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Biomedical subjects

G I Burd

Publications and source records attributed to G I Burd.

At least 19 recordsLinked to original sources
PubMed2000

Plant growth-promoting bacteria that decrease heavy metal toxicity in plants.

Kluyvera ascorbata SUD165 and a siderophore-overproducing mutant of this bacterium, K. ascorbata SUD165/26, were used to inoculate tomato, canola, and Indian mustard seeds which were then grown in soil for 25-42 days in the presence of either nickel, lead, or zinc. The parameters that were monitored included plant wet and dry weight, protein and chlorophyll content in the plant leaves, and concentration of heavy metal in the plant roots and shoots. As indicated by a decrease in the measured values of these parameters, in all instances, plant growth was inhibited by the presence of the added metal. Both bacterial strains were effective, although not always to a statistically significant extent, at relieving a portion of the growth inhibition caused by the metals. In most cases, the siderophore overproducing mutant K. ascorbata 165/26 exerted a more pronounced effect on plant growth than did the wild-type bacterium K. ascorbata SUD165. The data suggest that the ability of these bacteria to protect plants against the inhibitory effects of high concentrations of nickel, lead, and zinc is related to the bacteria providing the plants with sufficient iron.

Biodegradation, Environmental↗
PubMed1991

[A new pleiotropic mutation affecting purine metabolism, sporulation and biosynthesis of exoenzymes in Bacillus subtilis].

A pleiotropic mutation (cpm) which is localised in the vicinity of the spoA gene of Bacillus subtilis chromosome has been described. The mutation inhibits spore formation, renders bacteria auxotrophic for adenine and tyrosine, increases sensitivity to antibiotics, decreases cell motility and the ability to grow on D-ribose and D-xylose, inhibits growth of bacteriophages PBS1 and AR9 as well as enhances activity of alkaline proteinase and alpha-amylase. At the same time, the cpm mutants acquire the ability to produce inosine. Inosine excretion is connected with more than 50- and 5-fold increase in activity of 5'-nucleotidase in respect to IMP and AMP, accordingly, and 10-fold decrease in activity of purine nucleoside phosphorylase. Biosynthesis of inosine and Ade- phenotype of the cpm mutant are not mediated by the change in activity of sAMP synthetase. The nature and mechanism of action of the cpm mutation are under discussion.

5'-Nucleotidase↗
PubMed1983

[Mechanism of catabolite repression in Escherichia coli bacteria: interaction between transport proteins and adenylate cyclase].

The mechanism of catabolite repression caused by sugar transported via the phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS) and stipulated by the decrease of the adenylate cyclase activity was studied. It was demonstrated that the sensitivity of the adenylate cyclase and beta-galactosidase synthesis to methyl-L-D-glucoside (MeGlc) or sorbitol is correlated with the content and activity of glucose (EIIGlc) or mannitol enzyme II of the PTS, correspondingly. Under anaerobic conditions the cells become insensitive to catabolic repression caused by MeGlc and the adenylate cyclase activity does not decrease in the presence of the sugar despite the increased rate of MeGlc transport. The adenylate cyclase activity of the mutant with the Tn5 transposone inserted into the ptsG gene does not change in the presence of MeGlc, while the activity of adenylate cyclase and the differential rate of beta-galactosidase synthesis increase in these bacteria. The data obtained confirm the hypothesis on the "catabolite signal" which is generated when the substrate binds to its transporter, i. e. adenylate cyclase reacts to the conformational changes in the transporter being complexed with it. The strength of this complex depends on the affinity of adenylate cyclase for the transporter and on the value of the membrane potential, delta mu H+ A model is proposed, which explains the necessity of factor IIIGlc for EIIGlc binding to adenylate cyclase.

Adenylyl Cyclases↗
PubMed1981

[Interaction of the membrane transport proteins in E. coli K12].

The inhibition kinetics of NO2PheGal transport by MeGlc in E. coli K12 were studied. The inhibitory effect was observed only at definite ratio of the corresponding transport proteins -- enzyme IIglc and beta-galactoside permease. It was shown that in this case, beside the repressive effect of MeGlc on beta-galactoside transport, beta-galactosides (GalSGal) can also inhibit the rate of MeGle accumulation. The data obtained suggest that in the region of maximal inhibitory effect the conformation of both membrane proteins are changed, which leads to an increase in the activity of enzyme IIglc and its affinity for MeGlc. It was assumed that the phenomenon observed is not unique and is in general conformity with the postulate that under certain conditions many bacterial membrane proteins can come into interaction, thus changing their activity.

