|Oxygen uptake rates in the hyperthermophilic anaerobe Thermotoga maritima grown in a bioreactor under controlled oxygen exposure: clues to its defence strategy against oxidative stress. |
(Article) Publié: Archives Of Microbiology, vol. 193 p.429-38 (2011)
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A 2.3-L bioreactor was specially adapted to grow hyperthermophilic microorganisms under controlled conditions of temperature, pH, redox potential and dissolved O(2). Using this bioreactor regulated at 80°C and pH 7.0, we demonstrated that Thermotoga maritima recovered its growth despite being exposed to oxygen for a short time (30 min with a maximum concentration of 23 μM of dissolved oxygen). Under these conditions, we demonstrated that O(2) uptake rate, estimated at 73.6 μmoles O(2) min(-1) g proteins(-1) for dissolved oxygen, was optimal and constant, when dissolved oxygen was present in a range of 22-5 μM. Transcription analyses revealed that during short oxygen exposure, T. maritima expressed genes coding for enzymes to deal with O(2) and reactive oxygen species (ROS) such as peroxides. Thus, genes encoding ROS-scavenging systems, alkyl hydroperoxide reductase (ahp), thioredoxin-dependent thiol peroxidase (bcp 2) and to a lesser extent neelaredoxin (nlr) and rubrerythrin (rbr), were found to be upregulated during oxygen exposure. The oxygen reductase FprA, homologous to the rubredoxin-oxygen oxidoreductase (ROO) found in Desulfovibrio species, is proposed as a primary consumer of O(2) in T. maritima. Moreover, the expression of frpA was shown to depend on the redox (Eh) level of the culture medium.