The association of bdellovibrios with surfaces in the aquatic environment

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Abstract
In the aquatic environment, the association of microorganisms with surfaces represents an important phase in the life cycle and ecology of many microbial species. However, previous studies to understand the ecology of the bdellovibrios have ignored examination of the role of surfaces and surface association. In this report, the association of bdellovibrios with sterile surfaces and the stability of the organisms on abiotic and biotic surfaces were investigated. Sterilized oyster shells, glass slides, and steel and titanium surfaces were submerged in the Patuxent River. Following submersion for periods ranging from 2 h to 1 week, test surfaces were scraped or brushed to remove adherent biofilm surface material. The resulting suspension of surface biofilm was cultured for total numbers of bacterial colony-forming units and bdellovibrio plaque-forming units. In other experiments on the persistence of bdellovibrios on surfaces, mussel shells and tunicates with accumulated biofilm were exposed to repeated treatments of mechanical agitation. Following each treatment, the suspension supernatant was cultured for the numbers of predators released from the surface. The results of the two investigations revealed that bdellovibrios associate with surfaces following brief periods of submersion in natural waters, the type of surface influences the association, the number of the predators recovered increased with the time of submersion to a certain peak, and the predators on surfaces are relatively resistant to removal by physical agitation of the surrounding water.Key words: bdellovibrio, surface association.