Habitat as a determining factor for the reindeer rumen microbiome formation in Russian arctic

Reindeer ( Rangifer tarandus ) is geographically isolated from other subspecies of the ruminant family Cervidae . It is known that belonging to certain environmental conditions can have a significant impact on the composition of the ruminant rumen microbiome. With the use of molecular-biological analysis, we studied for the first time the patterns of formation of the reindeer’s rumen microbial communities for the Rangifer tarandus living in different natural and climatic zones of the Russian Federation. The purpose of the study is to assess the regional features of the reindeer’s rumen microbiome into the different Arctic regions of Russia using T-RFLP analysis and quantitative PCR. It was made a comparative analysis of the influence of a number of factors on the composition of the reindeer rumen microbiome, incl. gender and age peculiarities, regional habitat conditions and feeding ration features. Samples of the rumen content were collected in the summer-autumn period of 2017 from 58 individuals ( n ≥ 3 from each age group) in the Yamalo-Nenets Autonomous District (AO), Nenets Autonomous District and the Murmansk region. The total number of bacteria, archaea, and fungi of the Neocallimastigales was analyzed by quantitative PCR, and the composition of the bacterial community by T-RFLP (terminal restriction fragment polymorphism) method. The main determinant of all components of the microbial community of the reindeer’s rumen is regional habitat conditions, which, apparently, is due to differences in the composition of the pasture diet and the epizootic situation in the herd. The smallest similarity with other regions was found for samples from the Murmansk region, which is probably due to differences in reindeer pasture ration in this region, i.e. the differences in the composition of vegetation and lower nutritional values. Gender and age differences of animals were less significant though made a certain contribution to the ratio of microorganisms in the rumen. The clearest differences in the rumen microbiota were detected between groups of animals under 2 years of age and older than 2 years. In general, significant changes in the representation of a taxa number were noted in connection with the nutritional value of pasture ration. A statistically significant relationship was established between the level of fiber in grazing feed and members of the families Veillonellaceae ( r = -0.75), Nostocaceae ( r = 0.52), Rivulariaceae ( r = -0.88), etc. in addition to traditionally associated with the processes of cellulose degradation bacteria. There is no significant correlation between the content of conditionally pathogenic microorganisms from the Fusobacteria , Tenericutes ( Mycoplasmataceae ), Proteobacteria ( Enterobacteriaceae , Campylobacteraceae ) and the nutritional value of feeds and other groups of microorganisms, which indicates the need for more research in this direction. The obtained data clarify aspects of the interaction and cohabitation of symbionts in the complex-component system of the reindeer rumen, which is characterized by the diversity of sources of plant polysaccharides and the variety of enzymes produced by microorganisms.