3-O-Methylglucose↗
PubMed1980

[Study of a pts-gene-linked pleiotropic mutation influencing expression of catabolyte-sensitive genes of Escherichia coli K-12].

Properties of the pleiotropic mutation pts17 are described. This mutation is liked to pts1 gene, which specifies the synthesis of the enzyme I of phosphoenolpyruvate-dependent phosphotransferase system (PTS) in Escherichia coli K-12. Genetic analysis has shown that pts17 mutation is located between purC and pts1 markers and that the wild type allele pts17+ has transdominant character over the mutant allele pts17. The mutant strain J6217, isogenic to parent J62, shows normal growth properties in the minimal salt media with a number of carbohydrates used as a single carbon source. The pts17 mutations does not affect the enzyme I activity, but significantly suppresses the total PTS activity in the bacterial cell extracts. The intact mutant cells reveal the enhanced rate of accumulation and phosphorylation of alpha-methylglucoside. The pts17 bacteria show 3-fold enhanced phosphohydrolase activity with glucose-6-phosphate as substrate. It is established that pts17 mutation decreases the differential rate of the L-tryptophanase synthesis and makes the process of unductions resistant to glucose catabolite repression. It is suggested that this mutation affects the activity of the PTS factor III. One can suppose that the latter mediates the influence of ptsI and ptsH mutations upon the expression of catabolite-sensitive operons in E. coli.

Chromosome Mapping↗
PubMed1980

[Alpha-methylglucoside transmembrane phosphorylation and regulation of the beta-galactoside permease activity in E. coli K12].

The interaction between alpha-methylglucoside (MeGlc) and beta-galactoside transport systems in E. coli K12 was studied. It was shown that an addition of MeGlc to bacterial cells leads to repression of [14C] lactose accumulation and o-nitrophenyl-beta-D-galactopyranoside (NO2PheGal) hydrolysis. The mutational damage of one of the components of the MeGlc transport system is accompanied by elimination of the glucoside inhibitory action. Intracellular MeGlcP and GlcP lower the efficiency of the transmembraneous transfer of beta-galactosides. The data obtained suggest that repression of the beta-galactoside permease activity during transport of the MeGlc is a result of two processes: i.e. phosphorylation-coupled translocation of MeGlc and intracellular accumulation of MeGlcP. An assumption on the intramembraneous interaction of enzyme IIGlc with beta-galactoside permease is made.

Bacterial Proteins↗
PubMed1980

[Shigella flexneri mutation giving rise to the appearance of fosfomycin-resistant avirulent forms with disordered carbohydrate utilization].

The present work analyzes pt44 mutation in Sh. flexneri resulting in the appearance of the following phenotypical properties: resistance to phosphomycin, avirulence, pleiotropic disturbances in carbohydrate utilization. The data provided by the biochemical and genetic analysis have indicated that pts44 mutation occupies the region between purC and ptsI loci on the chromosome of Sh. flexneri. Merodiploids containing the mutant allele pts44 and the plasmid including purC-ptsI-ptsH genes from E. coli K12 acquired the capacity for fermenting carbohydrates, but at the same time retained resistance to phosphomycin and avirulent properties. The presence of phosphoenol pyruvate-dependent carbohydrate phosphotransferase system in Sh. flexneri has been proved.

Anti-Bacterial Agents↗
PubMed1980

[Characteristics of attenuated immunogenic mutants of shigella flexneri selected from phosphomycin-resistant clones].

Sh. flexneri mutants No. 2a, resistant to phosphomycin (25 microgram/ml), differ in their fermentability in respect to glucose, mannitol, mannose and fructose. The mutants fall into 7 groups by this characteristic. All the resistant mutants, irrespective of the type of hydrocarbon fermentation, have lost their ability of causing keratoconjunctivitis. The decreased virulence of the phosphomycin-resistant mutants is linked with the loss of their penetration properties, although their adhesiveness and proliferative capacity on the surface HeLa cells is retained. A change in the virulence of the mutants under study is not connected with disturbances in the synthesis of O-antigen LPS. Most of these mutants are highly immunogenic.

Animals↗
PubMed1979

[Effect of the dose of ptsI- and ptsH-genes on carbohydrate transport and regulation of lac-operon activity in Escherichia coli K-12].

