Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Evening Poster

B (Biogeosciences) » B-BG Biogeosciences & Geosphere-Biosphere Interactions

[B-BG03] Microbial ecology in earth and planetary sciences

Wed. May 23, 2018 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Michinari Sunamura(University of Tokyo Dept. of Earth & Planetary Science), Natsuko Hamamura(Kyushu University), Keisuke Koba(京都大学生態学研究センター, 共同), Yuki Morono(Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology)

[BBG03-P08] The structure determination of unsaturated archaeol derivatives characteristic for the halophilic archaea lipid-core

*Noriaki YAMAUCHI1 (1.Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University)

Keywords:archaea, halophilic, ether lipid, structure determination

Archaea has a characteristic lipid-core, archaeol. Further, a characteristic diether lipid-core (C20-C25 diether (1)) which is constructed from one C25 and one C20 isoprenoid is produced by halophilic archaea[1]. Recently, Dawson et al. showed the existence of several unsaturated isoprenoid diethers (such as tentative structure 2) in the lipid-core of several halophilic archaea which was incubated with very high salt concentration[2].
Then, 2 were chemically synthesized according to the reported method[3] and the comparison of the mass spectrum of trimethylsilyl (TMS) ether were presented previously at this meeting[4]. 2 is apparently different from those of Dawson’s unsaturated diether.
About these unsymmetrical diether, 1) the “real” structure of Dawson’s unsaturated archaeol derivative were assumed to the structure 3 or 4 from the intermediate of biosynthesis of tetraether lipid in thermophilic archaea[5], 2) 5, the resioisomer of 2 about the unsaturated ther bond linked at the glycerol 5 has the possibility of Dawson’s unsaturated diether because of the relation of hydroxyarchaeol in the methanogenic archaea. Then, the chemical synthesis and mass fragmentation analysis of the 4 isomer (2 to 5) was completed.
The comparison and analysis of the mass spectrum of TMS ether was conducterd for the 4 compound. The structure 2 and 5 is different from the “Dawson’s unsaturated diether”. The srtucture 3 and 4 are relatively similar compared with the structure 2 and 5, however, difference of the Dawson’s diether were observed. So, the all of the supoposed four structure were not the real structure. Dawson's unsaturated diether does not have a double bond at the methyl group branching position resulting from the usual isoprenoid biosynthesis (e.g. phytol), probably unsaturation is formed after the saturated isoprenoid formation. Or, it is a a mixture of 3 and 4 (including further double bond isomers).

[1] De Rosa et al., J. Gen. Microbiol., 128, 343 (1982). [2] Dawson et al. Org. Geochem., 48, 1 (2012). [3] Yamauchi Res. Org. Geochem., 29, 71 (2013). [4] Yamauchi (2016) JpGU meeting 2016 BA001-P05. [5] Nemoto et al. (2003) Extremophiles, 7, 235.