The focus of this research was to develop bacterial community indicators of
stream sanitary and ecological condition. The first study compared substrate utilization
patterns between centrifuged and uncentrifuged split samples. We found a shift in the
relative proportion of each group of bacteria following centrifugation, with a marked
increased in the fecal coliform group and relatively fewer heterotrophic and total coliform
bacteria. Centrifuged samples consistently responded faster and oxidized more substrate
than did their uncentrifuged counterparts. Substrate utilization patterns of centrifuged
sub-samples from 19 sites showed better separation between Willamette Valley and
Cascade ecoregions than did the uncentrifuged sub-samples in ordination space. We
recommend developing microtiter plates with substrates specific types of environmental
stress. The second study determined the minimum volume of water needed and the
maximum time and temperature that bacteriological water samples captured on a
membrane filter can be held in guanidine isothiocyanate buffer (GITC) prior to DNA
extraction for community fingerprint analysis. We found 100 ml water samples yielded
more information than the 50 ml or the 250 ml water samples and observed a marked
decrease in information for samples that were held at room temperature for more than 24
hours. We concluded that 100 ml samples were optimal for bacterial community DNA
fingerprint analysis. Furthermore, we recommended transporting filtered water samples
held in GITC on ice and keeping the samples frozen until DNA is extracted for further
analysis. The third study addressed questions of sampling error and response variability
of two PCR-based indicators, bacterial community-level Terminal-Restriction Fragment
Length Polymorphisms and Bacteroidetes ruminant and human specific fecal source
tracking markers. We found the T-RPLP and Bacteroidetes markers to show very little
sampling error, and suggested collecting a single 1-liter water sample. A high turbidity
scenario resulting in higher fecal pollution and lower bacterial species richness explained
why decreased TRF richness was strongly associated with high fecal coliform density,
turbidity, and human Bacteroidetes detection. We propose that in times of increased
turbidity, a disturbance in the bacterial community occurs, reducing bacterial richness
and increasing a few types of stress-resistant fecal bacteria. / Graduation date: 2004
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/30572 |
| Date | 08 September 2003 |
| Creators | Bracken, Caragwen L. |
| Contributors | Harding, Anna K. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
Page generated in 0.0024 seconds