Escherichia coli acid tolerance

Other bacterial mutants, such as a mutant Escherichia coli enzyme tolerant to glyphosate, have been described (47). The E. coli mutant had a single amino acid change from the wild type, resulting in substitution of glycine 96 with alanine. An identical mutation was reported in glyphosate-tolerant Klebsiella pneumoniae (48). The nature of changes in the kinetic constants of the K pneumoniae enzyme is similar to that of the E. coli enzyme. 

Enzyme preparations from liver or microbial sources were reported to show rather high substrate specificity [76] for the natural phosphorylated acceptor d-(18) but, at much reduced reaction rates, offer a rather broad substrate tolerance for polar, short-chain aldehydes [77-79]. Simple aliphatic or aromatic aldehydes are not converted. Therefore, the aldolase from Escherichia coli has been mutated for improved acceptance of nonphosphorylated and enantiomeric substrates toward facilitated enzymatic syntheses ofboth d- and t-sugars [80,81]. High stereoselectivity of the wild-type enzyme has been utilized in the preparation of compounds (23) / (24) and in a two-step enzymatic synthesis of (22), the N-terminal amino acid portion of nikkomycin antibiotics (Figure 10.12) [82]. 

Miller, L.G. and Kasper, C.W. (1994) Escherichia coli 0157 H7 acid tolerance and survival in apple cider. Journal of Food Protection 57(7), 645. 

Sulfurous acid inhibits molds and bacteria and to a lesser extent yeasts. For this reason, S02 can be used to control undesirable bacteria and wild yeast in fermentations without affecting the S02-tolerant cultured yeasts. According to Chichester and Tanner (1968), the undissociated acid is 1,000 times more active than HS03 for Escherichia coli, 100 to 500 times for Saccharomyces cerevisiae, and 100 times for Aspergillus niger. 

Cheng, H.Y., Yu, R.C., and Chou, C.C. 2003. Increased acid tolerance of Escherichia coli 0157 H7 as affected by acid adaptation time and conditions of acid challenge. Food Research International 36 49-56. 

Jordan, K.N., Oxford, L., and O Byrne, C.P 1999. Survival of low-pH stress by Escherichia coli 0157 H7 Correlation between alterations in the cell envelope and increased acid tolerance. Applied and Environmental Microbiology 65 3048-3055. 

Ryu, J.-H. and Beuchat, L.R. 1999. Changes in heat tolerance of Escherichia coli 0157 H7 after exposure to acidic environments. Food Microbiology 16 317-324. 

Brudzinski, L. and Harrison, M.A. 1998. Influence of incubation conditions on survival and acid tolerance response of Escherichia coli 0157 H7 and non-0157 H7 isolates exposed to acetic acid. Journal of Food Protection 61 542-546. 

Benjamin, M.M. and Datta, A.R. 1995. Acid tolerance of enterohemorrhagic Escherichia coli. Applied and Environmental Microbiology 61 1669-1672. 

Brown, J.L., Ross, T., McMeekin, T.A., and Nichols, P.D. 1997. Acid habituation of Escherichia coli and the potential role of cyclopropane fatty acids in low pH tolerance. International Journal of Food Microbiology 37 163-173. 

Studies on gene expression in Escherichia coli K12 during induced acid tolerance response identified gene arrays as having the potential to recognize relations between unknown regulatory or metabolic pathways. With this technique more information is obtained about induction mechanisms of acid tolerance mechanisms in enteropathogenic E. coli and E. coli 0157 H7 (Sainz et al., 2005). 

The study reported by Lin et al. used alginate microcapsules coated with poly-L-lysine followed by a further coating with an alginate layer. It was found that this kind of capsules does not increase the number of Escherichia coli strain during exposure to gastric juice. The strain used had high tolerance to acid and decreases over 120 min at pH 2 to 1 log/mL. 

Luo LH, Seo P, Seo J, Heo S, Kim D. (2009). Improved ethanol tolerance in Escherichia coli by changing the cellular fatty acids composition through genetic manipulation. Biotechnol Lett,3, 1867-1871. 

Warnecke, T.E., Lynch, M.D., Lipscomb, M.L., and Gill, R.T. (2012) Identification of a 21 amino acid peptide conferring 3-hydroxypropionic acid stress-tolerance to Escherichia coli. Biotechnol. Bioeng, 109 (5), 1347-1352. 

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