Biochemical, Transcriptional and Translational Evidences of the Phenol-<i>meta</i>-Degradation Pathway by the Hyperthermophilic <i>Sulfolobus solfataricus</i> 98/2

<div><p>Phenol is a widespread pollutant and a model molecule to study the biodegradation of monoaromatic compounds. After a first oxidation step leading to catechol in mesophilic and thermophilic microorganisms, two main routes have been identified depending on the cleavage of the aromatic ring: <i>ortho</i> involving a catechol 1,2 dioxygenase (C12D) and <i>meta</i> involving a catechol 2,3 dioxygenase (C23D). Our work aimed at elucidating the phenol-degradation pathway in the hyperthermophilic archaea <i>Sulfolobus solfataricus</i> 98/2. For this purpose, the strain was cultivated in a fermentor under different substrate and oxygenation conditions. Indeed, reducing dissolved-oxygen concentration allowed slowing down phenol catabolism (specific growth and phenol-consumption rates dropped 55% and 39%, respectively) and thus, evidencing intermediate accumulations in the broth. HPLC/Diode Array Detector and LC-MS analyses on culture samples at low dissolved-oxygen concentration (DOC = 0.06 mg.L⁻¹) suggested, apart for catechol, the presence of 2-hydroxymuconic acid, 4-oxalocrotonate and 4-hydroxy-2-oxovalerate, three intermediates of the <i>meta</i> route. RT-PCR analysis on oxygenase-coding genes of <i>S. solfataricus</i> 98/2 showed that the gene coding for the C23D was expressed only on phenol. In 2D-DIGE/MALDI-TOF analysis, the C23D was found and identified only on phenol. This set of results allowed us concluding that <i>S. solfataricus</i> 98/2 degrade phenol through the <i>meta</i> route.</p>