Chitinases produced by Paenibacillus illinoisensis and Bacillus thuringiensis subsp. pakistani degrade Nod factor from Bradyrhizobium japonicum

Chitinases are enzymes that hydrolyze internal β-1,4-N-acetyl-d-glucosamine linkages of chitin. Since the backbone of Nod factors is a chitin oligomer, we investigated whether chitinases produced by soil bacteria Paenibacillus illinoisensis KJA-424 and Bacillus thuringiensis subsp. Pakistani HD 395 are able to degrade Nod factor produced by Bradyrhizobium japonicum, a phenomenon that could disrupt B. japonicum-soybean signaling and nodule establishment when chitinases are present. Purified Nod factor [LCO Nod Bj-V (C_18:1, MeFuc)] was isolated from Bradyrhizobium japonicum and incubated with crude chitinases isolated from KJA-424 and HD395, with or without acetate buffer.

After 15 h of incubation, Nod factor in the resulting solution was quantified by HPLC. Degradation was greatest following treatment with KJA-424 (91.9%) and HD395 (86.5%) chitinases in acetate buffer. Treatments that included acetate buffer had higher levels of degradation than those without. For all treatments degradation was greater than 77%.