Changes in the Microbial Community of Japan Trench Sediment from a Depth of 6292 m under Environmental Pressure and Atmospheric Pressure, Using the DEEP-BATH System
Miki YANAGIBAYASHI*, Chiaki KATO, Lina LI, Yuichi NOGI, Tetsuya INADA, Kiyoshi TAIRA, Toshio KIKUMA, Kimio SUZUKI, and Koki HORIKOSHI
The DEEPSTAR Group, Japan Marine Science and Technology Center, 2-15 Natsushima-cho, Yokosuka, 237 Japan
The DEEP-BATH system (deep-sea baro/thermophiles collecting and cultivating system) constructed by JAMSTEC (1) is very useful for cultivating microorganisms at high pressures and high temperatures. We have reported the pressure and temperature effects on growth of the newly isolated deep-sea hyperthermophiles, Thermococcus peptonophilus (2) and Pyrococcus horikoshii (3), and identified that both of them show barophilic properties at higher temperatures (2-4). This system also contains a pressure retaining sampler which can maintain environmental pressure and temperature after sampling at the deep-sea bottom (1). In this study, we have analyzed changes in the microbial community of Japan Trench sediment obtained by the pressure retaining sampler (Shinkai 6500 dive #373, sampling point: inside of deep-sea fissure depth 6292 m, about 65 MPa), during cultivation without decompression (65 MPa) and at atmospheric pressure.
Cultivation was repeated five times at 65 MPa without decompression, and at atmospheric pressure, in marine broth 2216 medium using the cultivation chamber of the DEEP-BATH system. After cultivation, mixed cells were harvested and DNA was extracted from them. Bacterial 16S rRNA genes were amplified by PCR from the extracted DNA, and amplified DNAs were cloned and sequenced. The results indicated that: i) from 65 MPa cultivation, bacterial strains belonging to the Shewanella barophiles branch (5) and the genus Moritella existed together at the beginning of cultivation, and Moritella strains became dominant towards the end of cultivation, ii) from atmospheric pressure cultivation, strains belonging to the genus Pseudornonas were dominant at all times. We have also undertaken fatty acid analysis of the mixed cultivated cells, the results showed that the amount of icosapentaenoic acid (IPA, 20:5) which was observed in strains belonging to the Shewanella barophiles branch was decreasing, and the amount of docosahexaenoic acid (DHA, 22:6) which was observed in the genus Moritella was increasing during high pressure cultivation. This latter result corresponds to be changed the 16S rRNA analysis. In conclusion, a
