Study On The Diversity And Active Volatiles From Nematode-attracting Bacteria

Bacterial volatiles play an important role in the interaction between bacteria and nematodes.Furthermore,nematode-attracting.volatiles of bacteria have potential application value in the biological control of phytopathogenic nematodes.In this study,three contents were carried out.Firstly,a group of bacteria attracting nematodes were screened out from various habitats by taking Caenorhabditis elegans and Panagrellus redivivus as targets.Secondly,the classification statuses of nematode-attracting bacteria were identified based on the analysis of 16S rRNA gene sequences.Finally,the active volatile compounds were identified by GC-MS analysis and pure compound confirmation.The main results obtained were concluded as the follows.1.The screening of nematode-attracting bacteriaTotally,450 bacterial strains from endophyes of Panax notoginseng,Wasabia japonica,and from soil sample of cave were used as candidates for screening experiment.By using C.elegans and.redivivus as targets based on the Petri dish partition method,17 strains showed strong attracting activities against C.elegans(CI? 0.5),57 strains showed moderate attraction(0.3 ?Ci<0.5),and 77 strains displayed weak activities(0.1<CI<0.3).Among the 154 active strains,52 were the endophytes and 102 were isolated from cave soil.For.redivivus,There were 72 strains with strong bioattractant activity(CI?0.5),46 strains with moderate bioattractant activity(0.3<CI<0.5),and 44 strains with weak bioattractant activity(0.1? CI ?0.3).Of the 167 active bacteria,66 were endophytes and 101 were isolated from cave soil.2.Analysis on the bacterial diversity of nematode-attracting bacteriaSeventy-five strains were selected as the representatives in this experiment,and their classification statuses were determined based on 16S rRNA gene sequence analysis.The results indicated that the 75 strains mainly distributed in three large groups:Actinobacteria,Proteobacteria,and Firmicutes.Among them,45 strains,accounting for 60%of the total,were grouped into Actinomycetes.Streptomyces was the dominant genus,which including 13 strains of 5 species.3.Analysis of nematode-attracting volatiles from bacteriaEight strains with the highest attracting activities towards C.elegans were selected for this analysis,By GC-MS analysis and pure compound confirmation,11 bacterial volatiles were identified,which including 2-octanone and 2-undecanone,tetradecan-2-one,2-decanone,methyl disulfide,2-tridecanone,2-nonanone,2,5-two methyl ethyl phenolanisole,cyclopen,2-heptanone.Among them,2-tridecanone showed the strongest inducing activity at the concentration of 0.25 mg/mL.