Acetobacter is a genus of acetic acid bacteria characterized by the ability to convert alcohol (ethanol) to acetic acid in the presence of air. There are several species within this genus, and there are other bacteria capable of forming acetic acid under various conditions; but all of the Acetobacer are known by this characteristic ability.

Acetobacter are of particular importance commercially, because:

• they are used in the production of vinegar (intentionally converting the ethanol in the wine to acetic acid)
• they can destroy wine which it infects by producing excessive amounts of acetic acid or ethyl acetate, both of which can render the wine unpalatable.

The growth of Acetobacter in wine can be suppressed through effective sanitation, by complete exclusion of air from wine in storage, and by the use of moderate amounts of sulfur dioxide in the wine as a preservative.

Acetobacter can be easily distinguished in the laboratory by their growth of colonies on a medium containing about 7% ethanol, and enough calcium carbonate to render the medium partially opaque. When Acetobacter colonies form enough acetic acid from the ethanol, the calcium carbonate around the colonies dissolves, forming a very distinct clear zone.