Chitinase Expression in Listeria monocytogenes Is Influenced by , Which Encodes an Internalin-Like Protein.

The chitinolytic system of thus far comprises two chitinases, ChiA and ChiB, and a lytic polysaccharide monooxygenase, Lmo2467. The role of the system in the bacterium appears to be pleiotropic, as besides mediating the hydrolysis of chitin, the second most ubiquitous carbohydrate in nature, the chitinases have been deemed important for the colonization of unicellular molds, as well as mammalian hosts. To identify additional components of the chitinolytic system, we screened a transposon mutant library for mutants exhibiting impaired chitin hydrolysis. The screening yielded a mutant with a transposon insertion in a locus corresponding to of the EGD-e strain. encodes a large (1,349 amino acids [aa]) cell wall-associated protein that has been proposed to possess murein hydrolase activity. The single inactivation of , as well as of that codes for a putative transcriptional regulator functionally related to , led to an almost complete abolishment of chitinolytic activity. The effect could be traced at the transcriptional level, as both and transcripts were dramatically decreased in the mutant. In accordance with that, we could barely detect ChiA and ChiB in the culture supernatants of the mutant strain. Our results provide new information regarding the function of the locus in and link it to the expression of chitinolytic activity. Many bacteria from terrestrial and marine environments express chitinase activities enabling them to utilize chitin as the sole source of carbon and nitrogen. Interestingly, several bacterial chitinases may also be involved in host pathogenesis. For example, in the important foodborne pathogen , the chitinases ChiA and ChiB and the lytic polysaccharide monooxygenase Lmo2467 are implicated in chitin assimilation but also act as virulence factors during the infection of mammalian hosts. Therefore, it is important to identify their regulators and induction cues to understand how the different roles of the chitinolytic system are controlled and mediated. Here, we provide evidence for the importance of and , encoding a putative internalin/autolysin and a putative transcriptional activator, respectively, in the efficient expression of chitinase activity in and thereby provide new information regarding the function of the locus.