Xiao Qiming

The diversity of denitrifying bacteria in the alpine meadow soil of Sanjiangyuan natural reserve in Tibet Plateau

This is the first time to describe the diversity of denitrifying bacteria in Sanjiangyuan natural reserve in Tibet Plateau by investigating the molecular diversity and phylogenetic analysis of nirK and nosZ genes using PCR-RFLP and sequencing. Four soil samples were collected from alpine meadow communities from over an altitude of 4600 m which had different physicochemical properties by principal component analysis (PCA). For the genes fragment of nirK and nosZ, the diverse PCR products were characterized by cloning, restriction fragment length polymorphism (RFLP) analysis and sequenced. A total of 253 nirK clones and 283 nosZ clones were received in four samples, and 78 operational taxonomic units (OTUSs) of nirK and 120 OTUs of nosZ by the restriction enzymes Mspl and Rsal digested. The analysis of environmental factors showed that altitude and C/N ratio in soil may be the key factors to the denitrifying bacteria community. 36 nirK clones and 17 nosZ clones were sequenced, and their levels of nucleotide identity were from 69% to 98% and 57% to 97%, respectively. The phylogenetic tree was constructed using the Clustal W and Mega softwares, and all the sequenced clones could be subdivided into 4 groups. Some of clone sequences were related to the nirK and nosZ genes belonging to three phylogenetic subdivisions (α-, β-and γ subclasses of the Proteobacteria), while most of the clones were closely related to the genes of the uncultured bacteria. The sequence distributions were not clear relating to the sample sites in the tree.

Construction of dsRNA vector for a viral binding protein gene (groEL) from endosymbionts in Bemisia tabaci and its expression analysis in transgenic Nicotiana benthamianaa.

GroEL,a viral binding protein encoding by groEL gene from endosymbionts in Bemisia tabaci,is an important factor in transmission of plant viruses.In this study,502 bp fragment of groEL was amplified by polymerase chain reaction(PCR) and then ligated to the plant expression vector pBIN19.The recombination vector pBIN19::groEL was transformed into Agrobacterium tumefaciens strain LBA4404 by electroporation.Transgenic Nicotiana benthamiana plants were acquired by Agrobacterium-mediated approach.PCR and RT-PCR were performed to analyze groELs transformation and expression in transgenic plants,respectively.The results indicated that groEL gene was not only integrated into chromosome DNA of transgenic N.benthamiana,but also transcribed in transgenic plants successfully.

Rapid detection of tobacco bacterial wilt in the field.

The highest concentration of seven antibiotics on the growth of tobacco bacterial wilt, the inhabiting fungus and competitive bacterial were chosen with plate culture count. The results showed that ampicillin capsule was 9.996×10-5 μg/mL, ofloxacin tablets 9.990×10-7 μg/mL, roxithromycin tablets 2.998×10-6 μg/mL, cefradine capsules 3.000×10-6 μg/mL, acetylspiramycin tablets 1.998×10-5μg/mL, clarithromycin dispersible tablets 2.999×10-5 μg/mL, and azithromycin capsule was 1.999×10-6 μg/mL. The selected medium of the optimal concentration ratio of seven antibiotics to detect tobacco bacterial wilt in the soil from different areas was used, and it was found that the number of tobacco bacterial wilt in soil samples in Xiangxi was larger than in Yongzhou, and relatively smaller in Chenzhou. There was a positive correlation between the disease index and the number of bacterial wilt, and the tobacco bacteria in adding antagonistic bacterial fertilizer soil were less than in common soil. The method can be used to detect tobacco bacterial wilt quickly and to predict the occurrence of tobacco wilt as well.