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2,6,10,15,19-Pentamethylicosenes in bombayensis, a marine methanogenic archaeon, and in Methanosarcina mazei VanderMaarel, MJEC; Huber, R; Damste, JSS; Sinninghe Damsté, Jaap S.

Published in: Organic Geochemistry

DOI: 10.1016/S0146-6380(97)00011-9

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Citation for published version (APA): VanderMaarel, MJEC., Huber, R., Damste, JSS., & Sinninghe Damsté, J. S. (1997). 2,6,10,15,19- Pentamethylicosenes in Methanolobus bombayensis, a marine methanogenic archaeon, and in Methanosarcina mazei. Organic Geochemistry, 26(5-6), 409-414. https://doi.org/10.1016/S0146- 6380(97)00011-9

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Download date: 12-11-2019 Org. Geochem. Vol, 26, No. 5/6, pp. 409--414, 1997 Pergamon © 1997 Elsevier Science Ltd All rights reserved. Printed in Great Britain PII: S0146-6380(9"/)00011-9 0146-6380/97 $17.00 + 0.00

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2,6,10,15,19-Pentamethylicosenes in Methanolobus bombayensis, a marine methanogenic archaeon, and in Methanosarcina mazei

STEFAN SCHOUTEN', MARC J. E. C. VAN DER MAAREL 2, ROBERT HUBER 3 and JAAP S. SINNINGHE DAMSTI~ ~ JDepartment of Marine Biogeochemistry and Toxicology, Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands, ~Department of Microbiology, Centre for Ecological and Evolutionary Studies, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands and 3Lehrstuhl ffir Mikrobiologie, University of Regensburg, Universit/itstrasse 31, D-93053 Regensburg, Germany

(Received 3 January 1997; returned to author for revision 3 February 1997," accepted 6 February 1997)

Abstract--2,6,10,15,19-Pentamethylicosenes(PMEs) containing three to five double bonds have been found in the methanogenic Methanosarcina mazei (DSM 3338), a strain isolated from sewage sludge, and in Methanolobus bombayensis (OCM 438), a non-extremophilic archaeon isolated from a marine sediment. This finding gives additional support for the use of compounds with the PME carbon skeleton as markers for methanogenic activity in marine environments. © 1997 Elsevier Science Ltd

Key words--2,6,10,15,19-pentamethylicosane, methanogenic archaea, Methanolobus bombayensis, Methanosarcina mazei, archaeal biomarkers

INTRODUCTION (strain AH) indeed biosynthesizes C25 isoprenoid Steroids and hopanoids are specific biomarkers for alkenes with one to two double bonds but possesses eukaryotes and prokaryotes, respectively (e.g. the 2,6,10,14,18-pentamethylicosane carbon skeleton Ratledge and Wilkinson, 1989). Biomarkers for the (IV). The reason for these contradictory findings is third domain of life, archaea, include ether-linked unclear and may be due to the use of different lipids with isoprenoid side chains such as phytanyl strains of Methanobacterium thermoautotrophicum (I) and biphytanyl (II) (e.g. de Rosa and or different culture conditions. However, the meso- Gambacorta, 1988). These compounds have been philic methanogenic archaeon Methanosarcina bar- encountered frequently in hypersaline sediments, keri, which is considered to be predominantly a where they have been attributed to halophilic freshwater (Maestrojuan et al., 1992) but archaea (e.g. Teixidor et al., 1993), and in lacustrine which can also live under more saline conditions sediments, where they have been attributed to (Sowers and Gunsalus, 1988), was unambiguously methanogenic archaea (e.g. Pauly and van Vleet, shown to biosynthesize PME (Holzer et al., 1979; 1986). Risatti et al., 1984). Holzer et al. (1979) also Another compound considered to be a biomarker reported the tentative identification of pentamethyli- for methanogenic archaea is the irregular tail-to-tail cosenes in low amounts in Methanobacteriurn rumi- isoprenoid 2,6,10,15,19-pentamethylicosane (PME*, nantium, a methanogenic archaeon isolated from III; Brassell et al., 1981). This assumption was based bovine rumen, and Methanococcus vannielii, a meso- on the identification of PME and 2,6,10,15,19-penta- philic methanogenic archaeon. methylicosanes with one to four double bonds in PME (III) is frequently encountered in the mar- several , including the thermophilic ine water column (e.g. Wakeham, 1990) and in mar- methanogenic archaeon Methanobacterium thermo- ine sediments (e.g. Brassell et al., 1981; Kohnen et autotrophicum (Holzer et al., 1979; Tornabene et al., al., 1992). In these environments its origin remains 1979). However, Risatti et al. (1984) showed, using unclear since organisms which biosynthesize PME, authentic standards, that this thermophilic archaeon and commonly live under non-extreme marine con- ditions, have not yet been conclusively identified. The stable carbon isotopic composition of PME is *Earlier literature refer to this compound as 2,6,10,15,19- ntamethyleicosane. However, IUPAC rules are now sometimes similar to that of photoautotrophic bio- re'nt bui" for reason of compatibility the acronym markers (Kohnen et al., 1992; Freeman et al., PME is still used. 1994), which suggests an origin other than from OO 26/5-6~E 409 410 Note

