THESIS
2016
xvi, 114 pages : illustrations (some color) ; 30 cm
Abstract
Habitat transition of fecal bacterial community from animal host into the aquatic system
gained extra attention from microbial ecologist because of its implication on public health risk
and environmental impact. Fecal indicator bacteria (FIB) have been employed for health risk
assessment based on the assumption that these bacteria are unable to withstand these stresses
and gradually die off in the external environment. However, some studies reported prolonged
survival and growth of the bacteria occurred in marine sediment. This unexpected
phenomenon raises concerns on the origin, adaptation and diversity of these bacteria in the
external environment. We investigated the effects of habitat transition from animal host to
subtropical marine sediment on bacterial population dynamics...[
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Habitat transition of fecal bacterial community from animal host into the aquatic system
gained extra attention from microbial ecologist because of its implication on public health risk
and environmental impact. Fecal indicator bacteria (FIB) have been employed for health risk
assessment based on the assumption that these bacteria are unable to withstand these stresses
and gradually die off in the external environment. However, some studies reported prolonged
survival and growth of the bacteria occurred in marine sediment. This unexpected
phenomenon raises concerns on the origin, adaptation and diversity of these bacteria in the
external environment. We investigated the effects of habitat transition from animal host to
subtropical marine sediment on bacterial population dynamics and community structure via
microcosm experiments. The dynamic change of bacteria community structure was found
influenced by the indigenous microbes in the marine sediment. To the conventional FIB, i.e.
cultivable E. coli and Enterococcus spp., the indigenous microbes suppressed their initial
growth and promoted their decay, while high seawater temperature (30 °C) first accelerated
growth but also promoted subsequent die-off. Besides, prolonged survival of an emerging
FIB, i.e. Bacteroidales, and the uncertain correlation between abundances of FIB and some
pathogens were observed in marine sediment. Phylogenetic group and DNA fingerprinting
analysis of E. coli isolated from the microcosm revealed their differential survival. The
phenotypic tests revealed the ability of E. coli to resist predation and form biofilm, and the
energy tradeoff between storage and other survival strategies are important to their survival in
marine sediment. Results indicate that population dynamics and bacterial community
structure in marine sediment are affected by indigenous microbes and the variation of
seawater temperature, and particular strains of E. coli are more capable of surviving. These findings provide the first insight into the habitat transition event from ecological and practical
point of view.
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