Brett yeast is needed for brett beer. It is a sacc yeast and not a bacteria, just produces some funk. Acid malt, like stated, is just malt sprayed with lactic acid to adjust mash pH without using phosphoric or lactic acid. More so used for Reinheitsgebot. Brett is usually used in conjunction with lacto and peddio, but can be used by itself. Ive never heard of it requiring acid malt though.