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Trophic regulation of Vibrio cholerae in coastal marine waters

Authors

  • Alexandra Z. Worden,

    Corresponding author
    1. Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA.
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    • Present address: Marine Biology and Fisheries Division, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Cswy, Miami, FL 33149, USA.

  • Michael Seidel,

    1. Institute of Chemistry and Biology of the Marine Environment, Carl von Ossietzky University of Oldenburg, 26111 Oldenburg, Germany.
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  • Steven Smriga,

    1. Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA.
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  • Arne Wick,

    1. Institute of Chemistry and Biology of the Marine Environment, Carl von Ossietzky University of Oldenburg, 26111 Oldenburg, Germany.
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  • Francesca Malfatti,

    1. Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA.
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  • Douglas Bartlett,

    1. Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA.
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  • Farooq Azam

    1. Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA.
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*E-mail aworden@rsmas.miami.edu; Tel. (+1) 305 421 4616; Fax (+1) 305 421 4600.

Summary

Cholera disease, caused by the bacterium Vibrio cholerae, afflicts hundreds of thousands worldwide each year. Endemic to aquatic environments, V. cholerae's proliferation and dynamics in marine systems are not well understood. Here, we show that under a variety of coastal seawater conditions V. cholerae remained primarily in a free-living state as opposed to attaching to particles. Growth rates of free-living V. cholerae (µ: 0.6–2.9 day−1) were high (similar to reported values for the bacterial assemblages; 0.3–2.5 day−1) particularly in phytoplankton bloom waters. However, these populations were subject to heavy grazing-mortality by protozoan predators. Thus, grazing-mortality counterbalanced growth, keeping V. cholerae populations in check. Net population gains were observed under particularly intense bloom conditions when V. cholerae proliferated, overcoming grazing pressure terms in part via rapid growth (> 4 doublings day−1). Our results show V. cholerae is subject to protozoan control and capable of utilizing multiple proliferation pathways in the marine environment. These findings suggest food web effects play a significant role controlling this pathogen's proliferation in coastal waters and should be considered in predictive models of disease risk.

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