Acetate and Formate Stress: Opposite Responses in the Proteome of Escherichia coli

Abstract

Acetate and formate are major fermentation products of Escherichia coli. Below pH 7, the balance shifts to lactate; an oversupply of acetate or formate retards growth. E. coli W3110 was grown with aeration in potassium-modified Luria broth buffered at pH 6.7 in the presence or absence of added acetate or formate, and the protein profiles were compared by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Acetate increased the steady-state expression levels of 37 proteins, including periplasmic transporters for amino acids and peptides (ArtI, FliY, OppA, and ProX), metabolic enzymes (YfiD and GatY), the RpoS growth phase regulon, and the autoinducer synthesis protein LuxS. Acetate repressed 17 proteins, among them phosphotransferase (Pta). An ackA-pta deletion, which nearly eliminates interconversion between acetate and acetyl-coenzyme A (acetyl-CoA), led to elevated basal levels of 16 of the acetate-inducible proteins, including the RpoS regulon. Consistent with RpoS activation, the ackA-pta strain also showed constitutive extreme-acid resistance. Formate, however, repressed 10 of the acetate-inducible proteins, including the RpoS regulon. Ten of the proteins with elevated basal levels in the ackA-pta strain were repressed by growth of the mutant with formate; thus, the formate response took precedence over the loss of the ackA-pta pathway. The similar effects of exogenous acetate and the ackA-pta deletion, and the opposite effect of formate, could have several causes; one possibility is that the excess buildup of acetyl-CoA upregulates stress proteins but excess formate depletes acetyl-CoA and downregulates these proteins.

Metabolite stress and tolerance in the production of biofuels and chemicals: Gene‐expression‐based systems analysis of butanol, butyrate, and acetate stresses in the anaerobe Clostridium acetobutylicum

“…Moreover, acetate stress has been shown to upregulate select amino acid transporters (Kirkpatrick et al, 2001). The overall upregulation of methionine and select amino acid transporters (Fig.…”

“…Mechanisms of solvent and carboxylic acid toxicity/stress have been studied mostly in Gram-negative (Gram À ) organisms and notably in Escherichia coli (Arnold et al, 2001;Chang and Cronan, 1999;Hayashi et al, 2003;Isken and de Bont, 1998;Kirkpatrick et al, 2001;Roe et al, 2002;Russell and Diez-Gonzalez, 1998;Sardessai and Bhosle, 2002;Zaldivar and Ingram, 1999). For example, Gram À organisms have evolved adaptive mechanisms to tolerate solvents, including alterations in cell membrane, active secretion, and activation of general stress response (Isken and de Bont, 1998;Sardessai and Bhosle, 2002).…”

Lack of Protective Osmolytes Limits Final Cell Density and Volumetric Productivity of Ethanologenic Escherichia coli KO11 during Xylose Fermentation

“…Allosteric inhibition of this native enzyme by high NADH levels such as those associated with anaerobic growth (16) can be antagonized by acetyl-CoA (49). Two independent approaches that have been previously used to increase the availability of acetyl-CoA (and thereby promote cell growth) were investigated for their effects on the glutamate pool during fermentations in the CSL medium: (i) supplementing with 24 mM acetate (25,46) and (ii) inactivating the primary anaerobic acetate production pathway (⌬ackA) (25,46). Both approaches increased the glutamate pool to levels similar to that observed during aerobic growth (Table 1; Fig.…”

Integrating dark and light bio-hydrogen production strategies: towards the hydrogen economy

“…The formation of relatively reduced organic molecules is an integral part of all dark fermentations and some of these molecules (e.g. acetate) can 9 inhibit H 2 production if allowed to accumulate (Roe et al 1998;Kirkpatrick et al 2001;Van Ginkel & Logan 2005).…”