Expression of thurincin H, ChiA74 and Cry proteins at the sporulation phase in Bacillus thuringiensis HD1

The objective of this study was to produce thurincin H, ChiA74 and Cry proteins together using Bacillus thuringiensis subsp. kurstaki HD1 as a heterologous host.

pSTAB-ThurH and pSTAB-ChiA74 constructs were designed to produce thurincin H and chitinase, respectively, at the sporulation phase. They were transformed into Bt HD1 generating the recombinant strains HD1/pSTAB-ThurH and HD1/pSTAB-ThurH/pSTAB-ChiA74. Antimicrobial and chitinolytic activity tests were performed with recombinant strains. Both strains were able to produce thurincin H up to 72 h with antibacterial activity of ~4000 U mg^-1 . The HD1/pSTAB-ThurH/pSTAB-ChiA74 strain also showed chitinolytic activity of ~23 mU mg^-1 at 72 h. All B. thuringiensis strains exhibited crystal formation at 72, and 96 h. In addition, the application of thurincin H in corn seeds increased the germination percentage and root length by 7% and 10%, respectively.

We showed that is possible to produce three proteins of biotechnological interest at the sporulation stage in B. thuringiensis, which two of them (thurincin H, and ChiA74) are naturally expressed in the vegetative stage.

These results form the basis for developing of a biocontrol and biostimulator product that can be used as an alternative for chemical application.