Transformation studies in germinating spores of Bacillus subtilis 168



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Samples of germinating spores and vegetative cells of Bacillus subtilis 168 taken at 14 consecutive hour intervals and exposed to transforming DNA for 30 minutes demonstrated competence throughout the germination and growth processes. Peaks of competence were observed at periods in which DNA synthesis has been reported to be devoid or slow. The implication is that the integration of donor DNA into the recipient genome can occur at an inactive or slowly moving replication point. Employing 19 consecutive brief DNA exposure intervals during periods of growth in which genome replication is reported to be in synchrony and cell division phasing is implied, the adenine and methiorihe markers displayed a parallel periodicity of transformation frequencies opposite that of leucine. This observation implies that the integrative event can occur in the vicinity of a moving replication point and that the adenine and methionine markers are linked. Quantitative data from replica plating experiments indicate an approximate cotransfer index of 0.817 for adenine-methionine double transformants, and that these loci are separated by an approximate 'map distance' of 0.183. The implication is that Bacillus subtilis 168 genome is closed.