Antifungal activity and cell differentiation in Bacillus subtilis induced by Setophoma terrestris

ALBARRACIN ORIO, AG; TOBARES, RA; SMANIA, A; DUCASSE DA

Mar del Plata

Congreso; 51 Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2015

Onion is the second vegetable crop produced worldwide. Among the major limiting diseases of onion is pink root. As its causal agent, Setophoma terrestris (St), is one of the most severe pathogens in Argentina, we decided to address the biocontrol as a mean to control it. We have previously isolated bacteria with antagonistic activity against St from soil samples under continuous onion culture. The most efficient isolate was characterized by MALDI-TOF as Bacillus subtilis subsp. subtilis (Bss). Bss showed a strong capacity of fungal growth inhibition on co-culture plates. The inhibition was determined by the release of diffusible bacterial metabolites and, interestingly, we observed a high fungal growth inhibition on plates containing cell-free supernatant of Bss previously grown in the presence of the fungus (Bss post-St). In contrast, no significant differences in the fungal growth were obtained between control plates and plates containing cell-free supernatant from Bss grown without previous contact with St. In addition, an enhance biofilm forming ability and an increment in pellicle formation in Bss post-St compared to Bss grown without previous contact with St was observed. Consistently, Bss post-St showed an inhibition of swarming motility. These results suggest that there may be an association between biofilm formation pathways and the release of biocontrol compounds.