ANTIBIOTIC ACTIVITY IN CO-CULTURE: Influence of Bacillus subtilis on the Antibiotic Activity of Rhizopus peka

Abstract

The antibiotic activity produced in the co-cultures of Rhizopus peka P8 and Bacillus subtilis IF03335 (inhibition zone of 25 mm) was higher than that in each of the pure cultures (inhibition zones of 0-15 mm) . Both the concentration of B. subtilis and its mixing time with R. peka influenced the antibiotic production. The optimum condition was when the culture was inoculated at the same time with equal numbers of viable B. subtilis cells and R. peka spores. When the cell free culture broth of one was mixed with either the cell free culture broth or the cell free extract of the other and incubated at 30°C for 18 h, the antibiotic activity in the mixture was higher than that in the individual culture broth or cell extract. There was no antibiotic activity in a mixture that was not incubated at 30°C. Furthermore, the antibiotic activity was lost when either the cell free culture broth or the cell free extract was heat-treated (121°C, 20 min), indicating the involvement of an enzyme from B. subtilis in producing the active antibiotic from R. peka. Thus, the presence of B. subtilis in the culture effectively influences the production of the antibiotic from R. peka.