Table 1. Cultured methanogenic archaea Species Culture no. Origin Methanos~rcimt mazei DSM 3338 Sewage sludge Methanolobus bombayensis OCM 438 Sea sediment, Indian Ocean Methanosarcina acetivorans DSM 2834 Marine mud, U.S.A. Methanococcoidus rnethylutens DSM 2657 Marine sediment, U.S.A. Methanosarcina sp. MPT4 DSM 6636 Salt marsh sediment, France Methanosarcina siciliae DSM 3028 Lake sediment, Sicily methanogenic archaea. However, in other instances DCM (9:1, v/v) and DCM/methanol (1:1, v/v) as the ~3C content of PME may differ substantially eluents. Fractions were hydrogenated by dissolving from that of photoautotrophic biomarkers in ethyl , adding PtO2 and bubbling H2 (Schouten et al., in press). through for 1 h. The mixture was then stirred for Here we report the presence of unsaturated com- an additional 24 h. The samples were analysed by pounds with the PME carbon skeleton not only in gas chromatography (GC) and gas chromatog- a strain of Methanosarcina mazei, but also in the raphy-mass spectrometry (GC-MS). marine methanogenic archaeon Methanolobus bom- Gas chromatography bayensis, confirming previous ideas on a methano- genic archaeal origin for compounds possessing the GC was performed using a Hewlett-Packard 5890 PME carbon skeleton in marine environments. equipped with an on-column injector. A fused-silica capillary column (25 m x 0.32 mm) coated with CP Sil-5 (film thickness 0.12/~m) was used with helium EXPERIMENTAL as carrier gas. A flame ionization detector (FID) was used for detection. The samples were dissolved Culture conditions in ethyl acetate and injected at 70°C. Subsequently Cell masses of Methanosarcina mazei G I were the oven was programmed to 130°C at 20°C/rain grown at 37°C with stirring (50 rpm) at pH 6.9 in a and then at 4°C/min to 320°C, at which it was held 100 1 enamel-protected fermentor (HTE for 15 min. Bioengineering, Wald, Switzerland) pressurized with 200 kPa N2/CO 2 (80:20, v/v). For cultivation, modi- Gas chromatography mass spectrometry fied M3-medium (Balch et al., 1979) supplemented GC MS was performed using a Hewlett-Packard with methanol (0.5%, final concentration) was used. 5890 gas chromatograph interfaced with a VG Cells were harvested by continuous centrifugation Autospec Ultima mass spectrometer operated at (3000 rpm). 70 eV with a mass range of m/z 40-800 and a cycle The following strains (see Table 1) were culti- time of 1.7 s (resolution 1000). The gas chromato- vated according to the 1993 catalog of the Deutsche graph was equipped with a fused-silica capillary col- Sammlung von Mikroorganismen und Zellkulturen: umn (25 m x 0.32 ram) coated with CP Sil-5 (film Methanosarcina acetivorans and Methanosarcina sp. thickness 0.2 #m). The carrier gas was helium. The strain MTP4 (30c'C), Methanosarcina siciliae and samples were injected on column at 60°C and sub- Methanococcoides methylutens (30°C). Methanolobus sequently the oven was programmed to 130°C at bombayensis (30°C) was grown in mineral medium 20°C/min and then at 4°C/min to 300°C at which it according to the Oregon Collection of Methanogens was held for 10 min. guidelines. All strains were grown on a combination of (tri)methylamine (50mM) and methanol (50 mM) as growth substrates at 37°C, unless other- RESULTS AND DISCUSSION wise indicated. Cells were harvested by centrifu- gation at 16000g for 10rain and the pellet was Six different methanogenic archaea were cultured washed twice with a 25 mM potassium phosphate and analysed for apolar lipids (see Table 1). Only buffer (pH 7.1) containing 30g/1 NaC1 and 3.5 g/l two cultures, Methanosarcina mazei and MgC12.6H20. After washing, the pellet was resus- Methanolobus bombayensis, were found to contain pended in 1 ml sterile doubly-distilled water. significant amounts of apolar hydrocarbons. Subsequently the cells were lyophilized. Table 2. Pseudo Kovats indices of unsaturated PMEs Analysis of lipids Number of PseudoKovats The freeze-dried biomass was ultrasonically Archaea double bonds index(CP Sil 5) extracted with methanol (3x), methanol/dichloro- Methanosarcina mazei 4 2336 methane (DCM) (1:1, v/v; 3×) and DCM (3x). The 5 2347 extracts were combined and separated into an apo- Methanolobus bombayensis 3 2290, 2314 lar and a residual fraction using column chromatog- 4 2326, 2333 5 2347, 2366 raphy (A1203 as stationary phase) with hexane/ Note 411

