Identification Of A Gene Involved In Eps Production Of Xanthomonas Campestris Pv.campestris

Xanthomonas campestris pv. campestris (Xcc) is a gram-negative bacterium which can cause black rot on cruciferous plants around the world. One of the products of X.campestris is excellular polysacchride (EPS) named xanthan gum.EPS is always regarded as a pathogenicity factor during interaction between Xcc and host plants, hi addition,EPS was extensively used in many fields of industry, from the food processing to oil drilling, due to its exceptional rheological properties. Extensive researches have been carried out on mechanism of EPS production. In this study, wild type strains 8004 of Xcc were mutagenized by the insertion of transposon Tn5gusA5. An Xcc mutant library was constructed in this way, it holds 17,280 mutants. Insertion sites of mutants were decided by TAIL-PCR and sequencing. 17 mutants deficient in EPS production were screened from the mutant library by the plate method. In terms of their colony morphology, these mutants were classified into three types. We tested their pathogenecities, the results revealed that 11 mutants lost their pathogenecities, 4 mutants decreased their pathogenecities, and 2 mutants shared the same pathogenicities as wild type strain 8004. In the 17 EPS mutants,mutated gene functions of 14 TnSgusAS insertion mutants are known, and 3 gene functions of the other 3 insertion mutants are still unknown. So we carried out deletion to the three corresponding genes of wild type strain 8004, which are Xcc-1^ Xcc-224 and Xcc-3387. The results revealed that the deletion of Xcc-114 leaded to the deficiency in EPS production, and the other two deletion mutants still produce EPS. So we can conclude that Xcc-114 is a gene involved in EPS production. By the searching of NCBI blast, the results revealed that the deduced product encoded by Xcc-114, containing 756bp, showed 36% identities with a transmembrane protein. Its putative function may be relevant to EPS transport.