Naturally fermented dairy products contain a rich microbial biodiversity.This study aimed to provide an overview on the bacterial microbiota biodiversity of 85 samples,previously collected across a wide region of China,Mongolia,and Russia.Data from these 85 samples,including 55 yoghurts,18 naturally fermented yak milks,6 koumisses,and 6 cheeses,were retrieved and collectively analyzed.The most prevalent phyla shared across samples were Firmicutes,Proteobacteria,Bacteroidetes and Actinobacteria,together accounted for 99% of the bacterial sequences.The predominant genera were Lactobacillus,Lactococcus,Streptococcus,Acetobacter,Acinetobacter,Leuconostoc,and Macrococcus,together corresponded to 96.63% of the bacterial sequences.Yet,further multivariate statistical analyses revealed significant differences in the microbiota structure across sample geographic origin and type.Firstly,on the principal coordinate score plot,symbols representing the three main sample collection regions (Russia,Xinjiang,and Tibet) were mostly located respectively in the upper,left,and lower quadrants,although slight overlapping occurred.In contrast,symbols representing the minor sampling areas (Inner Mongolia,Mongolia,Gansu,and Sichuan) were predominantly distributed to the lower left quadrant.These results together suggest a possible association between the sample geographical origin and microbiota composition.Secondly,the bacterial microbiota structure was stratified by sample type.Particularly,the cheese microbiota was largely distinct from the other sample types due to its high abundances in Lactococcus and Streptococcus.The fermented yak milk mierobiota resembled most to that of the yoghurts.Koumisses have the lowest microbial diversity and richness.In conclusion,both the geographic origin and sample type are factors involving in shaping the microbial diversity of naturally fermented milk.