Strains | Survival rate (%)B |
|---|
| Â | UV radiation | Heat shock | Desiccation tolerance | SDS exposure | H2O2 exposure | Osmolarity stress | Saline stress |
|---|
306 | 3.2 ± 1.2a | 0.04 ± 0.02a | 2.7 ± 0.7a | 10.1 ± 3.1a | 1.6 ± 0.5a | 4.9 ± 2.3a | 6.1 ± 2.4 a |
223G4 (gpsX-) | 0.9 ± 0.3b | 0.004 ± 0.003b | 0.4 ± 0.1b | 0.05 ± 0.02 b | 0.05 ± 0.02b | 3.8 ± 1.4a | 3.9 ± 2.2 a |
223G4V (gpsX-) | 1.1 ± 0.5b | 0.005 ± 0.003b | 0.7 ± 0.2b | 0.08 ± 0.03 b | 0.12 ± 0.04b | 4.1 ± 1.7a | 5.5 ± 1.7 a |
C223G4 (gpsX+) | 4.2 ± 1.6a | 0.05 ± 0.03a | 3.5 ± 1.3a | 8.2 ± 2.5a | 2.2 ± 0.4a | 5.5 ± 2.4a | 7.4 ± 2.8 a |
- ABacterial cell viability was estimated by plating on NA agar before (T0) and after (T1) the treatment. Percentage survival was calculated as the ratio of viable cell counts at T1 to that at T0. The treatments were applied as follows: for UV radiation, overnight bacterial culture was exposed to short-wave UV irradiation (254 nm) for 20 min; for heat-shock, bacterial culture was incubated at 50°C for 15 min; for desiccation stress, bacterial culture was placed on glass coverslips and air dried in a laminar flow apparatus for 60 min and then resuspended in 0.85% NaCl and plated; for SDS exposure, bacterial culture was treated with 0.1% SDS for 20 min; for sensitivity to hydrogen peroxide, bacterial culture was exposed to 0.03% H2O2 for 20 min; for osmotic stress, bacterial culture was treated with 40% D-sorbitol for 40 min; for saline stress, bacterial culture was treated with 1.0 M NaCl for 20 min. Bacterial cells were serially diluted with NB medium and colony-forming units (cfu) were counted after being cultured on NA plates at 28°C for 48 h. Each test, plated in triplicate, was repeated three times with similar results. B Data shown are means and standard errors of three replicates from one representative experiment. Different letters in each data column indicate significant differences at P < 0.05 (Student's t-test).
