Evaluation of antimicrobial activity of Terfezia arenaria extracts collected from Saharan desert against bacteria and filamentous fungi.

Different desert truffles, collected from Algerian Saharan soils, were identified and their capacity to produce bioactive substances with antimicrobial activity was analyzed. Based on morphological characterization using Melzer's reagent staining, the collected strains were identified as Terfezia arenaria. The bioactive substances from T. arenaria were extracted using the following techniques: maceration with methanol and Soxhlet with dichloromethane. The former led to a yield much higher than that of the latter (i.e., 15% and 0.48%, respectively). Both extracts presented antifungal activities against all the tested strains (i.e., A. niger, Penicillium sp., and C. albicans). However, the dichloromethane extracts showed much higher antibacterial activities against all the tested bacteria (i.e., S. aureus, E. faecalis, E. coli, and P. aeruginosa) than the methanol extracts. The thin layer chromatography of both extracts confirmed the presence of polyphenols and flavonoids.

Isolation and characterization of a novel tyrosinase produced by Sahara soil actinobacteria and immobilization on nylon nanofiber membranes.

In the present study different actinomycete strains were collected and isolated from Algerian Sahara soil with the aim to select novel enzymes with promising features for biotechnological applications. The Ms1 strain was selected, amongst the others, for its capability to produce melanin in different solid media. Ms1 chromosomal DNA was sequenced and the strain assigned to Streptomyces cyaneofuscatus sp. A tyrosinase (MW∼30kD) encoding sequence was identified and the corresponding enzyme was isolated and biochemically characterized. The tyrosinase showed the highest activity and stability at neutral and alkaline pH and it was able to oxidize l-DOPA at T=55°C and pH 7. The enzyme showed variable stability in presence of various water-miscible organic solvents, while it was inactivated by reducing agents. The tyrosinase activity was unaffected by NaCl and enhanced by different cations. Furthermore, the enzyme showed a higher specificity for diphenols than monophenols showing a higher diphenolase than monophenolase activity. Finally, tyrosinase was stabilized by immobilization on nylon nanofiber membranes with a payload of 82% when 1% glutaraldeyde was used. Taken all together, these results show that the enzyme displays interesting properties for biotechnological purposes.

Screening and characterization of plant growth promoting traits of phosphate solubilizing bacteria isolated from wheat rhizosphere of Algerian saline soil

Aims: The capacity of some soil microorganisms to solubilize in soil is an important activity exhibited by plant growth promoting rhizobacteria (PGPR) to increase plant performance. This study aimed at isolation and selection of phosphate solubilizing bacteria from saline soil and in vitro evaluation of their plant growth promoting traits. Methodology and results: Phosphate solubilizing bacteria isolated from wheat rhizosphere, of saline soil in western region of Algeria were tested for their plant growth promoting traits such us indole acetic acid (IAA), hydrogen cyanide (HCN), siderophore and ammonia production and their ability to fix nitrogen. Among 104 bacterial isolates, 41 were selected for their phosphate solubilizing activity using tricalcium phosphate (TCP) as a sole phosphorus source. IAA production was shown by almost all the bacterial isolates. Twelve isolates were recorded positive for HCN production, 32 produced siderophore and 31 were able to fix nitrogen. The most dominant phosphate solubilizing bacteria found were identified as Pseudomonas followed by Aeromomas hydrophila Bacillus sp. and Burkholderia cepacia. Conclusion: Phosphate solubilizing bacteria that were isolated from saline soil showed a high potential in to producing growth promoting traits and can be used as inoculants to increase the phosphorus uptake by plants.