Resistance of acid-habituated Escherichia coli to organic acids and its medical and applied significance

Goodson, Margaret; Rowbury, R. J.

doi:10.1111/j.1472-765x.1989.tb00250.x

Cited by 57 publications

(27 citation statements)

References 6 publications

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“…Our results may resolve conflicting reports on the ability of E. coli to survive exposure to low acid. Early literature stated that an E. coli K-12 isolate was very acid sensitive (12), whereas a more recent examination of normal flora E. coli and several different K-12 strains has shown most E. coli strains to be very resistant to pHs below 3.0 (13). The fact that rpoS mutants arise frequently in various lineages of K-12 may explain these discrepancies (18,19,35).…”

Section: Discussionmentioning

confidence: 99%

Acid and base resistance in Escherichia coli and Shigella flexneri: role of rpoS and growth pH

et al. 1994

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Escherichia coli K-12 strains and Shigellaflexneri grown to stationary phase can survive several hours at pH 2 to 3, which is considerably lower than the acid limit for growth (about pH 4.5). A 1.3-kb fragment cloned from S. flexneri conferred acid resistance on acid-sensitive E. coli HB101; sequence data identified the fragment as a homolog of rpoS, the growth phase-dependent sigma factor Ci38. The clone also conferred acid resistance on S.flexneri rpoS::TnlO but not on Salmonella typhimurium. E. coli and S.flexneri strains containing wild-type rpoS maintained greater internal pH in the face of a low external pH than strains lacking functional rpoS, but the ability to survive at low pH did not require maintenance of a high transmembrane pH difference. Aerobic stationary-phase cultures of E. coli MC4100 and S. flexneri 3136, grown initially at an external pH range of 5 to 8, were 100% acid resistant (surviving 2 h at pH 2.5). Aerobic log-phase cultures grown at pH 5.0 were acid resistant; survival decreased 10-to 100-fold as the pH of growth was increased to pH 8.0. Extended growth in log phase also decreased acid resistance substantially. Strains containing rpoS::TnJO showed partial acid resistance when grown at pH 5 to stationary phase; log-phase cultures showed <0.01% acid resistance. When grown anaerobically at low pH, however, the rpoS::TnlO strains were acid resistant. E. coli MC4100 also showed resistance at alkaline pH outside the growth range (base resistance). Significant base resistance was observed up to pH 10.2. Base resistance was diminished by rpoS::TnlO and by the presence of Na+. Base resistance was increased by an order of magnitude for stationary-phase cultures grown in moderate base (pH 8) compared with those grown in moderate acid (pH 5). Anaerobic growth partly restored base resistance in cultures grown at pH 5 but not in those grown at pH 8. Thus, both acid resistance and base resistance show dependence on growth pH and are regulated by rpoS under certain conditions. For acid resistance, and in part for base resistance, the rpoS requirement can be overcome by anaerobic growth in moderate acid.

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Section: Discussionmentioning

confidence: 99%

Acid and base resistance in Escherichia coli and Shigella flexneri: role of rpoS and growth pH

et al. 1994

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“…An important stress condition that must be faced by many pathogenic micro-organisms is low pH. Upon ingestion, food-and water-borne microbial pathogens are exposed to an acid pH environment in the stomach and in the small intestine (Booth, 1985 ;Goodson & Rowbury, 1989a, b, c, 1990. Also, some of these microbial pathogens can be Abbreviations: ATR, acid tolerance response; DTPA, dipyridyl.…”

Section: Introductionmentioning

confidence: 99%

Adaptive acid tolerance response (ATR) in Aeromonas hydrophila

1994

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Aeromonas hydrophila, a gastrointestinal pathogen of humans, was shown t o exhibit a significant adaptive acid tolerance response (ATR) capable of protecting cells from severe acid at a pH of 3.5. The ATR was induced by exposure t o a relatively mild pH level of 5-0 for 20 min. Adaptation required protein Synthesis since treatment with chloramphenicol during adaptation t o pH 5-0 prevented the development of acid tolerance. The adaptation t o acid environment was found t o be a non-transient phenomenon. Also, iron was not required for acid adaptation in A. hydrophila. Two-dimensional protein analyses revealed an increased production of 28 proteins and decreased synthesis of 10 following pH shifts from 7.2 t o 5.0. The mild pH treatment must act as a signal t o A. hydrophila t o adapt and survive in acid environments by producing 'protective proteins. The adaptation and survival of this pathogen in low pH may provide valuable information about i t s ability t o withstand acid environments in nature and in the human gastrointestinal tract.

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“…Acetate, propanoate, butanoate, sorbate, and benzoate exhibit bacteriostatic effects (23)(24)(25). However, these same small organic acids are able to induce resistance to low pH and tolerance to bacteriostatic organic acids at low pH (26). Guilfoyle and Hirshfield found previously that E. coli cells grown in rich medium at pH 6.5 and exposed to 0.1% propanoate or 0.1% butanoate for 1 h exhibited significant survival when challenged (without organic acid) at pH 3.5 in rich medium (27).…”

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confidence: 99%

YfdW and YfdU Are Required for Oxalate-Induced Acid Tolerance in Escherichia coli K-12

et al. 2013

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Escherichia coli has several mechanisms for surviving low-pH stress. We report that oxalic acid, a small-chain organic acid (SCOA), induces a moderate acid tolerance response (ATR) in two ways. Adaptation of E. coli K-12 at pH 5.5 with 50 mM oxalate and inclusion of 25 mM oxalate in pH 3.0 minimal challenge medium separately conferred protection, with 67% ؎ 7% and 87% ؎ 17% survival after 2 h, respectively. The combination of oxalate adaptation and oxalate supplementation in the challenge medium resulted in increased survival over adaptation or oxalate in the challenge medium alone. The enzymes YfdW, a formyl coenzyme A (CoA) transferase, and YfdU, an oxalyl-CoA decarboxylase, are required for the adaptation effect but not during challenge. Unlike other SCOAs, this oxalate ATR is not a part of the RpoS regulon but appears to be linked to the signal protein GadE. We theorize that this oxalate ATR could enhance the pathogenesis of virulent E. coli consumed with oxalate-containing foods like spinach.

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Resistance of acid-habituated Escherichia coli to organic acids and its medical and applied significance

Cited by 57 publications

References 6 publications

Acid and base resistance in Escherichia coli and Shigella flexneri: role of rpoS and growth pH

Acid and base resistance in Escherichia coli and Shigella flexneri: role of rpoS and growth pH

Adaptive acid tolerance response (ATR) in Aeromonas hydrophila

YfdW and YfdU Are Required for Oxalate-Induced Acid Tolerance in Escherichia coli K-12

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