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Plants do not grow axenically in nature, but host a diverse community of microorganisms, termed as plant microbiota, colonizing different niches, both inside and outside their tissues, in the endosphere and ectosphere, respectively. These microorganisms are involved in major physiological processes, such as plant nutrition and plant resistance to biotic and abiotic stress factors. The aim of the research was to investigate the normal microbiota of rare plant species (listed with different degrees of danger in the "Red Book vascular plants in Romania", Red Lists, IUCN, Bern Convention Habitats Directive, CITES), found in natural habitats, in order to define some microbiological associate with soil composition that could be further used as parameters for measuring the plant growth. Our focus was oriented to several rare plant species from natural habitats of Romania, with localization in southern Dobrogea: Adonis vernalis, Opopanax chironium, Asphodeline lutea. Paeonia tenuifolia (Hagieni Natural Reserve, Constanta), Potentilla emilii-popii (Sipote, Constanta). In order to analyse the normal of composition associated soil microorganisms', we sampling the rhizosphere from each plant species and processed for isolation and biochemical identification of the cultivable microbial species. Also, the physical and chemical properties of the rhizosphere samples were investigated using modern technics (Inductive coupled plasma atomic emission spectrometry (ICP-AES)), in order to determinate the availability of metals in rhizosphere and the pH values. The results showed that the phylogenetic composition of these communities is composed by relatively few bacterial phyla, including Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria, with variations depending on the plant species and soil characteristics. The availability of different metals (Al, Fe, Mn, Cu, Zn) in rhizospheres was influenced by the pH change and chemical compositions of root exudates. [ABSTRACT FROM AUTHOR]