Citation: Boyarshin, K.S.; Adamova, V.V.; Wentao, Z.; Obuhova,O.Y.; Kolkova, M.V.; Nesterenko,V.A.; Bespalova, O.S.; Kluyeva, V.V.; Degtyareva, K.A.; Kurkina, Y.N.; et al. The Effect of Long-Term Agricultural Use on the Bacterial Microbiota of Chernozems of the Forest-Steppe Zone. Diversity 2023, 15, 191. https://doi.org/10.3390/d15020191 Academic Editor: Michael Wink Received: 30 December 2022 Revised: 24 January 2023 Accepted: 26 January 2023 Published: 30 January 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). diversity Article The Effect of Long-Term Agricultural Use on the Bacterial Microbiota of Chernozems of the Forest-Steppe Zone Konstantin S. Boyarshin 1 , Valeria V. Adamova 2, *, Zheng Wentao 1 , Olga Y. Obuhova 1 , Marina V. Kolkova 1 , Vitaliy A. Nesterenko 3 , Olga S. Bespalova 1 , Violetta V. Kluyeva 1 , Kristina A. Degtyareva 1 , Yulia N. Kurkina 1 , Olesia A. Makanina 1 and Irina V. Batlutskaya 1 1 International Laboratory for Applied Biotechnology, Institute of Pharmacy, Chemistry and Biology, Belgorod State University, Belgorod 308015, Russia 2 Department of Biology, Institute of Pharmacy, Chemistry and Biology, Belgorod State University, Belgorod 308015, Russia 3 V.V. Dokuchaev Soil Science Institute, Moscow 119017, Russia * Correspondence: adamova_v@bsu.edu.ru; Tel.: +7-(903)-884-80-74 Abstract: The structure of soil microbial communities and the factors that control it are still poorly understood and cause ongoing interest. The diversity of soil bacteria reflects the diversity of existing ecological niches and trophic connections between them and with other components of the ecosys- tem. The presence of certain taxa with their own characteristic properties depends on the specific environmental conditions. Analysis of the composition of soil microbiota in various physicochemical conditions allows identify landmarks for understanding the principles by which it is formed. Of particular interest in this regard are the features of cultivated fertile soils that assist agricultural production. In this paper, we have assessed the occurrence of representatives of different families of bacteria in arable and nonarable chernozems of three subtypes. The methodology of 16S microbial profiling was used. The general features of the taxonomic structure of bacterial communities of cher- nozem remain similar, with a high occurrence of the families Sphingomonadaceae, Xanthobacteraceae, Rubrobacteraceae and Chitinophagaceae. Notably, Gemmatimonadaceae, one of the most commonly occur- ring families, is approximately twice as represented in arable soils as in nonarable ones. Differences between subtypes of chernozem and between arable and nonarable areas concerned different sets of bacterial families. Among others, the occurrence of representatives of families characterized by nitrogen fixation, nitrite oxidation and reduction, ethanol oxidation, biodegradation and microbial predation is touched upon. The obtained results raise the question of the factors limiting the number of certain groups of bacteria in various soil conditions and so limiting their contribution to the properties of the ecosystem. Keywords: soil microbiota; chernozem; 16S microbial profiling 1. Introduction Chernozems, also known as Mollisols, Black Soils or Prairie Soils, are formed mostly on loess sediments in moderately moistened continental areas under grassland biomes in the middle latitudes, occupying about 916 million ha, or 7% of the ice-free surface of the Earth [1]. They are characterized by high content of humus, calcium, potassium, phosphates [2] and pH values near neutral [3]. High concentrations of ion-binding [4] and moisture-preserving humic substances ensure soil fertility [5], contributing to the conservation and usability of introduced nutrients. The chemical composition of chernozems, rich in organic and mineral substances, con- tributes to the maintenance of a variety of ecological niches occupied by bacterial microbiota. The bacterial branch of life has a special role in ensuring soil fertility, including participation in the synthesis of humic substances, fixation and oxidation of nitrogen, dissolution of phosphates, suppression of pathogens and symbiotic interactions with the root system of Diversity 2023, 15, 191. https://doi.org/10.3390/d15020191 https://www.mdpi.com/journal/diversity