The intensity of urea recycling in the wild herbivorous European hare has been investigated. The intensity of urease activity in the gastrointestinal tract has been selected as a convenient quantitative measure of nitrogen recycling. High urease activity was detected in the large intestine; it was higher than the previously detected activity in other mammals with postgastric fermentation: pigs, rats, and rabbits. The strong seasonal dynamics of urease activity has been noted: it increases during winter diet consumption, which is poor in available nitrogen.

The results of urease activity studies in the digestive tract of muroid rodents Microtus socialis and Meriones meridianusare considered. It was noted that the absolute values of urease activity...

Climate changes cause a dramatical increase in the ice-free season in the Arctic, forcing polar bears ashore, closer to human settlements associated with new and non-natural food objects. Such a diet may crucially transform the intestinal microbiome and metabolism of polar bears. The aim of this study was to characterize changes in the gut bacterial and fungal communities resulting from the transition to anthropogenic food objects by the means of 16S and ITS metabarcoding. Thus, rectal samples from 16 wild polar bears from the Kara–Barents subpopulation were studied. Human waste consuming resulted in a significant increase in the relative abundance of fermentative bacteria (Lactobacillaceae, Leuconostocaceae, and Streptococcaceae) and a decrease in proteolytic Enterobacteriaceae. However, the alpha-diversity parameters remained similar. Also, for the first time, the composition of the fungal community of the polar bear intestine was determined. Diet change is associated with the displacement of eurybiontic fungi (Thelebolus, Dipodascus, Candida (sake), and Geotrichum) by opportunistic Candida (tropicalis), Kazachstania, and Trichosporon. Feeding on human waste does not cause any signs of dysbiosis and probably leads to adaptive changes in the bacterial microbiome. However, the emergence of fungal facultative pathogens increases the risk of infections.

Emerald ash borer Agrilus planipennis (Coleoptera: Buprestidae) is a quarantine pest posing a threat to ash trees all over Europe. This wood-boring beetle native to Asia is quickly spreading in North America and European Russia, and approaching the European Union and the Middle East. It is important to study microorganisms associated with this pest, because the knowledge of its “natural enemies” and “natural allies” could be potentially used for the control of the pest. All previously published information about the A. planipennis microbiome was obtained in North America and China. We present the first study on procaryotes associated with A. planipennis in Europe. Alive larvae were sampled from under the bark of Fraxinus pennsylvanica in the Moscow Oblast and the gut microbiome was studied using metagenomic methods. Next-generation Illumina-based amplicon sequencing of the v3-v4 region 16S-RNA gene was performed. In total, 439 operational taxonomic units from 39 families and five phyla were detected. The dominant families in our samples were Pseudomonadaceae, Erwiniaceae and Enterobacteriaceae, in accordance with the published information on the larval gut microbiome in North America and China. We detected intracellular bacteria in A. planipennis for the first time, namely Rickettsia (Rickettsiaceae) and Rickettsiella (Diplorickettsiaceae). Representatives of the genus Rickettsia are known to be in mutualistic symbiosis with some phytophagous insects, while Rickettsiella bacteria are pathogenic to many arthropods. The finding of Rickettsia and Rickettsiella opens perspectives for future research on the interactions between these bacteria and A. planipennis and the possible use of these interactions for the control of the pest.