Taxonomic and functional characteristics of xerotolerant culturable bacterial community of Negev desert soil

Despite the significant expansion of the geography of soil microorganisms studies in various, including extreme natural environments, research on the biodiversity and metabolic activity of soil microbial communities under conditions of moisture deficiency are few. Biodiversity of culturable bacteria isolated from the surface horizon of the Negev desert soil (Aridic Calcisol) after pre-incubation of soil samples under the conditions of low water availability has been studied. An increase in the diversity of culturable bacteria after pre-incubation was revealed in comparison with the community isolated from the native soil. From the native and pre-incubated samples, 153 phenotypically unique pure cultures of bacteria from 22 genera belonging to the phyla Actinomycetota, Pseudomonadota, Bacillota, and Bacteroidota were isolated and identified. The taxonomic diversity of culturable bacteria isolated from the sample pre-incubated at a water activity (Aw) of 0.90 was two times higher than that obtained from the native soil. The strain of the genus Pedobacter has been identified, which may be a representative of a previously undescribed bacterial species. Bacteria of the genera Aerococcus, Bacillus, Brevibacterium, Staphylococcus, and Stenotrophomonas capable of growing at Aw 0.91 were found. One strain of the genus Microlunatus has been identified that is capable of growing on a nitrogen-free medium, exhibiting amylase and protease activity, and capable to growth on a medium with Aw down to 0.96. The obtained results confirm the hypothesis that arid ecosystems, in particular, desert soils and sediments, are a depository of a previously unexplored taxonomic diversity of bacteria with unique physiological properties that are promising for study and potential implementation in biotechnological processes.