Chitin is a major structural component of arthropod exoskeletons, and an important carbon and nitrogen source in marine environments. In anoxic sediments, its degradation generates chitooligosaccharides and N-acetylglucosamine (GlcNAc), which are fermented into smaller organic molecules and oxidized anaerobically using soluble electron acceptors or insoluble ones such as metal oxides. To date, many aspects of chitin degradation in deep-sea anoxic sediments have been overlooked, including the potential coupling of insoluble chitin degradation to metal oxide reduction, the involvement of extracellular electron transfer (EET), and the spatial organization of the microorganisms involved. Using anoxic deep-sea sediments recovered from a whale fall site, we developed an innovative workflow based on electrochemical reactors, to characterize chitin degradation in these environments. Sediment samples enriched on poorly crystalline iron oxides, and subsequently transferred into an electrochemical reactor poised at +0.22 V vs SHE, showed active anodic current production when supplied with chitin, which increased 2-fold when amended with GlcNAc. Chitin reactors were dominated byVallitalea(Firmicutes),Spirochaetota,GammaproteobacteriaandDesulfobacterota. Exoenzyme activity assays, metabolite profiling, and continued anodic current production confirmed ongoing chitin degradation linked to EET. We observed metabolic associations between chitin degraders and secondary consumers usingin situimaging (16S rRNA gene FISH coupled with BONCAT and nanoSIMS). These microbial partners, within the electrode-attached community, required close proximity to the poised electrode (≤ 10 µm) to remain metabolically active. Supporting these observations, cultured isolates ofVallitaleasp. andTrichloromonassp. recovered from the whale fall site exhibited chitin degradation and electrochemical activity, respectively. When co-cultured in an bioelectrochemical reactor, the acetate produced byVallitaleasp. during chitin degradation fueledTrichloromonassp., which facilitated EET, hereby demonstrating that syntrophic interactions are used to couple anoxic chitin degradation to EET in deep-sea sediments. These findings exemplify the interspecies interactions and resource optimization occurring in hard-to-reach and largely unknown deep-sea ecosystems.
", "doi": "10.1101/2025.06.30.662270", "publisher": "bioRxiv", "publication_date": "2025-06-30" }, { "id": "authors:bz6mp-4wh10", "collection": "authors", "collection_id": "bz6mp-4wh10", "cite_using_url": "https://authors.library.caltech.edu/records/bz6mp-4wh10", "type": "article", "title": "Methane-powered sea spiders: Diverse, epibiotic methanotrophs serve as a source of nutrition for deep-sea methane seep Sericosura", "author": [ { "family_name": "Dal B\u00f3", "given_name": "Bianca", "orcid": "0009-0007-1691-8181" }, { "family_name": "Guo", "given_name": "Yongzhao", "orcid": "0009-0005-3983-8382", "clpid": "Guo-Yongzhao" }, { "family_name": "Mayr", "given_name": "Magdalena J.", "orcid": "0000-0002-3182-1480", "clpid": "Mayr-Magdalena-J" }, { "family_name": "Pereira", "given_name": "Olivia S." }, { "family_name": "Levin", "given_name": "Lisa A.", "orcid": "0000-0002-2858-8622" }, { "family_name": "Orphan", "given_name": "Victoria J.", "orcid": "0000-0002-5374-6178", "clpid": "Orphan-V-J" }, { "family_name": "Goffredi", "given_name": "Shana K.", "orcid": "0000-0002-9110-9591" } ], "abstract": "Methane seeps harbor uncharacterized animal–microbe symbioses with unique nutritional strategies. Three undescribed sea spider species (family Ammotheidae; genus Sericosura) endemic to methane seeps were found along the eastern Pacific margin, from California to Alaska, hosting diverse methane- and methanol-oxidizing bacteria on their exoskeleton. δ13C tissue isotope values of in situ specimens corroborated methane assimilation (−45‰, on average). Live animal incubations with 13C-labeled methane and methanol, followed by nanoscale secondary ion mass spectrometry, confirmed that carbon derived from both compounds was actively incorporated into the tissues within five days. Methano- and methylotrophs of the bacterial families Methylomonadaceae, Methylophagaceae and Methylophilaceae were abundant, based on environmental metagenomics and 16S rRNA sequencing, and fluorescence and electron microscopy confirmed dense epibiont aggregations on the sea spider exoskeleton. Egg sacs carried by the males hosted identical microbes suggesting vertical transmission. We propose that these sea spiders farm and feed on methanotrophic and methylotrophic bacteria, expanding the realm of animals known to harness C1 compounds as a carbon source. These findings advance our understanding of the biology of an understudied animal lineage, unlocking some of the unique nutritional links between the microbial and faunal food webs in the oceans.
", "doi": "10.1073/pnas.2501422122", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences", "publication_date": "2025-06-16", "series_number": "26", "volume": "122", "issue": "26", "pages": "e2501422122" } ]