PARENT SESSION
Oral Session # 22: Pathogens, Toxins, and Disease I: Modeling ; Mammalian.
Presiding: J Foufopoulos
Tuesday, August 5. 8:00 AM to 11:30 AM, SITCC Meeting Room 201.
Genomic response of Vibrio cholerae to changes in aquatic nutrient levels.
Chiavelli, Deborah*,1, 2, Cottingham, Kathryn2, Ringelberg, Carol1, Taylor, Ronald1, 1 Dartmouth Medical School, Hanover, NH, USA2 Dartmouth College, Hanover, NH, USA
ABSTRACT- Vibrio cholerae is both the causative agent of the emerging infectious disease, cholera, and a common planktonic bacterium in aquatic ecosystems all over the world. With a fully sequenced and well-studied genome, microarray technology can be used to study changes in V. cholerae gene expression in varying environmental conditions, and to link these responses to both bacterial dynamics in aquatic ecosystems and cholera epidemiology in human populations that utilize these ecosystems. Seasonal outbreaks of cholera in some tropical regions appear to coincide with plankton blooms, and V. cholerae is often found attached to zooplankton and phytoplankton surfaces, a behavior believed to enhance survival, growth, and transmission to human hosts. Nutrient levels and the availability of attachment surfaces are also generally important to the dynamics and productivity of pelagic heterotrophic bacteria. We quantified the effect of nutrient conditions (three levels of C, N, and P spanning a typical annual range in natural aquatic habitats) on gene expression in V. cholerae at two time points after introduction into freshwater medium. Expression of many V. cholerae genes responded to nutrient conditions, including genes regulating nutrient uptake and metabolism, protein synthesis, cell growth and stress responses, environmental sensor systems, and flagellar structure and function. The same behaviors (motility changes, chemotaxis, attachment), and in some cases the same genes, are necessary for the initiation of cholera pathogenicity in the human intestine and for attachment to planktonic substrates. These processes are hypothesized to respond to poor environmental conditions (e.g. low nutrients) in a way that increases contact with, and attachment to, surfaces. However, we did not see nutrient-induced differences in expression of known pathogenicity or attachment genes. This indicated that signals from a substrate may also be needed. We are currently investigating V. cholerae gene response to the presence of zooplankton to test this hypothesis.
Key words: zooplankton, emerging infectious diseases, bacteria, genomics