Analysis Of Symbiotic Bacteria Diversity At Different Developmental Stages Of Spodoptera Exigua(Lepidoptera:Noctuidae)

Spodoptera exigua is a worldwide distribution,insecticide resistance and migration habits of omnivorous agricultural pest.Because of the influence from the global warming and vegetable greenhouse promotion and other external factors,the damaged area and degree is rising,and S.exigua from the sporadic pest into the major pest,from the intermittent outbreak into frequent hazards,cause a great threat to agricultural production.Now the study on the control of S.exigua is focused on the development of biological pesticides,the exploration of Bt toxins,the sex hormones and the use of insect pathogenic microorganisms.By using 16 S rDNA library analysis and the second-generation sequencing system Illumina HiSeq PE 250 sequencing technique to study the bacterial community composition of S.exigua egg,larvae,pupae and adult of manpower rearing indoor,the main results as following:The symbiotic bacteria in the newly-hatched and 1d old larvae,the three and five instar midgut were found that the dominat symbiotic bacteria is Acinetobacter,which accounted for 72.3% by using the 16 S rDNA library analysis.Pelomonas accounted for 12.8%,Acidovorax for 5.6%,Escherichia about for 3.2%,Citrobacter about for 2.5%,Burkholderiales about for 1.8%,Enterococcus about for 0.9%,Comanonadaceae about for 0.4% and the remaining Cruvibacter,Enterobacter,Enterobacteria and Massilia accounted for about 0.2%.The relative abundance of Acinetobacter was decreased and then increased with the age of different,and the relative abundance was the highest at the fifth instar larvae,while the relative abundance of Pelomonas and Acidovorax was decreased.These results show that the symbiotic microbial diversity of S.exigua by the manpower rearing indoor is dynamically changing with the growth and development of S.exigua.The results of the second-generation sequencing technique showed that the mainly class level of symbiotic microorganisms of S.exigua were Firmicutes,Proteobacteria,Actinobacteria,Bacteroidetes,Gemmatimonadetes,Acidobacteria,Cyanobacteria,Chloroflexi,Tenericutes and Planctomycetes,and a small number of other bacteria.The main symbiotic microorganisms in the S.exigua were Firmicutes and Proteobacteria,the relative abundance was 80.8% and even 97.1% entirely,both show a negative correlation relationship.At the genus level,the main bacteria of the Firmicutes were Enterococcus and Sprolactobacillus,the Proteobacteria were Pseudomonas,Methylobacterium,Halomonas and Asaia.There were two peaks in Enterococcus,two lows in Pseudomonas and first decreased then increased in Asaia in the growth and development of S.exigua,and the relative abundance of three main bacteria is dynamically changing with the growth and development of S.exigua.The 16 S V4 region was chosen to test by the Illumina HiSeq PE 250 secondary sequencing technology to overcome the limitations traditional culture techniques,and the datas had more higer abundance and accuracy,while 16 S rDNA library analysis can obtain the full length sequences of 16 S,so the results of these two methods are obvious difference.The diversity of symbiotic bacteria,main bacterial community and dominant flora in different development stages of S.exigua were studied,and analyzed the trends of symbiotic bacteria with the growing development,realized the influence on the growth and development,lay the theoretical foundation for further study the potential function of related bacteria,symbiotic relationship between symbiotic microbes and host and the biological control and micro ecological of S.exigua.