An understanding of cellular differentiation at any level requires answering a minimum of two basic questions. First, what are the signals (extracellular and intracellular) that induce the cell to embark along its new developmental pathway? Second, how are these signals sensed and then relayed to the effector molecules that can bring about the necessary changes in gene expression to determine cell fate? Obviously, formulating these questions and grasping their importance is relatively easy; finding the correct answers is often excruciatingly difficult. Our hypothesis is that these fundamental questions in developmental biology can be addressed (long-term goals) by studying primitive differentiation systems such as sporulation in bacteria. To accomplish with these ideas several interconnected lines of research using Bacillus subtilis, the workhorse in the field to solve fundamental questions relate to developmental biology, and Clostridium perfringens an important human food poisoning as models of endospore-forming bacteria are proposed. In this last case a better understanding of the sporulation process in C. perfringens, and pathogenic clostridia in general, in order to the development of ways to block spore formation or to inhibit enterotoxin production by these anaerobic bacteria would have an important impact for the prevention (inhibition of sporulation) or the treatment (inhibition of enterotoxin production) of food poisoning victims or groups under risk of clostridia infection (i.e. diabetic patients).