pH range mid2

Edge evidence

• modest alkaline-tolerance physiology enables pH range mid2 RO:0002327

  Modest alkaline-tolerance physiology enables growth across pH 7–8.

  • DOI:10.1016/j.tim.2007.02.005 proton motive force Supports balanced proton motive force at slightly alkaline pH as the range mechanism.
• pH range mid2 is a pH range rdfs:subClassOf

  pH range mid2 is a quantitative bin of the pH-range phenotype.

  • DOI:10.1038/nrmicro2549 cytoplasmic pH Supports the pH 7–8 range as a value within the pH-range distribution.
• external pH 7-8 permits maintenance of cytoplasmic pH homeostasis

  External pH 7-8 permits cells to keep internal pH near 7.0-7.5.

  • DOI:10.1093/femsre/fuad033 Internal pH kept within 7.0-7.5 and PMF relatively constant across external pH 5-8.
• cytoplasmic buffering stabilizes cytoplasmic pH homeostasis

  Cytoplasmic buffering stabilizes internal pH given very low free proton count.

  • DOI:10.1093/femsre/fuad033 A ~1 fL cytoplasm at pH 7.2 contains only ~10 free protons, so buffering is critical.
• Na+/H+ antiporter activity acidifies cytoplasm

  Na+/H+ antiporter activity acidifies the cytoplasm when internal pH rises.

  • DOI:10.1093/femsre/fuad033 Na+/H+ and K+/H+ antiporters acidify the cytoplasm by exchanging exported cations for H+.
• proton motive force remains relatively constant across external pH 5-8

  Neutralophiles keep PMF relatively constant across external pH ~5-8.

  • DOI:10.1093/femsre/fuad033 Neutralophilic bacteria adjust ΔpH vs Δψ so PMF stays relatively constant across external pH ~5-8.
• membrane potential / ΔpH rebalancing maintains proton motive force

  Rebalancing of ΔpH and Δψ with external pH maintains PMF.

  • DOI:10.1093/femsre/fuad033 The relative contribution of ΔpH and Δψ shifts with external pH to preserve PMF.
• F0F1-ATPase couples ATP synthesis

  F0F1-ATPase couples the proton motive force to ATP synthesis.

  • DOI:10.1093/femsre/fuad033 PMF drives ATP synthesis; F0F1 uses ~3-5 H+ per ATP.
• proton:ion antiporters maintain membrane potential (Δψ)

  Proton:ion antiporters have a direct role in maintaining membrane potential.

  • DOI:10.1146/annurev-biophys-030822-032215 Antiporters have a direct role in maintaining membrane potential in E. coli.