The Origin And Transmission Of Gut Bacteria In Plutella Xylostella

The diamondback moth Plutella xylostella(L.)feeds on cruciferous plants and has become an important pest worldwide due to its multiple generations,strong reproductive ability,wide host range and high levels of drug resistance.The intestinal tract of the diamondback moth has a wide variety of microorganisms.Long-term coevolution has led to a close symbiotic relationship between the diamondback moth and its intestinal microorganisms.With the continuous improvement of research methods for studying intestinal microorganisms,our understanding of intestinal microorganisms is becoming increasingly deep.Our group's previous studies have analyzed the relationship between the diversity of the intestinal microorganisms of the diamondback moth and food digestion,but so far,little is known about the origin and transmission pathways of the intestinal microorganisms of the diamondback moth.This project uses different research methods to analyze the sources and transmission routes of intestinal microbes of the diamondback moth,promote the understanding and subsequent in-depth study of the intestinal microorganisms of the diamondback moth,and contribute to the biological control of pests based on intestinal microbes as a target.The main findings are as follows:1.Preliminary study on the origin of intestinal bacteria in the diamondback mothThe gut bacteria in Plutella xylostella of different ages that fed on radish were separated and cultured using the traditional pure culture method of microbial isolation.This led to the discovery that the Proteobacteria Enterobacter spp.,Cedecea spp.and Pantoea spp.are widely distributed in the fourth intestine of Plutella xylostella fed radish,and Enterobacter ludwigii exists in the intestinal tract of diamondback moths of all ages.The intestinal bacteria content of Plutella xylostlla feeding on artificial diets with less bacteria was also low.This result suggests that there is a potential link between intestinal bacteria and food bacteria in the diamondback moth,and Plutella xylostella can obtain these bacteria from food and establish its intestinal flora.2.Vertical transmission of intestinal bacteria in the diamondback mothEnterobacter spp.were found not only in the intestinal tract but also in the ovaries and eggs of the diamondback moth by using the pure culture method of microbial isolation.Enterobacter spp.RE1 was stained with the live cell nucleic acid dye SYT09 and fed to the diamondback moth after staining.Using laser scanning confocal microscopy,we found that the target bacteria existed in the intestine of all ages of Plutella xylostella and in the ovary of the adults.Enterobacter spp.RE1-KN containing the kanamycin-resistant plasmid was fed to Plutella xylostella,and the presence of Enterobacter spp.RE1-KN was detected in the intestinal tracts of 4th-instar larva,the pupa,the adult,the adult ovary,and the egg surface of Plutella xylostella.It was suggested that Plutella xylostella can obtain bacteria from its food and establish its intestinal bacteria.At the same time,bacteria obtained from foods of the diamondback moth can be transferred from the intestine to the ovaries and eggs,i.e.,the reproductive organs.After the eggs of Plutella xylostella were sterilized,they were soaked in Enterobacter ssp.RE1-KN containing kanamycin-resistant plasmids,air-dried,and reared in culture bottles with sterile feed.The presence of Enterobacter ssp.RE1-KN was detected in the intestine after dissection of 4th instars.This phenomenon indicates that the eggs of Plutella xylostella can carry bacteria to the intestine.The above results indicate that the intestinal bacteria of the diamondback moth have vertical transmission through the eggs.3.Horizontal propagation of intestinal bacteria in the diamondback mothPlutella xylostella fed the Enterobacter ssp.RE1-KN strain containing the kanamycin-resistant plasmids were mixed with the 3rd-instar larvae that were fed a normal artificial diet.After mixing,they were allowed to feed on the normal artificial diet.The intestine was dissected after 4 generations.All intestinal tracts of P.xylostella in each replicate group contained Enterobacter spp.RE1-KN.The results showed that the social activities of Plutella xylostella could transmit the intestinal bacteria within the populations and that the intestinal bacteria of Plutella xylostella were horizontally transmitted.