Salinity causes significant agricultural losses in many areas in the world. Plant growth promoting bacteria (PGPB) are a promising solution to enhance plant growth and productivity under such stress conditions by different mechanisms, mainly phosphorous solubilization. This study aims to improve wheat seedling growth under salt stress by a halotolerant phosphorous-solubilizing bacterial strain. Soil sample was collected in the south of Algeria (Ghardaia), and bacterial isolation was carried out on nutrient agar (NA) at different NaCl concentrations (300; 600 and 900 mM). The ability of the halotolerant isolates to solubilize inorganic phosphorous at 0; 300; 600 and 900 mM NaCl was determined. The isolate that showed the highest solubilization indexes was selected and identified as Pseudomonas azotoformans. Sterile wheat (Triticum aestivum) seeds were inoculated by this strain and then sown in soil at different NaCl concentrations (0; 100; 200; 300 mM). Different growth parameters were measured after 15 days. The strain showed its highest capacity for phosphorous solubilization (255.152 ± 0.01 µg/mL) at 300 mM NaCl, and for phytate mineralization (0.168 ± 0.002 U/mL) at 100 mM NaCl. The highest amount of soluble phosphorous in the soil was 49.42 ± 0.36 ppm obtained at 100 mM NaCl. Seed germination percentage, shoot and root length and fresh and dry weights were found to be higher in bacterial inoculated seedlings compared to uninoculated ones. According to this study, the use of plant growth promoting bacteria represents an important biotechnological approach to restore phosphorous levels in saline soils and to promote plant growth in salt-affected agricultural land.

Microbial interactions, which regulate the dynamics of eco- and agrosystems, can be harnessed to enhance antagonism against phytopathogenic fungi in agriculture. This study tests the hypothesis that plant growth-promoting rhizobacteria (PGPR) can also be potential biological control agents (BCAs). Antifungal activity assays against potentially phytopathogenic fungi were caried out using cultures and cell-free filtrates of nine PGPR strains previously isolated from agricultural soils. Cultures of Bacillus sp. BS36 inhibited the growth of Alternaria sp. AF12 and Fusarium sp. AF68 by 74 and 65%, respectively. Cell-free filtrates of the same strain also inhibited the growth of both fungi by 54 and 14%, respectively. Furthermore, the co-cultivation of Bacillus sp. BS36 with Pseudomonas sp. BS95 and the target fungi improved their antifungal activity. A subsequent metabolomic analysis using Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) identified fengycin- and surfactin-like lipopeptides (LPs) in the Bacillus sp. BS36 cell-free filtrates, which could explain their antifungal activity. The co-production of multiple families of LPs by Bacillus sp. BS36 is an interesting feature with potential practical applications. These results highlight the potential of the PGPR strain Bacillus sp. BS36 to work as a BCA and the need for more integrative approaches to develop biocontrol tools more accessible and adoptable by farmers.

In this study, we constructed versatile microbial consortia (VMC) with agricultural and environmental interest. After sample and isolation procedure, the purified isolates were evaluated for their enzymatic potential such as cellulose-, xylan-, petroleum-, proteins -hydrolysis. Selected isolates were screened for other traits such as phosphate solubilization, nitrogen fixation and antimicrobial activity. Finally, the isolates were grouped into consortia according to their compatibility. The microorganisms selected for each consortium were identified by partial analysis of the 16S rRNA (bacteria) and the ITS region of the 18S RNA gene (fungi). Two microbial consortia were obtained and named VMC1 and VMC2. These two consortia are characterized by several activities of agricultural and environmental interest such as the degradation of recalcitrant and polluting organic compounds, nitrogen fixation, IAA production phosphate solubilization and antimicrobial activity. Molecular identification of the microorganisms forming the two consortia allowed us to identify two species of actinomycetes (Streptomyces sp. BM1B and Streptomyces sp. BM2B), one species of Actinobacteria (Gordonia amicalis strain BFPx) and three fungal species (Aspergillus luppii strain 3NR, Aspergillus terreus strain BVkn and Penicillium sp. BM3). The term "Versatile Microbial Consortia" is a term that we proposed in this study to establish a methodology for building multifunctional microbial groups for wide and efficient application.