The authors are in the Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Science 27 July 2007:
Vol. 317. no. 5837, pp. 463 - 464
In the classic view of cellular biology, cells are simply a product of genetic and environmental conditions, and all differences between individual cells can be attributed to one or both of these factors. Recent work, however, suggests that when grown in the same environment, cells from genetically identical populations can exhibit very different behaviors. Even simple attributes, such as the number of proteins produced from a constitutively expressed gene, can vary greatly from cell to cell. In other cases, individual cells will make vastly different phenotypic choices seemingly at random (1-4). Why some cells remain in one phenotypic state whereas others switch to a different one, and what the molecular processes are that cause cells to "play dice" when determining their fate, remain open questions.
On page 526 in this issue, Maamar et al. (5) tackle these questions using the soil bacterium Bacillus subtilis. They find that the random nature of the phenotypic choice made by these bacteria to remain vegetative (dormant) or become "competent" (able to take up DNA from the environment) can be traced to variable expression of a single protein. Although many organisms exhibit phenotypic variability driven by stochastic gene expression, the B. subtilis system is of particular interest because variation ("noise") in protein expression is thought to play a key role in the natural behavior of a population.
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