Methanosarcina mazei, a strain isolated from sew- thought to be 2,6,10,15,19-pentamethylicosenes con- age sludge, was found to contain only a limited taining four or five double bonds (Figs 1 and 2B). number of compounds which, on the basis of their The carbon skeleton of these compounds was con- mass spectra and retention indices (Table 2), are firmed by hydrogenation of the apolar fraction,

~ Methanosarcinamazei apolar fraction i

= rel. retention time

[ b~Methanolobusbombayensis h [

rel. retention time

] ~¢~fet~anolobus bombaveosis ~ J J. ^ ,[, ~ ...... J

reL retention time

Fig. 1. Gas chromatograms of (a) apolar fraction of lipid extract from Methanosarcina mazei, (b) apo- lar fraction of lipid extract from Methanolobus bombayensis and (c) hydrogenated apolar fraction of lipid extract from Methanolobus bombayensis. lOO~ 69

80 1 A T,o6O 109 5O 4O t- 30 81 95

.~_ 20

m lO I I IJ J, 183 191 233 261 303 [ 0 ..,;..'~ .~. .... '~. 9, .,.~., I,...k..~-,'.. ~--.'. .... ;..; ...... ' ...... 60 100 140 180 220 260 300 340 m/z = 100°.,j'o 69

B

70

60 50 123 =>, 40 81 t- 3O

13, 1 91,,2o 231 2, 3o 3,, 1:]1 L t t [ • d6 "' T0"O" .... "1'4"o" ..... 1'-'-"""8o ' ; 220"-'-"" .... "2~0" "''" "3'0"0..... "3~1-'0......

