Extraction,partial purification,and properties of a mycoplasmal growth inhibitor extracted from cells ofMycoplasma by ultrasonication

Inhibition of growth ofMycoplasma, but notAcholeplasma, by a substance extracted from mycoplasmal cells by ultrasonication (us-Mcin) was demonstrated. All species ofMycoplasma tested having the growth inhibitor also had arginine deiminase and, except forM. fermentans, those without the inhibitor lacked arginine deiminase. The grade of inhibiting activity was in parallel with that of arginine deiminase. However, the us-Mcin entity is not arginine deiminase itself, because us-Mcin was still active after treatment withp-chloromercuribenzoic acid, which is an inhibitor of the enzyme. The effect of us-Mcin on the growth ofMycoplasma is not mycoplasmastatic but mycoplasmacidal. The us-Mcin obtained from cells ofM. salivarium was partially purified by column chromatography after DNase treatment and was characterized as follows: nondialyzable; heat labile; pH stable between 5 and 9; iactivated by methanol, but insensitive to acetone as well as chloroform; completely or partially inactivated by pronase, trypsin, chymotrypsin, and RNase, but insensitive to phospholipase C and DNase; contained no detectable protease or lipase, but did have a detectable amount of arginine deiminase. The molecular weight of partially purified us-Mcin ofM. salivarium determined by SDS-polyacrylamide gel electrophoresis might be 46,000. Differences between the spectra of growth inhibition by growth inhibitors extracted with chloroform (ch-Mcin) and the spectra of inhibition by us-Mcin are discussed.