An in vitro model for the cultivation of polymicrobial biofilms under continuous-flow conditions

Abstract

The airways of people with cystic fibrosis (CF) are often chronically colonised with a diverse array of bacterial and fungal species. However, little is known about the relative partitioning of species between the planktonic and biofilm modes of growth in the airways. Existing <i>in vivo</i> and <i>in vitro</i> models of CF airway infection are ill-suited for the long-term recapitulation of mixed microbial communities. Here we describe a simple, <i>in vitro</i> continuous-flow model for the cultivation of polymicrobial biofilms and planktonic cultures on different substrata. Our data provide evidence for inter-species antagonism and synergism in biofilm ecology. We further show that the type of substratum on which the biofilms grow has a profound influence on their species composition. This happens without any major alteration in the composition of the surrounding steady-state planktonic community. Our experimentally-tractable model enables the systematic study of planktonic and biofilm communities under conditions that are nutritionally reminiscent of the CF airway microenvironment, something not possible using any existing <i>in vivo</i> models of CF airway infection.