Bacillus pumilus SG2 chitinases induced and regulated by chitin, show inhibitory activity against Fusarium graminearum and Bipolaris sorokiniana

The possible role of chitinase in in vitro growth inhibition of the wheat pathogens Fusarium graminearum and Bipolaris sorokiniana by Bacillus pumilus SG2 was investigated. B. pumilus SG2, a chitinolytic bacterium producing two different chitinases, was previously isolated from the saline deserts of Iran. When grown in Spizizen salts medium with colloidal chitin, B. pumilus SG2 secreted two chitinases into the medium, resulting in growth inhibition of F. graminearum and abortion of hyphal elongation of B. sorokiniana. In contrast, when glucose was used as the carbon source, the chitinases were not expressed and antifungal activity of the B. pumilus SG2 was completely abolished. These results confirmed that expression of the B. pumilus SG2 chitinases is under the control of two types of regulation, special regulation by chitin and global regulation by glucose. We demonstrated that chitinases are the main components that caused hyphal inhibition activity of B. pumilus SG2. Hyphal inhibition of F. graminearum and B. sorokiniana was stable in agar for a minimum of 14 days.