Identification and characterization of the endophytic microorganism, is gaining their underestimated significance in influencing health, performance, and other biological attributions of plants in general and forest tree species in particular. Because of the scarcity of information on the endophytic microbiome of the Hyrcanian forests species, including hornbeam (Carpinus betulus L.) trees, as a major constituent thereof, the present study aimed at the identification and partial characterization of the endophytic Bacillus species of Carpinus betulus as the first step in this context. Methods and results Shoot samples were collected from the Hyrcanian forest locations of Mazandaran and Golestan provinces in Iran. Bacterial strains were isolated from the surface-disinfected shoot segments and subjected to phenotypic characterization. Following assessment of the genetic diversity of the isolates by BOX-PCR fingerprinting, the representative isolates of each of the 15 groups were used for further characterization. Analysis of the nucleotide sequences of the 16S rDNA and HSP60 gene of the isolates led to the identification of 10 species. The predominant species was B. cereus followed by B. subtilis. The other species encountered were B. thuringiensis, Priestia filamentosa, B. velezensis, B. mojavensis, B. amyloliquefaciens, B. safensis, P. aryabhattai, and Gottfriedia acidiceleris. Most isolates possessed characteristics which could contribute to the biocontrol potential of the isolates, including formation of biofilm, production of hydrogen cyanide, tolerant to relatively high concentration of sodium chloride, and antibacterial activity. Conclusions Ten Bacillus species were identified as the prevailing endophytic species of C. betulus in the Hyrcanian forest of northern Iran, most turned up to possess biological activities involved in biocontrol capability of the isolates against some plant pathogens. These potentially capable bacteria could be implemented in the promotion of plant growth as well as in the biological control of pathogens. This is the first report on the characterization and elucidation of the diversity of the potentially beneficial endophytic species of Bacillus and the closely related genera living in the internal tissues of hornbeam trees.

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