A study of the ecology of bioluminescent bacteria in a marine environment

Bioluminescent bacteria were readily isolated from several niches in an estuarine environment of the East Lagoon in Galveston, Texas. These sites included the water column, sediment, shrimp and gastrointestinal tract of marine fishes. In this semi-tropical estuary, the numbers of luminous bacteria in the water column were observed to fluctuate with the water temperatures, with highest counts detected during the warmest months. During the cold weather, a larger percentage of luminous bacteria were found in the sediment. This niche may serve as a resevoir for "free-living" luminous bacteria in cold months. Unlike other studies, Beneckea harveyi was found to be the dominant, if not the only, species of bioluminescent bacteria isolated. The highest numbers and highest percentage of luminous organisms in the total bacterial population were isolated from the gastrointestinal tract of marine fishes. Bioluminescent bacteria were found to survive well in the fish intestines for up to five days of starvation. It was proposed that the gut may well be the preferred natural habitat of luminescent bacteria.