Fusarium culmorum affects expression of biofilm formation key genes in Bacillus subtilis

Abstract It is known that there is correlation between biofilm formation and antagonistic activities of Bacillus subtilis strains; but, the mechanism of this correlation is not clear. So, the effect of the plant pathogen (Fusarium culmorum) on the biofilm formation in a B. subtilis strain with high antagonistic and biofilm formation activities was studied. The expression of sinR and tasA genes involved in the biofilm formation was studied in both single culture of bacterium (B) and co-culture with F. culmorum (FB) using real-time PCR. The results revealed that the expression of the sinR gene in both B and FB conditions was continuously decreased during the biofilm formation period and, after 24 h (B4 and FB4), it reached 1% and 0.3% at the planktonic phase (B1), respectively, whereas the expression of the tasA was continuously increased and was 5.27 and 30 times more than that at the planktonic phase (B1) after 24 h, respectively. So, the expression reduction rate for sinR (3 times) and the expression increasing rate for tasA (6 times) were significantly higher in FB conditions than the B ones. The relative expression of sinR in FB1 (planktonic phase), FB2 (8 h), FB3(12 h), and FB4 (24 h) times was 0.65, 0.44, 0.35, and 0.29, whereas the tasA gene expression was 2.98, 3.44, 4.37, and 5.63-fold of the one at coordinate time points in B conditions, respectively. The significant expression reduction of sinR and increase of tasA confirmed that the presence of pathogen could stimulate biofilm formation in the antagonistic bacterium.

Screening of antifungal effects of pseudoclitocybe cyathiformis Bull. (Singer).

In this study, antifungal activities of Pseudoclitocybe cyathiformis extracts with the help of acetone and chloroform against to Fusarium species (Fusarium culmorum and Fusarium moniliforme) were investigated. Pseudoclitocybe cyathiformis was dried at aseptic conditions and put thru extractions for 12 hours in solvents. Than the evaporator at 40°C and finally dried material stored at + 4°C.(Jonathan and Fasidi, 2003). Antifungal activities were measured by Disc Diffusion method (Stoke and Ridgway, 1980). According to this method; the inoculums containing Fusarium culmorum and Fusarium moniliforme were spread agar medium. In result antagonistic effects of Pseudoclitocybe cyathiformis was found against both Fusarium spp.. The clear zone of inhibition was observed around the mushroom extracts. For control water and only acetone and chloroform saturated discs were used. The results were comprised with commercial antibiotics (amoxycillin and erythromycin).