The bacterial community structure of rhizosphere soil associated with Cicer montbretii Jaub. & Spach endemic to Strandzha Mountain

Cicer montbretii Jaub. & Spach (C. montbretii) is a species of plant in the Fabaceae family. It is a perennial herbaceous plant, a Tertiary relict found in the Strandzha Nature Park on brown oak soils. This protected species is of increasing interest for leguminous breeding programs. In the present study, the diversity of the bacterial community in C. montbretii roots was analyzed using a metagenomic approach. Soil testing has focused on soil chemical-nutrient contents, generally the macronutrients nitrogen (N), phosphorus (P) and potassium (K). The diversity of bacterial taxonomy was evaluated at different Operational Taxonomic Unit (OTU) levels using QIIME and MG-RAST. At the phylum level, Proteobacteria (89%) was the most dominant group followed by Bacteroidia (5%), Firmicutes (2%) and Actinobacteria (0.9%). Class level analysis revealed that the abundance of Gammaproteobacteria was 87%, and Alphaproteobacteria was only 2%. In the rhizosphere soil, the most abundant genera from the Gammaproteobacteria were Pseudomonas (24%), Pantoea (21%), and Stenotrophomonas (6%). The Alphaproteobacteria was represented by genus Bradyrhizobium (12%), Rhizobium (4%), Podomicrobium (4%), and Phenylobacterium (3%). The phylum Firmicutes consisted of genus Bacillus (61%), Paenibacillus (21%), and Sporocarcina (13%). The study discovered that 17% of bacterial sequences in the soil microbiome were unclassified OTUs. This result emphasizes the significance of metagenomics in assessing the diversity of microflora in the rhizosphere of these wild legumes.