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

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.

Diversity and bioprospecting of extremely halophilic archaea isolated from Algerian arid and semi-arid wetland ecosystems for halophilic-active hydrolytic enzymes.

The diversity of haloarchaea associated with different dry salt lakes in northeastern Algeria was investigated together with their potential of hydrolytic enzyme production. A total of 68 aerobic halophilic archaea were isolated from saline sediments. Based on the 16S rRNA gene sequencing, the isolates were assigned to seven phylotypes within the class Halobacteria, namely Haloarcula, Halococcus, Haloferax, Halogeometricum, Haloterrigena, Natrialba, and Natrinema. The results showed that Haloferax group was found to be dominant in all samples (30 isolates) (44%) with high diversity, followed by Halococcus spp. (13%) (9 isolates). All phylotypes are extreme halophiles and thermotolerant with the ability to grow at temperatures up to 48 °C. In addition, the screening for extracellular halophilic enzymes showed that 89.7% of the isolates were able to produce at least two types of the screened enzymes. The strains producing esterase, gelatinase, inulinase, cellulase and protease activities were the most diverse functional group. These data showed an abundant and diverse haloarchaeal community, detected in Algerian wetland ecosystems, presenting a promising source of molecules with important biotechnological applications.