M. M. Umarov

Some specific features of nitrogen fixation in the digestive tract of the European beaver (Castor fiber).

452 The European beaver ( Castor fiber L. (1758)) is an important component of aquatic and bog ecosystems; in the European part of Russia, its population density reaches nine animals per kilometer of the coastline [1]. Because of beaver activity (the so-called beaver dams), specific landscapes appear that differ from the surrounding ones in some parameters, in particular, the nitrogen content. As determined by Canadian specialists, nitrogen concentration in the water of a beaver dam and in bottom deposits exceeds that in water bodies unaffected by beavers by factors of 30 and 1000, respectively [2]. The accumulated nitrogen is retained in deposits for as long as 72 years and has long-term influence on these ecosystems.

Diazotrophs in the digestive tract of termite Neotermes castaneus

Normal vital activity of termites Neotermes castaneus requires the presence and continuous replenishment of transient nitrogen-fixing bacteria in their digestive tract, which is realized by coprophagy and repeated utilization of substrate enriched in termite feces. This is the first demonstration of significant changes in the complex of aerobic and facultatively anaerobic nitrogen fixers mediated by an extension of microbial group composition and a shift in dominant taxa in termites that cannot reutilize their feces.

Effect of Deficiency of Dietary Nitrogen on Cellulose Digestibility and Nitrogen-Fixing Flora Activity in Sibling Vole Microtus rossiaemeridionalis

The effect of feed composition on nitrogen-fixing activity of the symbionts living in the digestive tract of sibling vole Microtus rossiaemeridionalis was experimentally studied. In the control, the rodents were allowed to select any of three feeds: protein-rich, protein-free with low cellulose content, and protein-free with high cellulose content. The voles consumed the food in a proportion corresponding to 16% of protein and about 6% of cellulose. Exclusion of the protein-rich food considerably increased cellulose consumption (up to 12%) and digestibility (from 35 to 64%). The changes in the consumed feed composition were reflected in localization of nitrogenase activity in the digestive tract: the control level of nitrogen-fixing activity in the cecum was three times that in the proventriculus, while an inverse proportion was observed in the experimental groups. In all cases, the colon was the major locus of nitrogen fixation.

Specific Features of Nitrogen Fixation and Denitrification in Termites Neotermes castaneus, Zootermopsis angusticollis, and Reticulitermes lucifugus

We studied specific features of microbial nitrogen fixation and denitrification in laboratory cultures of the termites Neotermes castaneus, Zootermopsis angusticollis, and Reticulitermes lucifugus, as well as in their nest materials. The nitrogenase activity in the termites was much higher than in the materials of termitarium. Denitrification was found only in the nest materials of termitarium. Studies of the bacterial community of gut nitrogen fixers Neotermes castaneus have shown the predominance of anaerobic and facultatively anaerobic bacteria that amount to up to 60% of the total number of “gut” bacteria. In the materials of termitarium, aerobic cellulose-destroying myxobacteria predominated, which are typical inhabitants of plant substrates, a food for the termites.

Specific Features of Nitrogen Transformation in the Soddy-Podsolic Soil in the Colonies of the Common Vole Microtus arvalis

The influence of common vole Microtus arvalison processes of nitrogen fixation and denitrification in the soddy-podsolic soil was studied. In the common vole colonies, the level of nitrogen fixation was reliably lower and that of denitrification higher, than in the control soil outside these colonies. Nitrogen-containing excretory products of voles accumulating in the soil are among the main factors that determine the activity of these processes.

Microbiological activity in the anthills of fallow lands (Ryazan Region)

A bacterial complex associated with several species of ants, the inhabiting soil, and their anthills was studied. The biodiversity of bacteria in ants was higher than that in the anthills and control soil. The latter was dominated by Bacillus (more than 80%); the anthill of Formica was dominated by the Flavobacterium-Bacteroides-Cytophaga group. In addition, actinomycetes were widespread in the anthills of Formica and Lisius. Numerous staphylococci (20%) were found in the L. flavus ants, but the main dominants of the bacterial community were Streptomyces bacteria (68.5%). Tetramorium had no pronounced dominants and many Bacteroides bacteria (28%). Actinomycetes of Streptomyces were detected in the bacterial complexes of all studied ants, except for F. cunicularia.

Functional features of microbial communities in the digestive tract of field voles (Microtus rossiaemeridionalis and Clethrionomys glareolus)

The nitrogen-fixating and cellobiohydrolase activity, the nitrogen (N) and carbon (C) contents, and the number of microorganisms in the prestomach, cecum, and colon of two vole species were studied: the southern vole (Microtus rossiaemeridionalis) and the bank vole (Clethrionomys glareolus), which is characterized by a mixed type of diet. The nitrogen-fixating activity in the cecum was found to be the highest in the voles compared with the mammals studied earlier. The seasonal dynamics of both nitrogenase and cellobiohydrolase activities was registered in the southern vole. The structure of the microbial complex in the southern vole is more varied and includes microorganisms associated with plant substrates.

Soil biological activity in the Chernye Zemli, Kalmykia, inhabited by gerbils Meriones tamariscinus and M. meridianus

The influence of tamarisk (Meriones tamariscinus) and midday (M. meridianus) gerbils on soil biological activity in the Chernye Zemli, Kalmykia, was studied. Nitrogen fixation, denitrification, and CO2 emission were measured in soil samples from different parts of gerbil burrows. Functional biodiversity of the microbial community was evaluated using multisubstrate testing and comparison of bacterial group composition in samples from gerbil burrows. The impact of gerbils on soil biological activity was mediated by the changes in the group composition of microorganisms.

Role of microbiocenosis of the gastrointestinal tract in the nutrition of grouse

In order to assess the role of the microbiocenosis of the digestive tract of herbivorous birds in transforming poor forage, the activity of cellulolytic enzymes in all departments of the gastrointestinal tract of the black grouse (Lyrurus tetrix) and Western capercaillie (Tetrao urogallus) was studied. The functional diversity of microbial communities of different departments was also investigated. In both species of birds, nitrogenase and cellobiohydrolase activities were discovered in the digestive tract, with the maximum observed in the cecum.

Features of nitrogen and carbon transformation in nests of soil ants

Soil ants (Lasius niger, L. flavus, Formica cunicularia and Tetramorium caespitum) have a significant influence on the processes of organic matter transformation in the soil, including the most important biophilic elements, nitrogen and carbon, which is reflected in the accumulation and their vertical redistribution within an anthill profile. The amount of nitrogen and carbon in nests of different ant species was significantly higher than in control soil, where it decreased lower in the profile, while in ant nests the content of the elements increased with time. Microbial biomass is an important indicator that affects the accumulation and transformation of biophilic elements. It was found to be higher in anthills than in the control soil. The activity of nitrogen fixation and denitrification in the soil of anthills where the main activity of ants occurs was higher than in the control.