Activity of conessine at various temperatures and pH on inhibition of germination of Bacillus cereus and Bacillus stearothermophilus spores

摘要

This work reports the activity (at various conditions) of conessine isolated from methanolic extract of Holarrhena floribunda, on the inhibition of the germination of two Bacillus spores species. This activity was studied by treating spores of Bacillus cereus T and Bacillus stearothermophilus CNCH 5781 with effective concentrations of conessine at various temperature, pH and treatment times. The inhibition of germination was evaluated by the culture of treated spores on agar medium and the number of colony obtained was compared with that of control culture (not treated with conessine). We found that conessine used at 50 and 100 μg/ml for 20 min each decreased considerably the germination of spore of B. cereus T and B. stearothermophilus CNCH 5781. The maximum temperature of conessine activity for B. cereus T was at 30 and 60°C for B. stearothermophilus CNCH 5781 spores. Furthermore, the activity of conessine was sensitive to pH change and was more effective at pH 6 on both bacterial spore strains. The treatment of spores with conessine at various lengths of time demonstrated that, the activity of the compound on both bacterial spores was strongly related to the bacterial species. This study suggested that the activity of conessine on the inhibition of germination of Bacillus spore depends on physico-chemical factors and the bacterial species.