AUTHOR=Liu Guiqing , Cao Li , Han Richou 

TITLE=Plant quercetin degradation by gut bacterium Raoultella terrigena of ghost moth Thitarodes xiaojinensis

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1079550

DOI=10.3389/fmicb.2022.1079550

ISSN=1664-302X

ABSTRACT=<p>Associated microbes of several herbivorous insects can improve insect fitness. However, the contribution of specific insect gut bacterium to plant toxin toxification for its host fitness remains scarce. Here, a gut bacterium <italic>Raoultella terrigena</italic> from the ghost moth <italic>Thitarodes xiaojinensis</italic> larvae was identified. This bacterium grew unhindered in the presence of <italic>Polygonum viviparum</italic>, which is a natural food for ghost moth larvae but showed significant growth inhibition and toxicity against <italic>Spodoptera litura</italic>. <italic>S. litura</italic> reared on artificial diets containing 5, 15 and 25% <italic>P. viviparum</italic> powder after 7 days coculture with <italic>R. terrigena</italic> were found to have shorter larval and pupal durations than on the diets containing <italic>P. viviparum</italic> powder but without <italic>R. terrigena</italic> coculture. HPLC analysis revealed that the content of quercetin in mineral medium containing 15% <italic>P. viviparum</italic> powder after 7 days coculture with <italic>R. terrigena</italic> was significantly decreased (79.48%) as compared with that in <italic>P. viviparum</italic> powder without <italic>R. terrigena</italic> coculture. <italic>In vitro</italic> fermentation further verified that <italic>R. terrigena</italic> could degrade 85.56% quercetin in Lucia-Bertani medium. <italic>S. litura</italic> reared on artificial diets containing 0.01, 0.05 and 0.1 mg/g quercetin after 48 h coculture with <italic>R. terrigena</italic> were also found to have shorter larval, prepupal and pupal durations, as well as higher average pupal weight and adult emergence rate than on the diets containing quercetin, but without <italic>R. terrigena</italic> coculture. In addition, <italic>R. terrigena</italic> was detected in the bud and root tissues of the sterilized <italic>P. viviparum</italic>, indicating that <italic>T. xiaojinensis</italic> larvae might acquire this bacterium through feeding. These results demonstrate that the gut bacteria contribute to the degradation of plant toxic molecules to improve the development of herbivorous insects and provide fundamental knowledge for developing effective methods for beneficial insect rearing and pest control.</p>