The Escherichia coli baby cell column: a novel cell synchronization method provides new insight into the bacterial cell cycle

Summary

We describe a new method for synchronizing bacterial cells. Cells that have transiently expressed an inducible mutant ‘sticky’ flagellin are adhered to a volume of glass beads suspended in a chromatography column though which growth medium is pumped. Following repression of flagellin synthesis, newborn cells are eluted from the column in large quantities exceeding that of current baby machine techniques by approximately 10-fold. Eluted cultures of ‘baby cells’ are highly synchronous as determined by analysis of DNA replication, cell division and other events, over time after elution from the column. We also show that use of ‘minutes after elution’ as a time metric permits much greater temporal resolution among sequential chromosomal events than the commonly used metric of cell size (length). The former approach reveals the existence of transient intermediate stages that are missed by the latter approach. This finding has two important implications. First, at a practical level, the baby cell column is a particularly powerful method for temporal analysis. Second, at a conceptual level, replication-related events are more tightly linked to cell birth (i.e. cell division) than to absolute cell mass.