Analysis of rhizospheric bacterial community in soils affected by the formation of calcrete

Abstract

Crust of carbonate minerals, named calcrete, underlies the arable soils of Southeast Bulgaria. The basic microorganism groups from soil, developed on top of a massive calcrete and in the rhizosphere of Cichorium intybus (Common chicory) were estimated by culturable methods. In this plant's rhizosphere, microorganisms from some physiological groups were found in numbers 1 to 3 orders of magnitude higher, compared to non-rhizosphere samples of massive calcrete. The dominant microorganisms in this plant's rhizosphere are represented by genera Bacillus. 16S rRNA gene nucleotide sequences were used for identification of four strains, obtained from the rhizospheres of C. intybus. The sequences obtained were compared to those of Bacillus species held in GenBank. The strains CI R1 and CI R3 were found to belong to the species Bacillus subtilis and the strains CI R2 and CI R4 to the species Bacillus amyloliquefaciens. Numerous studies confirm that these species are good facilitators of plant growth in nutrient deficient carbonate environment. Study of the growth‐promoting potential of these bacterial species, for economically important plants cultivated in this region, is currently in progress.