Phage Mu-1 cts61 was used for transposition of pts1 and ptsH genes. The received F'-factors AUF2 and AUF3 carry short fragments of the bacterial chromosome. Merodiploid strains with double pts genes were selected in sexduction crosses with the appropriate recA recipients. Effect of the gene dose was not registered in pts+/pts+ strains in the case of accumulation of the substrates of the phosphoenolpyruvate-dependent phosphotransferase system (PTS) and in the case of bacterial growth in the presence of these carbohydrates. This indicates that the enzyme (enzymes) II of the PTS is the limiting step in the transpost process. Induction of beta-galactosidase and the growth on carbohydrates not transported via the PTS (maltose, lactose) were greatly reduced in pts mutant. Introduction of the pts+ allele with episome lead to the restoration of the two above processes. These data show that the phospho approximately HPr generating system of the PTS is directly (or in indirect manner) involved in the regulation of catabolite-sensitive operons. Glucose repression was markedly increased in pts+/pts+ merodiploids as compared with pts+/pts- ones and with pts+ bacteria. Possible mechanisms of this effect are discussed.

Bacteriophage mu↗
PubMed1977

[Isolation and properties of merodiploid strains with F-factor including the pts-region of the Escherichia coli K-12 chromosome].

A technique of hybridization of haploid methanol-utilizing yeast Pichia pinus MH4 is worked out using UV- and N-nitrosoguanidine-induced auxotrophic mutants. Vegetative diploid cultures are isolated. Tetrad analysis and random spore analysis have revealed a meiotic nature of spores, recombination of genetic material in the process of sporulation and the chromosomal nature of some mutations. A possibility to construct a genetic map of the yeast Pichia pinus MH4 is demonstrated on the basis of tetrad analysis. Three linkage groups are revealed. The life cycle in a homothalic haploid yeast, Pichia pinus, was demonstrated. They are capable to form zygotes and meiotic spores under conditions preventing vegetative growth.

Biological Transport↗
PubMed1977

[The alpha-methylglucoside transport in Escherichia coli K12 cells].

The transport of alpha-methylglucoside (MG) in the wild type cells of Escherichia coli K12 and the isogenic mutant strains, defective in the activity of phosphoenolpyruvate: sugar phosphotransferase system components was studied. It was shown that the enzyme IIB' in the absence of enzyme I and HPr is able to transport MG into the cells by a "facilitated" diffusion mechanism. Compounds which dissipate the energy of membrane protone potential such as NaN3, carbonylcyanide-m-chlorophenylhydrasone, dicyclohexylcarbodiimide, enhance the utilization of MG by the wild-type cells. However, the cells retaining intact enzyme IIB' but deficient in the phospho approximately HPr-generating system, were not sensitive to the action of poisons. The cells possessing the intact phospho HPr-generating system and inactive enzyme IIB' are also unaffected by the poisons. It seems that these results do not confirm the hypothesis of the direct delta mu H+ involvement in the regulation of transmembrane phosphorylation. The hypothesis is postulated that the energy metabolism inhibitors influence the phosphatase activity of factor III of the phosphotransferase system. The present data are well explained by this hypothesis.

Biological Transport↗
PubMed1975

[The role of the ability of Sh. flexneri to synthesize pili of the common type in the development of dysenteric infections].

HEp-2 epithelial cells infected with isogenic Sh. flexneri strains characterized by capacity to synthesize common pili (confirmed by electron microscopy) were studied. It was shown that although pili promoted an earlier adhesion of shigellae to the cells, they were not very significant for the penetration and intracellular development of dysentery bacilli in the epithelium. The use of bacteria labeled with 3H-glucose offers a possibility of an objective rapid and precise determination of the capacity of the microbes to adhere to the cell surface.

Animals↗
PubMedDate not supplied

[Glucose transport system and regulation of gene expression in Escherichia coli].

The object of this work was to study the effect of mutations damaging protein components of the phosphoenolpyruvate-dependent phosphotransferase system (PTS) of E. coli on the regulation of the activity of catabolite-sensitive operons. Mutations ptsI and ptsH affecting the activity of the enzyme I and HPr protein made the synthesis of catabolite-sensitive enzymes resistant to the action of glucose, and at the same time decreased the rate of transport of this compound. Mutation tgl affecting the activity of the glucose enzyme II lead to the same effect on the enzyme syntheses, though utilization was not altered in this case. The disturbance of beta-galactosidase synthesis in ptsI and ptsH mutants is due to interference of pts mutations into transcription of the lac operon at the lac promoter level. It is concluded that the proteins of the Escherichia coli PTS take part not only in glucose transport, but are also involved in the regulation of transcription of the catabolite sensitive operons.

Biological Transport, Active↗