Diseases’ bacterial markers in the rumen of Russian Arctic reindeer

Abstract

The study of symbiotic communities of the reindeers’ rumen remains one of the most interesting topics of microbial ecology. The physiological adaptations of reindeer allow them to use the scarce nutritional resources of the tundra and forest-tundra for feeding. The study is the first attempt to analyze the microbiome of the rumen of Russian Arctic reindeer's in the in terms of searching for microorganisms that are indicators of pathological processes caused by the change of seasons. We have sequenced (Miseq, Illumina) the rumen microbiome of 38 reindeer living in the Nenets and Yamalo-Nenets Autonomous Districts in summer and winter. NMDS analysis revealed significant differences between winter and summer microbiomes of the reindeers’ rumen (p = 0.001). By analyzing sequencing data using the VennDiagram package in the R software, common and unique OTUs were calculated. The share of unique species in winter was 7.1%, and in summer 10.6%. It was found that a number of pathogenic microorganisms that cause diseases develop in the rumen of reindeers in the summer. It is known that the incidence of parasitic diseases, necrobacteriosis, etc. in reindeers’ herds increases in summer. Necrobacteriosis is seasonal in nature and spreads mainly in July-August, when the temperature is highest and the gadflies and blood-sucking insects are active. Venngraph analysis showed the presence of unique DNA sequences of Fusobacterium sp. that were found only for the summer period. Fusobacteria can be called one of the main agents causing necrobacteriosis. In the summer period only, rumen bacteria that contribute to the development of inflammatory reactions in the chronic periodontitis (Parvimonas sp. and Porphyromonas endodontalis) were detected. Sharpea sp. was detected only for the summer period also. These bacteria produce lactic acid and are able to lower the pH of the rumen fluid, which leads to an imbalance in the metabolism of volatile fatty acids. It is known that in cattle, changes associated with a decrease in rumen pH lead to the development of acidosis. Thus, we have shown that in summer, in contrast to winter, various pathogenic bacterial species develop, causing diseases such as necrobacteriosis, chronic periodontitis. This is probably due to an increase in temperature in summer, which provokes the development of different groups of microorganisms, including pathogens, as well as the activity of parasitic insects that contribute to the spread of diseases in reindeer herds. In addition, the animal's body is weakened after a long winter period and a meager diet, which also contributes to the development of various infectious processes. We have identified a number of pathogenic bacteria, such as Fusobacterium sp., Parvimonas sp. and Porphyromonas endodontalis, which appear only in summer and can be distinguished as microorganisms-markers of pathological processes.