facultatively acidophilic

Edge evidence

• acidic external pH selects for facultatively acidophilic METPO:2007401

  Acidic pH selects for acidophilic growth capacity.

  • DOI:10.3389/fmicb.2021.822229 acidic optimal growth pH Supports acidophilic classification by acidic growth optimum.
• near-neutral external pH is compatible with facultatively acidophilic

  Facultatively acidophilic growth can extend into near-neutral pH.

  • DOI:10.1099/ijs.0.066175-0 capable of growth at pH 4.0-7.2 Species-level evidence supports acidic-to-near-neutral growth range; this edge is qualified rather than generalized to all taxa.
• acidic external pH increases gradient of proton METPO:2007601

  Acidic pH imposes an external-to-internal proton gradient.

  • DOI:10.3389/fmicb.2021.822229 external to internal proton gradient Supports proton-gradient stress during low-pH growth.
• proton export pumps and antiporters contributes to cytoplasmic pH homeostasis RO:0002326

  Proton export and antiport systems contribute to acid-stress homeostasis.

  • DOI:10.3389/fmicb.2021.822229 proton export pumps and antiporters Supports transporter-mediated pH homeostasis mechanisms.
• cytoplasmic buffering contributes to cytoplasmic pH homeostasis RO:0002326

  Buffering and proton-consuming reactions reduce cytoplasmic acidification.

  • DOI:10.3389/fmicb.2021.822229 cytoplasmic buffering Supports buffering as a proposed acid resistance mechanism.
• cytoplasmic pH homeostasis enables facultatively acidophilic RO:0002327

  Growth across acidic and near-neutral pH requires intracellular pH control.

  • DOI:10.1038/nrmicro2549 robust mechanisms for cytoplasmic pH homeostasis Supports cytoplasmic pH homeostasis for growth outside the preferred cytoplasmic pH range.
• acidic external pH necessitates maintenance of near-neutral cytoplasm

  Acidophilic growth requires preserving near-neutral cytoplasm against a steep proton gradient.

  • DOI:10.3389/fmicb.2021.822229 maintain a near-neutral cytoplasm despite an external-to-internal proton gradient up to 10^5-fold.
• potassium ion generates inside-positive membrane potential biolink:produces

  Intracellular K+ accumulation generates an inside-positive potential that opposes proton influx.

  • DOI:10.3389/fmicb.2021.822229 internal positive membrane potential thought to be generated by potassium ions.
• inside-positive membrane potential contributes to cytoplasmic pH homeostasis RO:0002326

  An inside-positive membrane potential is a first-line defense reducing proton entry, supporting pH homeostasis.

  • DOI:10.3389/fmicb.2021.822229 Inside-positive potential generated by K+ opposes proton influx as a first-line defense.
• hopanoid biosynthetic process reduces membrane proton permeability METPO:2000017

  Hopanoids stiffen the membrane and reduce proton permeability under low pH.

  • DOI:10.3389/fmicb.2021.822229 membrane alterations via inclusion of hopanoids linked to acidophilic lifestyle.
• rigid impermeable membrane limits proton RO:0002212

  A rigid, impermeable membrane acts as a barrier limiting proton entry into the cell.

  • DOI:10.3389/fmicb.2023.1149903 acidophiles use a rigid and impermeable membrane that resists proton entry.
• proton export pumps and antiporters expels proton

  Proton export pumps and antiporters directly remove protons that enter the cytoplasm.

  • DOI:10.3389/fmicb.2021.822229 proton export pumps and antiporters listed among mechanisms maintaining pH homeostasis.
• glutamate decarboxylase system consumes proton biolink:consumes

  Glutamate decarboxylation consumes intracellular protons as a second-line acid resistance route.

  • DOI:10.3389/fmicb.2021.822229 proton consuming reactions such as glutamate decarboxylase; gadABC among acid-adaptation genes.
• cytoplasmic buffering stabilizes intracellular pH

  Cytoplasmic buffering dampens pH fluctuations to stabilize intracellular pH.

  • DOI:10.3389/fmicb.2023.1149903 shared mechanisms include cytoplasmic buffering that stabilizes intracellular pH.