Isolation of Bdellovibrio bacteriovorus from a tropical wastewater treatment plant and predation of mixed species biofilms assembled by the native community members.

It is reported here that a predatory bacterium belonging to the Genus Bdellovibrio, was isolated from activated sludge at the Ulu Pandan Water Reclamation Plant, Singapore. 16S rDNA gene sequencing analysis revealed that this isolate was 99% identical to 'Bdellovibrio bacteriovorus strain Tiberius' and hence is designated as 'Bdellovibrio bacteriovorus UP'. Using a novel approach based on fluorescence in situ hybridization (FISH), a prey cell density-dependent growth pattern of B. bacteriovorus UP was established. B. bacteriovorus UP preyed upon a broad range of bacterial species (60 species) isolated from the activated sludge. Except for Ochrobactrum anthropi, all Gram-negative species were sensitive to predation by B. bacteriovorus UP irrespective of the mode of growth (planktonic or biofilm). Similarly, the predation-sensitive species were not protected by the predation-resistant species, O. anthropi, as determined in multiple dual-species planktonic and biofilm consortia. Given the broad prey spectrum, B. bacteriovorus UP may impact functional community members, which are largely members of the Proteobacteria. Thus, these results provide an important insight to the role of predatory bacteria in shaping of community structure and function in both natural and engineered ecosystems.