"Sporulation is a complex and mysterious process," Igoshin said. "For example, some cells choose to become spores and others don't -- even if they are exposed to the same conditions. Even more intriguing is the fact that some cells begin the process of converting into spores only to turn back and revert to normal behavior."
To decipher how B. subtilis decides to form a spore, Igoshin and Rice graduate student Jatin Narula created a set of sophisticated computer models that recreated the organism's genetic controls. The results from the computer model were compared and refined based on experimental observations by UH's Masaya Fujita and Seram Devi.
"The master regulator Spo0A is responsible for kicking off the process of spore formation, and our initial hypothesis was that this was the key player involved in the decision to become a spore," Igoshin said. "We found that the decision-making process was considerably more complex."
Signal processing in bacteria is complicated because the amount of information that their network can receive and process is related to the number of molecules inside the cells. The tiny size of the bacterial cell therefore leads to very noisy signals. The problem is akin to the challenge a political pollster would face in attempting to predict the outcome of a national election based on interviews with only 50 voters.
"It's a statistical sampling problem," Igoshin said. "Because the bacterial cell is small, master regulator genes have to contend with very noisy signals. One way to overcome the problem is to average the signals over a long period of time. We examined whether B. subtilis did this in making the decision to form a spore, but we found that if the cell waited for a clear signal, it may not complete the complicated spore-forming program before it would die."
Instead, the cell kicks off t
|Contact: David Ruth|