| Engineering
Support Services - Microbial Source Tracking
Today,
wastewater utilities face many regulatory challenges.
With the advent of Total
Maximum Daily Loads (TMDLs) for E. coli,
it is more important than ever to identify pollutant sources
so that contamination can be mitigated effectively.
Microbial
Source Tracking is a tool that can assist regulators
and engineers in the identification
of sources of E.
coli contamination such as concentrated animal feeding
operations (CAFOs)
and non-point source pollution from dogs, cats,
or other animals. The technology can also be employed
to help make decisions related to identifying contaminant
sources that affect
recreational waters (e.g. recreational beach closures).
SMI
offers multiple options for gathering E. coli source
tracking information. E. coli source data
can be obtained by characterizing coliphage serotypes within the affected water body. Dr. Fu-Chih Hsu, SMI's
Director of Operations, was one of the principal developers
of the EPA methods for detecting coliphages in water (EPA Methods 1601/1602). SMI scientists have further adapted
these techniques for application to microbial source tracking efforts to study the relationships between coliphages and the species of origin. It is now possible to perform analyses using coliphages as biomarkers to determine whether a water body is affected primarily by human wastewater or by nonpoint discharges of fecal contamination arising from animals.
Microbial
Source Tracking using oligoprobe hybridization to classify coliphages into genogroups
When
water samples are subjected to EPA method 1602, bacterial viruses are enumerated
within the plates by counting the small clearings, or viral 'plaques' within the opaque bacterial lawns. Viruses can be recovered from these plaques and subjected to oligoprobe hybridization
to determine the specific immunological groups to which the viruses belong. Hybridization
analysis relies upon the use of specific probes that are labeled with enzymes; probes will bind
only to the nucleic acid (RNA or DNA) of the specific coliphage serogroup of interest.
Classification of coliphage isolates into one of four serogroups then makes it possible to determine the probability that the indicator viruses originated from either an animal or a human host. Coliphages
that correspond to human feces are statistically associated
with phage groups 2 and 3, whereas animal coliphages are
associated with phage groups 1 and 4.
Microbial Source Tracking via Pulsed Field Gel Electrophoresis
SMI also employs advanced biotechnologies such as Pulsed Field Gel Electrophoresis (PFGE)
to determine the genetic relatedness of microorganisms isolated from treated wastewater
streams (human strains) and from pollutant sources that may harbor E. coli originating from animals. Confirmation of the genetic identities of these isolates can help regulators determine the appropriateness of implementing changes in wastewater treatment or instead focusing on watershed protection measures unrelated to wastewater utility practices. SMI has the capacity to collect and analyze sufficient numbers of isolates so that Microbial Source Tracking data can be interpreted appropriately and confidently.
REFERENCES
Hsu,
F.-C. , Shieh, Y.-S.C., Van Duin, J., Beekwilder,
M.J., and M.D. Sobsey. (1995). Genotyping
male-specific RNA coliphages by hybridization with oligonucleotide
probes.
Appl. Environ. Microbiol., 61:3960-3966.
Hsu,
F.-C. ,Weaver, J.A., Blum, K., C.-I. Wong, and J. Larkin . (1999). Distinguishing
sources of fecal contamination in surface water by isolating
and serotyping male-specific
RNA coliphages. The
1999 annual conference for the Association of State Drinking
Water Administrators, Orlando, FL.
For further information about SMI's services, please feel to contact a project manager at (574) 277-4078.
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