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J Virol. 1971 May; 7(5): 646-650
Copyright © 1971 American Society for Microbiology. All Rights Reserved.

Transfection of Escherichia coli Spheroplasts I. General Facilitation of Double-Stranded Deoxyribonucleic Acid Infectivity by Protamine Sulfate

Department of Biology, University of Virginia, Charlottesville, Virginia 22903

ABSTRACT

The addition of 25 µg of protamine sulfate per ml to lysozyme-ethylenediamine-tetraacetic acid spheroplasts of Escherichia coli stimulates transfection not only for T1 phage deoxyribonucleic acid (DNA; Hotz and Mauser, 1969) but also for the following phage DNA species: lambda, 10,000-fold to an efficiency of 10^–3 infective centers per DNA molecule; X174 replicative form, 300-fold to an efficiency of 5 x 10^–2; fd replicative form, 300-fold to 10^–6; T7, 300-fold to 3 x 10^–7. Three native phage DNA species were not infective at all in the absence of protamine sulfate but were infective in the presence of protamine sulfate with the following efficiencies: T4, 10^–5; T5, 3 x 10^–6; and P22, 3 x 10^–9. The effect of protamine sulfate is specific for double-stranded DNA. The application of infectivity assays to the study of phage DNA replication, recombination, prophage integration, prophage excision, and interspecies transfection are discussed.