The finding (Spizizen, 1958(Spizizen, , 1959) that a number of auxotrophic mutants of Bacillus subtilis could be transformed to prototrophy has provided a simple system for the study of transformation of biochemical characters. This is made possible by the fact that B. subtilis can be grown
, AND JOHN SPIZIZEN. Bacteriophage deoxyribonucleate infection of competent Bacillus subtilis. J. Bacteriol. 89:782-790. 1964.-Phenol extracts of the Bacillus subtilis bacteriophages (1, 4)25, and 4)29 contained infectious deoxyribonucleic acid. The infectivity was destroyed by catalytic amounts of deoxyribonuclease but not by specific phage antiserum, ribonuclease, or trypsin. An infectivity of > 106 infectious ceniters formed per ,ug of deoxyribonucleic acid (DNA) added was obtained. The stability of the infectious centers permitted an examination of a single cycle of phage replication in cells unable to adsorb the mature virus. A typical cycle was observed, although the latent period was increased and the burst size slightly reduced after DNA infection. The development of competence for bacterial transformation was strongly correlated with susceptibility to viral DNA infection. Both appeared and disappeared at the same phase of growth in the cell population. More than 4%7 of the viable cells in the competent population were infected by viral DNA. The kinetics of the transition of 029 I)NA infection to deoxyribonuclease insensitivity, and the relationship of infectivity to DNA dilution, were similar to the results obtained for bacterial transformation of a single marker. The doseresponse curve of 41 and 4)25 DNA was characteristic of that obtained in multiple transformation of unlinked genetic markers. Because of the low efficiency of infection, about 10-4 per phage equivalent of DNA added, it was not possible to prove that DNA alone was sufficient to initiate infection.
Populations of pneumococci (Hotchkiss, 1957) and Bacillus subtilis (Spizizen, 1959) are transformed at the highest frequency by deoxyribonucleic acid (DNA) during the latter half of the logarithmic stage of growth (competent period). Recent investigations with P32-labeled DNA in
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