Systematic fragmentation patterns of archaeal intact polar lipids by high‐performance liquid chromatography/electrospray ionization ion‐trap mass spectrometry

Abstract

Archaea are ubiquitous and abundant microorganisms on Earth that mediate key global biogeochemical cycles. The headgroup attached to the sn-1 position of the glycerol backbone and the ether-linked isoprenoid lipids are among the diagnostic traits that distinguish Archaea from Bacteria and Eukarya. Over the last 30 years, numerous archaeal lipids have been purified and described in pure cultures. Coupled high-performance liquid chromatography (HPLC) ion-trap mass spectrometry (ITMS) now enables the detection and rapid identification of intact polar lipids in relatively small and complex samples, revealing a wide range of archaeal lipids in natural environments. Although major structural groups have been identified, the lack of a systematic evaluation of MS/MS fragmentation patterns has hindered the characterization of several atypical components that are therefore considered as unknowns. Here, we examined mass spectra resulting from lipid analysis of natural microbial communities using HPLC/electrospray ionization (ESI)-ITMS(n), and depicted the systematics in MS(2) fragmentation of intact archaeal lipids. This report will be particularly useful for environmental scientists interested in a rapid and straightforward characterization of intact archaeal membrane lipids.

Unusual Butane- and Pentanetriol-Based Tetraether Lipids in Methanomassiliicoccus luminyensis, a Representative of the Seventh Order of Methanogens

“…While Ext-AR as major core lipid in M. luminyensis is widespread in halophilic archaea (54)(55)(56), it is present in only trace amounts in other methanogens, including Methanosarcina barkeri (57) and Methanothermobacter thermautotrophicus (58). In environmental samples, the detection of Ext-AR has been frequently associated with methane-oxidizing archaea (59)(60)(61). The diExt-AR that we detected in M. luminyensis has so far been reported only in halophiles (62) and as the dominant lipid in the thermophile Aeropyrum pernix (63) but not in methanogens.…”

Thermococcus kodakarensis modulates its polar membrane lipids and elemental composition according to growth stage and phosphate availability

“…IPL identification was based on: (1) characteristic mass losses of headgroups during MS/MS fragmentation (cf. Table 2; Yoshinaga et al, 2011), such as phosphatidyl inositol (PI; 242 Da), phosphatidyl ethanolamine (PE; 43 Da), phosphatidyl serine (PS; 87 Da), phosphatidyl glycerol (PG; 74 Da), phosphatidic acid (PA; 80 Da), monoglycosidic (G; 179 Da), and diglycosidic (2G; 342 Da) and/or 2) elemental formula derived from high precision mass determination after Q-TOF-MS, which were accurate to within 1.8 mDa of the predicted chemical formulae (Table 2). Reference numbers for specific ARs (i.e., IPLs 1–11) and GDGTs (i.e., IPLs 12–20) were generated according to retention time (cf.…”

“…IPL ions were identified based on fragmentation patterns as outlined by Yoshinaga et al (2011) and quantified relative to the response of a phosphatidyl choline diacyl glycerol (PC-DAG) internal standard. Response factors of 2.4 for ARs and 5.9 for GDGTs were applied, based on the averaged relative responses of an AR linked to a phosphatidyl ethanolamine headgroup and a GDGT linked to one glycosidic and one phosphatidyl glycerol headgroup, respectively (0.5–25 ng; n = 7; Avanti Polar Lipids, USA).…”

Biology of a widespread uncultivated archaeon that contributes to carbon fixation in the subsurface

“…IPLs were measured in positive ionization mode, while scanning a mass-to-charge (m/z) range of 150-2,000, with automated data-dependent MS/MS fragmentation of base peak ions. Compound identification was achieved by monitoring exact masses of possible parent ions (present mainly as H þ and NH 4 þ adducts) in combination with characteristic fragmentation patterns 62,64 . The reported relative distribution of microbial lipids is based on the peak areas of the respective molecular ions without differentiating for potential differences in response factors; the data should therefore be viewed as semi-quantitative.…”