Colicin E1 blocks proline accumulation by membrane vesicles prepared from wild-type sensitive Escherichia coli. Two classes of mutant cells are unaffected by colicin. Vesicles from colicin-resistant strains are sensitive to colicin E1, whereas vesicles from colicin-tolerant strains are unaffected by colicin El. These results suggest that the colicin E1 receptor is on the cell membrane and that colicin-tolerant strains have altered membranes while colicin-resistant strains have altered cell walls.
The gene for resistance to phage BF23 and colicins E 1; E a and E 3 , bfe, was mapped by a combination of conjugation and transduction crosses. Co-transduction of bfe was found with markers in the region between 76 and 79 min on the Escherichia coli genetic map. The highest frequency of co-transduction was found with argH (47 %). Three-factor transductional crosses showed unambiguously that bfe lies between argH and supM, at about 77-5 min on the map.
Manganese is growth inhibitory for Escherichia coli. The manganese concentration required for inhibition is dependent upon the magnesium concentration of the medium. Mutants have been isolated which are partially resistant to manganese inhibition in both liquid and solid media. From conjugation experiments, the genetic locus for manganese-resistance, mng, appears to be between 34 and 37 min on the E. coli genetic map. Experiments with radioactive 28Mg on August 1, 2020 by guest
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