||p.1100 right column bottom paragraph:"Because filamentation is a hallmark of the SOS response in bacteria, [investigators] asked how its suppression would affect [their] observation of filamentation. For this purpose [they] constructed an MG1655 derivative carrying a lexA allele, lexA3, whose protein product constitutively represses SOS gene expression even under conditions of DNA damage. Although the lexA3 mutant behaved virtually the same as MG1655 in terms of a constant growth rate, its filamentation rate, which was constant at approximately 1%, was significantly reduced, as expected. Note that B/r lacks sulA, a key SOS gene that inhibits cell division during the SOS response, and also shows a similar low filamentatin rate (Figure S3). A more important difference between lexA3 and MG1655 is that, with a constant death rate of 2.7% per cell per generation, the population of the lexA3 mutant cells decayed exponentially (Figure 4)."