Transcriptional profiling of the hyperthermophilic methanarchaeon <i>Methanococcus jannaschii</i> in response to lethal heat and non‐lethal cold shock

Temperature shock of the hyperthermophilic methanarchaeon Methanococcus jannaschii from its optimal growth temperature of 85 degrees C to 65 degrees C and 95 degrees C resulted in different transcriptional responses characteristic of both the direction of shock (heat or cold shock) and whether the shock was lethal. Specific outcomes of lethal heat shock to 95 degrees C included upregulation of genes encoding chaperones, and downregulation of genes encoding subunits of the H+ transporting ATP synthase. A gene encoding an alpha subunit of a putative prefoldin was also upregulated, which may comprise a novel element in the protein processing pathway in M. jannaschii. Very different responses were observed upon cold shock to 65 degrees C. These included upregulation of a gene encoding an RNA helicase and other genes involved in transcription and translation, and upregulation of genes coding for proteases and transport proteins. Also upregulated was a gene that codes for an 18 kDa FKBP-type PPIase, which may facilitate protein folding at low temperatures. Transcriptional profiling also revealed several hypothetical proteins that respond to temperature stress conditions.