Quantifying genome-specific carbon fixation in a 750-meter deep subsurface hydrothermal microbial community.

Dissolved inorganic carbon has been hypothesized to stimulate microbial chemoautotrophic activity as a biological sink in the carbon cycle of deep subsurface environments. Here, we tested this hypothesis using quantitative DNA stable isotope probing of metagenome-assembled genomes (MAGs) at multiple 13C-labeled bicarbonate concentrations in hydrothermal fluids from a 750-m deep subsurface aquifer in the Biga Peninsula (Turkey). The diversity of microbial populations assimilating 13C-labeled bicarbonate was significantly different at higher bicarbonate concentrations, and could be linked to four separate carbon-fixation pathways encoded within 13C-labeled MAGs. Microbial populations encoding the Calvin-Benson-Bassham cycle had the highest contribution to carbon fixation across all bicarbonate concentrations tested, spanning 1-10 mM. However, out of all the active carbon-fixation pathways detected, MAGs affiliated with the phylum Aquificae encoding the reverse tricarboxylic acid (rTCA) pathway were the only microbial populations that exhibited an increased 13C-bicarbonate assimilation under increasing bicarbonate concentrations. Our study provides the first experimental data supporting predictions that increased bicarbonate concentrations may promote chemoautotrophy via the rTCA cycle and its biological sink for deep subsurface inorganic carbon.

Alkaline vents recreated in two dimensions to study pH gradients, precipitation morphology, and molecule accumulation.

Alkaline vents (AVs) are hypothesized to have been a setting for the emergence of life, by creating strong gradients across inorganic membranes within chimney structures. In the past, three-dimensional chimney structures were formed under laboratory conditions; however, no in situ visualization or testing of the gradients was possible. We develop a quasi-two-dimensional microfluidic model of AVs that allows spatiotemporal visualization of mineral precipitation in low-volume experiments. Upon injection of an alkaline fluid into an acidic, iron-rich solution, we observe a diverse set of precipitation morphologies, mainly controlled by flow rate and ion concentration. Using microscope imaging and pH-dependent dyes, we show that finger-like precipitates can facilitate formation and maintenance of microscale pH gradients and accumulation of dispersed particles in confined geometries. Our findings establish a model to investigate the potential of gradients across a semipermeable boundary for early compartmentalization, accumulation, and chemical reactions at the origins of life.

White and green rust chimneys accumulate RNA in a ferruginous chemical garden.

Mechanisms of nucleic acid accumulation were likely critical to life's emergence in the ferruginous oceans of the early Earth. How exactly prebiotic geological settings accumulated nucleic acids from dilute aqueous solutions, is poorly understood. As a possible solution to this concentration problem, we simulated the conditions of prebiotic low-temperature alkaline hydrothermal vents in co-precipitation experiments to investigate the potential of ferruginous chemical gardens to accumulate nucleic acids via sorption. The injection of an alkaline solution into an artificial ferruginous solution under anoxic conditions (O2 < 0.01% of present atmospheric levels) and at ambient temperatures, caused the precipitation of amakinite ("white rust"), which quickly converted to chloride-containing fougerite ("green rust"). RNA was only extractable from the ferruginous solution in the presence of a phosphate buffer, suggesting RNA in solution was bound to Fe2+ ions. During chimney formation, this iron-bound RNA rapidly accumulated in the white and green rust chimney structure from the surrounding ferruginous solution at the fastest rates in the initial white rust phase and correspondingly slower rates in the following green rust phase. This represents a new mechanism for nucleic acid accumulation in the ferruginous oceans of the early Earth, in addition to wet-dry cycles and may have helped to concentrate RNA in a dilute prebiotic ocean.

Body-Plan Reorganization in a Sponge Correlates with Microbiome Change.

