Gluconate acts as a signal to induce biofilm in Bacillus subtilis

Bacillus subtilis, a widely studied Gram-positive microorganism, has been found to exhibit a unique response to the presence of gluconate, a carbon source. In a recent study, researchers have uncovered that gluconate induces the wrinkling of colony biofilms in B. subtilis, a phenomenon that was previously not well understood. This finding sheds new light on the role of carbon source utilization in the biofilm formation process.

Through targeted phenotypic analysis, the researchers identified that specific genes, tasA, epsA-O, and bslA, which encode the canonical structural components of biofilms, are essential for the gluconate-induced wrinkling response. However, the study reveals that the genes responsible for importing and metabolizing gluconate are not necessary for this effect. This suggests that there is a separate signal pathway being activated by the presence of gluconate.

Furthermore, the study establishes a link between gluconate treatment and iron availability. The researchers found that gluconate decreases the production of the siderophore bacillibactin, a molecule that helps B. subtilis acquire iron from its environment. As a result, B. subtilis mutants that are unable to import bacillibactin grow more effectively and exhibit greater wrinkling in the presence of gluconate.

Additionally, the study demonstrates that supplementing single-carbon media with iron can enhance the growth and wrinkling of a B. subtilis mutant lacking the bacillibactin import system when grown on gluconate. However, this iron supplementation does not have any impact on B. subtilis grown on glucose as a carbon source. This implies that gluconate acts as a signal to increase biofilm formation in B. subtilis by enhancing iron availability, independent of bacillibactin production.

In conclusion, this research provides valuable insights into the complex interplay between carbon source utilization and iron acquisition in B. subtilis biofilm formation. The identification of gluconate as a signal molecule that induces wrinkling while increasing iron availability opens up new avenues for understanding the regulation of biofilm development in this important model organism.