Table 1.

Comparison of production of extracellular products and sensitivity to oxidative stress between the L and S variants

Variant PyocyaninaPyoverdinebElastasecAlginate (mg of uronic acid/mg of protein) Rhamnolipids (mg/mg proteins)H2O2sensitivityd
Stationary-phase cellsLog-phase cells
L0.27 ± 0.02 29,700 ± 2,7002.26 ± 0.27 6.53 ± 0.56 2.01 ± 0.1217.2 ± 0.7 16.4 ± 0.5
S1 0.89 ± 0.0850,000 ± 1,100 1.43 ± 0.10 6.69 ± 0.311.82 ± 0.08 18.3 ± 0.5 23.0 ± 0.6
S1reve 0.23 ± 0.0233,000 ± 1,100NDf ND ND17.0 ± 0.6 16.3 ± 0.5
S2 1.36 ± 0.0448,100 ± 1,800 0.42 ± 0.07 7.15 ± 0.271.58 ± 0.13 18.5 ± 0.5 24.5 ± 1.0
  • a Measured as A 695of the supernatant of a 30-h culture at 37°C in King's A medium.

  • b Measured in the supernatant of a 16-h culture at 37°C in King's B medium. A 460 was determined after excitation at 400 nm and reported as relative fluorescence units.

  • c Measured in ECR assays of culture supernatants from 18-h cultures as described in Materials and Methods and reported as A 495.

  • d Filter paper disks (7-mm diameter) soaked with 10 μl of 30% H2O2 were placed on top of medium A agar plates covered with P. aeruginosa cells. Bacteria from exponential- or stationary-phase cultures in LB at 37°C were used as the inoculum, and the diameter of the zone of inhibited growth was measured after 5 h of incubation at 37°C. All values are means ± standard errors of triplicates.

  • e S1rev is an L variant resulting from the reversion of an S1 variant.

  • f ND, not determined.