Tsr-GFP accumulates linearly with time at cell poles, and can be used to differentiate 'old' versus 'new' poles, in Escherichia coli.

SUMMARY: In Escherichia coli, the chemotaxis receptor protein Tsr localizes abundantly to cell poles. The current study, utilizing a Tsr-GFP fusion protein and time-lapse fluorescence microscopy of individual cell lineages, demonstrates that Tsr accumulates approximately linearly with time at the cell poles and that, in consequence, more Tsr is present at the old pole of each cell than at its newborn pole. The rate of pole-localized Tsr accumulation is large enough that old and new poles can always be reliably distinguished, even for cells whose old poles have had only one generation to accumulate signal. Correspondingly, Tsr-GFP can be reliably used to assign new and old poles to any cell without use of information regarding pole heritage, thus providing a useful tool to analyse cells whose prior history is not available. The absolute level of Tsr-GFP at the old pole of a cell also provides a rough estimate of pole (and thus cell) age.