Effects Of Rice Varieties On Gut Bacterial Structure Of Cnaphalocrocis Medinalis Guenee

The Cnaphalocrocis medinalis Guenee is an important pest that is harmful to crops around the world and mainly attacks important crops such as rice,barley,wheat and sugar cane etc.Gut microbes play important roles in food degradation,growth and development,immune systems and metabolism,etc.To analyse the functions of intestinal microbes from C.medinalis,we examined the diversity and functions of the C.medinalis gut microbiota based on the methods of traditional microbial culture,denatured gradient gel electrophoresis(DGGE),16S rRNA sequencing and metagenome sequencing in this paper.The main results were as follows:1.The structure and function of the intestinal bacterial community of feeding yongyou 15 Strains of C.medinalisTen different bacteria were isolated from the intestine of the C.medinalis by a traditional microbial culture method.The proportion of Proteobacteria was 70%,and the proportion of Firmicutes was 30%,which indicated that Proteobacteria was the dominant bacteria.The proportion of the isolated Proteobacteria was 77%,and the proportion of the Firmicutes was 23%by the DGGE method,which was consistent with the traditional microbial culture method.Based on16S rRNA sequencing,the diversity of the C.medinalis gut bacteria was examined.The results showed that the bacteria were mainly composed of Proteobacteria(55.2%)and Bacteroidetes(6.2%),among which Proteobacteria were mainly composed of Pseudomonasdales(16.9%),Xanthomonadales(8.3%),Rickettsiales(4.9%)and Enterobacteriales(4.6%).Bacteroidetes were mainly composed of Sphingobacteriales(4.3%)and Bacteroidales(1.1%).Based onmetagenome sequencing,the diversity of the C.medinalis gut bacteria was examined.The results showed that the most abundant intestinal bacteria was Proteobacteria(89%)followed by Firmicutes(8%).Among these,the Proteobacteria were mainly composed of Enterobacteriales(65%),Rickettsiales(23%)and Pseudomonas(4%).Firmicutes were mainly composed of Bacillales(5%).At the phylum level,the conclusion was consistent in that Proteobacteria was the dominant bacteria by the above four methods.However,there were some differences in the results of 16S rRNA sequencing and metagenome sequencing at the(class,order,family,genus)level.Based on the metagenomic data of intestinal bacteria,it was found that the intestinal bacteria were involved in a number of metabolic pathways to assist the host metabolism,including participation in food degradation,nutrient supply,and detoxification.The endoglucanase,1,4-beta-xylosidase and pectinesterase took part in the high fibre food digestion.In addition,we found C.medinalis gut bacteria involved in the synthesis of amino acids,including Tryptophan,phenylalanine,valine,leucine,etc.,which provides a favourable guarantee for host nutrition.What is more,we also found that the C.medinalis gut bacteria were involved in the degradation of exogenous toxic substances,which improves the host's ability to adapt to hostile environments.2.The differences in intestinal bacterial community structure of C.medinalis within different strains of riceWe analysed the influence of the different strains of rice(minghui82,minghui2155 and yongyou15)on the diversity of the C.medinalis gut bacteria using 16S rRNA sequencing.The results showed that the gut bacteria of C.medinalis were mainly composed of Xanthomonadales,Pseudomonas,Rickettsiales and Enterobacteriales.The relative abundances of Pseudomonas and Enterobacteriaceae were significantly different among the three varieties.The relative abundance of the Xanthomonadales and Rickettsia were significantly different between Minghui 82 and Yongyou 15 and between Minghui 2155 and Yongyou 15,which indicated that the food could change the relative abundance of intestinal bacteria.3.The effects of Bt rice on intestinal bacterial community structure of C.medinalisInvestigation of the effects of transgenic rice(crylAb gene(mf-MH3301-1))on intestinal bacterial diversity in C.medinalis showed that there was a significant difference in the relative abundance of intestinal bacteria,indicating that transgenic rice changed the relative abundance of intestinal bacteria.The relative abundance of(Gammaproteobacteria,Enterobacteriales,Enterobacteriaceae and Enterbacter)the treatment group was higher than that of the control group,which may be because Bt poison protein destroyed the intestinal environment and affected the body's normal metabolism.Thus,these bacteria that maintain the body's normal metabolism may have played a positive role.