Abstract
Background: The house mite Dermatophagoides pteronyssinus is an important allergen source. In mite cultures used for anti-allergic vaccine production, both mite population growth patterns and microbiome composition can affect the level of allergen production. Here we analyzed mite microbial communities: “internal community” inside mites (ingested) and “environmental community” from culture environment) and their temporal changes during mite culture growth. To explain the microbiome temporal changes in mites and mite culture, the microbial profiles were correlated to the concentration of mite nitrogenous waste products (i.e., guanine) and mite population density.Results: The population dynamic of D. pteronyssinus showed a nonlinear humped-shaped pattern during mite culture growth, and a nonlinear pattern was also observed for the mite nitrogenous waste product guanine. Mite microbial communities were remarkably consistent between replicates within the same treatment and composed of relatively few dominant taxa – 11 bacterial and 3 fungal OTUs. Significant changes over time in microbial community structure in the bulk culture environment and internal mite microbiome were observed. The yeast Saccharomyces cerevisiae, which is a main component of the yeast extract used in the mite diet, gradually disappeared during the mite culture growth and was replaced by operational taxonomic units derived from the genera Aspergillus and Candida in both the internal mite community and the environment culture samples. In the ingested community, an OTU derived from the putative fungal pathogen Malasszia was detected at low relative abundance. In internal mite community, the relative abundance of bacteria from the genus Kocuria positively correlated with mite density but negatively correlated with guanine content. The relative abundance of the bacteria Virgibacillus pantothenticus was negatively correlated with mite density in the internal community. In the culture environment, the bacterial species Lactobacillus fermentum and yeast S. cerevisiae were present in high abundance in diet, but a significant negative relationship with guanine was observed. The fungal taxa Aspergillus penicillioides and Candida mucifera increased with the amount of guanine in the culture.Conclusion: The temporal changes in the internal and environmental microbiomes of the D. pteronyssinus culture are related to mite population density and guanine contents. The detection of an OTU derived from fungi of the genus Malassezia suggests that mites could serve as vectors for dissemination. The dominant bacterial species observed here were Gram-positive bacteria, indicating a limited source for potential vaccine contamination by endotoxins (heat-stable lipopolysaccharides produced mostly by Gram-negative bacteria) in the experimental design used in this study.