FIG. 1.

Genetic organization of the asnB, asnH, and asnO (yisO) regions and DNA stretches amplified by PCR for plasmid and mutant constructions and probe preparations. The genetic organization of the asnB (top), asnH (middle), and asnO (bottom) regions is shown schematically, and a scale bar with nucleotide positions within the whole genome sequence (10) is given for each of the regions. Genes are shown as thick arrows; solid arrows indicate genes within possible transcription units that contain one of the asparagine synthetase genes. DNA stretches amplified by PCR are shown as solid lines, and names of plasmids, mutants, and probes prepared with the respective PCR products are given on the left. The position and orientation of each specific primer are shown with small arrowheads. The length and orientation of each of antibiotic resistance gene cassette ligated with the PCR products are shown as thinner arrows. The antibiotic resistance genes are abbreviated as follows: cat, chloramphenicol acetyltransferase gene; neo, neomycin resistance gene; spc, spectinomycin resistance gene.