Carbon Dioxide Fixation in Extreme Environment

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Hydrogenovibrio marinus, a fast-growing CO_2-fixing marine bacterium produced significant amount of glycogen in the cells, when grown under the nitrogen limitting condition. The strain was shown to posess 3 RubisCO genes. At least 2 of them were expressed in H.marinus cells.Thermophilic microalgae were isolated from hotspring in Japan and Thailand, and taxonomic studies and improvement of cultivation procedure were achieved on the strains. The RubisCO gene of one of the obtained strains, Synechococcus strain a-1, was cloned and expressed in E.coli cells.Alcalophilic bacteria grown on formic acid were isolated from soil. RubisCO was purified from one of the isolated strains, which was identified as Moraxlla sp. The amino acid sequence of the N-terminal region of the purified RubisCO was similar to that of Alcaligenes eutrophus. But, kinetic studies revealed that Km value for CO_2 of RubisCO from Moraxlla sp.is about 10-fold higher than that from A.eutrophus.Halophilic bacteria, expecially Halofelux strains, were proved to posess distinct ability to fix CO_2 in heterotrophic culture condition.