Microbial Interactions in Biofilms: Impacts on Homeostasis and Pathogenesis

Abstract

Microbes in nature or in the human body are predominantly associated with surfaces and living in biofilms. Species diversity, high cell density and close proximity of cells are typical of life in biofilms, where organisms interact with each other and develop complex interactions that can be either competitive or cooperative. Competition between species is a well-recognized ecological force to drive microbial metabolism, diversity and evolution. However, it was not until recently that microbial cooperative activities are also recognized to play important roles in microbial physiology and ecology. Importantly, these microbial interactions in biofilms profoundly affect their overall function, biomass, diversity and pathogenesis. It is now known that every human body contains a personalized microbiome that is essential to maintain host health. Remarkably, the indigenous species in most microbial communities often maintain a relatively stable and harmless relationship with the hosts despite regular exposure to minor environmental perturbations and host defence factors. Such stability or homeostasis results from a dynamic balance of microbial–microbial and microbial–host interactions. Under some circumstances, however, the homeostasis may breakdown, predisposing a site to diseases. The evidence has accumulated that such biofilm or community-based diseases can be prevented or treated not only by targeting putative pathogens, but also by interfering with the processes that drive breakdown of the homeostasis in biofilms.