Glucose consumption in carbohydrate mixtures by phosphotransferase-system mutants of Escherichia coli.

Escherichia coli lacking the glucose phosphotransferase system (PTS), mannose PTS and glucokinase are supposedly unable to grow on glucose as the sole carbon source (Curtis SJ, Epstein W. J Bacteriol 1975;122:1189-1199). We report that W ptsG manZ glk (ALS1406) grows slowly on glucose in media containing glucose with a second carbon source: ALS1406 metabolizes glucose after that other carbon source, including arabinose, fructose, glycerol, succinate or xylose, is exhausted.

The Promiscuous sumA Missense Suppressor from Salmonella enterica Has an Intriguing Mechanism of Action.

While most missense suppressors have very narrow specificities and only suppress the allele against which they were isolated, the sumA missense suppressor from Salmonella enterica serovar Typhimurium is a promiscuous or broad-acting missense suppressor that suppresses numerous missense mutants. The sumA missense suppressor was identified as a glyV tRNA Gly3(GAU/C) missense suppressor that can recognize GAU or GAC aspartic acid codons and insert a glycine amino acid instead of aspartic acid. In addition to rescuing missense mutants caused by glycine to aspartic acid changes as expected, sumA could also rescue a number of other missense mutants as well by changing a neighboring (contacting) aspartic acid to glycine, which compensated for the other amino acid change.

Adaptation of Escherichia coli to elevated sodium concentrations increases cation tolerance and enables greater lactic acid production.

Adaptive evolution was employed to generate sodium (Na(+))-tolerant mutants of Escherichia coli MG1655. Four mutants with elevated sodium tolerance, designated ALS1184, ALS1185, ALS1186, and ALS1187, were independently isolated after 73 days of serial transfer in medium containing progressively greater Na(+) concentrations. The isolates also showed increased tolerance of K(+), although this cation was not used for selective pressure.

Effect of overexpressing nhaA and nhaR on sodium tolerance and lactate production in Escherichia coli.

Background: Like other bacteria, Escherichia coli must carefully regulate the intracellular concentration of sodium ion (Na+). During the bacterial production of any organic acid, cations like Na+ invariably accumulate during a process which must maintain a near neutral pH. In this study, the E.

A substrate-selective co-fermentation strategy with Escherichia coli produces lactate by simultaneously consuming xylose and glucose.

We describe a new approach for the simultaneous conversion of xylose and glucose sugar mixtures which potentially could be used for lignocellulosic biomass hydrolysate. In this study we used this approach to demonstrate the production of lactic acid. This process uses two substrate-selective strains of Escherichia coli, one which is unable to consume glucose and one which is unable to consume xylose.

High glycolytic flux improves pyruvate production by a metabolically engineered Escherichia coli strain.

We report pyruvate formation in Escherichia coli strain ALS929 containing mutations in the aceEF, pfl, poxB, pps, and ldhA genes which encode, respectively, the pyruvate dehydrogenase complex, pyruvate formate lyase, pyruvate oxidase, phosphoenolpyruvate synthase, and lactate dehydrogenase. The glycolytic rate and pyruvate productivity were compared using glucose-, acetate-, nitrogen-, or phosphorus-limited chemostats at a growth rate of 0.15 h(-1).