Which bacteria would thrive at pH 3.0?
pH profoundly affects physiology by shifting ionization of active site residues, modulating proton motive force for ATP synthesis via F0F1 ATPase and affecting metal solubility. Neutrophiles such as Escherichia coli grow optimally near neutrality pH 6.5 to 7.5 and maintain cytoplasm around pH 7.6 via proton pumps, cation proton antiporters NhaA and amino acid decarboxylase acid resistance systems. Acidophiles like Acetobacter aceti in vinegar, Acidithiobacillus ferrooxidans oxidizing iron and thermoacidophilic Ferroplasma thrive optimally below pH 4 some near pH 0 possessing highly acid-stable
Ref: Madigan et al., Brock Biology of Microorganisms, 16th ed., Chapter 7: Acidophiles and Low pH Growth Adaptation.