pH optimum low

Edge evidence

• acidic external pH selects for acidophile proton-exclusion physiology METPO:2007401

  Acidic environments select for proton-exclusion physiology.

  • DOI:10.1016/j.tim.2007.02.005 highly impermeable cell membranes Supports envelope-based proton barriers as the selected acidophile mechanism.
• acidophile proton-exclusion physiology produces pH optimum low METPO:2000202

  Acidophile proton-exclusion physiology yields an acidic pH-optimum setpoint.

  • DOI:10.1038/nrmicro2549 growing at pH 1.0-3.0 Supports growth at strongly acidic pH as the acidophile outcome.
• pH optimum low is a pH optimum rdfs:subClassOf

  pH optimum low is a quantitative bin of the pH-optimum phenotype.

  • DOI:10.1038/nrmicro2549 cytoplasmic pH Supports an acidic optimum as a value within the pH-optimum distribution.
• low external pH drives large transmembrane pH gradient

  Acidic external pH forces acidophiles to sustain a large transmembrane pH gradient.

  • DOI:10.1038/nrmicro2549 cytoplasmic pH ~6.0 while growing at external pH <3; broad physiological input edge.
• inside-positive membrane potential counteracts proton influx

  A reversed inside-positive membrane potential electrostatically opposes proton entry.

  • DOI:10.1038/nrmicro2549 sustain a large delta pH with a reversed inside-positive membrane potential; hallmark of extreme acidophiles.
  • DOI:10.3389/fmicb.2023.1149903 inside positive membrane potential creates an electrochemical barrier to proton influx.
• proton-pumping respiratory complexes removes cytoplasmic proton load

  Proton-pumping respiratory complexes actively extrude protons to lower cytoplasmic proton load.

  • DOI:10.1038/nrmicro2549 increased expression of proton-pumping respiratory chain complexes; broad mechanism, specific complexes vary by lineage.
• rigid proton-impermeable membrane decreases passive proton permeability RO:0002212

  A rigid proton-impermeable membrane reduces passive proton leak and the energetic burden of pH homeostasis.

  • DOI:10.3389/fmicb.2023.1149903 rigid and impermeable membrane that is highly resistant to the influx of protons; high-level trait edge.