So far, four species from the genus "Pediococcus" have been isolated in wines and grape must, "P. inopinatus, P. pentosaceus, P. parvulus", and "P. damnosus", with the last two being the species most commonly found in wine. All "Pediococcus" species are Gram-positive with some species being micro-aerophilic while others utilizing mostly aerobic respiration. Under the microscope, "Pediococcus" often appear in pairs of pairs or tetrads which can make them identifiable. Pediococci are homofermenters, metabolizing glucose into a racemic mixture of both L- and D-lactate by glycolysis. However, in the absence of glucose, some species, such as "P. pentosaceus", begin using glycerol, degrading it into pyruvate which later can be converted to diacetyl, acetate, 2,3-butanediol and other compounds that can impart unfavorable characteristics to the wine.