Effects of Bacillus in Pectobacterium quorum quenching: A survey of two different acyl-homoserine lactonases.

Numerous functions in pathogenic Pectobacterium are regulated by quorum sensing (QS). Two different aiiA genes isolated from Bacillus sp. A24(aiiA A24 ) and Bacillus sp. DMS133(aiiA DMS133 ) were used. Both genes encode acyl-homoserine lactonase (AiiA), which disrupts QS in Pectobacterium. To investigate the effect of different AiiAs on the inhibition of Pectobacterium carotovorum pathogenicity, two aiiA genes from different Bacillus strains were cloned and the resulting plasmids pME6863 (aiiA A24 ) and pME7080 (aiiA DMS133 ) were transformed into P. carotovorum EMPCC cells. The effects of different lactonases on virulence features such as enzymatic activity, twitching and swimming motilities, and production of pellicle and biofilm formation were investigated. In EMPCC/pME6863, twitching and swimming motilities, and pellicle production were significantly reduced compared with EMPCC/pME7080. Quantitative real-time PCR (qRT-PCR) was used to measure virulence gene expression in transformed cells compared with expression levels in wild-type EMPCC. The expression of peh and hrpL genes was greatly reduced in EMPCC/pME6863 compared with EMPCC/pME7080. The sequence alignment and molecular dynamic modeling of two different AiiA A24 and AiiA DMS133 proteins suggested that the replacement of proline 210 from AiiA A24 to serine in AiiA DMS133 caused the reduction of enzyme activity in AiiA DMS133 .