Ploidy studies on the large cells of Micrococcus aureus.

The determination of ploidy in bacterial cells has been unsatisfactory in most cases because the criteria of ploidy in higher forms can not as yet be applied directly to bacteria. The best evidence of diploidy in bacteria has been in the various "Het" strains of Escherichia coli strain K-I2 developed by Lederberg et al. (1951). Unfortunately, genetic recombination has not been found in many bacteria, so this means of ploidy determination has been very limited in use. Genetic and radiobiological studies indicate that bacteria are usually haploid (Lea, 1947); however, several instances have been reported in which cytological information suggests a diploid phase (Bisset, 1950). Lindegren (1942) presented cytological evidence for a meiotic division in Micrococcus orchraceous. Webb and Clark (1954) found evidence of a diploid or polyploid phase in a life cycle of M. aureus. These large cells appeared cytologically to undergo a meiotic division to yield normal haploid cells. This paper is a continuation of the studies of the large, apparently diploid cells of M. aureus.