Abstract

A novel phenotype was recently identified in which specific strains of Escherichia coli inhibit competing E. coli strains via a mechanism that was designated "proximity-dependent inhibition" (PDI). PDI-expressing (PDI(+)) E. coli is known to inhibit susceptible (PDI(-)) E. coli strains, including several enterohemorrhagic (EHEC) and enterotoxigenic (ETEC) E. coli strains. In this study, every strain from a genetically diverse panel of E. coli O157:H7 (n = 25) and additional strains of E. coli serovar O26 were susceptible to the PDI phenotype. LIVE/DEAD staining was consistent with inhibition by killing of susceptible cells. Comparative genome analysis identified the genetic component of PDI, which is composed of a plasmid-borne (Incl1) operon encoding a putative microcin and associated genes for transport, immunity, and microcin activation. Transfer of the plasmid to a PDI(-) strain resulted in transfer of the phenotype, and deletion of the genes within the operon resulted in loss of the inhibition phenotype. Deletion of chromosomally encoded tolC also resulted in loss of the inhibitory phenotype, and this confirmed that the putative microcin is most likely secreted via a type I secretion pathway. Deletion of an unrelated plasmid gene did not affect the PDI phenotype. Quantitative reverse transcription (RT)-PCR demonstrated that microcin expression is correlated with logarithmic-phase growth. The ability to inhibit a diversity of E. coli strains indicates that this microcin may influence gut community composition and could be useful for control of important enteric pathogens.

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Publisher Full Text

Authors

Eberhart LJ, Deringer JR, Brayton KA, Sawant AA, Besser TE, Call DR

Institution

Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, USA.

Source

Applied and environmental microbiology 78:18 2012 Sep pg 6592-9

MeSH

Anti-Bacterial Agents
Antibiosis
Bacteriocins
DNA, Bacterial
Enterohemorrhagic Escherichia coli
Escherichia coli Proteins
Gene Deletion
Gene Expression Profiling
Gene Transfer, Horizontal
Genes, Bacterial
Molecular Sequence Data
Operon
Plasmids
Real-Time Polymerase Chain Reaction
Sequence Analysis, DNA

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

22773653