TABLE 2.
Uptake of organic substrates under anaerobic conditions or with oxygen as the electron acceptor by RPAO in the three different WWTP investigated: incubation conditions and results based on MAR investigationsa
| Unlabeled substrate | Radioactive tracer | Electron acceptor | Substrate uptakea by RPAOb
|
||
|---|---|---|---|---|---|
| AAE WWTP | Egaa WWTP | Skagen WWTP | |||
| Formic acid | [1-14C]formic acid | Not added or O2c | − | − | − |
| Acetate | [3H]acetate (Na) | Not added or O2 | + | + | + |
| Acetate | [3H]acetate (Na) | Not added (+IO)d | − | − | − |
| Propionate | [1-14C]propionate (Na) | Not added or O2 | + | + | + |
| Butyrate | [2,3-3H]butyric acid | Not added or O2 | − | − | − |
| Pyruvate | [1-14C]pyruvate (Na) | Not added or O2 | + | + | + |
| Oleic acid | [9,10(n)-3H]oleic acid | Not added or O2 | − | − | − |
| Aspartic acid | d-[2,3-3H]aspartic acid | Not added or O2 | − | ND | ND |
| Glutamic acid | l-[G-3H]glutamic acid | Not added or O2 | + | ND | ND |
| Leucine | [4,5-3H]leucine | Not added or O2 | − | − | − |
| Glycine | [2-3H]glycine | Not added or O2 | − | − | − |
| Thymidine | [methyl-3H]thymidine | Not added or O2 | − | − | − |
| Glucose | d-[2-3H]glucose | Not added | + | + | + |
| Glucose | d-[2-3H]glucose | Not added (+IO) | − | − | − |
| Glucose | d-[2-3H]glucose | O2 | − | − | − |
| Ethanol | [1-3H]ethanol | Not added or O2 | − | − | − |
a
The final concentration of all substrates used was 1.5 mM, except for oleic acid (1.0 mM).
b
+, >95% of RPAO took up radioactive substrate; −, RPAO did not take up radioactive substrate; ND, not determined.
c
Not added indicates anaerobic conditions.
d
IO, iodoacetate added at a final concentration of 200 mg/liter.