Reverse gyrase is not a prerequisite for hyperthermophilic life.

We disrupted the reverse gyrase gene from a hyperthermophilic archaeon, Thermococcus kodakaraensis KOD1. An apparent positive supercoiling activity that was observed in the host strain was not found in the disruptant strain. We found that a lack of reverse gyrase led to a retardation in growth that was more striking at higher temperatures. However, the disruption of the reverse gyrase gene did not lead to a lethal phenotype at 90 degrees C. This study provides experimental evidence that reverse gyrase is not a prerequisite for hyperthermophilic life.