Consilience of iron in the ecology of Vibrio bacteria
Westrich, Jason Robert
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Vibrio are common heterotrophic bacteria found in marine waters around the world. Vibrio have a large repertoire of metabolic potential and are able to mount a rapid response to new sources of nutrients, they therefore play an important, but poorly defined role in nutrient cycling in the ocean. Members of this genus are also important pathogens able to cause disease in humans and many marine organisms. Key to Vibrio survival, both in the environment as well as in an animal host is the ability to acquire the essential trace element iron. In a series of studies I investigated the importance of iron in the survival and growth of both environmental and pathogenic strains of Vibrio, demonstrating that heterotrophic bacteria, like Vibrio play a key role in iron cycling in marine ecosystems. Most investigations have predominantly focused on autotrophic phytoplankton because of the high demand of iron in photosynthetic processes; therefore, there is a paucity of methodologies for directly studying iron limitation in marine heterotrophic bacteria. The initial efforts of this dissertation work were to develop a novel iron limited artificial seawater system in which to study Vibrio response to iron limitation as well as their response to various sources of iron. The remainder of the dissertation demonstrates the importance of heterotrophs, like Vibrio, in processing iron from Saharan dust. Because dust blown from the Sahara is a major source of iron to downwind marine communities, I investigated the effects of this ephemeral pulse of iron both in manipulative and in situ investigations in the Tropical Mid Atlantic and Caribbean. In this dissertation, I show the critical importance of iron in the growth and survival of Vibrio, having important implications in marine biogeochemical cycling of iron as well as disease potential.