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Biomedical subjects

D I Nikitin

Publications and source records attributed to D I Nikitin.

35 records · Page 2Linked to original sources
PubMedDate not supplied

[Relations of oligotrophic bacteria to oxygen].

Polluted air and the derived photochemical smog are the sources of free radicals in the atmosphere. Organic peroxides present in the smog mediate formation of peroxide radical. Oxygen species are formed by purely physical mechanisms, for instance, energy consumption converts molecular oxygen to an excited singlet state. Six active oxygen species are known: ozone, atomic oxygen, perhydroxyl, superoxide, and singlet oxygen. Singlet oxygen is the most harmful oxygen product for living cells, while hydrogen peroxide is the least harmful. Molecular oxygen is hardly toxic for prokaryotes due to an efficient protection of microbial cells by specific enzymes. This work experimentally confirms the harmlessness of molecular oxygen.

Alphaproteobacteria↗
PubMedDate not supplied

[Free iron in bacteria].

Free iron content has been estimated in autotrophic and heterotrophic bacteria. It constituted 40-50 micrograms/g dry weight as compared to 15 micrograms/g dry weight in animal cells. A method for estimation of free iron has been proposed. It is based on formation of paramagnetic dinitrosyl iron complexes by free iron and protein thiol groups or low molecular weight thiol ligands. The reasons for high iron content in bacteria have been discussed.

Bacteria↗
PubMedDate not supplied

[Clustering of oligotrophic microorganisms on the basis of their antibiotic resistance and dynamic membrane characteristics].

Some oligotrophic microorganisms were characterised in terms of their resistance against a broad spectrum of antibiotics and certain dynamic parameters of membranes obtained by analysing the EPR and NMR spectra. The oligotrophic bacteria differed in these characteristics from eutrophic microorganisms. The oligotrophic bacteria were subdivided into 3-4 subgroups different in many of the studied parameters. A new chemotaxonomic approach was proposed for the oligotrophic bacteria basing on the analysis of antibioticograms.

Anti-Bacterial Agents↗
PubMedDate not supplied

[Effect of aspartate amino acids on aspartokinase activity of oligotrophic bacteria].

The object of this work was to study the effect of aspartate amino acids taken separately or in combinations on the aspartokinase activity of Hyphomicrobium and Methylobacterium methylotrophous strains. Aspartokinase was shown to be a polyvalent enzyme regulated by the coordinated action of two amino acid pairs: lysine+threonine and threonine+methionine.

Amino Acids↗
PubMedDate not supplied

[The mixotrophy of pathogenic bacteria].

This work deals with materials on the utilization of carbon dioxide and hydrogen from gas-air mixture by Yersinia pseudotuberculosis and Listeria monocytogenes in the process of their cultivation in Hirsch's mineral medium. As follows from the data presented in these materials, the above-mentioned bacterial species are heterotrophic when the infectious process is reproduced in the body of warm-blooded animals and chemolithoautotrophic under the conditions of their life in environmental objects. Such a wide range of their metabolic plasticity ensures the dual character of their saprophytic and parasitic nature.

Biopolymers↗
PubMedDate not supplied

[High resistance of some oligotrophic bacteria to ionizing radiation].

The resistance against ionizing radiation of seven cultures of oligotrophic and eutrophic bacteria was investigated in the interval 0-360 Gr/h. It is determine that all of tested bacteria are distributed into three groups according to the lever of their resistance. Most resistant were: Methylobacterium organophilum, Pedodermatophilus halotolerans (LD50 = 270 Cr/h). These organisms are close to Deinococcus radiodurans in the survival. Middle resistance shown water-born ring-forming bacteria Flectobacillus major, Arcocella aquatica (LD50 = 173 and 210 Gr/h respectively). High sensitive were eutrophs: Pseudomonas fluorescens, Escherichia coli (LD50 = 43 and 38 Gr/h respectively). By use of X-ray microanalysis was shown that after the radiation potassium content in cell was increased and calcium content was decreased. The elements content in the cells of eutrophs (Escherichia coli) remains without change. In present paper are also discussed possible mechanisms of the resistance of oligotrophs against gamma-irradiation.

Bacteria↗
PubMedDate not supplied

[Element composition of bacterial cells of various taxa].

The elemental compositions of cells of representatives of five bacterial genera (Hyphomonas vulgare NP-160, Caulobacter bacteroides NP-105, Flectobacillus major Mm, Escherichia coli, and Spirulina platensis) was studied by electron microscopic x-ray microanalysis. The contents of P, S, Cl, K, and Ca were determined. The bacterial species studied in this work substantially differ by the contents of these elements. A high content of K is typical of S. platensis, whereas F. major, an aquatic form, is rich in Cl. The other bacterial species were had the levels of K, Ca, and the K/Ca index, which correlated with the stability of their cell membranes and resistance to stress. In E. coli, the spectrum of the elemental composition and the values of P/S and K/Ca are indicative of high energy potential and low tolerance of membranes.

Bacteria↗