Listeria monocytogenes EGD chitinolytic activity is regulated by 1 carbohydrates but also by the virulence regulator , PrfA

23 24 Chitin, an insoluble polymer of N-acetyl-D-glucosamine (GlcNAc), is one of the most 25 abundant carbohydrate polymers in marine and terrestrial environments. Chitin 26 hydrolysis by Listeria monocytogenes depends on two chitinase encoding genes chiA 27 and chiB, and the aim of this study was to investigate their regulation. Chitin induces 28 expression of both chitinases in late exponential growth phase, and chiA but not chiB 29 is furthermore induced by the monomer GlcNAc. Furthermore, expression is 30 subjected to catabolite control. Chitinases expressed by bacterial pathogens have 31 proven to be important not only for nutrient acquisition and environmental survival but 32 also for infecting animals and humans. Interestingly, the central L. monocytogenes 33 virulence gene regulator, PrfA, is required for the chitinolytic phenotype as chitinase 34 activity was significantly reduced in prfA mutant cells compared to wild type cells. In 35 agreement with this, northern blot analysis showed that the amounts of chiA and chiB 36 transcripts were significantly lower upon induction by chitin in the prfA mutant 37 compared with the wild type. The chitinolytic activity and chiA and chiB expression 38 was reduced in absence of the sigmaB gene indicating that SigmaB also is important 39 for production of chitinases. The chiA, chiB and chiA chiB double mutants were not 40 impaired for in vitro adhesion and invasion in epithelial cell lines, but the chiA chiB 41 double mutant showed less survival ability in a chitin enriched medium. Regulation of 42 chitinolytic activity in L. monocytogenes is complex and taken together, the results 43 indicate that the biological role of this activity may not be limited to the external 44 environment. 45 46 on N ovem er 2, 2017 by gest ht://aem .sm .rg/ D ow nladed fom