Do 'cheese factory-specific' mites (Acari: Astigmata) exist in the cheese-ripening cabinet?

ABSTRACT

To determine whether the mites used in the ripening process of traditional cheeses are genetically unique to cheese factories, we investigated mites from three types of traditional cheeses, that use mites in the ripening process 'Würchwitzer Milbenkäse' from Germany and 'Mimolette' and 'Artisou' from France. In addition, traditional ripened cheeses were purchased from cheese specialty stores in France (Mimolette) and Japan ('Laguiole' from France) as well as stores in temporary markets in France ('Salers' and 'Cantal vieux') and the mites obtained from those cheeses were analyzed in this study. Partial sequences of the 28S rRNA gene (28S) were determined and used to reconstruct a phylogenetic tree. Tyrolichus casei, the dominant cheese mite species from the ripening cabinets of three traditional cheese producers and two cheese specialty stores in France and Japan, had identical partial 28S sequences. All specimens from Cantal vieux from a store in the temporary market in France had an identical sequence with Acarus siro and Acarus immobilis in the determined region of the 28S sequences. Mite individuals from Salers from a store in the temporary markets in France shared the same haplotype as Acotyledon paradoxa. For the T. casei individuals from five different localities (19 individuals in total), the nuclear loci were obtained using MIG-seq. More than several thousand genomic regions are amplified simultaneously by multiplex PCR, and targeting regions surrounded by inter-simple sequence repeats (ISSRs) in the genome were sequenced using the MiSeq system (Illumina). SNPs extracted from this genome-wide analysis showed that no genetic structure existed in the populations from any region. Among the five samples from the three regions, which were more than 500 km apart and from completely different environments, the mites had no geographic bias, but all mite individuals were genetically nearly identical. Thus, we found no evidence to support the existence of 'cheese factory-specific' T. casei mites, at least in terms of genetic analysis.