"INTRODUCTION: The rhizosphere is a complex habitat with great bacterial heterogeneity, and their activity, diversity, and dynamics are dictated primarily by plant root exudates. Plant growth-promoting rhizobacteria (PGPR) can be distinguished as a specific functional group that elevates plant characteristics and performance by direct and indirect mechanisms and are often members of genus Bacillus and Pseudomonas. PGPR of oak species in Serbia is poorly understood. Sessile oak (Quercus petraea (Matt.) Liebl) is autochthonous and one of Serbia’s most significant forest species due to its economical, technical, ecological, and cultural importance. It is one of the most abundant tree species with a percentage of 7.7% in the growing stock (186.179 ha), and within the belt of its stands, there are 23 different forest types. The main problems of present sessile oak forests are continuous intensive decline, the domination of coppice forests (74.1%), age, and physiological susceptibility to (a)biotic stressors, which all guide to smaller seed yield and difficult natural regeneration. An additional problem is the low percentage of artificial reforestation success. OBJECTIVES: The objectives of this research were the isolation of bacteria of the genus Bacillus and Pseudomonas from the sessile oak rhizosphere, the in vitro investigation of their plant growth-promoting potential, and molecular identification of the most competent plant growth promoters. METHOD / DESIGN: The bacteria of the genus Bacillus and Pseudomonas were isolated by culturing methods from the sessile oak rhizosphere samples from mountain Rudnik where it naturally occurs. The Gram, catalase, and oxidase tests were performed, as did the fluorescent pigment production for potential pseudomonads. In addition, its plant growth-promoting abilities (IAA synthesis, siderophore production, and phosphate solubilization) were investigated in vitro. The selected isolates were molecularly identified based on the 16S rRNA gene sequence. RESULTS: A total of 179 bacteria were isolated from sessile oak rhizosphere samples, 75 of them being putative Bacillus and 48 putative Pseudomonas species. Of the total isolates, 155 of them were IAA producers, 81 siderophore producers, and 90 isolates were capable of phosphate solubilization. Fourteen most competent PGPR isolates were moleculary identified based on the 16S rRNA gene sequence as Lysinibacillus parviboronicapiens, Viridibacillus arvi, Viridibacillus arenosi, Brevibacterium frigoritolerans, Peribacillus simplex, Rahnella variigena, Pseudomonas koreensis, Pseudomonas helmanticensis, Serratia quinivorans, Pseudomonas vancouverensis and Pseudomonas migulae." Јовановић, Сања Станојевић, Оља Месарош, Александра Поповић, Владан Лучић, Александар Станковић, Славиша Берић, Тања Нови Сад: Природно-математички факултет eng All rights reserved 2021 Sessile oak rhizobacteria with plant growth-promoting potential in vitro https://unilib.phaidrabg.rs/o:3719 cobiss:53483017 Bioscience Conference and the 8th International PSU-UNS Bioscience Conference ,,IBSC 2021'' Book of Abstracts application/pdf 70979 bytes rhizobacteria; sessile oak; growth promotion; in vitro info:eu-repo/semantics/conferenceProceedings