title: Cell dualism: presence of cells with alternative membrane potentials in growing populations of bacteria and yeasts.
abstract: It is considered that all growing cells, for exception of acidophilic bacteria, have negatively charged inside cytoplasmic membrane (Δψ⁻-cells). Here we show that growing populations of microbial cells contain a small portion of cells with positively charged inside cytoplasmic membrane (Δψ⁺-cells). These cells were detected after simultaneous application of the fluorescent probes for positive membrane potential (anionic dye DIBAC⁻) and membrane integrity (propidium iodide, PI). We found in exponentially growing cell populations of Escherichia coli and Saccharomyces cerevisiae that the content of live Δψ⁻-cells was 93.6 ± 1.8 % for bacteria and 90.4 ± 4.0 % for yeasts and the content of live Δψ⁺-cells was 0.9 ± 0.3 % for bacteria and 2.4 ± 0.7 % for yeasts. Hypothetically, existence of Δψ⁺-cells could be due to short-term, about 1 min for bacteria and 5 min for yeasts, change of membrane potential from negative to positive value during the cell cycle. This change has been shown by the reversions of K⁺, Na⁺, and Ca²⁺ ions fluxes across the cell membrane during synchronous yeast culture. The transformation of Δψ(⁻-cells to Δψ⁺-cells can be explained by slow influx of K⁺ ions into Δψ⁻-cell to the trigger level of K⁺ concentration ("compression of potassium spring"), which is forming "alternative" Δψ⁺-cell for a short period, following with fast efflux of K⁺ ions out of Δψ⁺-cell ("release of potassium spring") returning cell to normal Δψ⁻ state. We anticipate our results to be a starting point to reveal the biological role of cell dualism in form of Δψ⁻- and Δψ⁺- cells.
authors: Department of Civil, Construction & Environmental Engineering, Iowa State University, 327 Town Engineering Building, Ames, IA, 50011, USA, vivanov@iastate.edu.
authors: Volodymyr
authors: V
authors: Ivanov
authors: Saeid
authors: S
authors: Rezaeinejad
authors: Jian
authors: J
authors: Chu
mesh_terms: D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D004926:Escherichia coli / Q000378:metabolism / Q000502:physiology*; D005434:Flow Cytometry; D008564:Membrane Potentials / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000378:metabolism / Q000502:physiology*
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