The acidity issue has it routes in the manner how the
bacteria generate their ATP. They set up proton
gradients accross their cell walls. The higher the
proton (H+) concentration already outside their cell
wall the more difficult it becomes to maintain the
gradient used to generate ATP. Eventually the proton
concentrations equilibriate between the medium and
cytoplasm and that is when the bacteria's ticket gets
punched... This type of inhibition is just as effective
under aerobic and anaerobic conditions.
Under anaerobic conditions bacteria can still live by
means of glycolysis (metabolism of glucose to pyruvate +
2H+). Increased proton concentration (a low pH) puts
pressure on the metabolism, slowing the rate of
glycolysis and making the bacteria very unhappy.
As a side note, some canned good are now being
innoculated with bacteria of the genus Leuconostoc (if I
recall correctly). These bacteria produce antimicrobial
peptides that rip the cells walls of other bacter apart
or punch holes through them and disrupting the ion
gradients the bacteria use to generate their ATP and
other "energy" carriers.