PubMed Health⌕ Search

Biomedical subjects

D I Nikitin

Publications and source records attributed to D I Nikitin.

At least 19 recordsLinked to original sources
PubMed2000

The polar-lipid composition of the sphingolipid-producing bacterium Flectobacillus major.

Polar lipids comprise about 90% of the total chloroform-methanol extractable lipids of the Gram-negative, fresh-water, ring-forming bacterium Flectobacillus major FM and consist of at least 10 constituents. These are aminophosphosphingolipids, 2-N-(2'-D-hydroxy-13'-methyltetradecanoyl)-15-methyl-4(E)-hexad ecasph ingenyl-1-phosphoethanolamine (36.8% of the total polar lipids) and its 2'-deoxy derivative (3.7%); sulfonic-acid analogues of ceramide, 2-D-(2'-D-hydroxy-13'-methyltetradecanoyl)amino-3-D-hydroxy-15-met hyl hexadecane-1-sulfonic acid (18.1%) and its 2'-deoxy derivative (3. 5%); a lipoamino acid, N-[3-D-(15'-methylhexadecanoyloxy)-15-methylhexadecanoyl]-gl ycine (3. 7%); a lipodipeptide, N-¿N'-[3"-D-(15"'-methylhexadecanoyloxy)-15"-methylhexadecanoyl ]glycy l¿-L-serine (7.8%); 1,2-diacyl-sn-glycero-3-phosphoethanolamine (7. 7%), 1,2-diacyl-3-alpha-D-galactopyranosyl-sn-glycerol (2.9%); ceramide phospho-myo-inositol (4.9%), and a previously described unusual glycosphingolipid, 7-deoxy-7-amino-D-manno-heptulosonopyranosyl (1-hydroxycarbonyl-6-deoxy-6-amino-alpha-D-mannopyranosyl) ceramide (10.9%); the last two lipids contain only 15-methyl-4(E)-hexadecasphingenine as a long-chain base. The sole structural type of amide-bound fatty acids in the sphingolipids, including the sulfonic-acid analogues, is iso-15:0, either non-hydroxylated or hydroxylated at 2-C, whereas 15-methylhexadecanoic acid is the major ester-bound fatty acid in the remaining lipids.

Chemical Fractionation↗
PubMed1999

A novel glycosphingolipid from gram-negative aquatic bacteria.

The chloroform-methanol extractable lipids of the Gram-negative fresh-water bacteria Arcocella aquatica NO-502 and Flectobacillus major FM were found to contain an unusual ninhydrin-positive glycolipid. It was purified by two-stage silica gel-column chromatography. By the use of IR and (1)H-NMR spectroscopy, mass spectrometry and chemical-degradation experiment, the lipid was established to be 1-O-monoglycosyl ceramide, the carbohydrate moiety of which was the alpha-pyranose-ring form of 7-desoxy-7-amino-D-manno-heptulosonic acid, or 1-hydroxycarbonyl-6-deoxy-6-amino-alpha-D-mannopyranose. The ceramide portion consisted mainly (by 95% in the A. aquatica glycolipid and 80% in the F. major glycolipid) of 2-N-(2'-D-hydroxy-13'-methyltetradecanoyl)-15-methyl-4(E)-hexad ecasph ingenine. The minor molecular species differed from the major one only in fatty acid structure. The glycolipid accounted for 8 and 11% of the total lipids extracted from A. aquatica NO-502 and F. major FM cells, respectively.

Glycosphingolipids↗
PubMed1998

A novel sulfonic-acid analogue of ceramide is the major extractable lipid of the gram-negative marine bacterium Cyclobacterium marinus WH.

The extractable lipids of the gram-negative, sea-water bacterium Cyclobacterium marinus strain WH contain about 94% of polar components which consist of two phospholipids, phosphatidylethanolamine (29% of the total lipids) and phosphatidylcholine (7%), and two phosphorus-free lipids. One of the latter has been shown to be a novel sulfonic-acid analogue of ceramide, 2-D-(2'-D-hydroxy-13'-methyltetradecanoyl) amino-3-D-hydroxy-15-methylhexadec-4 (E)-en-1-sulfonic acid (48%), and other is a lipodipeptide, N-[3-d-(13'-methyltetradecanoyloxy)-15-methylhexadecanoyl] glycyl-L-serine (11%), which has so far been found only in a Flavobacterium sp. strain. The dominant fatty acid residues of the phospholipids are iso-15:0, n-16:0, 16:1 and 18:1, the acyl residues linked to the sn-1 carbon of the glycerol moiety being somewhat more saturated as compared with those located at the sn-2 position. A new procedure for determination of the absolute configuration of 2- and 3-hydroxy fatty acids is briefly described.

