Figure 5

Effects of representative tau mutations on taurine metabolism and P _tauA expression. (A) S. meliloti Rm1021 wild-type and tau mutants were grown on M9 minimal medium supplemented with 100mM taurine as the sole carbon source. Plate images, captured after 7days of incubation at 30C, are shown on the left, while strain genotypes are shown on the right. Strains used were Rm1021, JOE3844, JOE3846, and JOE3848; plasmids used were pJC478, pJC479, pJC538, and pJC539. (B) Expression of a plasmid-borne P _tauA -uidA reporter was assessed in Rm1021 wild-type and tau mutant backgrounds in PYE rich medium. Strains with reporter plasmids containing or lacking the tauR gene (+ or - p-tauR) were grown in PYE with or without 10mM taurine (+ or - inducer). Error bars represent standard errors. Strains used were Rm1021, JOE3844, JOE3846, and JOE3848; plasmids used were pJC478 and pJC479. Wild-type strains carrying plasmids without the uidA gene (pJC472 or pJC473) exhibited negligible levels of GUS activity (<0.1 Miller units; data not shown). (C, D) Dose-dependent expression of a plasmid-borne P _tauA -mCherry reporter was measured in (C) PYE and (D) M9G media. Strains were grown for 20hours in PYE or M9G supplemented with different concentrations of taurine. Wild type carrying the vector (pBBR1 MCS-2) was used to determine background fluorescence levels. Error bars represent standard errors of the mean of at least five biological samples. Strains used were Rm1021, JOE3844, JOE3846, and JOE3848.