Abstract
Bacillus thuringiensis is an aerobic, Gram positive bacterium which produce spores when the environment goes against its growth. Some sorts of Bacillus thuringiensis have surrounding flagella while the others not. Those who possess flagella have the ability to swim. Bacillus thuringiensis cells usually gather in the form of chains while each chain is composed of 2-8 cells; they are frequently found in the soil. At least 38 strains are known to produce insecticides. This work is to study the role of the motility which plays in the physiology of Bacillus thuringiensis. We define a term "Average Motile Rate" (AMR) to describe the motivation of cells during the cultivation. The changing tendencies of AMR, biomass and yield of thuringiensin which respect to some environmental factors are observed to investigate the relationship between the AMR and the physiology of Bacillus thuringiensis. The results showed that: (1) The AMR gave new information of cell growth (2) The AMR could aid prediction of the yield of thuringiensin Also, it is desired to know whether each AMR period indicates a corresponding physiological period of Bacillus thuringiensis or not. Pulses of aeration rate, temperature and pH value which last 20 minutes were carried out during the peak period, the decay period and the stable period of the AMR. We then draw following conclusions: (1) It was harmful to the production of thuringiensin when the cultivation was disturbed during its early fermentation stage (2) The influence upon the cell physiology increased with higher values of AMR (3) The conventional exponential phase could be further split into two physiological active stages according to the AMR