In 1962 Cole and Hahn published in Science an unassuming sounding paper entitled Cell wall replication in Streptococcus pyogenes. The authors asked the question: do strep cells synthesize their cell wall by intercalating new parts at different sites on their surface or does this take place at one site only? The question was not trivial. Cocci do not have a clearly defined mid-cell region as do rod cells. Furthermore, some rod-shaped bacteria were thought to use an intercalation mechanism for cell division. So the authors kept an open mind and laid out the following premise: If bacterial cell wall could be differentially labeled during growth to distinguish portions of different relative ages, answers to some of these questions might be forthcoming.
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