## 3 Results and Discussion
### Determination of the Microbiota of Edam Cheeses by High-Throughput Sequencing (HTS)
Spore-forming bacteria of the genus _Bacillus_ also had a relatively high share of microbial communities, particularly in spring samples where the average frequency of _Bacillus_ was 0.81% higher than in autumn samples. The proportions of spore-forming bacteria of the genus _Bacillus_ were higher in spring cheeses than in autumn cheeses. The observed variations can be probably attributed to dietary factors because cows graze naturally on grass in summer and autumn. [PERSON] et al. [45] demonstrated that the abundance of bacterial genera in the bovine rumen changed with the cows' diet. The presence of bacteria in milk can also differ because raw milk microbiota are much more diverse and contain more environmental bacteria and microorganisms from the bovine digestive tract in summer and autumn. In winter and spring, cows are fed with hay and silage, which increases the counts of spore-forming bacteria of the genus _Bacillus_ in the environment, milk, and, consequently, cheese. The autumn samples were characterized by the greatest differences in the frequency of _Enterococcus_ spp. (0.06%), and they differed (\(p>0.05\)) from spring samples (Table S1). The analyzed cheeses also contained trace amounts of DNA of the microorganisms colonizing the natural environment and cows. The remaining identified bacterial genera of the phylum Firmicutes accounted for up to 0.2% of the analyzed microbial communities. On rare occasions, selected genera, including _Veillonella_, _Laceyella_, _Streptococcus_, _Eubacterium_, and _Ruminococcus_, were more abundant (Table S1). Bacteria of the phylum Proteobacteria accounted for 3.26% (spring samples) and 8.69% (autumns samples) of microbial communities. They were mostly represented by members of the class \(\gamma\)-Proteobacteria whose DNA sequences could not be identified to the genus level. The proportion of \(\gamma\)-Proteobacteria ranged from 1.11% in spring samples to 7.11% in autumn samples (Figure 2 and Table S1). Among the identified genera, the predominant class was \(\alpha\)-Proteobacteria of the genus _Acetobacter_, which accounted for 0.39-1.01% of microbial communities in spring and autumn samples, respectively. The class \(\gamma\)-Proteobacteria of the genus _Acinetobacter_ was also abundantly represented in spring samples at 1.56% (Table S1). The phylum Bacteroidetes accounted for 0.52-0.84% of microbial communities in the analyzed cheese samples, and it was represented mostly by the genus _Bacteroides_, whose abundance ranged from 0.15% in spring samples to 0.30% in autumn cheese samples. Other genera were sporadically noted, including _Prevotella_ and _Chryseobacterium_ (Table S1). Cheeses were also colonized by bacteria of the genera _Acinetobacter_, _Chryseobacterium_, and _Alkaliphylus_ which are ubiquitous in soil and water, as well as _Cellomonas_, _Eubacterium_, _Rothia_, and _Ruminococcus_, which are found in the bovine digestive tract [11; 13; 41]. Interestingly, the unexpected bacterial genera _Alloscardova_, _Prevotella_ and _Veillonella_ from animal respiratory and digestive systems [45; 46]--as well as _Laceyella_, which are found in bottom sediments, soil, and patients with farmer's lung disease [47]--were also identified at relatively high concentrations in individual samples. The DNA of _Erysipelothrix rhusipathiae_, a bacterium responsible for swine crysipelas disease [48], was detected in a single sample in our study. The proportion of this bacterium in the sample was surprisingly high at 0.22%, which can probably be attributed to the accidental contamination of raw milk by veterinarians or farm personnel. [PERSON] and [PERSON] [49] also identified various bacterial and fungal genera that were not added as starter cultures. The presence of the DNA of unexpected bacterial genera and species provides detailed information about the quality of raw milk, and it can be used to prevent contamination of milk and the final product.