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Highly polymerized deoxyribonucleate (DNA) is a component of some slimes that accumulate in ordinary broth cultures of a variety of bacteria (Smithies and Gibbons, 1955; Catlin, 1956a). Such DNA, designated as extracellular, may be distinguished from intracellular DNA of the same culture by its accessibility to crystalline pancreatic deoxyribonuclease. Small quantities of this enzyme destroy the sticky consistency of the DNA-containing slime. DNA within intact cells, however, is not affected by added deoxyribonuclease and, subsequent to enzyme action, may be isolated in a highly polymerized form by disrupting the washed cells in a medium that inhibits deoxyribonuclease. The origin of extracellular DNA may be obscured, in some cases, by cryptic multiplication. Investigation of Micrococcus halodenitrificans using radioactive phosphorus-labeled cells has shown that the DNA in culture slime was of intracellular origin (Takahashi and Gibbons, 1957). When this halophilic organism was cultivated in suboptimal concentrations of sodium chloride, some cells of the population apparently ruptured, releasing nucleic acid; much of the DNA adhered to the cells, whereas the ribonucleate diffused into the medium. Cellular lysis, also, can account for the DNA present extracellularly in cultures of Pseudomonasfluorescens (Catlin, unpublished data) and Neisseria meningitidis. In other cases the source remains to be determined. Extracellular accumulation of highly polymerized DNA can occur only in the absence of deoxyribonuclease activity. Staphylococcus aureus, P. fluorescens, and Alcaligenes faecalis produce enzymes which are different, but which have

TRANSFORMATION OF NEISSERIA MENINGITIDIS BY DEOXYRIBONUCLEATES FROM CELLS AND FROM CULTURE SLIME