Summary The Salmonella ugd gene is required for the incorporation of 4-aminoarabinose in the lipopolysaccharide and resistance to the antibiotic polymyxin B. Transcription of the ugd gene is induced by via the PmrA -- PmrB by low Mg2 + in a process .
Summary The Salmonella ugd gene is required for the incorporation of 4-aminoarabinose in the lipopolysaccharide and resistance to the antibiotic polymyxin B. Transcription of the ugd gene is induced by via the PmrA -- PmrB two-component system + in a process .
Other known PmrA-activated genes were not present , including pmrE ( ugd ) , other genes of the pmrHFIJKLM operon , dgoA [ 34 ] , or the more recently identified PmrA-activated genes found by in silico analyses [ 35 ] .
Other known PmrA-activated genes were not present , including pmrE ( ugd ) , other genes of the pmrHFIJKLM operon , dgoA [ 34 ] , or the more recently identified PmrA-activated genes found by in silico analyses [ 35 ] .
On the other hand , neither Ca2 + nor Co2 + , K + , Ni2 + , Zn2 + , Mn2 + , Cu2 + , Ga3 + or Ru3 + ( at concentrations of up to 1 mM ) could induce PmrA-activated genes ( Wosten et al. , 2000 ) or kill the DpmrC ugd pmrG triple mutant ( data not shown ) .
Inactivation of the PmrA-activated genes mediating the modification of the two lipid-A phosphates and the Hep ( II ) phosphate in the core region resulted in a strain ( i.e. the DpmrC ugd pmrG triple mutant ) that was as susceptible to Fe ( III ) as the DpmrAB mutant ( Table 1 ) and that bound more iron than the wild-type strain ( Fig. 1B ) .
DpbgE2 DpbgE3 pbgP Ugd DpbgE2/vector DpbgE2/ppbgE2 DpbgE3/vector DpbgE3/ppbgE3 pbgPDpbgE2 pbgPDpbgE3 ugdDpbgE2 ugdDpbgE3 DpmrAB/vector DpmrAB/ppmrAB DpmrAB/vector DpmrAB/ppbgE2 DpmrAB/ppbgE3 DpmrAB/ppbgE2E3 DpmrG DpmrC DpbgPE Dugd DyibD DpbgPE pmrC ugd pmrG yibD DpmrC ugd pmrG yibD DpmrC ugd DpmrC pmrG DpmrC yibD DyibD ugd DyibD pmrG Dugd pmrG DpmrC ugd yibD DpmrC pmrG yibD Dugd pmrG yibD DpmrC ugd pmrG pmrA505DpmrC ugd pmrG DpmrC ugd pmrG/vector DpmrC ugd pmrG/ppmrC DpmrC ugd pmrG/pugd DpmrC ugd pmrG/ppmrG DpmrG pbgPE DpmrC pbgPE DpmrC pbgPE pmrG The PmrA-activated ugd , pbgP , pmrC and pmrG genes are required for Fe ( III ) resistance To examine whether the pmrG and pmrC genes are necessary for Fe ( III ) resistance , we constructed strains deleted for the chromosomal copies of these genes ( see Experimental procedures ) .
DpbgE2 DpbgE3 pbgP Ugd DpbgE2/vector DpbgE2/ppbgE2 DpbgE3/vector DpbgE3/ppbgE3 pbgPDpbgE2 pbgPDpbgE3 ugdDpbgE2 ugdDpbgE3 DpmrAB/vector DpmrAB/ppmrAB DpmrAB/vector DpmrAB/ppbgE2 DpmrAB/ppbgE3 DpmrAB/ppbgE2E3 DpmrG DpmrC DpbgPE Dugd DyibD DpbgPE pmrC ugd pmrG yibD DpmrC ugd pmrG yibD DpmrC ugd DpmrC pmrG DpmrC yibD DyibD ugd DyibD pmrG Dugd pmrG DpmrC ugd yibD DpmrC pmrG yibD Dugd pmrG yibD DpmrC ugd pmrG pmrA505DpmrC ugd pmrG DpmrC ugd pmrG/vector DpmrC ugd pmrG/ppmrC DpmrC ugd pmrG/pugd DpmrC ugd pmrG/ppmrG DpmrG pbgPE DpmrC pbgPE DpmrC pbgPE pmrG The PmrA-activated ugd , pbgP , pmrC and pmrG genes are required for Fe ( III ) resistance To examine whether the pmrG and pmrC genes are necessary for Fe ( III ) resistance , we constructed strains deleted for the chromosomal copies of these genes ( see Experimental procedures ) .
Furthermore , a strain deleted for of all three pmrC , ugd and pmrG genes and harbouring the pmrA505 allele , which encodes a PmrA protein that promotes transcription of PmrA-activated genes even under noninducing conditions ( Kox et al. , 2000 ) , was as susceptible to Fe ( III ) as the DpmrAB mutant ( Table 1 ) .
Synthesis of Ara4N and addition to the lipid-A is mediated by the Salmonella PmrA-activated genes pmrE ( also known as ugd ) and pmrHFIJKLM ( the pmrH operon , also known as the pbgP or arn operon ) ( Gunn et al. , 2000 ) .
This is because inactivation of lpxT hindered the generation of lipid-A singly substituted with pEtN or L-Ara4N ( Figure 3E ) , and it eliminated the increased Fe3 + association to the bacterial cell and transcription of PmrA-activated genes displayed by pmrR and ugd mutants ( Figures 4A , 4D-E and 5D-F ) .
To test this hypothesis , we determined the β2 galactosidase activity produced by strains harboring chromosomal lac transcriptional-fusions to the PmrA-activated pbgP operon and ugd gene .
Deletion of the ugd gene in these mutant strains further enhanced mRNA levels of PmrA-activated genes ( Figures 5A and 5B ) .