Chitinolytic activity of phylogenetically diverse Bacillus cereus sensu lato from natural environments

Bacillus cereus s.l., Gram-positive endospore-forming bacilli, persist ubiquitously in different natural habitats and play various ecological roles. Nevertheless, although chitin is one of the most abundant polymer on Earth, the study of the ability of B. cereus s.l. to hydrolyze this polymer were limited to individual B. cereus and B. thuringiensis strains only. Thus, to fill this gap in this research we focused on (i) the linkage between the capability to chitin degradation and the phylogenetic relatedness of B. cereus s.l. strains, and (ii) the genetic background of chitinolytic properties of these bacilli. Our results showed that chitin degradation is common among the B. cereus group members, yet strains clustered into particular phylogenetic groups differ in their chitinolytic capacity. Separate clustering of chitinolytic and non-chitinolytic strains in the phylogenetic tree indicates the ecotypic structure of these isolates. Two proteins belonging to subfamily A (ChiA) and subfamily B (ChiB) of the glycoside hydrolase GH18 family exhibited simultaneous chitobiosidase and endochitinase activities, and are responsible for chitin utilization by environmental B. cereus s.l. isolates.