The Microbial Diversity And Screening Of Antagonists Against Ralstonia Solanacearum In Six Different Soil Types From Subtropical Montane Forest Ecosystem In China And The Degradation Mechanism Of Dichloroanilines

In this study, the traditional culturable way and molecular microbial ecology methods was used to analysis the relationshinp of bacterial diversity and soil type, altitude and seasonal factors.We also analyze the soil bacteria’s potential use in nitrogen-fixing, phosphorus dissolving, antagonistic pathogens and degradation of organic pesticide pollutions.The composition of soil bacterial communities and antagonistic edaphic bacterias in six different soil type sites (Red soil、Lateritic soil、Yellow soil、Yellow brown soil、Brown soil、Meadow soil) from subtropical montane forest ecosystem in China were examined by using PCR-denaturing gradient gel electrophoresis (DGGE) fingerprinting 16S rRNA gene-and culturable approach.The linkage of soil type and temporal factors and bacterial community was analyzed by the ordination technique of canonical correspondence analysis (CCA). CCA Ordination of DGGE profiles showing that the primary forcing factor for the soil bacteria communities appeared to be soil type. Cluster analysis based on DGGE profiles agreed well with ordination analysis (CCA) confirming the soil type effect on bacteria communities. Moreover, we explored the soil type effect of the abundance of antagonistic edaphic bacteria by Principal component analysis (PCA). The proportion and diversity of antagonistic bacteria consistent with the phylotype diversity index from DGGE community. The results obtained in our study demonstrate clearly that soil type is important factor affecting the structure of total bacterial and antagonistic edaphic bacteria community.ARDRA were used to profile the diversity of antagonistic edaphic bacteria, among the 125 antagonists,13 groups (G1 to G13) were formed according ARDRA fringerprint. There is 6 groups (G5, G13, G11, G9 and G10) contained only one isolate, respectively; 2 groups (G8 and G12) contained two isolates, respectively; G1, G2, G3, G4, G6 and G7 included 32, 18,36,14,5 and 11 isolates, respectively. A subset of representative isolates of each ARDRA group was identified by 16S rRNA gene sequence analysis. Results showed a wide variety of antagonists, comprising 12 different genera distributed in five bacterial divisions. High proportion of antagonistic edaphic bacteria were found in these types of soil (R= 22%, YR=23%, B=25%, and M=31%). In greenhouse, strain M19 had the best biocontrol efficiencies that about 59% and this is the first report of Rahnella sp. strain used as a BCA agaisnt R. solanacearum of tomato.A dichloroanilines degrading strain named as IMT21 was isolated from enriched soil sample and identified as Bacillus megaterium according to its morphology、biochemical properties and 16S rRNA gene sequence. IMT21 can use 3,4-DCA as sole carbon source, biological properties of strain IMT21 were studied. The optimal temperature and pH were 30-40℃and 7.0, respectively.Degradation of 3,4-DCA/3,5-DCA resulted in accumulation of a single metabolites with the retention time of 8.7/10.9 min, which had the same retention time and m/z (204) as 3,4-dichloroacetanilide, this suggests that the DCA were degraded via dichloroacetanilide metabolites. IMT21 can convert a wide variety of dichloroanilines to their corresponding acetanilides and dichloroaminophenol metabolites. In this study reported here, we cloned and expressed Arylamine N-acetyltransferases (NATs) in Escherichia coli. The expressed enzyme (BmNAT) was characterized.