Influence of Bacillus thuringiensis and avermectins on gut physiology and microbiota in Colorado potato beetle: Impact of enterobacteria on susceptibility to insecticides

Abstract

Gut physiology and the bacterial community play crucial roles in insect susceptibility to infections and insecticides. Interactions among Colorado potato beetle Leptinotarsa decemlineata (Say), its bacterial associates, pathogens and xenobiotics have been insufficiently studied. In this paper, we present our study of the survival, midgut histopathology, activity of digestive enzymes and bacterial communities of L. decemlineata larvae under the influence of Bacillus thuringiensis var. tenebrionis (morrissoni) (Bt), a natural complex of avermectins and a combination of both agents. Moreover, we estimated the impact of culturable enterobacteria on the susceptibility of the larvae to Bt and avermectins. An additive effect between Bt and avermectins was established regarding the mortality of the larvae. Both agents led to the destruction of midgut tissues, a decrease in the activity of alpha-amylases and alkaline proteinases, a decrease in the Spiroplasma leptinotarsae relative abundance and a strong elevation of Enterobacteriaceae abundance in the midgut. Moreover, an elevation of the enterobacterial CFU count was observed under the influence of Bt and avermectins, and the greatest enhancement was observed after combined treatment. Insects pretreated with antibiotics were less susceptible to Bt and avermectins, but reintroduction of the predominant enterobacteria Enterobacter ludwigii, Citrobacter freundii and Serratia marcescens increased susceptibility to both agents. We suggest that enterobacteria play an important role in the acceleration of Bt infection and avermectin toxicoses in L. decemlineata and that the additive effect between Bt and avermectin may be mediated by alterations in the bacterial community.

Bacillus thuringiensis Spores and Cry3A Toxins Act Synergistically to Expedite Colorado Potato Beetle Mortality

“…The present study shows all Bt treatment of CPB led to some changes in midgut microbiota of CPB larvae, e.g., Lactococcus and Raoultella presence. In a similar study, dramatic shifts in the midgut bacterial community under Bt treatment, which was mainly related with depletion of endosymbiotic bacteria Spiroplasma leptinotarsae, under bacterial toxicosis was observed [69]. In our study, the midgut of the Bt spore/toxin-inoculated CPB larvae was not conducive to Pseudomonas growth.…”

Effects of Host Plant and Insect Generation on Shaping of the Gut Microbiota in the Rice Leaffolder, Cnaphalocrocis medinalis

“…Enterobacteriaceae is one of the important dominant taxa in the gut microbiota of many insects ( Wang et al, 2014 ; Yun et al, 2018 ; Raza et al, 2020 ). Enterobacteriaceae are involved in insect metabolism ( Pers and Hansen, 2021 ; Zhou et al, 2021 ), insect resistance or susceptibility to parasites, and pathogens and insecticides ( Oliver et al, 2003 ; Álvarez-Lagazzi et al, 2021 ; Polenogova et al, 2021 ) and play an important role in the host adaptability and reproduction of insects ( Shi et al, 2012 ; Wang et al, 2020b ). Pectobacterium , a clade of Enterobacteriaceae , is known as a function of nitrogen fixation ( Behar et al, 2005 , 2008 ).…”

Role of Insect Gut Microbiota in Pesticide Degradation: A Review

“…The gut microbiota has been linked to promoting the insecticidal action of Bacillus thuringiensis , the frequently used biological pesticide for herbivore pest management in agriculture ( Mason et al, 2011 ; Eski et al, 2018 ). According to a study, when the gut microbial population was removed from gypsy moth larvae, the B. thuringiensis pesticide no longer worked as intended, whereas when some microbiota of the gut microbiome was added back in, the B. thuringiensis -facilitated mortality was reestablished ( Polenogova et al, 2021 ). Several insect species have similar mechanisms for degrading imidacloprid ( Thurman et al, 2013 ).…”