Forum 07/23/2009

“Nano to Microscale relationships in the time of Cholera”

Farooq Azam – Scripps Institution of Oceanography, UC San Diego

Marine microbes are extremely abundant and genetically diverse and they are the dominant metabolic force in the ocean’s carbon cycle. Bacteria and Archaea interact metabolically with the carbon fixed into organic matter by cyanobacteria and microalgae to utilize a variable but often large fraction of it. Therefore, they play a major role in the ocean’s response to global climate change. An intriguing challenge in microbial oceanography is that organic matter and microbes are distributed heterogeneously at the nanometer to micrometer scales– the scales at which microbes interact with it and with other microbes–to influence the /variability/ in ocean’s biogeochemical state (e.g. whether a large fraction of carbon is respired back to the atmosphere or sinks to the ocean’s depths). Microscale interactions with organic matter also appear to be important in the persistence and proliferation of human pathogens in the ocean, and may be a consideration in the future emergence of new pathogens. Vibrio cholerae, a marine bacterium, is one example. It’s environmental pool is regulated by multiple trophic interactions (involving bacterial antagonists, protists and phage) modulated by the microscale architecture of the ocean’s organic matter. High resolution imaging of the microbe’s and their natural settings in seawater is an exciting challenge that has broad implications for predicting the effects of marine microbes in ocean and human health.

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