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Biomedical subjects

A M Boronin

Publications and source records attributed to A M Boronin.

At least 19 recordsLinked to original sources
PubMed2003

[Transduction of plasmid antibiotic resistance determinants with pseudo-T-even bacteriophages].

Transduction of antibiotic resistance determinants of the plasmid pBR322 with pseudoT-even bacteriophages RB42, RB43, and RB49 was studied. It is established that antibiotic resistance determinants of plasmid pBR322 from Escherichia coli recA(+)- and recA(-)-donor strains do not differ significantly in respect to the efficiency of transduction. Amber mutants RB43-21, RB43-33, and a double amber mutant RB43am21am33 were obtained. These mutants facilitated transduction experiments in some cases. Transduction of antibiotic resistance markers of the vector plasmid pBR325 and recombinant plasmid pVT123, containing a DNA fragment with hoc segE uvsW genes of phage T4, was studied. The frequency of appearance of transductants resistant to pseudoT-even bacteriophages used in transduction was determined, and the sensitivity of resistant transductants to 32 RB bacteriophages and also to phages lambda, T2, T4, T5, T6, T7, and BF23 was estimated. The efficiency of plating pseudoT-even bacteriophages RB42 and RB43 on strain E. coli 802 himA hip carrying mutations in genes that encode subunits of the Integration Host Factor (IHF) was shown to be higher than on isogenic strain E. coli 802. The growth of pseudoT-even bacteriophages limited in vivo by modification-restriction systems of chromosomal (EcoKI, EcoBI), phage (EcoP1I), and plasmid (EcoRI, EcoR124I, and EcoR124II) localization was analyzed. It was shown that these phages were only slightly restricted by the type I modification-restriction systems EcoBI, EcoR124I, and EcoR124II. Phage RB42 was restricted by systems EcoKI, EcoP1I, and EcoRI; phage RB43, by systems EcoKI and EcoRI; and phage RB49, by the EcoRI modification-restriction system.

DNA Helicases↗
PubMed2003

[Structural and functional variability of genetic systems for catabolizing polycyclic aromatic hydrocarbons in Pseudomonas putida strains].

The genetic control of naphthalene, phenanthrene, and anthracene biodegradation was studied in three Pseudomonas putida strains isolated from coal tar- and oil-contaminated soils. These strains isolated from different geographical locations contained similar catabolic plasmids controlling the first steps of naphthalene conversion to salicylate (the nah1 operon), functionally inoperative salicylate hydroxylase genes, and genes of the metha-pathway of catechol degradation (the nah2 operon). Salicylate oxidation in these strains is determined by genes located in trans-position relative to the nah1 operon: in strains BS202 and BS3701, they are located on the chromosome, and in the strain BS3790, on the second plasmid.

Base Sequence↗
PubMed2001

Purification and characterization of a salicylate hydroxylase involved in 1-hydroxy-2-naphthoic acid hydroxylation from the naphthalene and phenanthrene-degrading bacterial strain Pseudomonas putida BS202-P1.

1-Hydroxy-2-naphthoate is formed as an intermediate in the bacterial degradation of phenanthrene. A monooxygenase which catalyzed the oxidation of 1-hydroxy-2-naphthoate to 1,2-dihydroxynaphthalene was purified from the phenanthrene- and naphthalene-degrading Pseudomonas putida strain BS202-P1. The purified protein had a molecular weight of 45 kDa and required NAD(P)H and FAD as cofactors. The purified enzyme also catalysed the oxidation of salicylate and various substituted salicylates. The comparison of the Km and Vmax values for 1-hydroxy-2-naphthoate and salicylate demonstrated a higher catalytic efficiency of the enzyme for salicylate as a substrate. A significant substrate-inhibition was detected with higher concentrations of 1-hydroxy-2-naphthoate. The aminoterminal amino acid sequence of the purified enzyme showed significant homologies to salicylate 1-monooxygenases from other Gram negative bacteria. It was therefore concluded that during the degradation of phenanthrene the conversion of 1-hydroxy-2-naphthoate to 1,2-dihydroxynaphthalene is catalysed by a salicylate 1-monooxygenase. Together with previous studies, this suggested that the enzymes of the naphthalene pathway are sufficient to catalyse also the mineralization of phenanthrene.

