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Tat pathway-mediated translocation pathway is essential for antibacterial activity of Pseudomonas fluorescens XW10against Ralstonia solanacearum

Xiaoqiang Wang;Peng Deng;Sonya M.Baird;Xiangdong Li;Shi'en Lu

  Strain XW10 was isolated from soybean rhizosphere and showed a broadspectrum of antimicrobial activities,especially against Ralstonia solanacearum.Phylogenetic analysis of the 16 S rRNA,gyrB,rpoB and rpoD genes revealed that strain XW10 belongs to the genus Pseudomonas but apparently different from any of established species of Pseudomonas,which indicated that XW10 could be a new species of Pseudomonas.To characterize the genes dedicated to antibacterial activities against R.solanacearum,a Mini Tn5-mutation library of strain XW10 was constructed.The mutant XW10-5206 was eliminated in antibacterial activity against R.solanacearum when compared to the wild-type strain XW10.Sequence analysis of the mutant indicated that the gene disrupted by transposon shared high sequence identity(98%) to Tat A gene in twin-arginine translocase(Tat) secretion system predicated in Pseudomonas fluorescens strain Pf0-1(GenBank accession number;CP000094).Constitutive expression plasmid pUCP26-TatA was constructed and electroporated into the mutant XWlO-5206.As expected,introduction of plasmid pUCP26-TatA restored the antibacterial activity of the mutant against R.solanacearum to the wild-type level.Thus the Tat pathway-mediated translocation pathway is essential for antibacterial activity of Pseudomonas sp.XW10 against R.solanacearum.……