INTERACTION OF THE BACILLUS SP, TD67 STRAIN WITH THE PLANT PATHOGEN FUSARIUM OXYSPORUM IN IN VITRO CONDITION

Abstract

In the fluid potato medium, a nutrient medium used to obtain the high F. oxysporum biomass, the Bacillus sp. TD67 strain appeared to have an equivalent growth as it was held in LB medium, its culture could reach a density of 2,0.10⁽⁹⁾ cells/ml, although its lag phase took one hour longer than in LB. As they were held to be common living in the fluid potato medium, the growth of the TD67 strain and of the F oxysporum with the different rations of the inoculation was followed. For the TD67 strain, in condition of the inoculation with the density 1,0.104 bacterial cells/ml (equivalent 0.001% v/v) and with 0.0010 mg of dried F. oxysporum biomass/ml of culture (equivalent 0.1 % v/v), its growth appeared almost to be not affected by the presence of F oxysporum and could get a density of 1,0.10⁹ cells/ml. In the case of the inoculation with 1,0.10⁽²⁾ cells/ml, the growth curve of the TD67 strain showed to be not changed, nevertheless its culture only could reach a density of 1,0.10⁸ celIs/ml. But the growth of F oxysporum appeared to be rather strongly suppressed by the presence of the TD67 strain, event at 1,0.10² cells/ml and at the time point of 24 hours common living with 1,0.10⁴ bacterial cells/ml, the accumulation of the fungal biomass began to be decreased. A morphological change of the fungal mycellia was observed under the light microscope: as the TD67 strain was not present in the culture medium, the F. oxysporum mycellia looked to be normal; but in the occurrence with 1,0.10² of TD67 cells/ ml, the F oxysporum occured mostly in the spore fonn, some else in mycel form, but those mycellia looked not to be normal, and with the inoculation of 1,0.10⁸ bacterial cells/ ml, both mycellia and spores showed to be some destroyed. The in LB cultured TD67 filtrate possessed the antibiotic activity against the growth of F. oxysporum, and showed that it is rather stable with the proteinase K, pH 10,0 and high temperature 100^oC for 10 minutes.