Vibrio are members of a bacterial group that thrive in diverse aquatic environments including on the surface of aquatic animals, free-living in the water column, and in association with suspended particles. The total Vibrio counts in the coastal ocean ranges from 103-105 per milliliter of water depending on seasons and water temperature. Although many different species of Vibrio persist in the water column, pathogenic strains, such as Vibrio cholerae and Vibrio parahaemolyticus are absent or rare in marine environments. We hypothesize that the low abundance of these pathogenic species may be due to interspecific competition among environmental strains, in which the pathogens are inhibited or out-competed by distantly related non-pathogenic isolates. In order to test this hypothesis, 3,456 environmental strains isolated from size fractionated marine particles were individually tested for their ability to inhibit Vibrio pathogens that cause disease in humans. Because pathogenic Vibrio species are not observed in coastal marine environments, natural strains exhibiting antagonistic activity are expected to produce antibiotics that inhibit the growth of Vibrio pathogens that cause cholera around the world. In this study, we identified 131 environmental isolates that showed an antagonistic phenotype against a panel of eight different Vibrio pathogens. Of the 131 environmental strains, eight isolates were able to kill six or more pathogens and were defined as super-killers (SKs) because of their ability to inhibit multiple pathogens. These SKs represent a promising source of novel antibiotics.
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Joy, Abigail, "Super-Killers: Environmental Isolates that Antagonize Pathogenic Vibrio" (2015). Honors Projects. 676.