Microbiome variation during culture growth of the European house dust mite,Dermatophagoides pteronyssinus

Abstract

In culture, the house dust mite, Dermatophagoides pteronyssinus, shows different growth patterns, but the composition and changes in the associated microbial community during mite culture growth are poorly known. In this study, we analyzed temporal changes in microbial communities including ‘internal’ communities (inside mites, ingested) and ‘environmental’ communities (from culture environment). Microbial community structure was correlated with guanine content (a nitrogenous waste product of mites) and mite population density. Both internal and environmental microbial communities were remarkably consistent between biological replicates from the same culture age group and were composed of relatively few dominant taxa–11 bacterial and 3 fungal operational taxonomic units (OTUs). Significant changes over time in microbial community structure in the bulk culture environment and in internal mite samples were observed. The yeast, Saccharomyces cerevisiae, a main component of the mite diet, gradually disappeared during mite culture growth and was replaced by fungi from the genera Aspergillus and Candida in both ‘internal’ and ‘environmental’ samples. In environmental samples, bacteria from the genus Lactobacillus and S. cerevisiae were negatively correlated, and Aspergillus and Candida positively correlated, with guanine content. The relative abundance of bacteria from the genus Kocuria increased with mite density but declined with increasing guanine content. The relative abundance of bacteria from the genus Virgibacillus was negatively correlated with mite density in ‘internal’ samples. Gram-positive bacteria dominated bacterial microbiomes at all time points in our experiments, indicating a more limited possibility for vaccine contamination by bacterial endotoxins (heat-stable lipopolysaccharides produced mostly by Gram-negative bacteria) in our experimental cultures.

The Negative Effects of Feces-Associated Microorganisms on the Fitness of the Stored Product Mite Tyrophagus putrescentiae

“…It is also possible that the positive presence of Bartonella -like bacteria cannot overcome the suppressive effects of the fecal-associated microorganisms that are correlated with decreased mite fitness. We have previously shown that some of the fecal treatment-associated microorganisms (i.e., Staphylococcus , Candida , and Aspergillus ) are correlated to the mite waste deposit guanine ( Nesvorna et al, 2021 ), and we hypothesize that these microbes decrease mite fitness either through the production of toxic metabolic wastes or through direct competition with the mites to nutrients, or both. In laboratory experiments, mite population growth has shown density-dependent patterns ( Pekar and Hubert, 2008 ; Rybanska et al, 2016 ), which lead to decreased growth rates at higher densities.…”

“…For the fungal communities, the genera Yamadazyma and Candida were associated with the fecal treatments. Although Saccharomyces cerevisise was a compound of mite diet, the other yeasts ( Candida , Hyphopichia , and Malassezia ) have been previously identified in mite cultures and have been associated with house dust mite culture development and were associatiated with mite feces ( Klimov et al, 2019 ; Molva et al, 2019 ; Nesvorna et al, 2021 ). Yamadazyma and have been elsewhere isolated from insects, also ( Suh et al, 2008 ).…”

“…The next indirect measures of successful surface cleaning are: (i) the lower number of bacterial and fungal rRNA gene copies in cleaned treatments relative to feces treatments and (ii) the pronounced presence of diet-associated bacterial and fungal taxa (e.g., S. cerevisiae and L. fermentum ) in the microbiome of cleaned mites. Both S. cerevisiae and L. fermentum have been previously shown to be replaced during mite culture growth ( Klimov et al, 2019 ; Nesvorna et al, 2021 ). These data, together with the higher alpha diversity in cleaned treatment samples relative to feces treatment samples, indicate that the microbial communities that developed in the cleaned treatment samples are based on the environment (diet) and the intracellular community.…”

“…We focused on the analyzes of the whole microbiome from chambers which includes the mites, their feces and remains of their bodies and the diet. The taxa associated with the clean treatment mites are derived from internal symbionts Wolbachia (Werren, 1997), from the diets themselves [S. cerevisiae, L. fermentum (Klimov et al, 2019;Nesvorna et al, 2021)], or random taxa that have not been previously detected in mite diet studies (e.g., bacteria from the genera Marimomonas, Nevskia, and Cobetia). Although the cleaned treatments had lower bacterial and fungal abundances than fecal treatments, as measured by qPCR of 16S and 18S rRNA genes, bacterial and fungal loads were still high (e.g., >10 6 copies/chamber for bacteria and >10 5 copies/chamber for fungi).…”

Growth, allergen profile and microbiome studies in Dermatophagoides pteronyssinus cultures

“…The wide range of allergens produced cause allergic rhinoconjunctivitis and asthma and contribute to other allergic skin diseases in genetically predisposed individuals. Therefore, mite allergen extracts are essential for allergy diagnosis and treatment of mite allergy [5].…”