Abstract

Several Bacillus strains were isolated from “Ouled Yelass” hot spring soil, located in Setif city (Eastern Algeria). Three isolates of them coded (4RH), (14 RH), and (Set-oxy), were screened for their ability to inhibit the growth of some phytopathogenic fungi, such as Fusarium oxysporium, Botrytis cinerea, Aspergillus niger, Cladosporium cucumerinium and Alternaria alternata. The molecular identification of the strain (4RH) based on the 16S-DNA and gyrase-A genes sequences analysis, showed that it is closely related (99.9%) to the Bacillus amyloliquefaciens species. This bacterium was characterized by a high sporulation yield reaching 22±0.86 × 10⁸ spores/ml and had important inhibition rates up to 80 and 70%, against F. oxysporium and B. cinerea, respectively. The bacterium (4RH) was able to produce cell wall degrading enzymes of cellulase and protease, in contrast to chitinase activity which was negative. Furthermore, it produced the three lipopeptides families, which are, iturins A (C14; C15), fengycin A (C14, C15, C16, C17, and C18), and surfactin (C12, C13, C14, C15, C16). Interestingly, LC-MS profiles of 80% acetonitrile fengycin extract of the (4RH) strain, showed the presence of some new molecular ions (MH+) with masses different, but near to conventional fengycin variants, which correspond to new variants described for the first time in this work. The isolate (4RH) produced 5 µg/ml of the phytohormone (IAA), on TGE medium and sidérophores with more than 10 mm of yellow-orange zones, on CAS medium. To conclude, B. amyloliquefaciens (4RH) strain possessed interesting biocontrol and biofertilization characteristics, in vitro, in addition to its high sporulation yield, which make it a potential agent for future biopesticide that could be efficient in the integrate pest management and organic agricultural production systems.

Key words: Bacillus, biocontrol, biofertilization, plant protection, hot spring, lipopeptides.