Amino Acid Sequence↗
PubMed2000

Involvement of naphthalene dioxygenase in indole-3-acetic acid biosynthesis by Pseudomonas putida.

Two variants of plant growth-promoting strain Pseudomonas putida BS1380 harboring the naphthalene degradative plasmid pBS2 and the recombinant plasmid pNAU64 that contains the genes encoding for naphthalene dioxygenase were constructed by conjugation. The ability of this strain to produce phytohormone indole-3-acetic acid from different carbon sources was studied. Indole-3-acetic acid synthesis by these transconjugants was 15-30 times as much in contrast to a wild-type strain with glucose as the sole carbon source. No difference was observed in other carbon or nitrogen sources. It is suggested that naphthalene dioxygenase is involved in the conversion of indole-3-pyruvic acid to indole-3-acetic acid.

Cloning, Molecular↗
PubMed2000

Involvement of the respiratory chain of gram-negative bacteria in the reduction of tellurite.

The terminal oxidases of the respiratory chain of seven strains of gram-negative bacteria were shown to be involved in the reduction of tellurite. The rate of tellurite reduction correlated with the intensity of respiration. The inhibitors of terminal oxidases, carbon monoxide and cyanide, inhibited the reduction of tellurite. In Pseudomonas aeruginosa PAO ML4262 and P. aeruginosa PAO ML4262 (pBS 10), the respiratory chain was found to contain three types of cytochrome c, one of which (the carbon monoxide-binding cytochrome c) was involved in the reduction of tellurite. Agrobacterium tumefaciens VKM B-1219, P. aeruginosa IBPM B-13, and Escherichia coli G0-102bd++ cells contained oxidases aa3, bb3, and bd, respectively. The respiratory chain of other strains contained two oxidases: E. coli DH5alpha of bb3- and bd-type, and Erwinia carotovora VKM B-567 of bo3- and bd-type. All the strains under study reduced tellurite with the formation of tellurium crystallites. Depending on the position of the active center of terminal oxidases in the plasma membrane, the crystallites appeared either in the periplasmic space [P. aeruginosa PAO ML4262 and P. aeruginosa PAO ML4262 (pBS10)], or on the outer surface of the membrane (A. tumefaciens VKM B-1219 and P. aeruginosa IBPM B-13), its inner surface (E. coli G0-102bd++), or on both surfaces (E. coli DHaalpha and E. carotovora VKM B-567).

Cell Compartmentation↗
PubMed1998

Effects of high oxygen concentrations on microbial biosensor signals. Hyperoxygenation by means of perfluorodecalin.

Amperometric biosensors register oxygen depletion in response to analyte catabolism, and thus are limited by the availability of dissolved oxygen. Microbial sensors containing immobilized cells of Gluconobacter oxydans were hyperoxygenated to 400% of control levels and the effects on sensor responses to glucose were determined. Oxygenated perfluorodecalin (a completely fluorinated organic substance) was as effective in hyperoxygenation as direct sparging with O2, increasing sensor base medium oxygen concentrations from 9.3 to 37 mg/l. Hyperoxygenation enhanced maximal biosensor response amplitudes, particularly at high cell loading densities. Maximal response rates were also improved, although less dramatically. Results suggest that hyperoxygenation may be a new general approach for modulating biosensor responses.

Acetobacteraceae↗
PubMed1998

A seven-gene locus for synthesis of phenazine-1-carboxylic acid by Pseudomonas fluorescens 2-79.

Pseudomonas fluorescens 2-79 produces the broad-spectrum antibiotic phenazine-1-carboxylic acid (PCA), which is active against a variety of fungal root pathogens. In this study, seven genes designated phzABCDEFG that are sufficient for synthesis of PCA were localized within a 6.8-kb BglII-XbaI fragment from the phenazine biosynthesis locus of strain 2-79. Polypeptides corresponding to all phz genes were identified by analysis of recombinant plasmids in a T7 promoter/polymerase expression system. Products of the phzC, phzD, and phzE genes have similarities to enzymes of shikimic acid and chorismic acid metabolism and, together with PhzF, are absolutely necessary for PCA production. PhzG is similar to pyridoxamine-5'-phosphate oxidases and probably is a source of cofactor for the PCA-synthesizing enzyme(s). Products of the phzA and phzB genes are highly homologous to each other and may be involved in stabilization of a putative PCA-synthesizing multienzyme complex. Two new genes, phzX and phzY, that are homologous to phzA and phzB, respectively, were cloned and sequenced from P. aureofaciens 30-84, which produces PCA, 2-hydroxyphenazine-1-carboxylic acid, and 2-hydroxyphenazine. Based on functional analysis of the phz genes from strains 2-79 and 30-84, we postulate that different species of fluorescent pseudomonads have similar genetic systems that confer the ability to synthesize PCA.

