Analysis Of The Bacterial Community Structure And Diversity In The Intestine Of Cnaphalocrocis Medinalis (Guenée)(Lepidoptera: Pyralidae)

Rice leaffolder,Cnaphalocrocis medinalis(Guenée)is one of the important migratory pests.It can endanger rice through folding and feeding rice leaves leading to photosynthesis reduction and the yield loss.Plenty of bacteria habitat in the gut of insects and formed a close symbiotic relationship with insects in the evolution.These bacteria play an important role on food digestion,growth and development,immunity and resistance to the disease and so on.So far,the researches on C.medinalis mainly focused on the biology,physiology,ecology,and chemical control,and few focused on the gut microbes in C.medinalis.Considering the important function of gut bacteria,composition and diversity of the community of the gut bacteria were analyzed in the C.mednalis with different treatments by 16 S r DNA library and Illumina MiSeq sequencing technology.This study will promote the understanding of the gut microbes in C.medinalis and also will provide clues for the biological control on C.medinalis.Main results were as below: 1 Diversity of gut bacteria in C.medinalis at different developmental periodsIn order to understand the composition and diversity of the bacterial community in C.medinalis at different developmental periods,gut bacteria were detected and analyzed in C.medinalis at four developmental periods(eggs,larvae,pupae and adults).Results showed that bacteria in the gut of C.medinalis at four developmental periods were annotated into 22 phyla,43 classes,82 orders,142 families,204 genera,and 244 species.The richness and diversity of bacteria at different developmental periods were different,and the bacteria in the egg and the 1st-instar larvae were of high richness,and the structure were complex.The dominant bacteria at phyla level were Proteobacteria and Bacteroidetes in eggs and 1st-instar larvae,and were Proteobacteria and Firmicutes in other developmental periods.The dominant bacteria at genus level were Myroide,Wautersiella,Acinetobacter,Alcaligenes,Pseudomonas in eggs,and were Wolbachia,Acinetobacter in the 1st-instar larvae;the common dominant bacteria in other developmental stages was Enterococcus.The composition of bacteria in eggs and 1st-instar larvae were of high similarity,and were less similar with microbial structure of other developmental stages;the bacterial composition in the 2nd-larvae,3rd-larvae and the adults were of high similarity,and so did the the 4th-larvae,5th-larvae and the pupae.There are differences in bacterial composition and diversity among intestines of C.medinalis at different developmental periods.The information from samples of different developmental stages of C.medinalis can promote the comprehensive understanding of the impact of external factors on the bacterial composition and diversity in the intestine of C.medinalis.2 Diversity of gut bacteria in Susumia exigua(Butler)In order to understand the composition and diversity of the bacterial community in S.exigua,which is a closely related specie to C.medinalis,gut bacteria were detected in S.exigua at different developmental periods.Results showed that bacteria in the gut of S.exigua were annotated into 30 phyla,55 classes,62 orders,127 families,269 genera,and 202 species.The gut bacteria of S.exigua were of high richness in larval period,whereas they were of high diversity in eggs.In composition,the dominant bacteria of S.exigua at phylum level were Proteobacteria,Bacteroidetes and Actinobacteria in eggs,and were Proteobacteria and Firmicutes in larvae,and was Proteobacteria in pupa.In genus level,the dominant bacteria in egg were Acinetobacter,Staphylococcus,Halomonas,Enterococcus,Enterobacters;the dominant bacteria in larval period were Enterococcus,Enterobacter and Acinetobacter,and were Acinetobacter,Serratia and Stenotrophomonas in female pupa,and were Acinetobacter,Enterobacter,Staphylococcus and Pseudomonas in male pupa.Among all the bacterial communities in the gut of S.exigua at different developmental periods,the composition of the bacteria in larval period were of high similarity,and the bacterial composition in eggs and pupa were of high similarity.3 Diversity of gut bacteria in C.medinalis of different geographical populationIn order to understand the composition and diversity of the bacterial community in C.medinalis of different geographical population,this research detected the bacterial community in C.medinalis of 6 geographical population—Thailand,Veitnam,Nanning,Changsha,Hangzhou,Leshan.Results showed that bacteria in the gut of C.medinalis of different geographical population were annotated into 22 phyla,43 classes,52 orders,96 families,172 genera,and 122 species.The bacteria in C.medinalis of Leshan population had highest richness and diversity,and the bacterial community of Thailand population had the lowest richness.In the bacterial composition,the common dominant bacteria was Firmicutes at phylum level and Enterococcus at genus level in C.medinalis of Thailand,Veitnam,Nanning,Changsha,Hangzhou population;the dominant bacteria in C.medinalis of Leshan population were Firmicutes and Proteobacteria at phylum level,and were Enterococcus and Streptophyta at genus level.In the aspect of compositional similarity,the bacterial communities in the gut of C.medinalis of Thailand,Veitnam,Nanning,Changsha,Hangzhou population were of high similarity,and had big difference with bacterial community of Leshan population.The difference of gut bacteria in C.medinalis of different geographical population are likely to have relationship with the specific environment.This study lays a foundation for further research of the characteristics of C.medinalis of different geographical populations.4 Diversity of bacteria in the gut of C.medinalis fed on different dietsIn order to clarify the effects of different diets on the bacterial community in the gut of C.medinalis,this research detected the gut bacterial community in C.medinalis fed on maize and rice,respectively,for 3 generations and 17 phyla,35 classes,50 orders,102 families,162 genera and 110 species were obtained.There were little difference in the richness and diversity of bacteria community in C.medinalis feeding maize or rice.The dominant bacteria in C.medinalis feeding maize or rice were Firmicutes and Proteobacteria based on phylum,and was Enterococcus based on genus.The percent of the common OTUs between bacterial community in C.medinalis feeding maize or rice were large.There were slight difference in the richness of some species in the gut bacterial communities of C.medinalis feeding different diets.5 Diversity of bacteria in the gut and frass of C.medinalis treated with antibioticsIn order to clarify the effects of different antibiotics on the gut bacterial communities,bacteria in the gut and frass of C.medinalis,which were treated with 5 different antibiotics,were detected and a total of 9 phyla,15 classes,28 orders,57 families,87 genera and 51 species were obtained.The bacterial abundance and diversity were relatively in the gut of C.medinalis treated with tetracycline.The dominant bacteria were Proteobacteria,Bacteroides and Firmicutes based on phylum in the C.medinalis treated with antibiotics,and compared with the control group,the rifampicin,streptomycin,chloramphenicol,tetracycline and ampicillin could reduce the relative abundance of Firmicutes in the gut of C.medinalis.The bacterial structure was complex at the genus level in the gut of C.medinalis treated with antibiotics and the abundance of Enterococcus decreased dramatically.The bacterial composition and diversity in the gut and frass of C.medinalis changed greatly when treated with rifampicin and streptomycin.This research contributes to the future functional study of bacteria using antibiotics.