MEMBRANE-ASSOCIATED NUCLEASE ACTIVITIES IN MYCOPLASMAS

Membrane-associated nucleases of various mycoplasmal species were inve stigated by using two nuclease assays. A lambda DNA assay was develope d to measure nuclease activity associated with whole-cell suspensions, activity released from intact cells, and activity associated with det ergent-disrupted cells. In most species, nuclease activities were enti rely membrane associated, and disruption by a detergent had a stimulat ory effect on these activities. All mycoplasmal species contained nucl ease activity, but Mycoplasma capricolum was unusual because its activ ity was dependent upon magnesium and was inhibited by calcium. We deve loped a sodium dodecyl sulfate-polyacrylamide gel electrophoresis syst em that produced reproducible nuclease patterns, and this system was u sed to determine the apparent molecular weights of the nuclease protei ns. An examination of 20 mycoplasmal species failed to identify common bands in their nuclease patterns. An examination of 11 Mycoplasma pul monis strains, however, indicated that nuclease patterns on polyacryla mide gels may provide a means for categorizing strains within a specie s. Our results suggest that nucleases are important constituents of my coplasmal membranes and may be involved in the acquisition of host nuc leic acids required for growth.