Antifungal activity and siderophore production of chitinolytic bacteria against Colletotrichum

DELFINI C. D,; PAJOT, H; VILLEGAS L. B; BAIGORÍ M

Potrero de los Funes, San Luis

Congreso; Sociedad Argentina de Bioquimica (SAIB); 2011

Four chitinolytic Bacillus strains were previously isolated from bat guano (Taradita brasilensis). These bacteria showed antagonistic properties, in vitro, against the phytopatogenic fungus Colletotichum acutatum and C. fragariae. Bacillus sp.PB1 showed the highest antifungal activity and was selected for further studies. The aim of this work was to study the stability of the fungal activity and its relationship with siderophore production. Selected bacterium was incubated in SPI-colloidal chitin, SPI-pupa and Standard nutrient (SN) liquid media, at 200 rpm 72h, at 28 ºC. Supernatants were assayed against C. cutatum and C. fragariae on potato dextrose agar. In order to evaluate the stability of the antifungal activity, supernatants were treated with proteinase K or heat-treated at 50ºC and 100ºC. Under all tested conditions, supernatants were able to inhibit fungal growth. Major activity was reached on SN medium. Heat and proteinase K treated supernatants could were only able to modify mycelial morphology. Bacillus sp. PB 1 produced siderophores as evidenced by positive reaction in FeCl3 test. The presence of hydroxamate type siderophores was also evidenced by standard the tetrazolium test. These results suggest that Bacillussp. PB 1 siderophores could play a significant role in antifungal activity of selected chitinolytic bacteria.