The endochitinase ChiA Btt of <i>Bacillus thuringiensis</i> subsp. <i>tenebrionis </i><scp>DSM</scp>‐2803 and its potential use to control the phytopathogen <i>Colletotrichum gloeosporioides</i>

Abstract

Bacillus thuringiensis subsp. tenebrionis DSM-2803 has been studied extensively and spore/crystal mixtures of this strain are used widely in commercial products to control coleopteran pests. The endochitinase chiA Btt gene of B. thuringiensis subsp. tenebrionis DSM-2803 was cloned and expressed in Escherichia coli. The recombinant 6x-histidine tagged protein (rChiA Btt, ~74 kDa), was purified by a HiTrap Ni affinity column. The K_m of rChiA Btt was 0.847 μmol L^-1 and its optimal activity occurred at pH 7 and ~40°C. Most divalent cations reduced endochitinase activity but only Hg⁺² abolished activity of the enzyme. We report for the first time the characterization of a chitinase synthesized by B. thuringiensis subsp. tenebrionis DSM-2803, and show that the purified rChiA74 Btt reduced the radial growth and increased the hyphal density of Colletotrichium gloeosporioides, the etiological agent of "anthracnose" in plants.