<human>:  What is the most abundant bacterial species in the Pacific Ocean?
<bot>: That would be the bacterium Vibrio fischeri. Vibrio fischeri is a marine bacterium that is found in the ocean, and is part of the normal microbial community in the ocean. It is one of the most abundant species in the Pacific Ocean, and is a well-known model organism for studying the biology of light-dependent bacterial photosynthesis.