Excision of phage Mu from Escherichia coli MCS2 was originally put forth as a clear example of directed mutation. This claim was considerably weakened, however, by subsequent evidence that Mu excision occurs during starvation regardless of fitness consequences. Here, I use the classical replica-plating technique to examine Mu excision during starvation of MCS2. The results support the conclusion that Mu excision is not directed but is, instead, nonspecifically induced by starvation.
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