[Soluble expression of AiiA protein and analysis of its antimicrobial activity]

AHLs are signaling molecules produced by Gram-negative bacterium during their proliferation. These molecules are closely related with bacteria pathogenicity. AiiA protein, functioning as a intracellular lactonase, hydrolyses AHLs at lactone loop in the molecule to reduce its biological activity and also dramatically reduces pathogenicity of bacterium at the same time. In this study, DNA fragment encoding aiiA gene was amplified from the plasmid derived from Bacillus thuringiensis by PCR. Expression vector, pET29a-aiiA, was constructed and transformed into bacteria strain of E. coli BL21 (DE3) for expression of AiiA protein. After 25 h induction with 0.8 mmol/L IPTG at 20 degrees C, the protein AiiA expressed in soluble form by recombinant strain reached about 54.4 microg/mL. The recombinant protein was purified with Ni-affinity chromatography. Biological activity analysis showed that AiiA protein had a capability to hydrolyse AHLs, and strong antimicrobial activity for Eriwinia carotovora.