pH Effects and Cooperativity among Key Titratable Residues for Escherichia coli Glycinamide Ribonucleotide Transformylase

2021 ◽  
Author(s):  
Pancham Lal Gupta ◽  
Justin S. Smith ◽  
Adrian E. Roitberg
Keyword(s):  
Escherichia Coli ◽  
Ph Effects ◽  
Glycinamide Ribonucleotide Transformylase

Inhibition of Escherichia coli by Bifidobacteria

1993 ◽  
Vol 56 (8) ◽  
pp. 713-715 ◽  
Author(s):  
SALAM A. IBRAHIM ◽  
ANATOLY BEZKOROVAINY
Keyword(s):  
Escherichia Coli ◽  
Acid Mixture ◽  
Ph Effects ◽  
Fermentation Products ◽  
E Coli ◽  
Antimicrobial Substances ◽  
Neutral Ph ◽  
Lactic Acids ◽  
Coli Growth

The ability of five ATCC bifidobacterial species to produce antimicrobial substances was investigated by testing the effects of spent bifidobacterial broths on the growth Escherichia coli in the thioglycollate medium. Such broths were most inhibitory if their pH was not readjusted to neutrality. When that was done, the inhibition ranged from 30 to 43%. Such inhibition of E. coli growth could be duplicated by a 3:2 aceticlactic acid mixture adjusted to neutral pH. It was concluded that no antibacterial substances other than acetic and lactic acids were produced by bifidobacterial strains used, and that the effects of these ubiquitous fermentation products, as well as pH effects, be taken into consideration before the existence of other antimicrobial factors is proposed.

Biofilm Growth of Escherichia coli Is Subject to cAMP-Dependent and cAMP-Independent Inhibition

2015 ◽  
Vol 25 (2-3) ◽  
pp. 209-225 ◽  
Author(s):  
Sarah L. Sutrina ◽  
Kia Daniel ◽  
Michael Lewis ◽  
Naomi T. Charles ◽  
Cherysa K.E. Anselm ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Catabolite Repression ◽  
Ph Effects ◽  
Wild Type ◽  
Inhibitory Effects ◽  
Phosphotransferase System ◽  
Biofilm Growth ◽  
E Coli ◽  
Low Concentrations ◽  
High Concentrations

We established that <i>Escherichia coli </i>strain 15 (ATCC 9723) produces both curli and cellulose, and forms robust biofilms. Since this strain is wild type with respect to the phosphoenolpyruvate:sugar phosphotransferase system (PTS), it is an ideal strain in which to investigate the effects of the PTS on the biofilm growth of <i>E. coli</i>. We began by looking into the effects of PTS and non-PTS sugars on the biofilm growth of this strain. All the sugars tested tended to activate biofilm growth at low concentrations but to inhibit biofilm growth at high concentrations. Acidification of the medium was an inhibitory factor in the absence of buffer, but buffering to prevent a pH drop did not prevent the inhibitory effects of the sugars. The concentration at which inhibition set in varied from sugar to sugar. For most sugars, cyclic (c)AMP counteracted the inhibition at the lowest inhibitory concentrations but became ineffective at higher concentrations. Our results suggest that cAMP-dependent catabolite repression, which is mediated by the PTS in <i>E. coli</i>, plays a role in the regulation of biofilm growth in response to sugars. cAMP-independent processes, possibly including Cra, also appear to be involved, in addition to pH effects.

scholarly journals Protective Effects of Organic Acids on Survival of Escherichia coli O157:H7 in Acidic Environments

2006 ◽  
Vol 72 (1) ◽  
pp. 660-664 ◽  
Author(s):  
K. Bjornsdottir ◽  
F. Breidt ◽  
R. F. McFeeters
Keyword(s):  
Escherichia Coli ◽  
Lactic Acid ◽  
Organic Acids ◽  
Protective Effect ◽  
Low Ph ◽  
Ph Effects ◽  
E Coli ◽  
Cell Numbers ◽  
Log Reduction ◽  
Cell Counts

ABSTRACT Outbreaks of disease due to acid-tolerant bacterial pathogens in apple cider and orange juice have raised questions about the safety of acidified foods. Using gluconic acid as a noninhibitory low-pH buffer, we investigated the killing of Escherichia coli O157:H7 strains in the presence or absence of selected organic acids (pH of 3.2), with ionic strength adjusted to 0.60 to 0.68. During a 6-h exposure period in buffered solution (pH 3.2), we found that a population of acid-adapted E. coli O157:H7 strains was reduced by 4 log cycles in the absence of added organic acids. Surprisingly, reduced lethality for E. coli O157:H7 was observed when low concentrations (5 mM) of fully protonated acetic, malic, or l-lactic acid were added. Only a 2- to 3-log reduction in cell counts was observed, instead of the 4-log reduction attributed to pH effects in the buffered solution. Higher concentrations of these acids at the same pH aided in the killing of the E. coli cells, resulting in a 6-log or greater reduction in cell numbers. No protective effect was observed when citric acid was added to the E. coli cells. d-Lactic acid had a greater protective effect than other acids at concentrations of 1 to 20 mM. Less than a 1-log decrease in cell numbers occurred during the 6-h exposure to pH 3.2. To our knowledge, this is the first report of the protective effect of organic acids on the survival of E. coli O15:H7 under low-pH conditions.

Crystal structure of glycinamide ribonucleotide transformylase from Escherichia coli at 3·0 Å resolution

1992 ◽  
Vol 227 (1) ◽  
pp. 283-292 ◽  
Author(s):  
Ping Chen ◽  
Ursula Schulze-Gahmen ◽  
Enrico A. Stura ◽  
James Inglese ◽  
Dana L. Johnson ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Escherichia Coli ◽  
Glycinamide Ribonucleotide Transformylase
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