Ceramides↗
PubMed1997

Unusual lipid composition of the gram-negative, freshwater, stalked bacterium Caulobacter bacteroides NP-105.

The extractable lipids of the gram-negative, stalked, freshwater bacterium Caulobacter bacteroides NP-105 account for about 9.5% by weight of dry cells, polar lipids comprising up to 95% of the total. The polar lipids consist of five glycolipids, namely, 1,2-diacyl-3-alpha-D-glucopyranosyl-sn-glycerol (I) (34% of the total), 1,2-diacyl-3-alpha-D-[6'-(1",2"-diacyl-sn-glycero-3-phospho)]glucopyranosyl-sn-glycerol (II) (7%), 1,2-diacyl-3-a-D-glucuronopyranosyl-sn-glycerol (III) (17%), 1,2-diacyl-3-alpha-D-(6'-sulfo)quinovopyranosyl-sn-glycerol (V) (9%), and 1,2-diacyl-3-alpha-D-[4'-(alpha-D-glucopyranosyl)] glucuronopyranosyl-sn-glycerol (VI) (28%), and one glycerophospholipid, 1,2-diacyl-sn-glycero-3-phosphoglycerol (IV) (5%). The main fatty acyls of the lipids are n-16:0, cis-18:1 omega7, and cis-11,12-methyleneoctadecanoic (lactobacillic) acid residue. Of the 6 lipids listed, only 3 (I, IV, and V) can be treated as widely encountered. However, sulfonic glycolipid V is a characteristic lipid component of photosynthetic organisms rather than non-photosynthetic ones. Phosphatidyl derivatives of glycosyldiacylglycerols of type II normally occur in gram-positive bacteria, among gram-negative bacteria they have been revealed only in two species of the Pseudomonas genus. Glucuronosyl and alpha-glucosyl-a-glucuronosyl diacylglycerols such as III and VI, respectively, are very rare lipids, the latter being found so far only in a Streptomyces strain.

Caulobacter↗
PubMed1996

Lipid composition of the gram-negative, budding, seawater bacterium Hyphomonas jannaschiana lacking in phospholipids.

The extractable polar lipids of the gram-negative, budding, seawater bacterium Hyphomonas jannaschiana VP-2T were shown to consist of five glycolipids, namely, 1,2-diacyl-3-alpha-D-glucopyranosyl-sn-glycerol (I) (25% of the total lipids), 1,2-diacyl-3-alpha-D-glucuronopyranosyl-sn-glycerol (II) (41%), taurine-amide of II (III) (32%), acyl-D-glucuronopyranoside (IV) (0.9%), and acyl-3-O-acyl-D-glucuronopyranoside (V) (0.4%); glycolipid (III) was described by the authors previously. In addition, small amounts of poly(beta-hydroxybutyrate) and free fatty acids were present in the lipids extracted. Neither phospholipids nor low-polarity lipids, such as fatty acid esters of glycerol or fatty alcohols, were detected. Glycolipids I, II, IV, V were isolated in chromatographically pure state by chromatography on DEAE-cellulose and silica-gel columns. Their structures were established using chromatographic, spectrometric and chemical-degradation methods. In glyceroglycolipids I and II, unsaturated fatty acid residues were located predominantly at the sn-1 carbon of the glycerol moiety while saturated ones were linked mainly to the sn-2 carbon.

Glucosides↗
PubMed1996

Lipid composition of the phosphatidylcholine-producing bacterium Hyphomicrobium vulgare NP-160.

