FIG. 1.

Presence of insertion element (IS) and phoA sequences in SK8 chromosomal DNA. Shown are Southern blots of BamHI-digested chromosomal DNA from SK8 probed with a probe which hybridizes to the TnphoA IS sequences and the gene encoding the kanamycin resistance determinant (A), a probe to the IS sequence (B), and a probe to the phoA sequence of TnphoA (C). The arrows indicate bands hybridizing to each probe. (D) Schematic representation of SK8 chromosomal DNA with insertion of TnphoA and IS50L containing ′phoA. The production of alkaline phosphatase activity from the latter is indicated by the arrow; the insertion which does not produce alkaline phosphatase activity is indicated by the crossed-out arrow. The probes derived from TnphoA are highlighted, as double-headed arrows, below the diagram. The letters under the probes refer to the Southern blots in panels A, B, and C.