Genetic Diversity And Phylogeny Of Siderophore Producing Bacteria Isolated From Cotton Rhizosphere In Xinjiang, China

A total of 68 silicate bacterial strains were isolated cotton rhizosphere and bulk soil from Shihezi,Kuerle and Bole in Xinjiang Province.Their siderophore producing ability was tested by CAS method,and the genetic diversity of these strains was analyzed by BOXAIR-PCR and 16S rRNA PCR-RFLP;furthermore,the phylogeny of the representtative strains were determined by 16S rRNA sequences anlysis.The results were as the following:Among the 68 bacterial strains,62 strains(91.2%of all the strains) were gramnegtive (G),while,there were only 8 bacteria(8.8%of all the strains) were grampositive(G~+). The results of CAS showed that the siderophore producing ability of G~- bacteria was higer than that of G~- bacteria,and the diversity of the siderophores producing ability among different strains was existed.Analysis of BOXAIR-PCR showed that all the were divided into 11 BOXAIR-PCR groups at the similarity of 84.5%,the largest one was groupâ…¤,and was further divided into four subgroups,which indicated that genetic diversity was existed among these strains.The results of 16S rRNA PCR-RFLP analysis suggested that there genetic diversity was also existed,and 10 genotypes were grouped at the level of 85.5%similarity.Group 1 was the largest,and consisted of four subgroups.Based on the results of 16S rRNA PCR-RFLP analysis,strain MK12,MK33,MK25, MK28,MK30,MB10,MK45,MK35,MK26 and MB2 were chosen to determine 16S rDNA sequences,and the phylogeny tree was constructed by MEGA3.1 software.The results revealed that all the strains formed six phylogenic branches,MK12,MK25,MB2 and MB10 were located in branch 1,which belonged genus of Pseudomonas,but cnsisted of different species;MK33 and MK26 were located in branch 2,which contained genus of Enerobacter and Pantoea;MK28,MK30,MK35 and MK45 beonged to Acinetobacter, Bacillus,Brachybacterium and Alcaligenes respectively.The homology of MK12 and Pseudomans corrugata(EF153018),MB2 and Pseudomonas aeruginosa(AB305018),MB10 and Pseudomans putia(AM184288), MK30 and Bacillus cereus(EU163266),MK35 and Brachybacterium sp.Phenol-A (DQ822566),MK45 and Alcaligenes sp.A72(DQ180141) was 99%;and the homology of strain MK25 and Pseudomans sp.GP11(AF326375),MK33 and Enerobacter sp.Px6-4 (EF175731) was 98%.The results from 16S rDNA sequence analysis of representatives strains revealed that, from the phylogeny point of view,these siderophores belong to seven genuses and most strains come from Pseudomonas,which indicated that maybe there are putative new species existed.And we first reported that siderophores distributed in Brachybacterium.