Article Figures & Data
Figures
- Fig. 1.
Decomposition of H2O2 by HPI in vitro and in vivo. (A) First-order decomposition of H2O2 by extracts from wild-type (MG1655) and HPI− cells (JI364). (B) Kinetics of decomposition of H2O2 by whole Ahp−HPII− HPI+ (JI372) cells suspended at 0.1 OD.
- Fig. 2.
Decomposition of H2O2 by equivalent amounts of extracellular and intracellular HPI. Extract and whole cells of JI372 (ahpCF katE) were prepared as described in Materials and Methods, and the decomposition of 1.5 μM H2O2 was monitored.
- Fig. 3.
Decomposition of H2O2 by Ahp in vivo. Rates of decomposition were measured in JI367 (Ahp+HPI− HPII−, diamonds). Solid line, curve predicted using JAhp = 2.1 × 10−18 mol/s (Hin) (Hin + 1.2 × 10−6 M). Note that the abscissa displays extracellular H2O2 concentrations; intracellular concentrations can be calculated from them by equation 8. Dashed line, the rate of H2O2 diffusion into the suspended cells, predicted from the permeability coefficient. Since cells can degrade H2O2 no faster than it penetrates them, this line represents the maximum possible rate of H2O2 decomposition.
- Fig. 4.
Catalase-proficient cells have a growth advantage over catalase-deficient cells in a mixed culture. JI372 (ahpCF katE) and JI377 (ahpCF katE katG) were mixed at a 9:1 ratio of JI372 to JI377 and diluted into aerobic minimal glucose CAA medium containing an additional 2 μM H2O2. The number of viable cells of each strain was then monitored by intermittent dilution and plating on selective plates.
Tables
- Table 1.
E. coli strains
Strain Genotype Source or reference MG1655 F−, wild type E. coli Genetic Stock Center JI364 Δ(katG17::Tn10)1(Tets) 16 JI367 As JI364 pluskatE12::Tn10 16 JI372 Δ(katE12::Tn10)1ΔahpCF′ kan::′ahpF 16 JI377 As JI367 plus ΔahpCF′ kan::′ahpF 16 MC4100 araD139 Δ(argF-lac)169λ−flhD5301 fruA25 relA1 rpsL150 rbsR22 deoC1 E. coli Genetic Stock Center MC4100 Δahp As MC4100 plus ΔahpCF′ kan::′ahpF Gisela Storz GS022 As MC4100 plus λRS45 Φ(katG::lacZ) Gisela Storz LC70 As GS022 plus ΔahpCF′ kan::′ahpF 16
