Acetobacter bacteria. Coloured scanning electron micrograph (SEM) of several Acetobacter sp. bacteria (blue/green) on wood. Acetobacter are rod-shaped, Gram-negative bacteria which are commonly found on organic matter such as fruit and flowers. They are also responsible for the spoilage of beers and wines, as they metabolise the alcohol (ethanol) these contain into ethanoic acid, the main flavouring of vinegar. Acetobacter bacteria are used in industry to turn wines, beers and spirits into wine vinegar, malt vinegar and spirit vinegar respectively. Magnification: x2800 at 6x6cm size.