BDELLOVIBRIO SP - A PREDATOR UNDER GROUNDWATER CONDITIONS - A SHORT COMMUNICATION

The role of Bdellovibrio sp. in affecting the development of gram-negative bacteria under natural conditions is not yet completely understood. In our investigations, no predatory activity was observed in groundwater samples from a deep pristine aquifer. As limiting factors, temperature and pH may play a role. Their respective ambient values were T = 10-degrees-C and pH 6.07. In laboratory experiments using a collection strain of B. bacteriovorus and a wild type from sewage, appreciable numbers of plaques appeared at a minimum temperature of 18-degrees-C. The optimum temperature at which more than 100 plaques were counted was 26-degrees-C and 30-degrees-C. At pH values lower than 6 no plaques were formed but more than 100 were observed at pH 7, 8 and 9. From the individual plaques, different growth stages of Bdellovibrio sp. have been identified using a transmission electron microscope.