The extractable lipids of the PC-producing, methylotrophic, budding bacterium Hyphomicrobium vulgare NP-160 grown in a mineral-salts medium containing methanol as the carbon source, were studied by chromatographic and spectrometric methods. They were found to be comprised of PC (35% of the total lipids), PDME (33%), PMME (1%), PE (9%), PG (10%), DPG (6%), and a non-phosphorus, ornithine-containing lipoamino acid, OL (6%). No low-polarity lipids, such as fatty acid esters of glycerol or of other alcohols, were detected. The sole fatty-acyl constituents of PDME and PMME were cis-octadec-11-enoic (cis-vaccenic) acid residues, whereas the other phospholipids contained, in addition, 1 to 5 mol % of MOA (lactobacillic acid) residues located predominantly at the sn-1 position of their glycerol residues. OL consisted of two molecular species, 2-N-[3'-(cis-octadec-11"-enoyloxy)octadecanoyl]-L- ornithine and 2-N-[3'-(cis-11", 12"-methyleneoctadecanoyloxy)octadecanoyl]-L-ornithine in the molar ratio 94:6. When the culture medium was devoid of phosphate, a threefold increase in OL together with a three-fold decrease in PE were observed, no significant changes in proportions of the remaining lipids occurring. The most striking feature of the lipid composition in this case was the presence of considerable amounts of fatty acid methyl esters, mainly methyl cis-vaccenate, along with minute amounts of wax esters.

Bacteria↗
PubMed1996

A novel glycolipid, 1,2-diacyl-3-alpha-D-glucuronopyranosyl-sn-glycerol taurineamide, from the budding seawater bacterium Hyphomonas jannaschiana.

A previously unknown glycolipid has been isolated from the budding seawater bacterium Hyphomonas jannaschiana VP-2T devoid of phospholipids. Using a combination of chromatographic, spectrometric, enzymic- and chemical-degradation methods, the structure of the lipid has been determined to be 1,2-diacyl-3-alpha-D-glucuronopyranosyl-sn-glycerol taurineamide. Its main fatty acyls are n-16:0, cis-16:1 omega 7, n-18:0, cis-18:1 omega 7, and n-19:0. The hydroxyl at the sn-1 position of the glycerol residue is acylated predominantly with unsaturated fatty acids, and the secondary hydroxyl at the sn-2 carbon is acylated mainly with saturated ones.

Bacteria↗
PubMed1991

[Some aspects of antibiotic resistance of oligotrophic bacteria].

Antibiotic resistance spectra of a large group of oligotrophic and eutrophic bacteria from the open soil and aquatic ecosystems were studied. It was shown that sometimes antibiotic resistance of the oligotrophs was of plasmid nature. A possible transfer of plasmid antibiotic resistance from oligotrophs to pathogenic eutrophic soil and aquatic bacteria in the natural ecosystems is discussed. It was demonstrated that there was no insurmountable transcription/translation barriers between oligotrophic and eutrophic bacteria though the two bacterial groups are taxonomically and evolutionally very distant. A hypothesis was proposed that oligotrophic bacteria are likely to be one of the possible pools of plasmid antibiotic resistance for pathogenic microbes. Plasmid-free strains of some oligotrophic bacteria were selected. With the method of antibioticograms, taxonomic patterns for oligotrophic bacteria of the central group were developed.

Drug Resistance, Microbial↗
PubMed1990

Evolutionary relationship of some stalked and budding bacteria (genera Caulobacter, "Hyphobacter", Hyphomonas and Hyphomicrobium) as studied by the new integral taxonomical method.

A new approach was developed for the determination of taxonomic and evolutional relationships among four genera of oligotrophic bacteria. The main idea of this approach is the algorithmized integrative analysis of the morphological and physiological specificity of these bacteria, their 5S rRNA sequences, fatty acid and lipid composition of their membranes, as well as their sensitivity to a large variety of antibiotics. It was shown that the genera Caulobacter and Hyphomonas are closely related to each other, but they are both distant from Hyphomicrobium species. The new genus, "Hyphobacter", is placed between Caulobacter and Hyphomonas. Taxonomic heterogeneity was found to exist within the genera Caulobacter and Hyphomicrobium. Evolutional pathways from Caulobacter to Hyphomicrobium are proposed on the basis of the present data. No correlations were found between the cell morphology of the organisms and their geno- and chemotaxonomy.

Anti-Bacterial Agents↗
PubMed1990

Taxonomic studies on methylotrophic bacteria by 5S ribosomal RNA sequencing.

