TABLE 2.
Requirements for production of the red chromophores
| Conditions | Red pellet |
|---|---|
| Completea | + |
| −tnaA | − |
| −tnaB | − |
| −narG | − |
| −nirB | + |
| +O2b | − |
| −NO3− | − |
| 20 mM NO3− | + |
| −NO3− + 20 mM NO2− | − |
| +0.1 M 3-(N-morpholino)propanesulfonic acid/NaOH buffer (pH 7.8) | − |
| Tryptophan-free mediumc | − |
| +tryptophan (0.5 mM) | + |
| +indole (0.5 mM) | + |
a
Cultures were grown to saturation at 37°C in sealed, filled tubes using an initial concentration of 100 to 200 cells/ml. After 20 h the cultures were centrifuged, and the pellets were observed. The complete conditions for chromophore production included a tna+ strain (RV) grown anaerobically in glycerol-fumarate medium containing 100 mM NaNO3. Additional strains used were BW2018 (tnaA), BW2019 (tnaB), BW2020 (narG), and JCB387 (nirB).
b
The culture was aerated by shaking in an open flask.
c
Vitamin assay Casamino Acids (Difco) was substituted for tryptone and yeast extract in the growth medium.