Locations of the lip, poxB, and ilvBN genes on the physical map of Escherichia coli

The lip locus, located at ca. 14.5 min on the Escherichia coli chromosome (6), is thought to encode an enzyme (or enzymes) involved in the terminal step(s) of lipoic acid biosynthesis (1, 14). We have used a representative mutant (JRG26) from the single genetic class of lipoic acid-auxotro-phic strains described by Herbert and Guest (7) to identify the Kohara A phage which carries the complementing lip gene (Table 1). This phage also carries a DNA segment corresponding to a second genetic class of lipoic acid-auxotrophic mutants recently isolated in our laboratory (to be published elsewhere). Our restriction data from the lip locus are in general agreement with the data of Kohara et al. (9). However, we have not attempted to exhaustively verify the Kohara physical map of phage X168. Our restriction data (4, 5) for EcoRV, PvuII, BamHI, HindIII, EcoRI, KpnI, and PstI sites around the poxB gene are in agreement with the Kohara restriction map (9). The restriction data of Wek et al. (15) for the ilvBN gene agrees with the Kohara map except for an EcoRV site not present in the Kohara map. It should be noted that our result (ilvBN at 3860 kbp) is essentially identical to those of Kohara (8) and Brewer (2), who systematically compared the directly determined re-striction map (9) with that predicted from data base DNA sequences. In contrast, Medigue et al (10) and Rudd et al. (11) report ilvBN at 3919 and 3923 kbp, respectively. The apparent disagreement is due to computer-simulated rever-sal of the rrnD-rrnE inversion of strain W3110 mapped by TABLE 1. Physical locations of the poxB, ilvBN, and lip genes Genetic map Physical map Phage(s)a