TABLE 1.
Viable cell number (% initial) upon depletion of carbon substrate (at t = 0) in wild type and in an FeSII− mutant strain of A. vinelandiia
| Medium and strain (% O2) | Mean viable cell no. (±SD) at:
|
||
|---|---|---|---|
| 1.5 h | 3 h | 4.5 h | |
| N-free mediumb | |||
| WT (20) | 108 ± 13 | 129 ± 15 | 138 ± 5 |
| FeSII− (20) | 74 ± 13 | 66 ± 10 | 72 ± 8 |
| WT (40) | 82 ± 8 | 80 ± 14 | 117 ± 23 |
| FeSII− (40) | 64 ± 4 | 44 ± 11 | 39 ± 7 |
| NH4+ medium | |||
| WT (20) | 116 + 6 | 113 ± 9 | 143 ± 4 |
| FeSII− (20) | 136 ± 5 | 152 ± 12 | 142 ± 8 |
| WT (40) | 128 ± 10 | 146 ± 11 | 152 ± 10 |
| FeSII− (40) | 126 ± 11 | 141 ± 6 | 149 ± 7 |
The t = 0 (100%) viable cell numbers (at an OD585 of approximately 0.60 to 0.64) was about the same for the wild type (WT) (2.02 × 106/ml) and the mutant (1.88 × 106/ml). Cultures were grown in 300-ml baffled sidearm flasks with 25 ml of culture media (Burk plus 10 mM sucrose) and were shaken (210 rpm) at 30°C. Ammonium media contained 25 mM ammonium acetate. The plating medium was Burk plus ammonium. Results are the mean ± the standard deviation for five replicate plates.
Statistical analysis (Student t test) of the results for the N-free medium showed that the FeSII− strain values were significantly less (α′ = 0.01, confidence level of 99%) than the wild-type values at all points for the 20% O2 values and for the 3-h and 4.5-h 40% O2 values. The FeSII− strain is significantly less than the wild type at α′ = 0.05 for the 1.5-h 40% O2 values (N-free medium).