The Effect of Residual Pesticide Application on Microbiomes of the Storage Mite Tyrophagus putrescentiae.

Arthropods can host well-developed microbial communities, and such microbes can degrade pesticides and confer tolerance to most types of pests. Two cultures of the stored-product mite Tyrophagus putrescentiae, one with a symbiotic microbiome containing Wolbachia and the other without Wolbachia, were compared on pesticide residue (organophosphate: pirimiphos-methyl and pyrethroid: deltamethrin, deltamethrin + piperonyl butoxide)-containing diets. The microbiomes from mite bodies, mite feces and debris from the spent mite diet were analyzed using barcode sequencing. Pesticide tolerance was different among mite cultures and organophosphate and pyrethroid pesticides. The pesticide residues influenced the microbiome composition in both cultures but without any remarkable trend for mite cultures with and without Wolbachia. The most influenced bacterial taxa were Bartonella-like and Bacillus for both cultures and Wolbachia for the culture containing this symbiont. However, there was no direct evidence of any effect of Wolbachia on pesticide tolerance. The high pesticide concentration residues in diets reduced Wolbachia, Bartonella-like and Bacillus in mites of the symbiotic culture. This effect was low for Bartonella-like and Bacillus in the asymbiotic microbiome culture. The results showed that the microbiomes of mites are affected by pesticide residues in the diets, but the effect is not systemic. No actual detoxification effect by the microbiome was observed for the tested pesticides.

Do the microorganisms from laboratory culture spent growth medium affect house dust mite fitness and microbiome composition?

The interaction of house dust mites (HDM) and microorganisms is the key factor in the survival of these mites in human-made environments. Spent growth medium (SPGM) provides the rest of the diet, along with dead mite bodies and microorganisms. SPGM represents a source of microorganisms for the recolonization of mite food and the mite digestive tract. An experiment was performed to observe how adding SPGM to the HDM diet affects HDM population growth, the microbiome composition and the microbial respiration in microcosms. We analyzed American house dust mite (Dermatophagoides farinae) and European house dust mite (Dermatophagoides pteronyssinus) originating from control diets and diets treated with an extract of SPGM from 1- and 3-month-old mite cultures. The microbiome was described using 16S and 18S barcode sequencing. The composition of the bacterial and fungal microbiomes differed between the HDM species, but the SPGM treatment influenced only the bacterial profile of D. farinae. In the D. farinae microbiome of specimens on SPGM-treated diets compared to those of the control situation, the Lactobacillus profile decreased, while the Cardinium, Staphylococcus, Acinetobacter, and Sphingomonas profiles increased. The addition of SPGM extract decreased the microbial respiration in the microcosms with and without mites in almost all cases. Adding SPGM did not influence the population growth of D. farinae, but it had a variable effect on D. pteronyssinus. The results indicated that the HDM are marginally influenced by the microorganisms in their feces.