<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 lives symbiotically in the light organs of squid and other cephalopods. It is a very common bacterium, and is found in a wide range of environments, including the ocean. It is commonly used in laboratory experiments to study the behavior of bacteria in response to light.