The adaptive acid tolerance response in root nodule bacteria and Escherichia coli

1994 ◽  
Vol 161 (4) ◽  
pp. 286-292
Author(s):  
Graham W. O'Hara ◽  
Andrew R. Glenn
Keyword(s):  
Escherichia Coli ◽  
Root Nodule ◽  
Acid Tolerance ◽  
Nodule Bacteria ◽  
Acid Tolerance Response ◽  
Root Nodule Bacteria ◽  
Tolerance Response

Acid tolerance in legume root nodule bacteria and selecting for it

2001 ◽  
Vol 41 (3) ◽  
pp. 435 ◽  
Author(s):  
M. J. Dilworth ◽  
J. G. Howieson ◽  
W. G. Reeve ◽  
R. P. Tiwari ◽  
A. R. Glenn
Keyword(s):  
Root Nodule ◽  
Acid Soils ◽  
Acid Tolerance ◽  
Interactive Effects ◽  
Regulator Gene ◽  
Nodule Bacteria ◽  
Root Nodule Bacteria ◽  
Acid Ph ◽  
Wide Range ◽  
Concentration Changes

Bacteria face a variety of problems in trying to survive and grow in acidic environments. These include maintaining intracellular pH (pHi) in order to protect internal cell components, modifying or abandoning those external structures inevitably exposed to acidity, and resisting stresses whose interaction with pH may be the actual determinant of survival or growth rather than H+ toxicity per se. An important aspect of acid resistance in Gram-negative bacteria (including the root nodule bacteria) is the adaptive acid tolerance response (ATR), whereby cells grown at moderately acid pH are much more resistant to being killed under strongly acidic conditions than are cells grown at neutral pH. Survival during pH shock is also markedly affected by the calcium concentration in the medium. The pH at which commercial legume inoculants are grown and supplied for inoculation into acid soils may therefore be of considerable importance for initial inoculant survival. The mechanisms of resistance to acidity in root nodule bacteria have been investigated via 3 approaches: (i) creation of acid-sensitive mutants from acid-tolerant strains, and identification of the genes involved; (ii) random insertion of reporter genes to create mutants with pH-dependent reporter expression; and (iii) proteomics and identification of proteins regulated in response to acidity. The results of the first approach, directed at genes essential for growth at acid pH, have identified a sensor–regulator gene pair (actS–actR), a copper-transporting ATPase (actP), and another gene involved in lipid metabolism (actA), inactivation of which results in sensitivity to heavy metals. While the ActS–ActR system is undoubtedly required for both acid tolerance and the ATR, it is also involved in global regulation of a wide range of cellular processes. The second approach has allowed identification of a range of acid-responsive genes, which are not themselves critical to growth at low pH. One of these (phrR) is itself a regulator gene induced by a range of stresses including acid pH, but not controlled by the ActS–ActR system. Another, lpiA, responds specifically to acidity (not to other stresses) and may well be an antiporter related to nhaB, which is involved in Na+ transport in other bacteria. The third approach indicates a number of proteins whose concentration changes with a switch from neutral to acidic growth pH; most of these seem to have no homologues in the protein databases, while the blocked N-terminal sequences of others have prevented identification. It has been common experience that strains of root nodule bacteria selected for acid tolerance in the laboratory are not necessarily successful as inoculants in acid soils. In the light of the complex interactive effects on growth and survival of H+, Ca2+ and Cu2+ concentrations in our studies, this lack of correlation is no longer surprising. It remains to be seen whether it will be possible to improve the correlation between growth on laboratory media and performance in acid soils by determining which strains show an ATR, and by screening on media with defined ranges of concentration of some of these critical metal ions, perhaps approximating those to be expected in the soils in question.

Influence of Incubation Conditions on Survival and Acid Tolerance Response of Escherichia coliO157:H7 and Non-O157:H7 Isolates Exposed to Acetic Acid

1998 ◽  
Vol 61 (5) ◽  
pp. 542-546 ◽  
Author(s):  
LESLYE BRUDZINSKI ◽  
MARK A. HARRISON
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Organic Acids ◽  
Adaptive System ◽  
Acid Tolerance ◽  
Effect Of Temperature ◽  
Escherichia Coli O157 ◽  
Acid Tolerance Response ◽  
E Coli ◽  
Tolerance Response

The increasing frequency of Escherichia coli O157:H7 outbreaks, especially in acidic foods, raises the concern of an acid tolerance response (ATR). Organic acids can be present in processed and preserved foods: shifts in the acid levels of foods due to these acids may allow E. coli to adapt and later tolerate pH levels that would normally inactivate the organism. The effect of temperature and agitation on the ATRs of three E. coli O157:H7 and two non-O157:H7 isolates were determined. Triggered at pH 5.0, the adaptive System of the ATR allowed for up to nearly 1,000-fold enhanced survival of E. coli O157:H7 cells in some cases compared to survival of nonadapted cells at pH 4.0. E. coli O157:H7 isolates revealed greater acid tolerance responses when incubated statically at 32°C, whereas the non-O157:H7 coli isolates exhibited a greater acid tolerance response with orbital agitation at 25°C. The magnitude of response changed over the incubation period.

scholarly journals An acid-tolerance response system protecting exponentially growing Escherichia coli

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Ying Xu ◽  
Zhe Zhao ◽  
Wenhua Tong ◽  
Yamei Ding ◽  
Bin Liu ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acid Tolerance ◽  
Acid Tolerance Response ◽  
Response System ◽  
Tolerance Response

scholarly journals Global Analysis of Escherichia coli Gene Expression during the Acetate-Induced Acid Tolerance Response

2001 ◽  
Vol 183 (7) ◽  
pp. 2178-2186 ◽  
Author(s):  
Carrie N. Arnold ◽  
Justin McElhanon ◽  
Aaron Lee ◽  
Ryan Leonhart ◽  
Deborah A. Siegele
Keyword(s):  
Escherichia Coli ◽  
Global Analysis ◽  
Acid Tolerance ◽  
Short Chain Fatty Acids ◽  
Low Ph ◽  
Insertion Mutation ◽  
Acid Tolerance Response ◽  
E Coli ◽  
Serovar Typhimurium ◽  
Tolerance Response

ABSTRACT The ability of Escherichia coli to survive at low pH is strongly affected by environmental factors, such as composition of the growth medium and growth phase. Exposure to short-chain fatty acids, such as acetate, proprionate, and butyrate, at neutral or nearly neutral pH has also been shown to increase acid survival of E. coli and Salmonella enterica serovar Typhimurium. To investigate the basis for acetate-induced acid tolerance in E. coli O157:H7, genes whose expression was altered by exposure to acetate were identified using gene arrays. The expression of 60 genes was reduced by at least twofold; of these, 48 encode components of the transcription-translation machinery. Expression of 26 genes increased twofold or greater following treatment with acetate. This included six genes whose products are known to be important for survival at low pH. Five of these genes, as well as six other acetate-induced genes, are members of the E. coli RpoS regulon. RpoS, the stress sigma factor, is known to be required for acid tolerance induced by growth at nonlethal low pH or by entry into stationary phase. Disruption of therpoS gene by a transposon insertion mutation also prevented acetate-induced acid tolerance. However, induction of RpoS expression did not appear to be sufficient to activate the acid tolerance response. Treatment with either NaCl or sodium acetate (pH 7.0) increased expression of anrpoS::lacZ fusion protein, but only treatment with acetate increased acid survival.

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