Metabolic shifts in Zymomonas mobilis in response to growth conditions

Bringer-Meyer, Stephanie; Sahm, Hermann

doi:10.1016/0378-1097(88)90173-5

FEMS Microbiology Letters

1988

DOI: 10.1016/0378-1097(88)90173-5

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Metabolic shifts in Zymomonas mobilis in response to growth conditions

Stephanie Bringer-Meyer

Hermann Sahm

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Cited by 10 publications

(13 citation statements)

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“…Thus, up to 11% of the carbon source(s) was converted into sorbitol and afterwards detected in the media, the sorbitol yield being proportional to the increased sugar concentrations (2,6,11,(30)(31)(32). It was suggested (2, 31) that sorbitol formation resulted from an inhibition of fructokinase by glucose.…”

mentioning

confidence: 99%

Sorbitol promotes growth of Zymomonas mobilis in environments with high concentrations of sugar: evidence for a physiological function of glucose-fructose oxidoreductase in osmoprotection

et al. 1994

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The gram-negative ethanologenic bacterium Zymomonas mobilis is able to grow in media containing high concentrations of glucose or other sugars. A novel compatible solute for bacteria, sorbitol, which enhances growth of Z. mobilis at glucose concentrations exceeding 0.83 M (15%), is described. Added sorbitol was accumulated intracellularly up to 1 M to counteract high external glucose concentrations (up to 1.66 M or 30o). Accumulation of sorbitol was triggered by a glucose upshift (e.g., from 0.33 to 1.27 M or 6 to 23%) and was prevented by the uncoupler CCCP (carbonyl cyanide m-chlorophenylhydrazone; 100 tIM). The sorbitol transport system followed Michaelis-Menten kinetics, with an apparent Km of 34 mM and a Vm.. of 11.2 nmol -min-' mg-' (dry mass). Sorbitol was produced by the cells themselves and was accumulated when growing on sucrose (1 M or 36%) by the action of the periplasmic enzyme glucose-fructose oxidoreductase, which converts glucose and fructose to gluconolactone and sorbitol. Thus, Z. mobilis can form and accumulate the compatible solute sorbitol from a natural carbon source, sucrose, in order to overcome osmotic stress in high-sugar media. No other major compatible solute (betaine, proline, glutamate, or trehalose) was detected.The gram-negative, strictly fermentative and ethanologenic bacterium Zymomonas mobilis tolerates high concentrations of both ethanol (up to 13% [24]) and sugar (16,28) in the growth medium. An early report stated that Z. mobilis, (then called Termobacterium mobile), which had been isolated from pulque

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mentioning

confidence: 99%

Sorbitol promotes growth of Zymomonas mobilis in environments with high concentrations of sugar: evidence for a physiological function of glucose-fructose oxidoreductase in osmoprotection

et al. 1994

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“…Zymomonas mobilis is an obligately fermentative, gramnegative bacterium of commercial interest (6,34,35,54). Using an Entner-Doudoroff glycolytic pathway, each mole of glucose is metabolized to produce 2 mol of ethanol and of carbon dioxide plus a single mole of ATP.…”

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confidence: 99%

Gel electrophoretic analysis of Zymomonas mobilis glycolytic and fermentative enzymes: identification of alcohol dehydrogenase II as a stress protein

Scopes

Rodríguez

et al. 1991

J Bacteriol

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The 13 major enzymes which compose the glycolytic and fermentative pathways in Zymomonas mobilis are particularly abundant and represent one-half of the soluble protein in exponential-phase cells. One-and two-dimensional polyacrylamide gel electrophoresis maps were developed for 12 of these enzymes. Assignments were made by comigration with purified proteins, comparison with overexpressed genes in recombinant strains, and Western blots (immunoblots). Although most glycolytic enzymes appeared resistant to turnover and accumulated in stationary-phase cells, the protein levels of pyruvate kinase, alcohol dehydrogenase I, and glucokinase declined. Alcohol dehydrogenase II was identified as a major stress protein and was induced both by exposure to ethanol and by elevated temperature (45°C). This enzyme, encoded by the adhB gene, is expressed from tandem promoters which share partial sequence identity with the Escherichia coli consensus sequence for heat shock proteins.

