<human>:  What is the most abundant bacterial species in the Pacific Ocean?
<bot>: The most abundant bacterial species in the Pacific Ocean is Vibrio fischeri. Vibrio fischeri is a marine bacterium that lives in symbiosis with squid. Vibrio fischeri is found in the light organ of the squid, where it provides the squid with nutrients. Vibrio fischeri is also found in the light organ of the lantern fish, where it is believed to help the fish digest its food.