Low temperature adaptation of hyperthermophile

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Both Thermococcus and Pyrococcus species belong to the Thermococcales order and share various physiological features. They grow near or above at 100℃ and are strictly anaerobic heterotrophs that utilize a variety of carbon substrates, such as peptides and/or carbohydrates. The unique difference is the growth temperature range. For example, the minimum growth temperatures of Thermococcus spp. (ex. Thermococcus kodakaraensis, 60℃) are generally lower than those of Pyrococcus spp. (P.abyssi, 67℃ ; P.furiosus, 70℃ ; P.horikoshii, 80℃). Thermococcus kodakarensis possesses a single circular genome and 747 genes are unique in T.kodakaraensis that are not identified in Pyrococcus spp. Some of these genes are considered to be involved in low temperature survival in T. kodakaraensis. Transcriptome and proteome studies revealed that some genes are induced specifically at low temperature environment. Among them, we mainly focused on chaperonin CpkA and RNA helicase (Tk0306) and their induction pro … More files were analyzed. The expression of low temperature inducible chaperonin cpkA was regulated at the post-transcriptional level. In contrast, high temperature inducible chaperonin cpkB was regulated at the level of transcription. When we compare promoter sequences of cpkA and cpkB, only slight difference was observed, suggesting that these genes were evolved from the same common ancestor and only cpkA acquired low temperature inducible mechanism in the course of evolution. As for RNA helicase, it was regulated at the level of transcription. RNA helicase showed highest enzymatic activity at 50℃. It is unusual because Tkodakaraensis does not grow at the temperature. The RNA helicase seems functional in T. kodakaraensis only to survival at low temperature environments. Further study is needed to confirm the idea. Besides these two genes, enzymatic characteristics for isopentenyl diphasphate isomerase, glucosamine-6-phosphate deaminase, methylguanine-DNA methyltransferase and homing endnuclasell were examined. Less