Editorial: Bacterial Chromosomes Under Changing Environmental Conditions

The bacterial cell cycle comprises chromosome replication and segregation of newly replicated chromosomes into daughter cells prior to cell division. Unlike in eukaryotic organisms, DNA replication, chromosome segregation, and transcription occur simultaneously in bacteria. Several molecular mechanisms act in concert to allow chromosome replication initiation once-and-only-once per cell cycle (Skarstad et al., 1986; Boye et al., 2000). Other mechanisms ensure that replication is coordinated with cell growth (Murray, 2016) and linked to chromosome segregation in a tightly coordinated manner (Blow and Tanaka, 2005; Reyes-Lamothe et al., 2012). Considering that the chromosome is a massively compact structure, organization of the bacterial nucleoid adds an extra level to cell cycle coordination. In particular, a balance has to be reached between the requirement of significant compaction and an unobstructed accessibility to molecular processes underlying essential cellular functions, such as replication, transcription, DNA repair and homologous recombination (Badrinarayanan et al., 2015; Magnan and Bates, 2015).