Expression of the <i>ydaJKLMN</i> operon increases the adhesion of <i>Bacillus subtilis</i> spores to biotic and abiotic surfaces

ABSTRACT The adhesion of microbial cells to biotic and abiotic surfaces is generally mediated by molecules present on the cell envelope. In the case of spore forming bacteria, the exosporium, pilus-like appendages and surface-exposed molecules have been identified as mediators of the adhesion of spores of various species to different surfaces. Here, it is reported that in Bacillus subtilis, the expression of the ydaJKLMN operon increases the adhesion of spores to both biotic and abiotic surfaces. The ydaJKLMN operon codes for enzymes putatively involved in the production of an exopolysaccharide and is expressed in vegetative cells under stress conditions by the action of the alternative sigma factor of the RNA polymerase SigB. Although ydaJKLMN is not expressed in sporulating cells, its expression in vegetative cells increases the adhesion efficiency of spores. A model is presented suggesting that the exopolysaccharide synthesized by the YdaJKLMN enzymes, once secreted by vegetative cells, binds spores released by sporulating cells present in the same culture increasing their adhesion to biotic and abiotic surfaces. The in vitro observation that in a heterogeneous population, such as a B. subtilis culture, a subpopulation of cells secretes molecules that modify the phenotype of another set of cells could reflect a common behavior of microbial populations in nature. IMPORTANCE For their ability to efficiently and tightly bind industrial and medical equipment, bacterial spores are a serious concern for food and pharmaceutical industries as well as for health care institutions. Spore adhesion to surfaces is due to outermost molecules or, in the Bacillus cereus group species, to pilus-like appendages. This study reports that in a heterogenous culture of Bacillus subtilis, molecules secreted by vegetative cells, not committed to sporulation, increase the efficiency of adhesion of spores produced by sporulating neighbor cells. Such in vitro observation could reflect a common behavior of microbial populations in a natural environment, with the products of the metabolic activities of some cells used by other cells to expand their own biological functions.