Summary: Mutations in three Escherichia coli K12 genes, tonB, exbB and the newly discovered semA, reduce sensitivity to the low Mr polypeptide antibiotic microcin E492. The products of the tonB and exbB genes were previously shown to be involved in the uptake of siderophore-complexed iron and in the action of a number of colicins. Strains mutated at or close to semA (collectively referred to as sem mutations) remained fully sensitive to these colicins, and grew as well as wild-type strains under conditions of iron starvation. Expression of a number of sem-lacZ operon fusions was not affected by iron limitation, and sem mutations did not affect the production of iron-regulated outer membrane proteins which are known or thought to be involved in iron uptake. Hfr conjugation and P1 phage transduction experiments indicated that semA is located close to pabB at 40 min on the E. coli K12 chromosome. This places semA close to the mng locus, wherein mutations result in decreased manganese sensitivity. However, strains carrying the semA mutation exhibited increased manganese sensitivity.
BaggA.,
NeilandsJ. B.1985; Mapping of a mutation affecting regulation of iron uptake systems in Escherichia coli K-12. Journal of Bacteriology 161:450–453
BakerT. A.,
HoweM. M.,
GrossC. A.1983; MudX, a derivative of MudI (lac ApR) which makes stable lacZ fusions at high temperature. Journal of Bacteriology 156:97–974
DaviesJ. K.,
ReevesP.1975a; Genetics of resistance to colicins in Escherichia coli K-12: crossresistance among colicins of group B. Journal of Bacteriology 123:96–101
DaviesJ. K.,
ReevesP.1975b; Genetics of resistance to colicins in Escherichia coli K-12: cross resistance among colicins of group A. Journal of Bacteriology 123:102–117
GroismanE. A.,
CastilhoB. A.,
CasadabanM. J.1984; In vivo cloning and adjacent gene fusing with a mini-Mu-lac bacteriophage containing a plasmid replicon. Proceedings of the National Academy of Sciences of the United States of America 81:1480–1483
HerreroM.,
MorenoF.1986; Microcin B17 blocks DNA replication and induces the SOS system in Escherichia coli
. Journal of General Microbiology 132:393–402
LavinaM.,
PugsleyA. P.,
MorenoF.1986; Identification, mapping, cloning and characterization of a gene (sbmA) required for microcin B17 action on Escherichia coli K12. Journal of General Microbiology 132:1685–1693
de LorenzoV.,
PugsleyA. P.1985; Microcin E492, a low molecular weight peptide antibiotic which causes depolarization of the Escherichia coli cytoplasmic membrane. Antimicrobial Agents and Chemotherapy 25:666–669
PugsleyA. P.1985; Escherichia coli K12 strains for use in the identification and characterization of colicins. Journal of General Microbiology 131:369–376
PugsleyA. P.,
ReevesP.1976; Characterization of group B colicin-resistant mutants of Escherichia coli K-12: colicin resistance and the role of enterochelin. Journal of Bacteriology 127:2182–228
PugsleyA. P.,
ReevesP.1977; The role of colicin receptors in the uptake of ferrienterochelin by Escherichia coli K-12. Biophysical and Biochemical Research Communications 74:903–911
PugsleyA. P.,
SchnaitmanC. A.1979; Factors affecting the electrophoretic mobility of the major outer membrane proteins of Escherichia coli in polyacrylamide gels. Biochimica et biophysica acta 581:163–178