Mounting evidence suggests that animals and their associated bacteria interact via intricate molecular mechanisms, and it is hypothesized that disturbances to the microbiome influence animal development. Here, we show that the loss of a key photosymbiont (i.e., bleaching) upon shading correlates with a stark body-plan reorganization in the common aquarium cyanosponge Lendenfeldia chondrodes. The morphological changes observed in shaded sponges include the development of a thread-like morphology that contrasts with the flattened, foliose morphology of control specimens. The microanatomy of shaded sponges markedly differed from that of control sponges, with shaded specimens lacking a well-developed cortex and choanosome. Also, the palisade of polyvacuolar gland-like cells typical in control specimens was absent in shaded sponges. The morphological changes observed in shaded specimens are coupled with broad transcriptomic changes and include the modulation of signaling pathways involved in animal morphogenesis and immune response, such as the Wnt, transforming growth factor ß (TGF-ß), and TLR-ILR pathways. This study provides a genetic, physiological, and morphological assessment of the effect of microbiome changes on sponge postembryonic development and homeostasis. The correlated response of the sponge host to the collapse of the population of symbiotic cyanobacteria provides evidence for a coupling between the sponge transcriptomic state and the state of its microbiome. This coupling suggests that the ability of animals to interact with their microbiomes and respond to microbiome perturbations has deep evolutionary origins in this group.

Sargasso Sea Vibrio bacteria: Underexplored potential pathovars in a perturbed habitat.

We fully sequenced the genomes of 16 Vibrio cultivars isolated from eel larvae, plastic marine debris (PMD), the pelagic brown macroalga Sargassum, and seawater samples collected from the Caribbean and Sargasso Seas of the North Atlantic Ocean. Annotation and mapping of these 16 bacterial genome sequences to a PMD-derived Vibrio metagenome-assembled genome created for this study showcased vertebrate pathogen genes closely-related to cholera and non-cholera pathovars. Phenotype testing of cultivars confirmed rapid biofilm formation, hemolytic, and lipophospholytic activities, consistent with pathogenic potential. Our study illustrates that open ocean vibrios represent a heretofore undescribed group of microbes, some representing potential new species, possessing an amalgam of pathogenic and low nutrient acquisition genes, reflecting their pelagic habitat and the substrates and hosts they colonize.

A rapid method for measuring ATP + ADP + AMP in marine sediment.

In this report, I describe a method for rapid measurement of total adenylate (ATP + ADP + AMP) in marine sediment samples for estimating microbial biomass. A simple 'boil and dilute' method is described here, whereby adding boiled MilliQ water to sediments increases the detection limit for ATP + ADP + AMP up to 100-fold. The lowered detection limit of this method enabled the detection ATP + ADP + AMP in relatively low-biomass sub-seafloor sediment cores with 104 16S rRNA gene copies per gram. Concentrations of ATP + ADP + AMP correlated with 16S rRNA gene concentrations from bacteria and archaea across six different sites that range in water depth from 1 to 6000 m indicating that the ATP + ADP + AMP method can be used as an additional biomass proxy. In deep sea microbial communities, the ratio of ATP + ADP + AMP concentrations to 16S rRNA genes >1 m below seafloor was significantly lower compared to communities in the upper 30 cm of sediment, which may be due to reduced cell sizes and or lower ATP + ADP + AMP concentrations per cell in the deep sea sub-seafloor biosphere. The boil and dilute method for ATP + ADP + AMP is demonstrated here to have a detection limit sufficient for measuring low biomass communities from deep sea sub-seafloor cores. The method can be applied to frozen samples, enabling measurements of ATP + ADP + AMP from frozen sediment cores stored in core repositories from past and future international drilling campaigns.

Carbon metabolism and biogeography of candidate phylum "Candidatus Bipolaricaulota" in geothermal environments of Biga Peninsula, Turkey.

Terrestrial hydrothermal springs and aquifers are excellent sites to study microbial biogeography because of their high physicochemical heterogeneity across relatively limited geographic regions. In this study, we performed 16S rRNA gene sequencing and metagenomic analyses of the microbial diversity of 11 different geothermal aquifers and springs across the tectonically active Biga Peninsula (Turkey). Across geothermal settings ranging in temperature from 43 to 79°C, one of the most highly represented groups in both 16S rRNA gene and metagenomic datasets was affiliated with the uncultivated phylum "Candidatus Bipolaricaulota" (former "Ca. Acetothermia" and OP1 division). The highest relative abundance of "Ca. Bipolaricaulota" was observed in a 68°C geothermal brine sediment, where it dominated the microbial community, representing 91% of all detectable 16S rRNA genes. Correlation analysis of "Ca. Bipolaricaulota" operational taxonomic units (OTUs) with physicochemical parameters indicated that salinity was the strongest environmental factor measured associated with the distribution of this novel group in geothermal fluids. Correspondingly, analysis of 23 metagenome-assembled genomes (MAGs) revealed two distinct groups of "Ca. Bipolaricaulota" MAGs based on the differences in carbon metabolism: one group encoding the bacterial Wood-Ljungdahl pathway (WLP) for H2 dependent CO2 fixation is selected for at lower salinities, and a second heterotrophic clade that lacks the WLP that was selected for under hypersaline conditions in the geothermal brine sediment. In conclusion, our results highlight that the biogeography of "Ca. Bipolaricaulota" taxa is strongly correlated with salinity in hydrothermal ecosystems, which coincides with key differences in carbon acquisition strategies. The exceptionally high relative abundance of apparently heterotrophic representatives of this novel candidate Phylum in geothermal brine sediment observed here may help to guide future enrichment experiments to obtain representatives in pure culture.