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“…Among the eight ethanologenic genes examined, differences in transcript stability were found to directly correlate with differences in functional message pools and cytoplasmic protein levels. These differences in transcript stability are hypothesized to have evolved as a primary mechanism to balance the levels of individual enzymes within the glycolytic and fermentative pathways.Zymomonas mobilis is an obligately fermentative, gramnegative bacterium commonly found in plant saps and honey (6,18). This organism is prototrophic, except for straindependent vitamin requirements.…”

mentioning

confidence: 99%

“…Zymomonas mobilis is an obligately fermentative, gramnegative bacterium commonly found in plant saps and honey (6,18). This organism is prototrophic, except for straindependent vitamin requirements.…”

mentioning

confidence: 99%

Coordination of expression of Zymomonas mobilis glycolytic and fermentative enzymes: a simple hypothesis based on mRNA stability

Mejia

Burnett

et al. 1992

J Bacteriol

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Although Zymomonas mobilis is prototrophic, glycolytic and fermentative enzymes (ethanologenic enzymes) constitute over half of the cytoplasmic protein. In this study, transcript stability, functional message pools, and the abundance of cytoplasmic products were compared for genes encoding eight of these essential enzymes. The transcripts of all were very stable, with half-lives ranging from 8 to 18 min. This transcript stability is proposed as an important feature in Z. mobiis that may distinguish highly expressed genes for energy generation from biosynthetic genes, which are required at much lower levels. The evolution of multiple promoters to enhance transcription from single-copy genes, of structural features that alter translational efficiency, and of differences in protein turnover is hypothesized to serve a subordinate role in the regulation of Z. mobiis gene expression. Among the eight ethanologenic genes examined, differences in transcript stability were found to directly correlate with differences in functional message pools and cytoplasmic protein levels. These differences in transcript stability are hypothesized to have evolved as a primary mechanism to balance the levels of individual enzymes within the glycolytic and fermentative pathways.Zymomonas mobilis is an obligately fermentative, gramnegative bacterium commonly found in plant saps and honey (6,18). This organism is prototrophic, except for straindependent vitamin requirements. Glycolysis proceeds through an Entner-Doudoroff pathway to ethanol and carbon dioxide, with the net production of a single mole of ATP per mole of glucose metabolized. High rates of glycolytic flux (1,15,22) allow this organism to compete effectively in the natural environment, despite this inefficient pathway for ATP generation. High levels of glycolytic and fermentative enzymes (ethanologenic enzymes) are required to permit this flux. Together, these enzymes constitute approximately half of the cytoplasmic protein (1, 2, 22).The mechanism that allows Z. mobilis to produce large amounts of ethanologenic enzymes for energy generation while maintaining low but sufficient levels of the many biosynthetic enzymes needed for prototrophic growth is of general interest as a model for procaryotic gene expression. A variety of features have been identified in other organisms as contributing to high-level expression (15,25). Investigations of the ethanologenic genes and enzymes in Z. mobilis offer an opportunity to decipher the extent to which these features have been recruited during the evolution of this unusual organism.All ethanologenic enzymes in Z. mobilis have been purified, and each appears to be represented by a single enzymatic species (3,7,19,20,23,(25)(26)(27)(28)(29) (9,13,14). However, the GAP protein is present in Z. mobilis at higher levels than the PGK protein. This higher abundance of GAP appears to result from a slower degradation of the 3' gap mRNA segment (hence the larger pool) than of the full-length transcript (13). The current study was undertaken to i...

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Metabolic shifts in Zymomonas mobilis in response to growth conditions

Cited by 10 publications

References 90 publications

Sorbitol promotes growth of Zymomonas mobilis in environments with high concentrations of sugar: evidence for a physiological function of glucose-fructose oxidoreductase in osmoprotection

Sorbitol promotes growth of Zymomonas mobilis in environments with high concentrations of sugar: evidence for a physiological function of glucose-fructose oxidoreductase in osmoprotection

Gel electrophoretic analysis of Zymomonas mobilis glycolytic and fermentative enzymes: identification of alcohol dehydrogenase II as a stress protein

Coordination of expression of Zymomonas mobilis glycolytic and fermentative enzymes: a simple hypothesis based on mRNA stability

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