In spore-forming bacteria, chromosomal locations of genes can couple the DNA replication cycle to critical, once-in-a-lifetime decisions about whether to reproduce or form spores. The new finding by Rice University bioengineers and colleagues at the University of California at San Diego and the University of Houston was published online on July 9, 2015 in the journal Cell. The article is titled “Chromosomal Arrangement of Phosphorelay Genes Couples Sporulation and DNA Replication.” As most microorganisms, Bacillus subtilis bacteria are single-celled creatures with one goal: to reproduce by making copies of themselves. But survival isn't always that simple. For example, when food gets scarce, B. subtilis must decide between two possible paths: shut down, form a dormant spore (image) -- a process called "sporulation" -- and wait for better times, or split into two cells and gamble that there is enough food for at least one more generation. "The decision about whether to form a spore and when is a very important one for B. subtilis," said Dr. Oleg Igoshin, Associate Professor of Bioengineering at Rice and one of the lead researchers on the new study. "If the organism waits too long, it can starve before it finishes transforming into a spore. If it acts too early and forms a spore too soon, it can be overwhelmed and out-reproduced by competitors." Dr. Igoshin's lab specializes in describing the workings of the complex genetic regulatory networks that cells use to make such decisions. He said dozens of studies over the past 25 years have identified a network of more than 30 genes that B. subtilis uses to bring about sporulation. When food is plentiful, this network is largely silent. But during times of starvation the genes work in concert to form a spore. B.
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