総説
海底熱水系における生物活動の指標としてのアミノ酸
キーワード:
sub-seafloor,
hydrothermal condition,
hydrothermal experiment,
decomposition,
synthesis,
dehydration
2008 年 42 巻 2 号 p. 43-53
詳細
2008 年 42 巻 2 号 p. 43-53
Geochemical studies on amino acids (AAs) in hydrothermal system and laboratory are reviewed to examine the reliability and applicability of AAs as indicator of bioactivity under sub-seafloor extreme environment. AA analyses of the sediment cores revealed the presence of AAs and the change of AA compositions by microbial mediated decarboxylation in sub-seafloor around the hydrothermal vents. Isomer (D/L) ratios indicated the AAs were biologically formed in the hydrothermal fluids and sediments, although the allochthonous AAs are possibly supplied from ambient sediment through pore water. The AAs were decomposed in water solution and sediment with increasing temperature higher than 100℃. However, laboratory experiment showed that the AAs could be inorganically synthesized under present hydrothermal condition, and were continuously dehydrated to form peptide at temperatures between 100 and 200℃. The AAs were well preserved in the conditions containing silica and clay minerals, presumably due to restriction for dissolution and decomposition of AAs at high temperature, although its mechanism is not clear.
