The role of isocitrate lyase and the glyoxylate cycle in Escherichia coli growing under glucose limitation.
Escherichia coli changes its metabolism in response to environmental circumstances, and metabolic adaptations are evident in hungry bacteria growing slowly in glucose-limited chemostats. The role of isocitrate lyase (AceA) was examined in E. coli growing under glucose limitation. AceA activity was elevated in a strain-dependent manner in the commonly used E. coli K-12 laboratory strains MG1655 and MC4100, but an aceA disruption surprisingly increased fitness under glucose limitation in both strains. However, in bacteria adapted to limiting glucose in long-term chemostats, mutations outside aceA changed its role from a negative to a positive influence. These results suggest that a recently proposed pathway of central metabolism involving the glyoxylate cycle enzymes is redundant in wild-type bacteria, but may take on a beneficial role after context adaptation. Interestingly, the aceA gene sequence did not alter during prolonged selection, so mutations in unidentified genes changed the metabolic context of unaltered AceA from a negative to a positive influence in bacteria highly adapted to limiting glucose.
Prasad Maharjan
Ram
R
School of Molecular and Microbial Biosciences G08, University of Sydney, N.S.W. 2006, Sydney, Australia.
Yu
Pak-Lam
PL
Seeto
Shona
S
Ferenci
Thomas
T
D001426:Bacterial Proteins; D001709:Biotechnology / Q000379:methods; D003470:Culture Media; D019020:Directed Molecular Evolution; D048168:Escherichia coli K12 / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism*; D006038:Glyoxylates / Q000378:metabolism*; D018869:Heat-Shock Response; D007522:Isocitrate Lyase / Q000235:genetics / Q000378:metabolism*; D008292:Malate Synthase / Q000378:metabolism; D009154:Mutation
D001426:Bacterial Proteins; D003470:Culture Media; D029968:Escherichia coli Proteins; D006038:Glyoxylates; D008292:Malate Synthase; D007522:Isocitrate Lyase; D005947:Glucose