A thermophile under pressure: Transcriptional analysis of the response of Caldicellulosiruptor saccharolyticus to different H2 partial pressures

► Effect of H2 partial pressure on metabolism of Caldicellulosiruptor saccharolyticus was studied. ► High PH2 causes a metabolic shift to lactate and ethanol formation. ► Under high PH2 conditions pathways involved in reductant disposal were upregulated. ► The Rex regulator is involved in the transcriptional response to a high PH2.