A major protein component of the <i>Bacillus subtilis</i> biofilm matrix

TLDR

Microbes build complex biofilms by producing an extracellular matrix. The study aims to model how *B. subtilis* switches between nomadic and sedentary lifestyles by regulating matrix component synthesis via the global regulator SinR. The authors identify TasA protein and exopolysaccharide as the main matrix components, show that SinR controls their synthesis, and model their role in lifestyle switching.

Abstract

Microbes construct structurally complex multicellular communities (biofilms) through production of an extracellular matrix. Here we present evidence from scanning electron microscopy showing that a wild strain of the Gram positive bacterium Bacillus subtilis builds such a matrix. Genetic, biochemical and cytological evidence indicates that the matrix is composed predominantly of a protein component, TasA, and an exopolysaccharide component. The absence of TasA or the exopolysaccharide resulted in a residual matrix, while the absence of both components led to complete failure to form complex multicellular communities. Extracellular complementation experiments revealed that a functional matrix can be assembled even when TasA and the exopolysaccharide are produced by different cells, reinforcing the view that the components contribute to matrix formation in an extracellular manner. Having defined the major components of the biofilm matrix and the control of their synthesis by the global regulator SinR, we present a working model for how B. subtilis switches between nomadic and sedentary lifestyles.