This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A research team led by professor Qian Peiyuan, chair professor in the Department of Ocean Science at The Hong Kong University of Science and Technology (HKUST), in collaboration with international partners, has made progress in uncovering how deep-sea chemosynthetic symbioses cope with environmental change. The findings reveal that metabolic flexibility in the symbionts, coupled with the host's finely regulated population of bacterial symbionts, helps sustain the host's energy stability.
This provides in situ evidence of how chemosynthetic holobionts at deep-sea cold seeps remain resilient when energy supplies fluctuate and highlights the key role of a tiered adaptation strategy in sustaining the stability of cold seep ecosystems. In addition to HKUST, the research involved the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (Guangzhou Marine Laboratory), Ocean University of China (OUC), the Institute of Oceanology, Chinese Academy of Sciences (IOCAS), and the University of Calgary in Canada. It represents an outcome within the framework of two U.N.
Decade programs, "CliMetS" and "MOCSI." The research was recently published in the journal Science Advances under the title "In situ evidence of tiered adaptations buffering a chemosynthetic clam holobiont against environmental sulfide fluctuations." In chemosynthetic ecosystems, such as deep-sea hydrothermal vents and methane seeps, hydrogen sulfide is a crucial chemical energy source for supporting biological communities. However, its concentration can fluctuate substantially due to tectonic activity, seepage intensity and processes such as the anaerobic oxidation of methane in sediments. Direct evidence has long been lacking on how deep-sea symbiotic organisms adapt to such dynamic environments and how hosts and symbionts work together to maintain system stability.
The Haima cold seep comprises seep sites at different developmental stages, providing a "natural laboratory" for studying biological responses to environmental change. The research team focused on a dominant species of deep-sea clam (Archivesica marissinica) at the Haima cold seep and its sulfur-oxidizing bacterial symbionts. By combining deep-sea in situ transplant experiments with in situ sample fixation, the research team conducted transplantation studies at two sites, HM-3 and HM-2.
The clams were moved from their native sediments into transplantation cages positioned approximately 0.5 m (1.6 feet) above the seafloor, preventing them from accessing hydrogen sulfide–rich sediment. This setup simulates decreased hydrogen sulfide availability, leading to reduced energy and nutrient acquisition: HM-2 represents severe hydrogen sulfide limitation, whereas HM-3 represents relatively moderate limitation. By integrating metagenomics, transcriptomics, proteomics, quantitative PCR, in situ hybridization, transmission electron microscopy and protein structure prediction, the research team elucidated a tiered adaptation strategy in the holobiont, encompassing symbiont metabolism, host regulation of symbiosis and resource transport.
The study revealed that reduced hydrogen sulfide availability first triggered pronounced metabolic reprogramming in the bacterial symbionts. Transcriptomic and proteomic analyses showed that pathways involved in sulfide oxidation, including dsrAB, aprAB and sat, were suppressed, whereas the soxXYZ gene cluster associated with thiosulfate oxidation was upregulated. These results indicate that when hydrogen sulfide becomes limiting, the bacterial symbionts can adjust their sulfur-oxidation strategies and potentially enhance their capacity to use thiosulfate, thereby maintaining energy metabolism and carbon fixation.
Extract — continue reading at the source.
