TABLE 1.
Phenotypic characteristics of R. sphaeroides cultures in Sistrom's medium supplied with 1% initial O2 and 1 mM nitrite or nitrate during 40 h of incubation at 30°Ca
| Strain | Added NOx | Initial [O2] (%) | [NO]max (nM) | Δtstart-N depl (h) | μNOx (h−1) | End FN2O |
|---|---|---|---|---|---|---|
| 2.4.3 | NO3− | 0 | 276 ± 44 | 27 ± 1 | 0.09 ± 0.03 | 1 |
| 1 | 16 ± 1 | 18 ± 2 | 0.16 ± 0.05 | 1 | ||
| NO2− | 0 | 75 ± 3 | 13 ± 2 | >0d | 1 | |
| 1 | 38 ± 1 | 15 ± 2 | >0d | 1 | ||
| 2.4.3 ΔnorEF | NO3− | 0 | 823 ± 240 | ∼40 | 0.027 ± 0.002 | 1 |
| 1 | 5 ± 1 | 35 ± 2 | ≤0 | 1 | ||
| NO2− | 0 | 5,846 ± 4,211 | >40 | ≤0 | 0.057 ± 0.065 | |
| 1.5 | 4,179 ± 3,821 | >40 | ≤0 | 0.192 ± 0.139 | ||
| 2.4.1 pAK1b | NO3− | 0 | 245 ± 9 | >40 | ≤0 | 0.158 ± 0.008 |
| 1 | 2 ± 1 | >40 | ≤0 | 0.523 ± 0.069 | ||
| NO2− | 0 | 14,745 ± 1,011 | >40 | ≤0 | 0.004 ± 0.001 | |
| 1 | 3,230 ± 1,604 | >40 | ≤0 | 0.012 ± 0.002 | ||
| 2.4.1 pAK1 + norEFb | NO3−c | 1 | 37 ± 44 | >40 | ≤0 | 0.157 ± 0.013 |
| NO2−c | 1 | 236 ± 85 | 27 ± 1 | 0.06 ± 0.02 | 1 |
[NO]max is the maximum measured concentration of either transiently accumulated NO or NO still increasing at the end of an incubation. Δtstart-N depl is the time from inoculation to nitrate or nitrite depletion (100% recovery as N2O). μNOx is apparent anoxic growth rates based on electron flow kinetics. R. sphaeroides usually initiates denitrification long before O2 is depleted; thus, μNOx as estimated represents a combination of anoxic growth and recruitment of cells to denitrification while still respiring O2. μNOx of ≤0 indicates nearly constant or slightly declining rates of denitrification after O2 depletion. End FN2O is the fraction of added NOx recovered as N2O at t = 40 h. The values given are averages from 2 or 3 replicates ± standard deviations.
norEF deficient.
Two mM initial nitrate or nitrite.
Depletion was too fast to estimate growth rate (Fig. 1).