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...[ Read more ]

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.