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Table 4 Characteristics of Staphylococcus aureus and Bacillus subtilis-based luminescent heavy metal sensors and toxicity control strains

From: A suite of recombinant luminescent bacterial strains for the quantification of bioavailable heavy metals and toxicity testing

  Sensor strains Control strains
  S. aureus RN4220 (pcadCPcadAlux) B. subtilis BR151 (pcadCPcadAlux) S. aureus RN4220 (p602/22lux)a B. subtilis BR151 (pBL1/p602/22lux)b
Background luminescence c 81 ± 30 84 ± 30 750 ± 70 120 ± 40
Maximum induction d 30 4 no induction no induction
No of cells in the test (100 μl) 107 107 107 107
Compound Limit of determinatione/Toxicityf, M (mg of compound l-1) Toxicity (2-h EC50g), M (mg of compound l-1)
HgCl 2 10-8 (0.003)/5 × 10-7 (0.1) 4 × 10-8 (0.01)/5 × 10-7 (0.1) 5 × 10-8 (0.01) 10-7 (0.04)
CdCl 2 4 × 10-8 (0.007)/10-5 (2.75) 10-8 (0.002)/10-7 (0.027) 8 × 10-7 (0.2) 3 × 10-6 (0.6)
ZnSO 4 h 2 × 10-5 (3.2)/5 × 10-4 (81) 10-5 (1.6)/10-4 (24) 8 × 10-5 (13) 10-4 (22)
Pb(NO 3 ) 2 10-7 (0.03)/10-3 (500) 10-7 (0.03)/10-3 (500) 10-3 (530) 3 × 10-3 (990)
  1. a control for RN4220(pcadCPcadAlux)
  2. b control for BR51(pcadCPcadAlux)
  3. c luminescence (relative light units, RLU) of 100 μl of bacterial suspension before the test as measured by plate luminometer Fluoroskan (ThermoLabsystems). Average of at least three assays.
  4. d as fold over the (non-induced) background
  5. e see equation 4 in Methods
  6. f the lowest tested concentration causing a measurable decrease in the bioluminescence of the sensor strains (read from concentration-induction curves in Figure 1)
  7. g concentration causing 50% decrease in the bioluminescence production (calculated from Figure 2)
  8. h tested as ZnSO4 × 7H2O