Biologically Controlled Biomineralization Drives Biofilm Formation and Persistent Infections

In bacterial biofilms, coordinated actions of different subpopulations improve the ability of the community to attach to hosts and protect it from environmental assaults, such as antibiotics. Until recently, the complex architectures of the biofilm colony was attributed exclusively to the organic extracellular matrix (ECM) produced by the bacteria.

We found that microbial biofilms contain an additional component - a robust internal calcite mineral layer, which serves as a scaffold and protects the community from antibiotics. The mineral is spatially organized and might be a common phenomenon in the bacterial kingdom. In this work, using scanning transmission electron microscopy (STEM) and high-resolution single-cell imaging, we have shown that biomineralization initiates within the cytoplasm of some biofilm cells, further supporting the notion that it is a controlled at a cellular level. Transcriptomic analysis revealed pathways promoting biomineralization, and lead to the identification of central regulators of calcite biomineralization and biofilm development. Finally, we have shown that inhibition of bacterial biomineralization is of clinical relevance, as we could detect it in the lungs of cystic fibrosis patients infected with P. aureginosa. Moreover, by inhibiting enzymes key to biomineralization, we could prevent the formation of P. aureginosa biofilms in an ex-vivo mouse lung model. Taken together, this work suggests that bacterial calcification is conserved, robust, initiates within a subpopulation of biofilm cells and is biologically regulated. Identifying new genes central to biomineralization will ultimately lead to the development of completely novel classes of broad-spectrum antibiotics.