A. bovis is a branching, rod-shaped bacterium.[1] In its diploid phase, it is Gram-positive; during the haploid phase, it is club-shaped and is Gram-negative.[2] A. bovis is catalase-negative, which can differentiate it from other anaerobic diptheroids.[15] A. bovis microcolonies on brain heart infusion agar can be distinguished from the closely related organisms Actinomyces israelii and Actinomyces naeslundii.[1] The ability for A. bovis to hydrolyze starch is another way to distinguish it from A. israelli and A. naeslundii.[1]