Biology Reference
In-Depth Information
Abstract
Although
E. coli
is an indicator of fecal contamination in aquifers, limited research has been
devoted to understanding the biological processes involved in the initial attachment of
E. coli
transported in abiotic porous media. The roles of the various surface structures of
E. coli
, like
lipopolysaccharides (LPS), auto-transporter proteins, and fimbriae are unknown. The objective
of this research was to establish the effects of variations in surface characteristics of the outer
membrane of
E. coli
on the attachment efficiency of 54
E. coli
strains upon transport in saturated
quartz sand under identical flow conditions. We used column experiments to assess retention of
the
E. coli
strains, and we determined sphericity, motility, zeta-potential, and aggregation of all
strains. LPS composition was determined based on known serotypes, and the presence/absence
of 22 genes encoding surface characteristics was determined with qualitative PCR. The results
indicated that under identical flow conditions, there was a variation of two orders of magnitude
in the maximum breakthrough concentrations of the 54
E. coli
strains. Of all factors we
investigated, no single factor was able to explain attachment efficiency variations statistically
significantly. However, low attachment efficiencies were associated (
=
p
) with LPS
containing saccharides with phosphate and/or carboxyl groups. These saccharide groups are
acidic and likely charged with a negative O-atom, which reduced attachment to the negatively
charged quartz surface. In addition, of the 22 genes tested,
Afa
was most associated (
0
13
=
p
)
with attachment efficiency. The work presented here bridges knowledge on colloid transport and
molecular microbiology, and tries to offer a more holistic view on the attachment of planktonic
E. coli
bacteria to (abiotic) quartz grain surfaces. Future research should evaluate the use of
microbiological techniques in order to be able to map the unique or grouped characteristics of
E.
coli
in aquifers, and to assess the usefulness of
E. coli
as a fecal indicator in aquifers.
0
21
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