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 exhibit significant phenotypic changes that render them resistant to many antibacterial agents that can kill their free-swimming counterparts. Biofilms in the environment can consist of either a single or multiple microbial species. Previous investigations in this group demonstrated that Bdellovibrio bacteriovorus, a gram-negative predatory bacterium that consumes other gram-negative bacteria, could eradicate a single-species E.coli biofilm in some conditions1. These results suggest the potential value of B. bacteriovorus in biofilm eradication in industrial, medical and environmental contexts. Here we carried out investigation of the potential of Bdellovibrio bacteriovorus to interact with and remove multi-species biofilms, specifically dual-species biofilms of E. coli (gram-negative prey) and M. luteus (gram-positive decoy) at interfaces between liquid and air. We examined whether this kind of dual-species biofilms 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 exploited to gain an insight into Bdellovibrio's interaction with biofilms. Our experiments showed that 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 keeps in check 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.