Growth medium constituents contaminating mycoplasma preparations and their role in the study of membrane glycoproteins in porcine mycoplasmas.

Several Mycoplasma and Acholeplasma species chosen at random and solubilized with sodium dodecyl sulphate showed a common periodic acid-Schiff positive band with an apparent molecular weight of about 64 000, when examined by polyacrylamide gel electrophoresis. Another more cathodic minor band was detected in M. hyopneumoniae and M. flocculare. The common periodic acid-Schiff positive band appeared when a precipitate of serum constituents of the uninoculated growth medium after incubation was examined. The minor band was identified as a serum glycoprotein contaminating mycoplasmas grown in the presence of swine serum. We draw attention to the compounds as a possible source of error in serological tests or in the lymphocyte stimulation response. After lithium diiodosalicylate solubilization and aqueous phenol extraction, polyacrylamide gel electrophoresis showed a periodic acid-Schiff positive band in membranes from M. hyopneumoniae (molecular weight 75 000) and M. hyorhinis (molecular weight 80 000), suggesting the presence of a membrane glycoprotein. Such a glycoprotein was absent from A. granularum. Since the common periodic acid-Schiff positive band was not extracted by aqueous phenol, this growth medium constituent did not contaminate the preparations of membrane glycoproteins. However, the minor band was present in glycoprotein preparations of M. hyopneumoniae grown in the presence of swine serum.