Journal Highlight: Biofilm development: Bolstering bacterial infrastructure
Historically, bacterial biofilms, have been thought to be held together solely by a self-produced extracellular matrix. A new study has identified a novel mechanism maintaining Bacillus subtilis and Mycobacterium smegmatis biofilms—active production of calcite minerals. For the first time, researchers studied the effects of mutants defective in biomineralization and calcite formation on biofilm development, resilience and morphology and demonstrated that an intrinsic rise in carbon dioxide levels within the biofilm is a strong trigger for the initiation of calcite-dependent patterning. The calcite-dependent patterns provide resistance to environmental insults and increase the overall fitness of the microbial community.
Bacteria reinforce the three-dimensional structure of their biofilms with a mineralized mixture of amorphous and crystalline calcium. The soil bacterium Bacillus subtilis forms biofilms with numerous wrinkles, which scientists have generally attributed to the organization of the proteins and polysaccharides forming the underlying extracellular matrix. Ilana Kolodkin-Gal and colleagues at the Weizmann Institute of Science now reveal that these microbes also construct communities atop a robust interior layer of calcium carbonate. The researchers identified bacterial genes and environmental triggers that contribute to this mineralization process, and observed identical behavior in another, distantly related bacterial species. Their results suggest that this mineral matrix strengthens the integrity of the biofilm and allows it to support larger bacterial populations. This process may also reduce bacterial vulnerability to antibiotics, making it a potentially interesting target for fighting biofilm-associated infections.