Lipid characteristics of a seep clam,Mesolinga soliditesta: Comparison with those of two coastal clams,Meretrix lamarckii and Ruditapes philippinarum     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

The lipids and fatty acids of two coastal clams, Meretrix lamarckii and Ruditapes philippinarum, collected at 5 and 1 m of depth, and a seep clam, Mesolinga soliditesta, collected at 331 m of depth, were examined to assess their lipid physiology and trophic relationship with their diets. The major fatty acids of lipids in Mer. lamarckii and R. philippinarum were 14:0, 16:0, 18:0, 16:1n-7, 18:1n-9, 18:1n-7, 20:4n-6, 20:5n-3, and 22:6n-3, while those of Mes. soliditesta were 16:0, 18:0, 16:1n-7, 18:1n-7, 20:1n-7, 20:1n-13, 20:2n-7, 15 (Δ5,13-20:2), and 22:2n-7,15 (Δ7,15-22:2). The major polyunsaturated fatty acids (PUFAs) in the Mer. lamarckii and R. philippinarum lipids consisted of various n-3 and n-6 long-chain (LC) PUFAs, such as 20:4n-6, 22:4n-6, 20:5n-3, 22:5n-3, and 22:6n-3, while those in Mes. soliditesta muscle and viscera included various n-4 family PUFAs (18:3n-7, 18:4n-4, 20:2n-7, and 20:3n-7) with limited kinds of n-3 and n-6 PUFAs (20:4n-6 and 20:5n-3). These findings indicate that, like other common shallow-water clams, Mer. lamarckii and R. philippinarum ingest phytoplanktonic n-3 and n-6 LC-PUFAs, whereas Mes. soliditesta utilizes limited kinds of n-3 and n-6 LC-PUFAs. In contrast to the other two bivalves species, Mes. soliditesta yielded various n-4 and n-7 (n-4/n-7) PUFAs, which were assimilated from the chemosynthetic symbionts. The high diversity of PUFAs contained in the Mes. soliditesta lipids (n-3, n-4 family, and n-6 PUFAs) suggests that this species mixotrophically utilized both photosynthetic products and vent chemosynthetic nutrition derived from geothermal energy.  相似文献   

Ancient wet aeolian environments on Earth: clues to presence of fossil/live microorganisms on Mars     

William C Mahaney  Michael W Milner  David Malloch  Victor R Baker  Trent M Hare 《Icarus》2004,171(1):39-53

Ancient wet aeolian (wet-sabkha) environments on Earth, represented in the Entrada and Navajo sandstones of Utah, contain pipe structures considered to be the product of gas/water release under pressure. The sediments originally had considerable porosity allowing the ingress of living plant structures, microorganisms, clay minerals, and fine-grained primary minerals of silt and sand size from the surface downward in the sedimentary column. Host rock material is of a similar size and porosity and presumably the downward migration of fine-grained material would have been possible prior to lithogenesis and final cementation. Recent field emission scanning electron microscopy (FESEM) and EDS (energy-dispersive spectrometry) examination of sands from fluidized pipes in the Early Jurassic Navajo Sandstone reveal the presence of fossil forms resembling fungal filaments, some bearing hyphopodium-like structures similar to those produced by modern tropical leaf parasites. The tropical origin of the fungi is consistent with the paleogeography of the sandstone, which was deposited in a tropical arid environment. These fossil fungi are silicized, with minor amounts of CaCO₃ and Fe, and in some cases a Si/Al ratio similar to smectite. They exist as pseudomorphs, totally depleted in nitrogen, adhering to the surfaces of fine-grained sands, principally quartz and orthoclase. Similar wet aeolian paleoenvironments are suspected for Mars, especially following catastrophic sediment-charged floods of enormous magnitudes that are believed to have contributed to rapid formation of large water bodies in the northern plains, ranging from lakes to oceans. These events are suspected to have contributed to a high frequency of constructional landforms (also known as pseudocraters) related to trapped volatiles and water-enriched sediment underneath a thick blanket of materials that were subsequently released to the martian surface, forming piping structures at the near surface and constructional landforms at the surface. This constructional process on Mars may help unravel the complex history of some of the piping structures observed on Earth; on Earth, evidence for the constructional landforms has been all but erased and the near-surface piping structures exposed through millions of years of differential erosion and topographic inversion now occur as high-standing promontories. If the features on both Earth and Mars formed by similar processes, especially involving water and other volatiles, and since the piping structures of Earth provided suitable environments for life to thrive in, the martian features in the northern plains should be considered as prime targets for physico/mineral/chemical/microbiological analyses once the astrobiological exploration of the red planet begins in earnest.  相似文献   

Seasonal distribution of bacteria in salt marsh sediments in North Carolina     

Parke A. Rublee 《Estuarine, Coastal and Shelf Science》1982,15(1):67-74

The number and size of bacteria at four depths (0–1, 5–6, 10–11 and 20–21 cm) in a North Carolina salt marsh were minotored by direct counts for 13 months. The number of bacteria reached a maximum of about 1·4 × 10¹⁰ cells cm^?3 at the sediment surface in October, corresponding to the period of Spartina alterniflora die-back. Cell numbers were lowest and most consistent throughout the year at the 20 cm depth of sediment. Cell volumes averaged 0·2 μm³ at the marsh surface and decreased with depth. Mean standing crop of bacteria to a depth of 20 cm of sediment was about 14 g bacterial carbon m^?2. In surface sediments bacteria contribute up to 15% and algae up to 10% of total living microbial biomass as estimated by adenosine triphosphate (ATP). Bacteria were the major biomass component at sediment depths of 5, 10 and 20 cm. At all depths the microbial community contributes < 4% total organic carbon and < 8% of total nitrogen.  相似文献   

应用矿物学未来和发展——第十一届国际应用矿物学大会综述     

赵学钦  董发勤 《岩石矿物学杂志》2014,33(1):194-198

以“应用矿物学未来和发展”为主题的第十一届国际应用矿物学大会于2013年7月8～10日在绵阳召开,会议发表的技术报告内容涉及环境与医用矿物学、工业矿物、生物矿物学与生物材料、先进材料、工艺矿物学、矿业与冶金、矿物结构与表面、矿物与微生物的相互作用、固体废物处理与资源化等9个方面。  相似文献   

开垦年限对黑土农田土壤微生物功能多样性的影响     

董炜华  刘青源  李晓强  耿云灿  李瑞英 《地理科学》2022,42(7):1316-1324

开垦年限对黑土农田土壤微环境产生影响,土壤微生物的功能多样性发生变化。于2019年7月在黑龙江省黑河市黑土区采集不同土层（0~10 cm、10~20 cm、20~30 cm）开垦98 a、50 a和10 a的黑土农田土壤,采用Biolog-Eco微平板法研究开垦年限对黑土农田土壤微生物的活性、功能多样性和微生物对不同碳源的利用情况的影响。结果表明,开垦98 a的农田土壤微生物活性最强。农田土壤微生物群落组成及功能多样性开垦98 a >开垦10 a >开垦50 a。开垦年限和土层深度影响黑土农田土壤微生物对碳源的利用能力。在0~10 cm层中,土壤微生物对碳源的利用程度最高。主成分分析结果表明,黑土农田土壤中的微生物主要利用的是糖类和氨基酸类。  相似文献   

3种益生素配伍对异育银鲫(Carassius auratus gibelio)生长、消化及肠道茵群组成的影响   总被引：4，自引：1，他引：4