Bacterial community diversity of yak milk dreg collected from Nyingchi region of Tibet, China

Altitude-associated trends in bacterial communities in ultrahigh-altitude residences

BACKGROUND

Indoor bacterial communities may change with altitude because their major contributors, outdoor bacterial communities, vary with altitude. People's health effects from bacteria inhalation exposure can also vary with altitude because human respiratory physiology changes with oxygen content in air. Accordingly, adjusting indoor bacterial communities may help to acclimate newcomers from low-altitude environments to ultrahigh-altitude environments. To lay the groundwork for further research, we aimed to first elucidate the bacterial communities in ultrahigh-altitude residences and the effects of altitude on these communities. We collected 187 environmental samples from residential communities at ultrahigh altitudes of 3811-4651 m in Ngari, China and sequenced bacterial 16S rRNA genes.

RESULTS

On one hand, when abundant genera in ultrahigh-altitude residences and those reported by previous studies on low-altitude residences were compared, nine genera were shared, whereas other five genera were abundant only at ultrahigh altitudes. On the other hand, when the bacterial communities of residences at different ultrahigh altitudes were further compared, the bacterial composition in indoor surface samples varied significantly with altitude. The relative abundance of five bacterial genera in indoor air samples and 10 genera and three phyla in indoor surface samples varied monotonically with altitude.

CONCLUSIONS

Altitude may be a long-neglected factor that shapes residential bacterial communities and thus warrants attention.

Tibetan Plateau yak milk: A comprehensive review of nutritional values, health benefits, and processing technology

Yak milk is a characteristic animal product of yaks in the Qinghai-Tibet Plateau. Although yak milk production is low, it is richer in nutrients such as protein, fat, and lactose, a more comprehensive range of bioactive components, and unique microbial resources than Holstein cow milk. The plateau environment makes yak milk resistant to hypoxia, anti-fatigue, antioxidant, antibacterial, and relieves chronic diseases. In this paper, based on the systematic analysis of yak milk research results in the past 20 years using CiteSpace 6.1.R2, we reviewed yak lactation performance and nutritional efficacy of yak milk. This paper summarizes the improvement of traditional yak dairy processing technology, and also focuses on the microbial diversity of yak milk sources and their beneficial effects. The purpose of this review is to provide scientific support for the development of a quality yak milk industry on the Tibetan plateau.

Composition and factors influencing community structure of lactic acid bacterial in dairy products from Nyingchi Prefecture of Tibet

This study investigated the community composition of lactic acid bacteria (LAB) from yaks' milk (YM) Tibetan yellow cattle milk (TM) and their fermented products from different counties in the Nyingchi Prefecture, Tibet using Pacific Biosciences (PacBio) single-molecule real-time (SMRT) sequencing. Sequencing revealed 26 genera and 94 species from 71 dairy samples; amongst these Lactobacillus delbrueckii (36.17%), Streptococcus thermophilus (19.46%) and Lactococcus lactis (18.33%) were the predominant species. This study also identified the main factors influencing LAB community composition by comparing amongst samples from different locations, from different milk types, and from different altitudes. The LAB communities in YM and TM were more diverse than in fermented yaks' milk (FYM) and fermented Tibetan yellow cattle milk (FTM) samples. Similarly, whether milk was fermented or not accounted for differences in LAB species composition while altitude of the dairy products had very little effect. Milk source and production process were the most likely causes of drastic shifts in microbial community composition. In addition, fermented dairy products were enriched in genes responsible for secondary metabolic pathways that were potentially beneficial for health. Comprehensive descriptions of the microbiota in different dairy products from the Nyingchi Prefecture, Tibet might help elucidate evolutionary and functional relationships amongst bacterial communities in these products.

Data on microbial diversity of camel milk microbiota determined by 16S rRNA gene sequencing

Raw camel milk samples were collected from three geographical locations (south, north and middle Kuwait) during two seasons. Next generation sequencing of the V3-V4 regions of the 16S rRNA gene was used to analyze the bacterial community in camel milk. DNA was extracted from one hundred thirty-three samples, and libraries were prepared using custom fusion primers of the 16S rRNA gene and sequenced on Illumina HiSeq 2500 platform. 16S rRNA gene sequences were aligned against the SILVA database SSU release 138. The high-throughput sequencing data are available at the NCBI database under the Bioproject PRJNA814013. This work describes camel milk's bacterial diversity among different geographical locations and seasons. The distribution of alpha diversity measures among camel milk sample groups collected from different geographical locations and seasons is presented. A significant effect of these parameters on camel milk's bacterial diversity was shown. Linear discriminant analysis (LefSe) showed significant differentially abundant bacteria at the phylum, class, order, family and genus level among the three locations and seasons. LefSe identified a total of 83 and 40 differentially abundant genera in the different geographical locations and seasons, respectively. More details about the bacterial composition of raw camel milk at the phylum and genus level can be found in research article [1]. These data can be used to compare the diversity of milk bacterial community between different milk producing species and camels from different parts of the world. Besides, these findings will contribute to our understanding of the camel microbiome structure and might be useful for designing an appropriate control program in the camel dairy herd. The data described in this article are available in Mendeley Data [2].