Detection of carboxylesterase and esterase activity in culturable gut bacterial flora isolated from diamondback moth, Plutella xylostella (Linnaeus), from India and its possible role in indoxacarb degradation

Abstract

Diamondback moth (DBM), Plutella xylostella (Linnaeus), is a notorious pest of brassica crops worldwide and is resistant to all groups of insecticides. The insect system harbors diverse groups of microbiota, which in turn helps in enzymatic degradation of xenobiotic-like insecticides. The present study aimed to determine the diversity of gut microflora in DBM, quantify esterase activity and elucidate their possible role in degradation of indoxacarb. We screened 11 geographic populations of DBM in India and analyzed them for bacterial diversity. The culturable gut bacterial flora underwent molecular characterization with 16S rRNA. We obtained 25 bacterial isolates from larvae (n = 13) and adults (n = 12) of DBM. In larval gut isolates, gammaproteobacteria was the most abundant (76%), followed by bacilli (15.4%). Molecular characterization placed adult gut bacterial strains into three major classes based on abundance: gammaproteobacteria (66%), bacilli (16.7%) and flavobacteria (16.7%). Esterase activity from 19 gut bacterial isolates ranged from 0.072 to 2.32 μmol/min/mg protein. Esterase bands were observed in 15 bacterial strains and the banding pattern differed in Bacillus cereus – KC985225 and Pantoea agglomerans – KC985229. The bands were characterized as carboxylesterase with profenofos used as an inhibitor. Minimal media study showed that B. cereus degraded indoxacarb up to 20%, so it could use indoxacarb for metabolism and growth. Furthermore, esterase activity was greater with minimal media than control media: 1.87 versus 0.26 μmol/min/mg protein. Apart from the insect esterases, bacterial carboxylesterase may aid in the degradation of insecticides in DBM.

Diversity of fall armyworm, Spodoptera frugiperda and their gut bacterial community in Kenya

“…We found that the gut bacterial communities of most S. frugiperda samples were dominated by Proteobacteria. This observation is similar to proportions reported in other phytophagous insects, in particular lepidopterans (Belda et al 2011; Xia et al 2013, 2017; Landry et al 2015; Ramya et al 2016; Snyman et al 2016; Strano et al 2017; Chen et al 2018). Only three samples, two adult males from Kitale (Kitale-m2 and Kitale-m3) and one larvae from Ngeria (Ngeria-l2) were dominated by Firmicutes.…”

Gut Bacterial Diversity of Insecticide-Susceptible and -Resistant Nymphs of the Brown Planthopper Nilaparvata lugens Stå l (Hemiptera: Delphacidae) and Elucidation of Their Putative Functional Roles

“…Furthermore, these genera were found to be more abundant in the IR population than in the IS population. All the three genera were previously reported from insect guts [28,35]. The gut-associated enterococci are known to contribute to the fitness of the insect host in several ways, including the prevention of proliferation of the pathogen [36,37].…”

Fitness costs of infection with Serratia symbiotica are associated with greater susceptibility to insecticides in the pea aphid Acyrthosiphon pisum

“…These bacteria are mainly associated with the detoxification of organophosphates, although Bacillus spp. can also detoxify oxadiazine insecticides …”

“…can also detoxify oxadiazine insecticides. 26,28,60,61 S. symbiotica is one of the most common symbionts of aphids with predominantly mutualistic functions. 11,21,23,62 Some members of genus Serratia are known to be involved in the degradation or detoxification of insecticides and plant toxins.…”