Structure of deoxyribonucleic acid on the cell surface during uptake by pneumococcus.

We exposed competent cells of Diplococcus pneumoniae to high-molecular-weight donor deoxyribonucleate (DNA) and examined the state of the DNA bound to them in forms sensitive to deoxyribonuclease I. The portion elutable with 5 M guanidine hydrochloride was shown to be native, of much lower molecular weight (4 x 10(6) to 5 x 10(6)) than the donor, and as active in further transformation as sheared DNA of the same size. The portion resistant to release by guanidine hydrochloride was also shown to be native and active in transformation. These results, along with previous ones, imply that the breaks produced outside the cell are not at genetically specific sites. Furthermore, it was found that entry past the cell barrier to deoxyribonuclease could occur at 0 C by a process sensitive to ethylenediaminetetraacetate.