Figure 10. In-frame deletion strains for chitinase genes show reduced chitinolytic activity in vitro. Chitinase assay was done with supernatants of overnight grown cultures of wild type (WT) and chitinase/ chitin binding protein deletion (ΔchiA, ΔchiB and Δlmo2467) of L. monocytogenes. Culture supernatants were incubated with the substrate 4 nitrophenyl N,N´ – diacetyl- β- D chitobioside for 2 hours at 30ºC. The reaction was then stopped by adding 1 M Na2CO3. OD405 of the reaction mixture was measured to assess the enzymatic activity of the chitinases. OD600 values were also taken in order to normalize the OD405 values with respect to the bacterial population density of the cultures.