Leaf Bacterial Microbiome of Alpine Plants in the Northwest Caucasus: Factors of Taxonomic Diversity

Endophytic bacterial communities in leaves participate in pathogen control, plant immune responses, and the induction and mediation of stress resistance through the production of hormones and antioxidants. Understanding the composition, structure, and factors influencing microbiome formation will enable us to consider plants as holobionts. Consequently, adaptation can be viewed not merely as a physiological and biochemical response but rather as the ability of plants to shape the composition of their own microbiome. For the first time, data were obtained on the composition and structure of bacterial endophytes in the leaves of plants from four communities of the alpine belt of the Northwest Caucasus. These communities differed significantly in the number of bacterial taxa and the Shannon diversity index. However, no significant differences were observed between alpine snow bed communities and Geranium–Hedysarum meadows at various taxonomic levels. The factors studied had differing effects on abundant and less-represented bacterial taxa; the factor often has a significant effect only at the level of one group. The greatest influence on the composition of bacterial endophytes in plant leaves in the alpine communities was exerted by the community type and plant taxonomy. The contribution of the factors examined to the formation of leaf endophytic bacterial communities decreased in the following order: host plant taxonomy → community type → plant functional traits ≈ topographic factors.