Caldococcus
Caldococcus is a genus of Archaea in the order Desulfurococcales. Characteristics Caldococcus are a genus of Archaea found in the class Desulfurococcales. Members of the genus are strictly anaerobic, hyperthermophilic cocci that reduce sulfide and oxidize sulfur. They can be found in hyperthermal vents and hot springs such as those at Yellowstone National Park Species Caldococcus noboribetus Isocitrate Dehydrogenase Research Caldococcus noboribetus genes have been mutated to understand the characteristics of the isocitrate dehydrogenase ancestral protein. The mutant isocitrate dehydrogenase genes contain inferred ancestral sequences that have been expressed in E. coli cells. Expression of these genes resulted in proteins with ancestral amino acid sequences, which provided evidence for relationships with a hyperthermophilic universal ancestor. Thermostabilities of the purified enzymes had greater thermal stabilities than wild-type isocitrate dehydrogenase. This supports a hypothesis that last universal common ancestor was thermophilic or hyperthermophilic. This finding has implications for understanding the evolutionary history of other proteins as well for engineering protein thermostability for experimental or industrial purposes. A gene coding for isocitrate dehydrogenase (ICDH) was cloned from Caldococcus noboribetus and sequenced. An amino acid sequence of ICDH displayed similarities to bacterial ICDH genes found in both Vibrio and E. coli species. Sequences from