Dynamic Spatial Regulation in the Bacterial Cell

the spatial dimension into temporally controlled cellular events. and proteins are actively moved around the cell in di-Cambridge, Massachusetts 02138 rected traffic patterns. What is surprising is that in the small (1–3 ␮m) bacterial cell, with no known directed transportation systems, dynamic subcellular localiza-The broad and rich history of prokaryotic biology in the tion of regulatory and structural proteins, in fact, accom-20th century has been driven by the power of genetics panies, and in many cases directs, cell cycle progression applied to vast populations of haploid cells. This history and the generation of diverse cell types. begins in 1943 with the statistical demonstration by Sal-The progression of the cell cycle reflects the basic vidor Luria and Max Delbrü ck that bacteria obey the genetic network that maintains life—it is the primitive Darwinian principles of random mutation and natural brain of the cell. The business of a newly divided progeny selection. This discovery set the stage over the decade cell is to grow, replicate its genome, ensure chromo-that followed for using bacteria and their phage to elu-some segregation, and carry out cytokinesis culminating cidate the fundamental nature the genetic material. in the production of two progeny with the same genetic In 1944, Oswald Avery, Colin MacLeod, and Maclyn makeup. The cellular machinery required to accomplish McCarty made the seminal discovery that the " trans-these tasks and the factors that regulate their ordered forming principle, " which was known to alter the heredi-expression operate at different places in the cell and tary properties of streptococci, is DNA. This indicated at different times in the cell cycle. For example, the that the genetic material is DNA, a concept that was replication complex has a specific cellular address, as reinforced a few years later by the work of Alfred Hershey do the chromosome segregation proteins, the origin and and Martha Chase. Their experiments showed that terminus of DNA replication, and the tubulin-like protein phage T2 injects its DNA into host cells and hence that that is responsible for constriction at division. Similarly, viral DNA is likely to suffice for viral propagation. During the signal transduction proteins that regulate the initia-this extraordinary 10 year period, Joshua Lederberg and tion of DNA replication, and the proteins that discrimi-Edward Tatum discovered conjugation in bacteria, and nate midcell and quarter cell sites for the position of Lederberg and Norton Zinder showed that certain phage the division plane, are …