Lack of cations in flow cytometry buffers affect fluorescence signals by reducing membrane stability and viability of Escherichia coli strains.

•Fluorescence signals from E. coli cells decay in (cold) flow cytometry buffers.•The magnitude of fluorescence decay depends on expression strength.•Alterations in fluorescence are a consequence of increased membrane permeability.•Viability in cold buffers is reduced due to cold shock.•The observed effects are found in many, but not all E. coli strains.