Ohio Water Microbiology Lab
Research Topics
Internal Information
Ohio Water Science Center
USGS In Your State
USGS Water Science Centers are located in each state.
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OWML: QA/QC
Quality Assurance/Quality Control Manual: Ohio Water Microbiology
Laboratory
Research
Methods
Rapid methods for fecal-indicator bacteria
Traditional microbiological methods for detecting fecal-indicator bacteria and
pathogenic organisms can take at least 18 hours to obtain results. Because water
quality can change significantly during this timeframe, the safety of the water
may not be accurately assessed. The need for rapid detection methods that
provide reliable results of the current day’s water-quality conditions is widely
recognized. The USGS Ohio Water Microbiology Laboratory (OWML) is currently
testing two rapid detection methods for the enumeration of E. coli and
enterococci.
The immunomagnetic separation/adenosine triphosphate (IMS/ATP) rapid method
requires approximately 1 hour from sample collection to availability of results
(Bushon and others, 2007; Bushon and others, in press; Lee and Deininger, 2004).
Magnetic beads that are coated with antibodies for either Escherichia coli (E.
coli) or enterococci are added to a water sample. This mixture is then subjected
to IMS, in which the bacteria-antibody-bead complex is separated from extraneous
materials in the sample by use of a strong magnet. Following several
wash/concentration steps, the bacterial cells are ruptured by an enzymatic
process, releasing ATP, which is the energy molecule found in living cells. The
amount of ATP in the sample is measured with a microluminometer and results are
reported in relative light units (RLUs).
The quantitative polymerase chain reaction (qPCR) method enumerates targeted
genetic sequences within microorganisms in less than three hours. First, water
samples are concentrated either by passing through a 0.4 µm filter. The
concentrated organisms are lysed by both physical and chemical disruption and
the genetic material that was contained in these organisms is then isolated and
purified. The qPCR is run and the genetic sequence unique to the organism of
interest is quantified by detecting the accumulation of a fluorescent probe. |