The bacterial tubulin homolog FtsZ generates electrical oscillations

Abstract

FtsZ, a major cytoskeletal protein in all bacteria and archaea, forms a ring that directs cytokinesis. Bacterial FtsZ is considered the ancestral homolog of the eukaryotic microtubule (MT)-forming tubulins, sharing GTPase activity and the ability to assemble into protofilaments, rings, and sheets, but not MTs. Previous studies from our laboratory demonstrated that structures of isolated brain MTs spontaneously generate electrical oscillations and bursts of electrical activity similar to action potentials. No information about whether the prokaryotic tubulins may share similar properties is available. Here, we obtained by ammonium sulfate precipitation an enriched protein fraction of the endogenous FtsZ from wild-type Escherichia coli ATCC 25922 without any transfection or overexpression of the protein. As revealed by electron microscopy, FtsZ was detected by dot blot analysis and immunofluorescence that assembled into filaments and sheets in a polymerization buffer. We used the patch-clamp technique to explore the electrical properties of sheets of FtsZ and bacterial cells. Electrical recordings at various holding potentials ranging from ±200 mV showed a complex oscillatory behavior, with several peak frequencies between 12 and 110 Hz in the power spectra and a linear mean current response. To confirm the oscillatory electrical behavior of FtsZ we also conducted experiments with commercial recombinant FtsZ, with similar results. We also detected, by local field potentials, similar electrical oscillations in K+-depolarized pellets of E. coli cultures. FtsZ oscillations had a wider range of frequency peaks than MT sheets from eukaryotic origin. The findings indicate that the bacterial cytoskeleton generates electrical oscillators that may play a relevant role in cell division and unknown signaling mechanisms in bacterial populations.