RESUMO
Clostridium perfringens enterotoxin (CPE) is an important virulence factor for food poisoning and non-food borne gastrointestinal (GI) diseases. Although CPE production is strongly regulated by sporulation, the nature of the signal(s) triggering sporulation remains unknown. Here, we demonstrated that inorganic phosphate (Pi), and not pH, constitutes an environmental signal inducing sporulation and CPE synthesis. In the absence of Pi-supplementation, C. perfringens displayed a spo0A phenotype, i.e., absence of polar septation and DNA partitioning in cells that reached the stationary phase of growth. These results received support from our Northern blot analyses which demonstrated that Pi was able to counteract the inhibitory effect of glucose at the onset of sporulation and induced spo0A expression, indicating that Pi acts as a key signal triggering spore morphogenesis. In addition to being the first study reporting the nature of a physiological signal triggering sporulation in clostridia, these findings have relevance for the development of antisporulation drugs to prevent or treat CPE-mediated GI diseases in humans.
Assuntos
Clostridium perfringens/efeitos dos fármacos , Enterotoxinas/biossíntese , Fosfatos/farmacologia , Clostridium perfringens/fisiologia , Meios de Cultura , Concentração de Íons de Hidrogênio , Morfogênese/efeitos dos fármacos , Esporos Bacterianos/efeitos dos fármacos , Esporos Bacterianos/crescimento & desenvolvimentoRESUMO
Spore development and stress resistance in Bacillus subtilis are governed by the master transcription factors Spo0A and sigma(B), respectively. Here we show that the coding genes for both regulatory proteins are dramatically induced, during logarithmic growth, after a temperature downshift from 37 to 20 degrees C. The loss of sigma(B) reduces the stationary-phase viability of cold-adapted cells 10- to 50-fold. Furthermore, we show that sigma(B) activity is required at a late stage of development for efficient sporulation at a low temperature. On the other hand, Spo0A loss dramatically reduces the stationary-phase viability of cold-adapted cells 10,000-fold. We show that the requirement of Spo0A for cellular survival during the cold is independent of the activity of the key transition state regulator AbrB and of the simple loss of sporulation ability. Furthermore, Spo0A, and not proficiency in sporulation, is required for the development of complete stress resistance of cold-adapted cells to heat shock (54 degrees C, 1 h), since a loss of Spo0A, but not a loss of the essential sporulation transcription factor sigma(F), reduced the cellular survival in response to heat by more than 1,000-fold. The overall results argue for new and important roles for Spo0A in the development of full stress resistance by nonsporulating cells and for sigma(B) in sporulation proficiency at a low temperature.