The incidence of bdellovibrios in an artificial environment: the national aquarium in Baltimore

Abstract

The presence of bdellovibrios was established in three aquatic tanks in the National Aquarium in Baltimore and the incidence of the predators was studied. Each of three tanks differed in physical and chemical properties and in the kinds of animal inhabitants. Samples of water, sediment, and bioring surface film were collected from various tanks and were cultured for bdellovibrios and heterotrophic bacteria. The total number of bacteria in the samples was estimated by the direct count method. At the time of sampling, measurements were taken of the water temperature and salinity. Of 12 samples collected periodically from each of two tanks over a 12-month period, bdellovibrios were recovered from 8 samples. In a third tank the predators were recovered from 7 of the 12 samples. Of samples collected daily over a 10-day period from two tanks, bdellovibrios were recovered from one tank each day, but the organisms were not recovered from the second tank during the 10-day period. The predators were recovered more often from water and sediment samples than from samples of the surface film of biorings. With few exceptions, a greater number of the predators were recovered from sediment samples than from samples of water and bioring surface film. From each tank the number of bdellovibrios recovered was observed to fluctuate greatly. The basis for the observed fluctuations was not determined. The incidence of recovery of bdellovibrios from aquarium tanks in this study suggests that the organisms are capable of becoming established as resident flora in an artificial environment such as an aquarium. An aquarium with suitable environmental conditions presents great opportunities to conduct carefully selected studies on the ecology of bdellovibrios in an environment in which certain chemical and physical factors are controlled. Studies of bdellovibrios in controlled environments may lead to a greater understanding of the activities and role of these predators.