Amino Acid Sequence↗
PubMed1997

Competition of plasmid-bearing Pseudomonas putida strains catabolizing naphthalene via various pathways in chemostat culture.

Plasmid-carrying Pseudomonas putida strains degrade naphthalene through different biochemical pathways. The influence of various combinations of host bacteria and plasmids on growth characteristics and competitiveness of P. putida strains was studied in chemostat culture at a low dilution rate (D = 0.05 h-1) with naphthalene as the sole source of carbon and energy. Under naphthalene limitation, the plasmid-bearing strains degrading naphthalene that use catechol 1,2-dioxygenase for catechol oxidation (ortho pathway), were the most competitive. The strains bearing plasmids that control naphthalene catabolism via catechol 2,3-dioxygenase (meta pathway), were less competitive. Under these conditions the strain carrying plasmid pBS4, which encodes for naphthalene catabolism via gentisic acid, was the least competitive.

Bacterial Proteins↗
PubMed1997

[Genetic control of naphthalene biodegradation by a strain of Pseudomonas sp. 8909N].

The ability of Pseudomonas sp. 8909N to grow using Naphthalene and salicylate as the sole source of carbon and energy is mediated by the presence of an 80-kb conjugative pBS1145 plasmid in this strain. Structural genes for naphthalene degradation in pBS1145 plasmid are homologous to those in the known NAH7 plasmid. Conjugational transfer of pBS1145 from the original strain is accompanied by a deletion of a plasmid DNA fragment that does not affect the Nah+Sal+ phenotype. Plasmid pBS1145 specifies a low constitutive level of catechol-2,3-dioxygenase, the key enzyme of the metha-pathway of catechol degradation. Activity of this enzyme is induced in the presence of salicylate. Enzymes of both the metha and ortho-pathway of catechol degradation (catechol-2-3-dioxygenase) were shown to operate in the process of naphthalene degradation in Pseudomonas sp. 8909N. The ability of this strain to bring about transformation of polycyclic aromatic hydrocarbon phenanthrene is also controlled by pBS1145 plasmid.

Biodegradation, Environmental↗
PubMed1996

FET-microbial sensor for xylose detection based on Gluconobacter oxydans cells.

A potentiometric biosensor for xylose was devised utilizing Gluconobacter oxydans whole cells. Immobilization methods based on physical adsorption were used for G. oxydans cells and extracellular pH changes resulting from xylose dehydrogenation were monitored by a field effect transistor (FET). The G. oxydans, FET-based sensor detected xylose at a lower limit of 0.5 mM. From 5.0 to 30 mM xylose, the response of the sensor was linear. Expectedly, output signals were significantly suppressed by buffer (Tris-HCl). Responses were essentially stable for at least four weeks of storage and showed only a slight loss of initial xylose sensitivity. Xylitol exerted an insignificant influence on the sensor's response to xylose. However, the response to glucose was 5 times higher in relation to that of xylose at the same concentration (1 mM). For xylose determinations in the presence of glucose, a two-step assay is discussed.

Acetobacteraceae↗
PubMed1995

Cytological aspects of resistance to potassium tellurite conferred on Pseudomonas cells by plasmids.

The ultrastructure of strains Pseudomonas putida BS228 and Pseudomonas aeruginosa ML4262 harboring plasmids pBS10, pBS31, and pBS221, which determine resistance to potassium tellurite, was studied. Bacteria were grown in media containing increasing concentrations of potassium tellurite. Crystalline structures containing tellurium appeared in their periplasmic space. The dynamics of crystal growth was studied. Crystals were released into the medium by pinching off of the outer membrane vesicles containing growing crystals. A possible mechanism of this process was described; cytobiochemical peculiarities were discussed.

Crystallization↗