Figure 3.

Deletion of fis resulted in decreased production of extracellular enzymes. (A) Quantitative measurement of extracellular enzymes activity for wild-type strain EC1 and derivatives. The quantitative determination, the protease activity was determined through measuring the absorbance at 440 nm with azocasein as substrate; the cellulose activity was determined through absorbed spectrum value under 550 nm with carboxymethylcellulose sodium as substrate and 3,5-dinitrosalicylic acid as colorant; the pectate lyase activity was determined via the absorbed spectrum value under 235 nm with polygalacturonic acid as substrate. The experiment was repeated three times. The data were the means of three repeats and the standard deviation is represented using error bar. (B) Extracellular enzymes production on bioassay plates. Twenty microlitres of culture supernatants of wild-type strain EC1 and its derivatives strains were added into the wells on assay plates and incubated at 28 °C. Final results of fis mutant were normalized to that of the wild-type EC1, which was set to a value of 100%, for easy comparison. Experiments were repeated at least three times in triplicates. Symbol: ***P < 0.0001 (Student’s t-test).