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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The influence of sodium molybdate and sodium tungstate on formate dehydrogenase activity was studied in H2-CO2-grown cultures of Methanobacterium formicicum. Depletion of molybdate from the growth medium resulted in a 75-fold decrease of intracellular molybdenum and a 35-fold decrease in enzyme activity; however, growth rate and cell yields were not influenced. By using an indirect enzyme-linked immunoassay, the amount of formate dehydrogenase approximated 3% of the total protein in cells grown in the presence of molybdate. Molybdenum-starved cells contained approximately 15-fold less formate dehydrogenase protein; Western blot (immunoblot) analysis revealed that both subunits of the enzyme were synthesized. Molybdenum starvation resulted in an increase in the amount of mRNA that hybridized to fdh-specific DNA. The results indicated an inverse relationship between the amount of transcript and the amount of formate dehydrogenase protein detected in response to molybdenum starvation. The addition of 1 mM tungstate to molybdate-containing media resulted in nearly complete loss of enzyme activity and decreased the intracellular concentration of molybdenum 10-fold. Cells grown in the presence of tungstate synthesized high amounts of inactive formate dehydrogenase and contained mRNA that hybridized to fdh-specific DNA in amounts similar to that in cells grown with sufficient molybdate. Inactive formate dehydrogenase, purified from cells grown in the presence of tungstate, had the same subunit composition and contained amounts of molybdopterin cofactor, albeit metal-free, comparable to those in the active enzyme.
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PMID:Effect of molybdenum and tungsten on synthesis and composition of formate dehydrogenase in Methanobacterium formicicum. 245 11

Anaerobic metabolism of the simplest, best understood enteric bacteria such as Escherichia coli is unexpectedly complex. Recent studies of the biochemistry and genetics of nitrate reduction via nitrite to ammonia by enteric bacteria have provided insights into the reasons for this complexity. An NADH-dependent nitrite reductase in the cytoplasm works in partnership with the respiratory nitrate reductase on the cytoplasmic side of the membrane when nitrate is abundant. There is also an electrogenic, formate-dependent nitrite reductase ready to work in partnership with a periplasmic nitrate reductase when nitrite is available but nitrate is scarce. A third E. coli nitrate reductase, NarZYWV, and the poorly expressed formate dehydrogenase O possibly facilitate rapid adaptation to oxygen starvation pending the synthesis of the major respiratory formate-nitrate oxidoreductase. Although most anaerobically expressed genes are subject to transcription control, none of them are totally switched off. This enables the bacteria to be ready for a change in fortune: when growing anaerobically with nitrate, they can respond equally rapidly whether times get better with the arrival of oxygen, or get worse when the nitrate is depleted. Far from being redundant, the complexity is essential for survival in a changing environment.
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PMID:Nitrate reduction to ammonia by enteric bacteria: redundancy, or a strategy for survival during oxygen starvation? 891 48

Genes whose expression levels are enhanced or reduced during the cultivation process that uses cane molasses in baker's yeast production were identified in this study. The results showed that baker's yeast grown in molasses medium had higher fermentation ability and stress tolerance compared with baker's yeast grown in synthetic medium. Molasses apparently provided not only sugar as a carbon source but also provided functional components that enhanced or reduced expression of genes involved in fermentation ability and stress tolerance. To identify the genes whose expression is enhanced or reduced during cultivation in molasses medium, DNA microarray analysis was then used to compare the gene expression profile of cells grown in molasses with that of cells grown in synthetic medium. To simulate the commercial baker's yeast production process, cells were cultivated using a fed-batch culture system. In molasses medium, genes involved in the synthesis or uptake of vitamins (e.g., biotin, pyridoxine and thiamine) showed enhanced expression, suggesting that vitamin concentrations in molasses medium were lower than those in synthetic medium. Genes involved in formate dehydrogenase and maltose assimilation showed enhanced expression in molasses medium. In contrast, genes involved in iron utilization (e.g., siderophore, iron transporter and ferroxidase) showed enhanced expression in synthetic medium, suggesting that iron starvation occurred. The genes involved in the metabolism of amino acids also showed enhanced expression in synthetic medium. This identification of genes provides information that will help improve the baker's yeast production process.
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PMID:Identification of genes whose expressions are enhanced or reduced in baker's yeast during fed-batch culture process using molasses medium by DNA microarray analysis. 1592 3

Hydrogenotrophic methanogenic Archaea are defined by an H2 requirement for growth. Despite this requirement, many hydrogenotrophs are also capable of growth with formate as an electron donor for methanogenesis. While certain responses of these organisms to hydrogen availability have been characterized, responses to formate starvation have not been reported. Here we report that during continuous culture of Methanococcus maripaludis under defined nutrient conditions, growth yields relative to methane production decreased markedly with either H2 excess or formate excess. Analysis of the growth yields of several mutants suggests that this phenomenon occurs independently of the storage of intracellular carbon or a transcriptional response to methanogenesis. Using microarray analysis, we found that the expression of genes encoding coenzyme F420-dependent steps of methanogenesis, including one of two formate dehydrogenases, increased with H2 starvation but with formate occurred at high levels regardless of limitation or excess. One gene, encoding H2-dependent methylene-tetrahydromethanopterin dehydrogenase, decreased in expression with either H2 limitation or formate limitation. Expression of genes for the second formate dehydrogenase, molybdenum-dependent formylmethanofuran dehydrogenase, and molybdenum transport increased specifically with formate limitation. Of the two formate dehydrogenases, only the first could support growth on formate in batch culture where formate was in excess.
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PMID:Effects of H2 and formate on growth yield and regulation of methanogenesis in Methanococcus maripaludis. 2333 20