FIG. 2.

Plasmid pSD15 is not present in non-agar-degrading isolates. (A) Total DNA isolated from Microscilla colonies that had lost the ability to degrade agar (lane 1; PRE1-0) and from colonies capable of degrading agar (lane 2; PRE1). Lane 3 is DNA isolated from Rhizobium meliloti, harboring three plasmids, used as a molecular mass marker with sizes as indicated. The position of chromosomal DNA on the gel is also indicated (chr). (B) PCR amplification to identify the presence of a 1.5-kb pSD15 fragment in PRE1 colonies (lane 2), PRE1-0 colonies (lane 3), supercoiled pSD15 DNA (lane 4), a library clone carrying this fragment (from which primers were designed) (lane 5), and a library clone selected at random (lane 6). Lane 7 is a no-DNA template control. Lane 1 has a molecular mass marker (1-kb ladder; Gibco).