Fig. 2.

Gene arrangements of parental strains and their mutants. Chromosomal DNA regions corresponding to the DNA fragments used for transformation of S. mutans to construct the mutants are depicted in the figure and these regions in the five mutants are drawn with their background DNA, since we cannot identify the actual recombination points between the two homologous sequences. Positions and directions of the Kan^r and Em^r cassettes are indicated but their sizes are not drawn to scale. Open squares in (B) and (F) indicate 20 bp deletions, sparsely and densely doted small boxes in (F) and (G) indicate the first 15 identical codons of the spaP genes in strains Z1 and UA159.