterotroph Rhodopseudomonas palustris are catalyzed by isocitrate dehydrogenases. A comparative study of these enzymes isolated from the two bacteria showed that they virtually do not differ in the enzymatic and kinetic properties.

[Participation of inorganic phosphates as electron donors in the primary reactions of photosynthesis in Rhodobacter sphaeroides].

The formation of ATP during photophosphorylation in chromatophores from purple nonsulfur bacterium Rhodobacter sphaeroides in the presence of phenazine methosulfate and without exogenous electron carriers under constant illumination and by the action of single light flashes was studied. It was shown that the photoinduced transport of electrons to the exogenous electron acceptor depends on phosphate. It was assumed that phosphate ions are electron donors in the reaction center P870; by the action of light, P870 converts the phosphate ion HPO4(2-) into anion radical HPO4-.

[Dark metabolism of acetate in Rhodospirillum rubrum cells, grown under photoheterotropic conditions].

The mechanism of the dark assimilation of acetate in the photoheterotrophically grown nonsulfur bacterium Rhodospirillum rubrum was studied. Both in the light and in the dark, acetate assimilation in Rsp. rubrum cells, which lack the glyoxylate pathway, was accompanied by the excretion of glyoxylate into the growth medium.

[On the mechanism of autotrophic fixation of carbone dioxide by Chloroflexus aurantiacus].

The activity of two carboxylating enzymes was studied in the green filamentous bacterium Chloroflexus aurantiacus. The carboxylation reaction involving pyruvate synthase was optimized using 14CO2 and cell extracts. Pyruvate synthase was shown to be absent from cells of Cfl.

[The glutamine synthetase-glutamate synthase system in Rhodopseudomonas sphaeroides].

The phototrophic purple bacterium Rhodopseudomonas sphaeroides, strain 2R, can assimilate ammonium by means of glutamine synthetase and glutamate synthase. A higher activity of glutamine synthetase is displayed by cells grown in the medium with glutamate or in the atmosphere of molecular nitrogen. The activity of glutamate synthase also rises when cells grow in the atmosphere of N2.

[Propionate metabolism of Ectothiorhodospira shaposhnikovii during growth in the dark].

Assimilation of propionate by Ectothiorhodospira shaposhnikovii growing under the aerobic conditions in the dark, like in the light involves carboxylation of propionyl-CoA with the participation of biotin-dependent carboxylase. The succinate being formed is transformed in the reactions of the citric acid cycle and the glyoxylate shunt. This is corroborated by the determination of the enzyme activity manifested by cell extracts, by the composition and kinetics of labeled products, as well as by the action of the inhibitors of the citric acid cycle (fluoroacetate, malonate) and avidin on the assimilation of 14C-propionate and 14CO2 by the cells.

[Ectothiorhodospira shaposhnikovii respiration when growing in light and in darkness].

The respiration of the purple phototrophic bacterium Ectothiorhodospira shaposhnikovii grown in the light under the anaerobic conditions or in the dark in the presence of oxygen is stimulated with sulfide, NNNN-tetramethyl-p-phenylenediamine (TMPD) + ascorbate and, to a less extent, organic substrates. The electron transport system of the organism is characterized by weak activities of NADH- and NADPH-oxidoreductases and a weak activity of the oxidase region. The respiration of intact cells in the presence of various substrates and the activity of enzymes of the respiration chain in E.

[ATP-dependent citrate lyase in the green phototrophic bacterium, Chlorobium limicola].

Cell-free extracts of the green sulfur bacterium Chlorobium limicola forma thiosulfatophilum, strains 1C and L, grown autotrophically and in media with organic substances were shown to cleave citrate with the formation of oxaloacetate and acetyl-CoA only when ATP, CoA and Mg2+ were added. These results suggest that C. limicola f.

[Acetate metabolism in Ectothiorhodospira shaposhnikovii growing in the dark].

When the cells of Ectothiorhodospira shaposhnikovii assimilated 1- and 2-14C-acetate for a short period of time in the dark under aerobic conditions, the greatest amount of 14C was found after 5 sec in malate, succinate and aspartate. The content of 14C in these compounds decreased in due time, but increased in phosphoglyceric acid and in phosphoric esters of sugars, citrate, alanine and glutamate. The composition and kinetics of labeled products formed during the assimilation of 14C-acetate by the cells in the dark did not depend on the presence of thiosulfate.