Affiliation:
1. Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania 19104
Abstract
Escherichia coli
K-12 strains tested so far (approximately 20) can be separated into three groups on the basis of their abilities to form colonies on nutrient agar supplemented with nalidixic acid (NAL): (i) Nal
s
or wild type (no growth at 1 to 2 μg/ml); (ii) NalA
r
(growth at 40 μg/ml or higher); and (iii) NalB
r
(growth at 4 μg/ml, but no growth at 10 μg/ml). The NalA
r
group has a spectrum of sensitivity ranging from 60 to over 100 μg/ml. All Hfr strains of the NalA
r
and NalB
r
groups transfer NAL resistance to recipient cells at genetic loci which are at 42.5 ± 0.5 and 51 ± 1 min, respectively, on the Taylor-Trotter map. Some members of the NalA
r
group also have the genetic locus for NalB
r
. The
nalA
s
allele is completely dominant to
nalA
r
in a partial diploid configuration. In haploids,
nalA
r
-
nalB
r
is phenotypically NalA
r
;
nalA
r
-
nalB
s
is NalA
r
; and
nalA
s
-
nalB
r
is NalB
r
. The map location of
nalA
and the easy differentiation between NalA
r
and NalA
s
allow this marker to be used as a counterselector in bacterial conjugation experiments.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
270 articles.
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