Transport of lactate and succinate by membrane vesicles of Escherichia coli, Bacillus subtilis and a pseudomonas species.
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Azides↗
Biomedical subjects
A Matin
Publications and source records attributed to A Matin.
Kinetics of deoxyribonucleic acid destruction and synthesis during growth of Bdellovibrio bacteriovorus strain 109D on pseudomonas putida and escherichia coli.
During the growth of Bdellovibrio bacteriovorus on Pseudomonas putida or Escherichia coli in either 10(-3)m tris(hydroxymethyl)aminomethane or in dilute nutrient broth, the host deoxyribonucleic acid (DNA) was rapidly degraded, and by 30 to 60 min after the initiation of the bdellovibrio development cycle essentially all host DNA became nonbandable in CsCl gradients. At this stage the host DNA degradation products were nondiffusable, and there was no appreciable pool of low-molecular-weight (cold acid soluble) DNA fragments in the cells or in the suspending medium. Bdellovibrio DNA synthesis occurred only after degradation of host DNA to a nonbandable form was complete. The synthesis occurred in a continuous fashion with P. putida as the host and in two separate periods with E. coli as host. By using E. coli containing a (3)H-thymidine label, it was shown that 73%, on the average, of the thymine residues of host DNA were incorporated into bdellovibrio DNA when E. coli was the only source of nutrient. In the presence of dilute nutrient broth, the host cells still served as the major source of precursors for bdellovibrio DNA synthesis, with only 20% of the precursors arising from the exogenous nutrients. The data indicate an efficient and controlled utilization of host DNA by the bdellovibrio. The host DNA is apparently degraded early in the developmental cycle to oligonucleotides of intermediate molecular weight from which the biosynthetic monomers are generated only as they become needed for bdellovibrio DNA synthesis.
Bacteria↗
Inhibition of growth of obligately chemolithotrophic Thiobacilli by amino acids.
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Amino Acids↗
Enzymes of carbohydrate metabolism in Thiobacillus species.
A study was made of enzymes of carbohydrate metabolism in representative thiobacilli grown with and without glucose. The data show that Thiobacillus perometabolis possesses an inducible Entner-Doudoroff pathway and is thus similar to T. intermedius and T. ferrooxidans. T. novellus lacks this pathway. Instead, a non-cyclic pentose phosphate pathway along with the Krebs cycle is apparently the major route of glucose dissimilation in this organism. Glucose does not support or stimulate the growth of strains of T. neapolitanus, T. thioparus, and T. thiooxidans examined, nor does its presence in the growth medium greatly influence their enzymatic constitution. These obligately chemolithotrophic thiobacilli do not possess the Entner-Doudoroff pathway. Their nicotinamide adenine dinucleotide (NAD)-linked isocitrate dehydrogenase activity predominates over their nicotinamide adenine dinucleotide phosphate (NADP)-linked activity; the converse is true for the other thiobacilli. The data suggest that NAD-linked isocitrate dehydrogenase activity in thiobacilli is involved in biosynthetic reactions.
Adenosine Triphosphate↗
Utilization of glucose in heterotrophic media by Thiobacillus intermedius.
The growth yield of Thiobacillus intermedius is greater in glucose-yeast extract or glucose-casein hydrolysate broth than in comparable media without glucose. The quantity of glucose utilized in the glucose-supplemented media is much greater than the increase in cell yield observed relative to the unsupplemented media. Addition of glucose to cell-free extracts of glucose-yeast extract or glucose-casein hydrolysate grown cells results in the reduction of endogenous cytochrome c. Thus, in these media, glucose serves as a source of energy. This is in contrast to thiosulfate-glucose broth in which glucose provides only cell carbon. The presence of thiosulfate in glucose-casein hydrolysate broth results in a marked decrease in glucose consumption. Cytochrome c in extracts of cells grown in this medium is not reduced by glucose addition. The data suggest that thiosulfate prevents the utilization of glucose for energy generation. The final growth yield in glucose-casein hydrolysate broth is directly proportional to the initial glucose concentration, although not all the glucose was utilized even at the lowest concentration tested. This effect may be due to an inefficient glucose transport in this organism.
Caseins↗
Regulation of glucose metabolism in Thiobacillus intermedius.
Glucose-yeast extract or glucose-casein hydrolysate-grown Thiobacillus intermedius cells, which use glucose for energy generation, possess high specific activities of the Entner-Doudoroff pathway and related enzymes, 6-phosphogluconate dehydrase, 2-keto-3-deoxy-6-phosphogluconate aldolase, glucokinase, and glucose-6-phosphate dehydrogenase, but low activities of enzymes unique to the pentose shunt and Embden-Meyerhof pathways. Although the synthesis of the latter enzymes remains largely unaffected by the growth environment, that of the former is stimulated by glucose. Radiorespirometric measurements demonstrate an early and parallel respiration of glucose carbon atoms one and four in glucose-casein hydrolysate broth. It is concluded that the Entner-Doudoroff pathway performs an energetic role in glucose metabolism by T. intermedius with the pentose shunt and Embden-Meyerhof pathways functioning mainly in biosynthesis. The presence of thiosulfate in the growth medium inhibits the synthesis of the Entner-Doudoroff pathway and related enzymes. In addition, both thiosulfate and glucose inhibit the synthesis of the Krebs cycle enzymes, nicotinamide adenine dinucleotide phosphate-linked isocitrate and alpha-ketoglutarate dehydrogenases. Thus, repression of enzymes is of significance in the adaptation of T. intermedius to its nutritional environment. The activity of glucose-6-phosphate dehydrogenase of T. intermedius is inhibited by adenosine triphosphate. Such a control could afford the organism a mechanism to regulate the flow of glucose into major energetic and biosynthetic routes.
Carbon Dioxide↗
Role of alternate sigma factors in starvation protein synthesis--novel mechanisms of catabolite repression.
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Bacteria↗
Mutant SV40 large T antigen as a therapeutic agent for HER-2/neu-overexpressing ovarian cancer.
The HER-2/neu gene is frequently amplified and/or its protein product, p185, is overexpressed in a number of human cancers. Overexpression of p185 correlates with poor prognosis and low survival rates in ovarian cancer patients. We previously found that the K1 mutant of SV40 large T antigen inhibits rat neu promoter and suppresses mutation-activated rat neu transformation in mouse fibroblasts. We show here that K1 also inhibits human HER-2/neu promoter in human ovarian cancer cells. To investigate whether K1 can suppress HER-2/neu transformation and thus is a potential therapeutic agent, we used an orthotopic ovarian cancer model in which mice were injected intraperitoneally with HER-2/neu-overexpressing human ovarian cancer cells to induce tumor development. The tumor-bearing mice were then treated with K1-liposome complex weekly. We found that liposome-mediated K1 gene transfer decreased the p185 protein level by K1 expression in these cancer cells and significantly prolonged mice survival; about 40% of these treated mice were alive for more than 1 year without any tumor development. On the other hand, the animals from control groups that did not receive this gene therapy all developed tumors and died within 7 months. The results indicate that liposome-mediated K1 gene transfer is able to suppress tumor development from HER-2/neu-overexpressing ovarian cancer cells in mice.
Animals↗