100% 69 m/z =

90180 "' C

70

60 5oi ', 81 40 e-

e- 30 • i 20 '

10 95 137

"~6 'l'o0"~l~Oe"i'ao"'"2'2o" .... 2~o ..... 3~oo" .... 3',;,o ..... m/z .~

Fig. 2. Mass spectrum of (A) 2,6,10,15,19-pentamethylicosene with three double bonds present in Methanolobus bombayensis, (B) 2,6,10,15,19-pentamethylicosene with four double bonds present in Methanosarcina mazei and (C) 2,6,10,15,19-pentamethylicosene with five double bonds present in Methanolobus bombayensis. Note 413

which yielded PME as the only compound as ident- requires the presence of functionalities in the orig- ified by comparison with the mass spectrum and inal lipid; e.g. Kohnen et al., 1992). Our results and retention index of synthetic PME (Rowland et al., those of Tornabene et al. (1979) show that metha- 1982; Risatti et al., 1984). When the apolar fraction nogens in culture produce abundant unsaturated of the extract of Methanolobus bombayensis was PMEs, although Risatti et al. (1984) found only the analysed, a cluster of compounds was found which saturated compound in their culture of were identified as 2,6,10,15,19-pentamethylicosenes Methanosarcina barkeri. It is unclear why in their containing three to five double bonds (Fig. l b, 2b case and possibly also in the natural environment and 2c). Indeed, hydrogenation of the fraction only PME is biosynthesized. This may be due to yielded PME as the only compound (Fig. lc). the particular environments where they thrive or Methanosarcina sp. MPT4 and Methanosarcina sici- due to the nutrients and carbon sources supplied to liae contain only trace amounts of pentamethylico- the methanogenic archaea. Growth of senes with three and four double bonds, cultures under different conditions may help to respectively, but their low amounts prevented any explain this observation. firm identification through hydrogenation of the fractions. The apolar fractions of the lipid extracts of Methanosarcina acetivorans and CONCLUSION Methanococcoidus methylutens did not contain any 2,6,10,15,19-Pentamethylicosenes containing three significant amounts of apolar hydrocarbons. to five double bonds have been found in high The identification of alkenes with the PME car- amounts in the methanogenic archaeon bon skeleton in Methanosarcina mazei, a species Methanosarcina mazei, a strain isolated from sewage which can thrive under mesophilic conditions sludge, and in Methanolobus bombayensis, a strain (Maestrojuan et al., 1992), and, more importantly, isolated from marine sediments of the Indian in Methanolobus bombayensis, an archaeon isolated Ocean. This result gives additional support to the from a marine sediment of the Indian Ocean contention that compounds possessing a PME car- (Kadam et al., 1994), gives additional support for bon skeleton are biomarkers for past methanogenic the hypothesis that compounds with this carbon activity in marine environments. skeleton can serve as a marker for methanogenic activity in marine environments (Brassell et al., Associate Editor--A. G. Douglas 1981). Previous unambigous identifications of com- pounds possessing the PME carbon skeleton were Acknowledgements--Dr R. E. Summons is thanked for either in an archaeon living at temperatures of 60- helpful discussions. Professor S. Rowland provided helpful 80°C (Methanobacterium thermoautotrophicum) or comments on an earlier draft of this paper. M. Dekker is in archaea living predominantly in freshwater or thanked for analytical support. This study was supported mesophilic conditions (Methanosarcina barkeri, by a PIONIER grant to JSSD by the Netherlands Organization for Scientific Research (NWO). NIOZ Methanobacterium ruminantum, Methanococcus van- Contribution No. 3158. nielii). Although it cannot be excluded that other organisms are biosynthesizing this compound, methanogenic archaea are the only organisms REFERENCES known to date which biosynthesize this particular Balch, W. E., Fox, G. E., Magrum, L. J., Woese, C. carbon skeleton. Furthermore, it has been shown R. and Wolfe, R. S. (1979) Methanogens: re-evaluation for a few marine sediments that the stereochemistry of a unique biological group. Microbiology Review 43, of the sedimentary PME is in full accordance with 260-296. a biological origin from methanogenic archaea Brassell, S. C., Wardroper, A. M. K., Thomson, I. D., Maxwell, J. R. and Eglinton, G. (1981) Specific acyclic (Rowland et al., 1982; Risatti et al., 1984). 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APPENDIX

R - 0 -'~ R - O -"~

I R = e.g. c-i II C - OH I C - OH

III IV