Two Populations of Mites (Tyrophagus putrescentiae) Differ in Response to Feeding on Feces-Containing Diets

Abstract

<b>Background:</b> <i>Tyrophagus putrescentiae</i> is a ubiquitous mite species in soil, stored products and house dust and infests food and causes allergies in people. <i>T. putrescentiae</i> populations harbor different bacterial communities, including intracellular symbionts and gut bacteria. The spread of microorganisms via the fecal pellets of <i>T. putrescentiae</i> is a possibility that has not been studied in detail but may be an important means by which gut bacteria colonize subsequent generations of mites. Feces in soil may be a vector for the spread of microorganisms. <b>Methods:</b> Extracts from used mite culture medium (i.e., residual food, mite feces, and dead mite bodies) were used as a source of feces-inhabiting microorganisms as food for the mites. Two <i>T. putrescentiae</i> populations (L and P) were used for experiments, and they hosted the intracellular bacteria <i>Cardinium</i> and <i>Wolbachia</i>, respectively. The effects of the fecal fraction on respiration in a mite microcosm, mite nutrient contents, population growth and microbiome composition were evaluated. <b>Results:</b> Feces from the P population comprised more than 90% <i>Bartonella</i>-like sequences. Feces from the L population feces hosted <i>Staphylococcus, Virgibacillus, Brevibacterium, Enterobacteriaceae</i>, and <i>Bacillus</i>. The mites from the P population, but not the L population, exhibited increased bacterial respiration in the microcosms in comparison to no-mite controls. Both L- and P-feces extracts had an inhibitory effect on the respiration of the microcosms, indicating antagonistic interactions within feces-associated bacteria. The mite microbiomes were resistant to the acquisition of new bacterial species from the feces, but their bacterial profiles were affected. Feeding of P mites on P-feces-enriched diets resulted in an increase in <i>Bartonella</i> abundance from 6 to 20% of the total bacterial sequences and a decrease in <i>Bacillus</i> abundance. The population growth was fivefold accelerated on P-feces extracts in comparison to the control. <b>Conclusion:</b> The mite microbiome, to a certain extent, resists the acquisition of new bacteria when mites are fed on feces of the same species. However, a <i>Bartonella-</i>like bacteria-feces-enriched diet seems to be beneficial for mite populations with symbiotic <i>Bartonella</i>-like bacteria. Coprophagy on the feces of its own population may be a mechanism of bacterial acquisition in <i>T. putrescentiae</i>.