title: The role of isocitrate lyase and the glyoxylate cycle in Escherichia coli growing under glucose limitation.
abstract: 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.
authors.affiliation: School of Molecular and Microbial Biosciences G08, University of Sydney, N.S.W. 2006, Sydney, Australia.
authors.forename: Ram
authors.initials: R
authors.lastname: Prasad Maharjan
authors.forename: Pak-Lam
authors.initials: PL
authors.lastname: Yu
authors.forename: Shona
authors.initials: S
authors.lastname: Seeto
authors.forename: Thomas
authors.initials: T
authors.lastname: Ferenci
mesh_terms: 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
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D029968:Escherichia coli Proteins; D006038:Glyoxylates; D008292:Malate Synthase; D007522:Isocitrate Lyase; D005947:Glucose