11:00 AM - 1:00 PM
[BBG01-P05] The exploration of C25-C20 archaeol isomer in halophilic archaea especially living in high salt concentration
Keywords:halophilic archaea, ether lipid, archaeologists, high salinity environment
The exploration of C25-C20 archaeol isomer in halophilic archaea especially living in high salt concentration
Archaea has a characteristic lipid-core, archaeol(1). Further, a characteristic diether lipid-core (C20-C25 diether (2), extended archaeol) 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 in the lipid-core of several halophilic archaea isolated from very high salt concentration[2]. On the other hands, existence of regioisomer 3 were shown in halite from Spain[3].
In my study, chemically synthesized unsaturated diether were different from those of Dawson’s unsaturated diether, the existence of the regioisomeric mixture were strongly suggested[4]. And the chemical synthesis of 2 and 3 revealed diether in halite is the mixture of 2 and 3[5].
Although 2 and 3 are regioisomer of the ether on the glyccerol, it has always been assumed that only 2 exists in cultured microorganisms[6]. I am investigating whether 3 really does not exist in microorganisms, and whether it is possible to analyze in detail the existence and structure of unsaturated compounds produced by the producing bacteria, by culturing and analyzing strains isolated from high salt concentration field and rock salt obtained at the RIKEN BRC[7]. We will report here on the progress. About the the preparation of lipid core, alkaline hydrolysis of polar head group used by the preparation of hydroxyarchaeol[8] were adopted instead of acid hydrolysis usually performed and showed the divirsity of unsaturtion of archaeol derivative in each halophilic archaea species.
There is a major problem here: in most cases, lipid cores undergo acidic hydrolysis, where ether compounds may be hydrolyzed. Model compound 4, which has one double bond, was prepared and hydrolyzed to produce monoethers. This indicates the importance of alkaline hydrolysis. As for the coexistence of 2 and 3, based on the results of the halite [3] (which probably exists to an equal extent), it seems that more micororgamism should be exisited producting isomers of 3, but there is currently only one species in which 3 is the main component. However, minor contents of 3 are existed in the several species. The search for strains that clearly contain 3 will continue and the results will be reported. The decomposition rate of 3 (and 2) and the possibility of isomerization will be investigated using chemically synthesized reference compound 2 and 3.
[1] De Rosa et al., J. Gen Microbiol (1982) 265: 343. [2] Dawson et al., Org Geochem (1982) 48: 1. [3] Teixidor et al., Geochem Cosmochim Acta (1993) 57: 4479. [4] Yamauchi, (2019) JpGU meeting 2019, BBG02-P03. [5] Yamauchi, Res Org Geochem (2019) 35: 1. [6] Morita et al., Biosci.Biotechnol. Biochem. (1998) 62: 596. [7] Yamauchi, JpGU meeting 2020 (2020), BBC02-P05. [8] Sprott et al., J Biol Chem (1990) 265: 13735.
Archaea has a characteristic lipid-core, archaeol(1). Further, a characteristic diether lipid-core (C20-C25 diether (2), extended archaeol) 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 in the lipid-core of several halophilic archaea isolated from very high salt concentration[2]. On the other hands, existence of regioisomer 3 were shown in halite from Spain[3].
In my study, chemically synthesized unsaturated diether were different from those of Dawson’s unsaturated diether, the existence of the regioisomeric mixture were strongly suggested[4]. And the chemical synthesis of 2 and 3 revealed diether in halite is the mixture of 2 and 3[5].
Although 2 and 3 are regioisomer of the ether on the glyccerol, it has always been assumed that only 2 exists in cultured microorganisms[6]. I am investigating whether 3 really does not exist in microorganisms, and whether it is possible to analyze in detail the existence and structure of unsaturated compounds produced by the producing bacteria, by culturing and analyzing strains isolated from high salt concentration field and rock salt obtained at the RIKEN BRC[7]. We will report here on the progress. About the the preparation of lipid core, alkaline hydrolysis of polar head group used by the preparation of hydroxyarchaeol[8] were adopted instead of acid hydrolysis usually performed and showed the divirsity of unsaturtion of archaeol derivative in each halophilic archaea species.
There is a major problem here: in most cases, lipid cores undergo acidic hydrolysis, where ether compounds may be hydrolyzed. Model compound 4, which has one double bond, was prepared and hydrolyzed to produce monoethers. This indicates the importance of alkaline hydrolysis. As for the coexistence of 2 and 3, based on the results of the halite [3] (which probably exists to an equal extent), it seems that more micororgamism should be exisited producting isomers of 3, but there is currently only one species in which 3 is the main component. However, minor contents of 3 are existed in the several species. The search for strains that clearly contain 3 will continue and the results will be reported. The decomposition rate of 3 (and 2) and the possibility of isomerization will be investigated using chemically synthesized reference compound 2 and 3.
[1] De Rosa et al., J. Gen Microbiol (1982) 265: 343. [2] Dawson et al., Org Geochem (1982) 48: 1. [3] Teixidor et al., Geochem Cosmochim Acta (1993) 57: 4479. [4] Yamauchi, (2019) JpGU meeting 2019, BBG02-P03. [5] Yamauchi, Res Org Geochem (2019) 35: 1. [6] Morita et al., Biosci.Biotechnol. Biochem. (1998) 62: 596. [7] Yamauchi, JpGU meeting 2020 (2020), BBC02-P05. [8] Sprott et al., J Biol Chem (1990) 265: 13735.