Acne bacteria. Black and white scanning electron micrograph (SEM) of a skin tape sample showing acne bacteria (Propionibacterium acnes). This bacteria is found deep in the hair follicles and pores of the skin, where it is part of the normal flora and usually causes no problems. However, if there is an overproduction of sebum (sebaceous oil), the bacteria proliferate, producing enzymes that damage the skin and cause acne. Here acne bacteria are visible on skin cells from the skin tape sample from a cheek. Magnification x 2500 at 10cm wide