Development of antibacterial agents targeting an extracellular signal transduction.

One mutant strain of C.perfringens strain13，SI112that scarcely produce alpha-，kappa-，and theta-toxins was isolated。When the strain SI112was cross-streaked with the virR/virS-mutant strain TS133，production of theta-toxin from SI112was clearly observed in the crossing portion on a sheep blood agar plate。This indicated that an extracellular stimulating substance released from TS133 activated the production of theta-toxin from SI112that could not produce the substance.We tentatively named the substance as VAP(Virulence Activating Pheromone)and analyzed further。VAP in conditioned medium(CM)was produced mainly during the exponential phase and activated theta-toxin production at the transcriptional level.The stimulation of the pfoA gene by CM appeared to be dose-dependent。CM activated the pfoA transcription mostly at 15min after addition，indicating a quick response to VAP exists in C.perfringens。VAP in CM seemed to be highly unstable loosing its activity within30min at 37°C，and appeared to be a small molecule(M.W.&lt；10，000)。Since this extracellular communication for the virulence of C.perfringens would be important for understanding the pathogenicity and preventing infections，we are now trying to purify VAP from the culture medium of strain13。

One mutant strain of C. perfringens strain 13, SI112 that scarcely produce alpha-, kappa-, and theta-toxins was isolated. When the strain SI112 was cross-streaked with the virR/virS- mutant strain TS133, production of theta-toxin from SI112 was clearly observed in the crossing portion on a sheep blood agar plate. This indicated that an extracellular stimulating substance released from TS133 activated the production of theta-toxin from SI112 that could not produce the substance. We tentatively named the substance as VAP (virulence activating pheromone) and analyzed further. VAP in conditioned medium (CM) was produced mainly during the exponential phase and activated theta-toxin production at the transcriptional level. The stimulation of the pfoA gene by CM appeared to be dose-dependent. CM activated the pfoA transcription mostly at 15 min after addition, indicating a quick response to VAP exists in C. perfringens. VAP in CM seemed to be highly unstable loosing its activity within 30 min at 37゜C, and appeared to be a small molecule (M.W.<10,000). Since this extracellular communication for the virulence of C. perfringens would be important for understanding the pathogenicity and preventing infections, we are now trying to purify VAP from the culture medium of strain 13.