BDELLOVIBRIO BACTERIOVORUS PREDATION IN DUAL-SPECIES BIOFILMS OF E. COLI PREY AND M. LUTEUS DECOYS

Abstract

Biofilms are matrix-enclosed microbial communities that grow at interfaces. They are highly robust and exhibit significant phenotypic changes that render them resistant to many antibacterial agents that can kill their free-swimming counterparts. Researchers have tried to find an effective, alternative and bio-friendly way to eliminate biofilms. Previous investigations in this group demonstrated that Bdellovibrio bacteriovorus, a small gram-negative predatory bacterium that consumes other gram-negative bacteria, could eventually eradicate a single-species E. coli biofilm in some conditions. These results suggest the potential value of B. bacteriovorus in biofilm eradication in industrial, medical and environmental contexts.

Biofilms in the environment can consist of either a single or multiple microbial species including both gram-negative bacteria and gram-positive bacteria. Here we investigated the potential of Bdellovibrio bacteriovorus to interact with and remove multi-species biofilms, specifically dual-species biofilms of gram-negative E. coli prey and gram-positive M. luteus decoy at interfaces betwee is more, less, or equally susceptible to B. bacteriovorus attack compared to their single-species counterparts.

Different research methods including bacterial culture, cell counting, crystal violet staining, gram staining, optical microscopy, scanning electron microscopy, and atomic force microscopy were explored to gain an insight into Bdellovibrio s interaction with biofilms in a macroscale and microscale. Our experiments showed that in a biofilm of E. coli gram-negative prey and M. luteus gram-positive decoy, M. luteus tend to form clusters in a columnar fashion and mostly grow on top of E. coli cells. However, with the presence of B. bacteriovorus, B. bacteriovorus not only consumes E. coli but also weakens the attachment of M. luteus to the solid surface, rendering the biofilms susceptible to removal. B. bacteriovorus controls not only prey but also decoy bacterial populations in the surrounding media, the latter probably via competition for nutrients. These experiments encourage us to consider how B. bacteriovorus might be used to control biofilms in the environment.