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Title: Identification of genes required for growth of Escherichia coli MG1655 at moderately low pH
Authors: Vivijs, Bram
Aertsen, Abram
Michiels, Chris # ×
Issue Date: 2016
Publisher: Frontiers Research Foundation
Series Title: Frontiers in Microbiology vol:7
Article number: 1672
Abstract: The survival of some pathotypes of E. coli in very low pH environments like highly acidic foods and the stomach has been well
documented and contributes to their success as foodborne pathogens. In contrast, the ability of E. coli to grow at moderately low
pH has received less attention, although this property can be anticipated to be also very important for the safety of mildly acidic
foods. Therefore, the objective of this study was to identify cellular functions required for growth of the non-pathogenic strain E.
coli MG1655 at low pH. First, the role of the four E. coli amino acid decarboxylase systems, which are the major cellular
mechanisms allowing extreme acid survival, was investigated using mutants defective in each of the systems. Only the lysine
decarboxylase (CadA) was required for low pH growth. Secondly, a screening of 8544 random transposon insertion mutants
resulted in the identification of six genes affecting growth in LB broth acidified to pH 4.50 with HCl. Two of the genes, encoding
the transcriptional regulator LeuO and the elongation factor P‐β‐lysine ligase EpmA, can be linked to CadA production. Two other
genes, encoding the diadenosine tetraphosphatase ApaH and the tRNA modification GTPase MnmE, have been previously implicated
in the bacterial response to stresses other than low pH. A fifth gene encodes the LPS heptosyltransferase WaaC, and its mutant has
a deep rough colony phenotype, which has been linked to reduced acid tolerance in earlier work. Finally, tatC encodes a
secA-independent protein translocase that exports a few dozen proteins and thus is likely to have a pleiotropic phenotype. For
mnmE, apaH, epmA,and waaC, de novo in frame deletion and genetic complementation confirmed their role in low pH growth, and
these deletion mutants were also affected in growth in apple juice and tomato juice. However, the mutants were not affected in
survival in gastric simulation medium at pH 2.5, indicating that growth at moderately low pH and survival of extremely low pH
depend mostly on different cellular functions.
ISSN: 1664-302X
Publication status: accepted
KU Leuven publication type: IT
Appears in Collections:Centre for Food and Microbial Technology
× corresponding author
# (joint) last author

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