Nucleotide sequences of 5S ribosomal RNA (rRNA) isolated from 19 strains of Gram-negative methylotrophic bacteria were determined. Comparison of these sequences allowed construction of a tentative phylogenetic tree and showed that the bacteria analysed belong to the Proteobacteria and fell into several clusters, including obligate methanotrophs, obligate methylotrophs and several groups of facultative methylotrophs. Taxonomic relations between methylotrophic and non-methylotrophic bacteria are discussed, and the polyphyletic nature of methylotrophy as a taxonomic feature is highlighted.

Base Sequence↗
PubMed1989

[Classification of methylotrophic bacteria according to 5S ribosomal RNA sequencing].

5S ribosomal RNA sequences of 33 strains of methylotrophic bacteria were determined. Tentative phylogenetic tree was constructed using the maximum topological similarity principle. Strains under study can be divided into 7 separate branches consistently with the current classification of methylotrophic bacteria. More extensive tree was also built to show the position of methylotrophic bacteria with respect to non-methylotrophic ones. One can conclude that the in contrast to obligate methane-oxidizing bacteria, facultative methylotrophic bacteria do not comprise phylogenetically separate domain on the tree.

Base Sequence↗
PubMedDate not supplied

[Use of gamma-irradiation of soil for analyzing the state of microbial coeneses].

Increasing doses of gamma-irradiation eliminate some physiological and ecologo-trophical groups from microbial cenoses in soil. Soil fungi are least resistant to the action of gamma-irradiation (do not grow on agarized soil (AS) at a dose of 0.5 Mrad). Actinomycetes are more resistant (do not grow on AS at a dose of 0.75 Mrad). Bacteria are most resistant to irradiation. Asporogenous bacteria do not grow on agarized soil at a dose of 1.25 Mrad. Sporogenous bacteria survive at higher doses (1.75 Mrad). The method of gamma-irradiation permits to accomplish differential analysis of ecological groups of soil microflora and experimental synthesis of microbial associations. The effect of gamma-irradiation on soil enzymes is weak compared with autoclaving. gamma-Irradiated soils may serve as a substrate for model experiments during analysis of microbial associations.

Bacteria↗
PubMedDate not supplied

[Species specificity and reaction of bacteria to a 50 GHz magnetic field].

The growth of cultures of bacteria with different lipid content of cell membranes in response to a 40 min exposure to alternating magnetic field of 50 Hz, 18 mT was studied. Three important phenomena were revealed. A species specificity of responses of bacteria to the magnetic field, including both inhibition and activation, was observed. The changes in the kinetics of growth of bacterial culture correlate with the type of membrane lipid complex. The information on the exposure to magnetic field is memorized by the previously exposed distilled water, which makes itself evident in responses much more intensive than the responses of the same cultures exposed immediately in the culture medium.

Bacteria↗
PubMedDate not supplied

[Specificity of bacterial response to variation of isotopic composition of water].

Culture growth of bacteria with different membrane lipid composition was studied in liquid media with different isotope content of water. The concentration of deuterium in water was varied from 0.01 to 90%. It was shown that large concentrations of deuterium cause the inhibition of all cultures except Deinococcus radiodurans, the most stable living cell. Two cultures, Methylobacterium organophilum and Hyphomonas jannaschiana, showed a pronounced activation at a deuterium concentration of 0.01%. At higher deuterium concentrations, the inhibition of culture growth was observed. The strains Renobacter vacuolatum, Arcocella aquatica NO502 and Caulobacter crescentus did not show any significant effect at low concentrations of deuterium.

Bacterial Physiological Phenomena↗
PubMedDate not supplied

[Influence of the incubation temperature on the reaction of oligotrophic bacteria to stress].

Representatives of five genera of psychroactive oligotrophic bacteria, Arcocella, Renobacter, Spirosoma, Caulobacter, and Methylobacterium, were for the first time shown to be capable of growing at a negative temperature (-2 degrees C). Long-term cultivation (for 116 days) at a low temperature under limitation by the carbon source is stressful for oligotrophic bacteria and leads to the death of a part of the cell population. The number of viable cells of Caulobacter crescentus decreased by two-three orders of magnitude. Over the studied period of time, Renobacter vacuolatum cells retained viability at a low temperature, whereas at the room temperature, the titer of colony-forming cells decreased by two orders of magnitude under starvation stress.

Alphaproteobacteria↗