Table 2.
Comparison of characteristics of sulfate-reducing isolates from IODP Site U1301: temperature range of growth, morphology, substrate utilization, and alternative electron acceptors.
| Isolated strain | P20 | P23 | P18 |
|---|---|---|---|
| Closest relative in GenBank | Desulfovibrio aespoeensisT | Desulfovibrio indonesiensisT | Desulfotignum balticumT |
| Sediment depth (mbsf) | 1.30 | 260.43 | 260.43 |
| Trange | 20–35°C | 10–48°C | 4–48°C |
| Topt | 25°C | 25–35°C | 25–35°C |
| Morphology | Highly motile, thin, vibrio like, spirilloid cells, 3.8 μm (±0.9 μm) long, 0.4 μm (±0.1 μm) thick | Motile, vibrio shaped cells, 2.7 μm (±0.4 μm) long, 0.7 μm (±0.1 μm) thick | Non-motile, short thick rods with rounded ends, 2.3 μm (±0.4 μm) long, 1.0 μm (±0.1 μm) thick |
| ELECTRON DONORS AND SUBSTRATES IN THE PRESENCE OF SULFATE | |||
| H2, CO2 + acetate (1 mM) | + | + | +** |
| H2, CO2 (excess) | − | +* | +** |
| Acetate (5 mM) | − | − | (+) |
| Benzoate (2.5 mM) | − | − | + |
| Betaine (2 mM) | n.t. | − | + |
| Butanol (5 mM) | − | + | + (No H2S) |
| Butyrate (5 mM) | − | − | (+) |
| Ethanol (5 mM) | − | + | − |
| Formate (5 mM) | + | + | (+) Slow |
| Fumarate (5 mM) | − | + | + |
| Lactate (5 mM) | + | + | + |
| Propanol (5 mM) | − | (+) | − |
| Pyruvate (5 mM) | − | + | + |
| Succinate (5 mM) | − | − | (+) Slow |
| FERMENTATION | |||
| Ethanol (5 mM) | − | (+) Slow | (+) Slow |
| Betaine (2 mM) | n.t. | n.t. | + |
| Pyruvate (5 mM) | (+) | + | − |
| ELECTRON ACCEPTORS*** | |||
| Sulfate (28 mM) | + | + | + |
| Sulfite (10 mM) | + | + | + |
| Thiosulfate (10 mM) | + | + | + |
| Fe(III) hydroxide (∼40 mM) | − | (+) | (+) |
| Mn(IV) (20 mM) | − | (+) | (+) |
+, Substrate used for growth as indicated by turbidity increase and production of H2S in the presence of sulfate, sulfite, or thiosulfate; (+), poor growth, no turbidity increase, but significant production of H2S, in the presence of sulfate; −, no growth; n.t., not tested.
*Even in absence of vitamins and resazurin as redox-indicator; **In presence of vitamins only.
***In presence of N2/CO2 or H2/CO2 and lactate or ethanol.
The culture medium contained 28 mM sulfate as electron acceptor. For fermentation tests and utilization of alternative electron acceptors, a sulfate-free culture medium was used. No strain grew on amino acid mix (1 mM), glucose (5 mM), malate (5 mM), methanol (5 mM), propionate (2 mM), or yeast extract (0.005% v/v). None of the strains fermented malate (5 mM) or used nitrate (10 mM) as alternative electron acceptor.