The Diversity of Vibrio Bacteria in Sediment and Surface Waters of Boca Ciega Bay, Florida

Vibrios are among the most abundant culturable bacteria in coastal waters. The genus Vibrio has a large number of species, which include several bioluminescent forms. This laboratory has spent many years studying bioluminescent Vibrios in Boca Ciega Bay, Florida, and has amassed a large amount of data on species diversity and seasonal variations in the bioluminescent Vibrio community. There are definite summer species, dominated by Vibrio campbellii and Vibrio harveyi, and winter species, dominated by Vibrio chagasii. Since seasonal seawater temperatures vary from as low as 15oC in the winter to as high as 35oC in the summer, it is likely that seasonal variations in the community are driven primarily by temperature. A question that has arisen over the course of this work is whether the sediment acts as an off-season reservoir for bioluminescent Vibrios. The work described here explores and expands that question, addressing the diversity of both bioluminescent and non-bioluminescent Vibrios in Boca Ciega Bay. Vibrios were isolated on Vibrio-select TCBS (thiosulfate-citrate-bile salts-sucrose) growth medium from sediment at various depths. In addition, Vibrios were isolated from surface water during the same time period. Species identification was done using gene sequencing. Bioluminescent Vibrios were identified using the luxA gene, and non-bioluminescent Vibrios were identified using the mreB gene. Genes were amplified using PCR, purified, fingerprinted using the restriction enzyme Alu1, sequenced, identified using the BLAST program, and then subjected to phylogenetic analysis. Among the conclusions: (1) A wide variety of Vibrios, including summer and winter bioluminescent species, can be found in sediment as deep as 9 cm. (2) Both sediment and surface water harbor a wide diversity of non-bioluminescent Vibrios, some of which have sufficiently low identity scores that they might represent previously undescribed species