Acholeplasma are wall-less bacteria in the Mollicutes class. They include saprotrophic or pathogenic species. There are 15 recognised species. The G+C content is low, ranging from 26 - 36% (mol%). The genomes of Acholeplasma species range in size from 1.5 to 1.65 Mbp. Cholesterol is not required for growth. The species are found on animals, and some plants and insects. The optimum growth temperature is 30 to 37 degrees Celsius.
Acholeplasma laidlawii may contaminate bovine serum and also occurs in serum-free cell culture media products. Unsubstantiated evidence of A. laidlawii contamination of tryptone soya broth existed for some years prior to proof of the organism's contaminating nutrient broth powders. The presence of A. laidlawii in broth powders is a serious problem in routine biopharmaceutical operations where filtration is used as a sterilisation procedure. A. laidlawii may flourish and survive for prolonged periods at refrigeration and ambient temperatures in serum-free cell culture media.