Sollai Martina, Villanueva Laura, Hopmans Ellen C, Keil Richard G, Sinninghe Damsté Jaap S
Royal Netherlands Institute for Sea Research (NIOZ), Department of Marine Microbiology and Biogeochemistry, Utrecht University, Den Burg, Netherlands.
School of Oceanography, University of Washington, Seattle, WA, United States.
Front Microbiol. 2019 Apr 11;10:765. doi: 10.3389/fmicb.2019.00765. eCollection 2019.
Archaea are ubiquitous in the modern ocean where they are involved in the carbon and nitrogen biogeochemical cycles. However, the majority of Archaea remain uncultured. Archaeal specific membrane intact polar lipids (IPLs) are biomarkers of the presence and abundance of living cells. They comprise archaeol and glycerol dibiphytanyl glycerol tetraethers (GDGTs) attached to various polar headgroups. However, little is known of the IPLs of uncultured marine Archaea, complicating their use as biomarkers. Here, we analyzed suspended particulate matter (SPM) obtained in high depth resolution from a coastal and open ocean site in the eastern tropical South Pacific (ETSP) oxygen deficient zone (ODZ) with the aim of determining possible biological sources of archaeal IPL by comparing their composition by Ultra High Pressure Liquid Chromatography coupled to high resolution mass spectrometry with the archaeal diversity by 16S rRNA gene amplicon sequencing and their abundance by quantitative PCR. Thaumarchaeotal Marine Group I (MGI) closely related to . Nitrosopelagicus and dominated the oxic surface and upper ODZ water together with Marine Euryarchaeota Group II (MGII). High relative abundance of hexose phosphohexose- (HPH) crenarchaeol, the specific biomarker for living Thaumarchaeota, and HPH-GDGT-0, dihexose- (DH) GDGT-3 and -4 were detected in these water masses. Within the ODZ, DPANN (Diapherotrites, Parvarchaeota, Aenigmarchaeota, Nanoarchaeota, and Nanohaloarchaea) of the Woesearchaeota DHVE-6 group and Marine Euryarchaeota Group III (MGIII) were present together with a higher proportion of archaeol-based IPLs, which were likely made by MGIII, since DPANN archaea are supposedly unable to synthesize their own IPLs and possibly have a symbiotic or parasitic partnership with MGIII. Finally, in deep suboxic/oxic waters a different MGI population occurred with HPH-GDGT-1, -2 and DH-GDGT-0 and -crenarchaeol, indicating that here MGI synthesize membranes with IPLs in a different relative abundance which could be attributed to the different detected population or to an environmental adaptation. Our study sheds light on the complex archaeal community of one of the most prominent ODZs and on the IPL biomarkers they potentially synthesize.
古菌在现代海洋中广泛存在，参与碳和氮的生物地球化学循环。然而，大多数古菌仍未被培养。古菌特有的膜完整极性脂类（IPLs）是活细胞存在和丰度的生物标志物。它们包括古菌醇和连接到各种极性头部基团的甘油二植烷甘油四醚（GDGTs）。然而，对于未培养的海洋古菌的IPLs了解甚少，这使得它们作为生物标志物的应用变得复杂。在这里，我们分析了从东热带南太平洋（ETSP）缺氧区（ODZ）的一个沿海和公海站点以高深度分辨率获得的悬浮颗粒物（SPM），目的是通过将超高压液相色谱与高分辨率质谱联用分析其组成，与通过16S rRNA基因扩增子测序分析古菌多样性以及通过定量PCR分析其丰度相比较，来确定古菌IPLs可能的生物来源。与亚硝化浮游菌属密切相关的奇古菌门海洋类群I（MGI）和海洋广古菌门类群II（MGII）在有氧的表层和ODZ上层水体中占主导地位。在这些水体中检测到了活的奇古菌门特有的生物标志物己糖磷酸己糖（HPH）-奇古菌醇以及HPH-GDGT-0、二己糖（DH）-GDGT-3和-4的高相对丰度。在ODZ内，沃氏古菌门DHVE-6类群的DPANN（包括Diapherotrites、Parvarchaeota、Aenigmarchaeota、Nanoarchaeota和Nanohaloarchaea）和海洋广古菌门类群III（MGIII）同时存在，且基于古菌醇的IPLs比例更高，这些IPLs可能是由MGIII产生的，因为DPANN古菌据推测无法合成自身的IPLs，可能与MGIII存在共生或寄生关系。最后，在深层亚缺氧/有氧水体中出现了一个不同的MGI种群，含有HPH-GDGT-1、-2以及DH-GDGT-0和-奇古菌醇，这表明在这里MGI合成的膜中IPLs的相对丰度不同，这可能归因于检测到的不同种群或环境适应性。我们的研究揭示了最显著的ODZ之一的复杂古菌群落以及它们可能合成的IPL生物标志物。
