The effect of aiiA gene on the motility and enzymatic properties of Pectobacterium carotovorum, the causal agent of bacterial soft rot

Quorum sensing (QS) is a regulatory mechanism used by Pectobacterium carotovorum for the genes expression and the production of virulence determinants. Recently, some soil inhabiting bacteria were isolated that degraded bacterial signaling molecules such as Acyl homoserine lacton (AHL). The aiiA gene is responcible for AHL lactonase enzymes in Bacillus species. In this research the effects of aiiA genes from Bacillus sp. DMS133 and Bacillus sp. A24 were evaluated on the motility properties and enzyme production in P. carotovorum. The results revealed that swimming, swarming and twitching motilities were significantly reduced in aiiA mutant pectobacteria (EMPCC/aiiA1 and EMPCC/aiiA2 strains) in comparison with the wild type EMPCC strain. The expression of aiiA genes in mutant Pectobacteria significanlty inhibited production of pectinase, protease and cellulase enzymes. According as the means of enzymes production in EMPCC twenty time more than mutant EMPCC/aiiA1 and EMPCC/aiiA2 strains. Motility and plant cellwall degradation enzymes are two most virulence determinants in Pectobacterium, which are regulated by AHL mediated quorum sensing. Heterologous production of AiiA lactonase enzyme in Pectobacterium causes degradation of signaling molecules and decreases accumulation of them around the bacterium. As a result, the quorum sensing and related phenotypes are inhibited in P. carotovorum.