Spontaneous production of lambda particles with transducing activity.

HE transductions by lambda bacteriophage have been described previously (MORSE, LEDERBERG and LEDERBERG 1956a,b; MORSE 1957; E. LEDERBERG 1960; WEIGLE 1957). The lambda particles accomplishing transduction have been shown to be defective (ARBER, KELLENBERGER and WEIGLE 1957; ARBER 1958; CAMPBELL 1957; CAMPBELL and BALBINDER 1959). The origin of transducing particles in haploid cultures of Escherichia coli K-12 has not been established. One possibility is that they are produced from pre-existing cells (homogenotes) which are merely induced to form phage by the radiation exposure. Alternatively the transducing particles could be the direct consequence (fortuitous chromosome breaks) of the ultraviolet radiation used to induce phage growth. A high statistical variance in number of transducing particles would be observed if there were pre-existing cells because of fluctuations in the time of formation of these cells. If the UV irradiation were the cause of transducing particles, lysates produced from a series of independent cultures by a constant UV dose might be expected to have a low statistical variance with regard to the number of transducing particles they contain. We wish to report that some lambda particles produced spontaneously are capable of transducing Gal genes. This provides, in cultures capable of adsorbing lambda, a mechanism for forming homogenotic clones spontaneously (Gal,-x Gal; + Gal,-/,,Galc-) and leading to high “between culture” variance. However, analysis of a series of cultures incapable of adsorbing lambda particles also yielded a high variance, a finding which indicates that homogenotes are not the sole source of high “between culture” variance.