Integrative Oceanography Division, Scripps Institution of Oceanography, University of California-San Diego, La Jolla, CA, USA.
ISME J. 2012 Aug;6(8):1602-12. doi: 10.1038/ismej.2012.16. Epub 2012 Mar 8.
Although the importance of trophic linkages, including 'top-down forcing', on energy flow and ecosystem productivity is recognized, the influence of metazoan grazing on Archaea and the biogeochemical processes that they mediate is unknown. Here, we test if: (1) Archaea provide a food source sufficient to allow metazoan fauna to complete their life cycle; (2) neutral lipid biomarkers (including crocetane) can be used to identify Archaea consumers; and (3) archaeal aggregates are a dietary source for methane seep metazoans. In the laboratory, we demonstrated that a dorvilleid polychaete, Ophryotrocha labronica, can complete its life cycle on two strains of Euryarchaeota with the same growth rate as when fed bacterial and eukaryotic food. Archaea were therefore confirmed as a digestible and nutritious food source sufficient to sustain metazoan populations. Both strains of Euryarchaeota used as food sources had unique lipids that were not incorporated into O. labronica tissues. At methane seeps, sulfate-reducing bacteria that form aggregations and live syntrophically with anaerobic-methane oxidizing Archaea contain isotopically and structurally unique fatty acids (FAs). These biomarkers were incorporated into tissues of an endolithofaunal dorvilleid polychaete species from Costa Rica (mean bulk δ(13)C=-92±4‰; polar lipids -116‰) documenting consumption of archaeal-bacterial aggregates. FA composition of additional soft-sediment methane seep species from Oregon and California provided evidence that consumption of archaeal-bacterial aggregates is widespread at methane seeps. This work is the first to show that Archaea are consumed by heterotrophic metazoans, a trophic process we coin as 'archivory'.
虽然人们已经认识到营养联系（包括“自上而下的强迫”）对能量流动和生态系统生产力的重要性，但后生动物的摄食对古菌以及它们所介导的生物地球化学过程的影响尚不清楚。在这里，我们检验了以下三个假设：（1）古菌是否提供了足够的食物来源，使后生动物能够完成其生命周期；（2）中性脂质生物标志物（包括克罗烷）是否可用于鉴定古菌消费者；（3）古菌聚集体是否是甲烷渗漏后生动物的一种饮食来源。在实验室中，我们证明了一种多毛类环节动物 Dorvilleid Ophryotrocha labronica 可以在两种生长速度与细菌和真核生物相同的广古菌菌株上完成其生命周期。因此，古菌被确认为一种可消化且有营养的食物来源，可以维持后生动物种群。作为食物来源的两种广古菌菌株都有独特的脂质，这些脂质不会被 O. labronica 组织吸收。在甲烷渗漏点，形成聚集体并与厌氧甲烷氧化古菌共生的硫酸盐还原细菌含有同位素和结构独特的脂肪酸（FA）。这些生物标志物被整合到来自哥斯达黎加的内共生多毛类环节动物 Dorvilleid 物种的组织中，证明了它们对古菌-细菌聚集体的消耗。来自俄勒冈州和加利福尼亚州的其他软沉积物甲烷渗漏物种的 FA 组成提供了证据，证明在甲烷渗漏点普遍存在古菌-细菌聚集体的消耗。这项工作首次表明后生动物会消耗古菌，我们将这种营养过程称为“archivory”。
