TABLE 3.

Deletion frequencies of cassettes borne on class 1 and 2 integrons promoted by class 1 and 2 integrases

PlasmidaattI classIntegraseCassette deletion frequencies (%)b
dfr1sataadA1dfr1 aadA1sat dfr1aadA1 sataadA1 sat dfr1
6702IntI2*0000000
2IntI2*179E1.113100.171.50.80
2IntI11.55.2730.330.502.00.17
6712IntI2*0000000
2IntI2*179E00.670.670000
2IntI10018002.50
22801IntI2*-c-0----
1IntI2*179E--0----
1IntI1--59----
6782IntI2*--0----
2IntI2*179E--0.33----
2IntI1--0.7----
  • a See Fig. 3 for maps of cloned integron fragments in plasmids 670, 671, 2280, and 678.

  • b Phenotypic tests were used as described in Materials and Methods to detect cassette excisions. DNA fragments were cloned in pSU18 or pSU19 to obtain substrates in either direction in respect to the lac promoter (in plasmid 671 the lac promoter is directed from the 5′ end of the cassettes, and in plasmids 670, 2280, and 678 the promoter is directed from the 3′ end of the cassettes). Excision rates are given as the percentage of sensitive colonies among 600 to relevant antibiotics.

  • c -, Not done.