Phenotypic characterization of rhizobia nodulating legumes Genista microcephala and Argyrolobium uniflorum growing under arid conditions

Abstract

A phenotypic characterization of thirteen root nodule bacteria recovered from wild legumes (Genista microcephala and Argyrolobium uniflorum) growing in arid eco-climate zones (Northeastern Algeria) was conducted using analysis of sixty-six phenotypic traits (carbohydrate and nitrogen assimilation, vitamin requirements, growth temperature, salinity/pH tolerance and enzyme production). Furthermore, SDS-PAGE profiles of total cell protein, antibiotic susceptibility and heavy metal resistance were performed. The results showed that the isolates can grow at pH 4 to 10, salt concentration (0–5%) and temperature up to 45 °C. The rhizobia associated with Genista microcephala and Argyrolobium uniflorum were able to produce different hydrolytic enzymes including cellulose, pectinase and urease, with remarkable tolerance to toxic metals such as zinc, lead, copper, and mercury. Numerical analysis of the phenotypic characteristics revealed that the rhizobial isolates formed four main distinct groups showing high levels of similarity with Gammaproteobacteria. The salt tolerant and heavy metals resistance patterns found among the indigenous rhizobial strains are reflecting the environmental stresses pressure and make the strains good candidates for plant successful inoculation in arid areas. Keywords: Rhizobia, Genista microcephala, Argyrolobium uniflorum, SDS-PAGE, Gammaproteobacteria, Heavy metal tolerance