FIG. 5.

(a) PCR analysis of wild-type C. tepidum (lanes 1 and 3) and a Gm^r mutant (lanes 2 and 4). Primers specific for nifD, nif-F4 and nif-B4, were used in lanes 1 and 2, and primers specific for the gentamicin resistance cassette (accC1), GmR-F1 and GmR-B1, were used in lanes 3 and 4. (b) Southern hybridization analysis of wild-type C. tepidum (lanes 1 and 3) and an Em^r mutant (lanes 2 and 4). A probe specific for nifD was used in lanes 1 and 2, and a probe specific for the erythromycin-chloramphenicol resistance cassette (ermC-cat) was used in lanes 3 and 4.