Rouwendaal Simon E, Birgel Daniel, Natalicchio Marcello, Dela Pierre Francesco, Guibourdenche Laetitia, Bauersachs Thorsten, Aloisi Giovanni, Labrado Amanda L, Brunner Benjamin, Peckmann Jörn
Fachbereich Erdsystemwissenschaften, Centrum für Erdsystemforschung und Nachhaltigkeit, Universität Hamburg, Hamburg, Germany.
Dipartimento di Scienze della Terra, Università degli Studi di Torino, Torino, Italy.
Geobiology. 2025 Mar-Apr;23(2):e70015. doi: 10.1111/gbi.70015.
The microbially mediated replacement of sulfate-bearing evaporites by authigenic carbonate and native sulfur under anoxic conditions is poorly understood. Sulfur-bearing carbonates from the Monte Palco ridge (Sicily) replacing Messinian gypsum were therefore studied to better characterize the involved microorganisms. The lack of (1) sedimentary bedding, (2) lamination, and (3) significant water-column-derived lipid biomarkers in the secondary carbonates implies replacement after gypsum deposition (epigenesis). Allochthonous clasts from the older Calcare di Base and the younger Trubi Formation within these carbonates further evidence epigenetic formation. The sulfur-bearing carbonates are significantly C-depleted (δC as low as -51‰), identifying methane as a major carbon source. The O-enrichment of the carbonates (δO as high as 5.4‰) probably reflects precipitation from O-enriched fluids transported along adjacent faults or precipitation in a closed system with very little water. Native sulfur with variable S-enrichment (δS as high as 18.9‰), a relatively small maximum offset (12.3‰) between the sulfate source (gypsum) and native sulfur, and high δS values of carbonate-associated sulfate (as high as 61.1‰) suggest a high conversion to native sulfur in a (semi-)closed system, with insignificant sulfate removal. Anaerobic methanotrophic archaea (ANME) apparently affiliated with the ANME-1 clade mediated secondary mineral formation as evidenced by the biomarker inventory, which contains abundant C-depleted isoprenoids including sn3-hydroxyarchaeol as the sole hydroxyarchaeol isomer and glycerol dibiphytanyl glycerol tetraethers (GDGTs). A series of various, tentatively identified C-depleted non-isoprenoidal dialkyl glycerol diethers (DAGEs), 10me-C fatty acid, hydroxy C fatty acids, and cyclopropyl-C fatty acid agree with sulfate-reducing bacteria participating in the anaerobic oxidation of methane. Specific conditions during gypsum replacement, unlike those at marine methane seeps, are reflected by the occurrence of C-depleted lipids such as lycopane, 9me-C fatty acid, and novel DAGEs. As a response to a confined environment probably characterized by high sulfate concentrations, sulfidic conditions, and elevated salinity, ANMEs and sulfate-reducing bacteria apparently adapted their membrane compositions to cope with such stressors.
在缺氧条件下，微生物介导的自生碳酸盐和自然硫对含硫酸盐蒸发岩的替代作用目前还知之甚少。因此，对来自西西里岛蒙特帕尔科海脊、替代墨西拿石膏的含硫碳酸盐进行了研究，以更好地描述其中涉及的微生物特征。次生碳酸盐中缺乏：（1）沉积层理；（2）纹层；以及（3）明显的水柱来源的脂质生物标志物，这意味着在石膏沉积后发生了替代作用（后生作用）。这些碳酸盐中来自较老的钙质基底和较年轻的特鲁比组的异地碎屑进一步证明了后生作用的形成。含硫碳酸盐的碳同位素显著贫化（δC低至-51‰），表明甲烷是主要的碳源。碳酸盐的氧富集（δO高达5.4‰）可能反映了沿相邻断层运移的富氧流体的沉淀，或者是在一个几乎没有水的封闭系统中的沉淀。自然硫的硫同位素富集程度各异（δS高达18.9‰），硫酸盐源（石膏）与自然硫之间的最大偏移相对较小（12.3‰），以及与碳酸盐相关的硫酸盐的高δS值（高达61.1‰）表明，在一个（半）封闭系统中，向自然硫的转化率很高，且硫酸盐去除量微不足道。生物标志物清单显示，厌氧甲烷氧化古菌（ANME）显然与ANME-1分支相关，介导了次生矿物的形成，该清单包含丰富的贫碳类异戊二烯，包括sn3-羟基古菌醇作为唯一的羟基古菌醇异构体以及甘油二植烷甘油四醚（GDGTs）。一系列初步鉴定的各种贫碳非类异戊二烯二烷基甘油二醚（DAGE）、10me-C脂肪酸、羟基C脂肪酸和环丙基-C脂肪酸与参与甲烷厌氧氧化的硫酸盐还原细菌相符。石膏替代过程中的特定条件与海洋甲烷渗漏处的条件不同，这体现在贫碳脂质如番茄烃、9me-C脂肪酸和新型DAGE的出现上。作为对可能以高硫酸盐浓度、硫化条件和盐度升高为特征的受限环境的一种反应，ANME和硫酸盐还原细菌显然调整了它们的膜组成以应对这些压力源。
