Characterization of Environmentally Persistent Escherichia coli
Isolates Leached from an Irish Soil
Fiona P. Brennan,1,2 Florence Abram,2 Fabio A. Chinalia,3 Karl G. Richards,2 and Vincent O’Flaherty2*
Department of Microbiology,
School of Natural Sciences and Environmental Change Institute,
National University of Ireland, Galway, Ireland.
Soils are typically considered to be suboptimal environments for enteric organisms, but there is increasing
evidence that Escherichia coli populations can become resident in soil under favorable conditions. Previous
work reported the growth of autochthonous E. coli in a maritime temperate Luvic Stagnosol soil, and this study
aimed to characterize, by molecular and physiological means, the genetic diversity and physiology of environmentally
persistent E. coli isolates leached from the soil. Molecular analysis (16S rRNA sequencing, enterobacterial
repetitive intergenic consensus PCR, pulsed-field gel electrophoresis, and a multiplex PCR method)
established the genetic diversity of the isolates (n = 7), while physiological methods determined the metabolic
capability and environmental fitness of the isolates, relative to those of laboratory strains, under the conditions
tested. Genotypic analysis indicated that the leached isolates do not form a single genetic grouping but that
multiple genotypic groups are capable of surviving and proliferating in this environment. In physiological
studies, environmental isolates grew well across a broad range of temperatures and media, in comparison with
the growth of laboratory strains. These findings suggest that certain E. coli strains may have the ability to
colonize and adapt to soil conditions. The resulting lack of fecal specificity has implications for the use of E.
coli as an indicator of fecal pollution in the environment.
Keywords:Escherichia coli;16S rRNA sequencing;microorganism;taxonomy.
Corresponding author: Tel 353 (0) 91493734,
Fax 353 (0) 91494598.