[Cloning, expression and functional analysis of the dhbC gene from the siderophore producing bacterium Bacillus subtilis CAS15].

We amplified dhbC gene from the siderophore producing bacterium CAS15 by PCR. After ligated the PCR product to pMD18-T vector and then sequenced, we obtained a 1197 bp fragment. The blast result showed that the nucleotide acids of dhbC gene (Accession No. FJ194456) of CAS15 shared 99.7% identity with that of dhbC gene of Bacillus subtilis (GenBank Accession No. Z99120), and was predicted to encode a 43.8 kD polypeptide with 398 amino acid residues. We cloned the dhbC gene into expression vector pET-30a(+) and then transformed into Escherichia coli BL21(DE3) via calcium chloride transformation method, and obtained the recombinant E. coli BL21(DE3)/pET-30a-dhbC. Induced by 1 mmol/L IPTG the fusion protein 6His-DhbC, a 48.8 kD polypeptide was successfully expressed mainly in soluble form in E. coli BL21(DE3), and the amount reached highest at 30 degrees C for 4 h. According to the N-terminal fusion 6 His-tag, we purified the recombinant polypeptide by Ni2+ metal affinity chromatography and finally identified it by Western blotting. The result indicated that the recombinant DhbC had the antigenicity to rabbit anti-his-tag polyclonal antibody, which provides the basis for the study of practical utilization in production and the biocontrol mechanism of B. subtilis. Finally, we deleted dhbC gene by gene knockout and then retransformed it into the dhbC gene-delected mutant, which confirmed that dhbC gene play an important role in siderophore biosynthesis.

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