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Japanese extremophile, O. iheyensis, from the deep sea

In 1998, Japanese researchers discovered a previously unknown organism in mud taken from the deep sea near Okinawa, Japan. It soon became clear they had stumbled upon a new species in a new genus, and they named the organism Oceanobacillus iheyensis—or 'small ocean bacillus pertaining to the Iheya Ridge.'

Japanese researchers discovered O. iheyensis at a depth of 1050 m.

Now, this extremely salt-tolerant and alkaliphilic organism has been sequenced. Hideto Takami, of the Japan Marine Science and Technology Center in Kanagawa, led the study.

The researchers discovered that O. iheyensis has at least 29 'proteolytic' enzymes, which can be used as additives in laundry detergent. "This number is higher than Bacillus subtilis and Bacillus halodurans," says Takami. "So, I think that O. iheyensis may have industrial applications."

By looking at the genome sequence, Takami's team identified about 3,500 genes, of which 243 are shared only between the two other alkaliphiles. They also discovered genes that help the organism adapt to the highly saline and alkaline environment.

"The genomic sequence of O. iheyensis should facilitate the study of the model transport systems in alkaliphiles and extremely halotolerant bacteria," says Takami. Comparing several sequenced species may provide clues as to how organisms adapt to extreme environments and withstand stress.

With 3.6 million base pairs, the O. iheyensis genome is almost the same size as the other two sequenced Bacillus species, B. halodurans and B. subtilis, the researchers report in Nucleic Acids Research.

The researchers were surprised to find that O. iheyensis grows at depths of up to 3,000 m. The bacteria thrive under high hydrostatic pressure and grow optimally at about 30 degrees Celsius.

Comparison to another salt-loving microbe, called Halobacterium, revealed that the two organisms adapt in different ways to hypersaline environments. Halobacterium requires sodium ions, but O. iheyensis does not, according to Takami.

Takami and his team will use the sequence to prepare a DNA chip to analyze all the O. iheyensis genes. They will focus on how the genes function in hypersaline and moderate saline conditions, and also in alkaline and neutral conditions.

For more information on the O. iheyensis genome project, visit ExtremoBase.

See related GNN article
»Some like it salty: Halobacterium genome sequenced

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Takami, H. et al. Genome sequence of Oceanobacillus iheyensis isolated from the Iheya Ridge and its unexpected adaptive capabilities to extreme environments. Nucleic Acids Res 30, 3927-3935 (September 15, 2002).

Lu, J. et al. Oceanobacillus iheyensis gen. nov., sp. nov., a deep-sea extremely halotolerant and alkaliphilic species isolated from a depth of 1050 m on the Iheya Ridge. FEMS Microbiol Lett 205, 291-297 (December 18, 2001).

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