Decoding geobiological evolution from microbiomes.

Genomic records of genetic recombination and mutation rates indicate that freshwater ammonia-oxidizing archaea have evolved through paleoclimate and geohydrological history.

Microbial Activities and Selection from Surface Ocean to Subseafloor on the Namibian Continental Shelf.

Oxygen minimum zones (OMZs) are hot spots for redox-sensitive nitrogen transformations fueled by sinking organic matter. In comparison, the regulating role of sulfur-cycling microbes in marine OMZs, their impact on carbon cycling in pelagic and benthic habitats, and activities below the seafloor remain poorly understood. Using 13C DNA stable isotope probing (SIP) and metatranscriptomics, we explored microbial guilds involved in sulfur and carbon cycling from the ocean surface to the subseafloor on the Namibian shelf. There was a clear separation in microbial community structure across the seawater-seafloor boundary, which coincided with a 100-fold-increased concentration of microbial biomass and unique gene expression profiles of the benthic communities. 13C-labeled 16S rRNA genes in SIP experiments revealed carbon-assimilating taxa and their distribution across the sediment-water interface. Most of the transcriptionally active taxa among water column communities that assimilated 13C from diatom exopolysaccharides (mostly Bacteroidetes, Actinobacteria, Alphaproteobacteria, and Planctomycetes) also assimilated 13C-bicarbonate under anoxic conditions in sediment incubations. Moreover, many transcriptionally active taxa from the seafloor community (mostly sulfate-reducing Deltaproteobacteria and sulfide-oxidizing Gammaproteobacteria) that assimilated 13C-bicarbonate under sediment anoxic conditions also assimilated 13C from diatom exopolysaccharides in the surface ocean and OMZ waters. Despite strong selection at the sediment-water interface, many taxa related to either planktonic or benthic communities were found to be present at low abundance and actively assimilating carbon under both sediment and water column conditions. In austral winter, mixing of shelf waters reduces stratification and suspends sediments from the seafloor into the water column, potentially spreading metabolically versatile microbes across niches. IMPORTANCE Microbial activities in oxygen minimum zones (OMZs) transform inorganic fixed nitrogen into greenhouse gases, impacting the Earth's climate and nutrient equilibrium. Coastal OMZs are predicted to expand with global change and increase carbon sedimentation to the seafloor. However, the role of sulfur-cycling microbes in assimilating carbon in marine OMZs and related seabed habitats remain poorly understood. Using 13C DNA stable isotope probing and metatranscriptomics, we explore microbial guilds involved in sulfur and carbon cycling from ocean surface to subseafloor on the Namibian shelf. Despite strong selection and differential activities across the sediment-water interface, many active taxa were identified in both planktonic and benthic communities, either fixing inorganic carbon or assimilating organic carbon from algal biomass. Our data show that many planktonic and benthic microbes linked to the sulfur cycle can cross redox boundaries when mixing of the shelf waters reduces stratification and suspends seafloor sediment particles into the water column.

Quantifying the effects of hydrogen on carbon assimilation in a seafloor microbial community associated with ultramafic rocks.

Thermodynamic models predict that H2 is energetically favorable for seafloor microbial life, but how H2 affects anabolic processes in seafloor-associated communities is poorly understood. Here, we used quantitative 13C DNA stable isotope probing (qSIP) to quantify the effect of H2 on carbon assimilation by microbial taxa synthesizing 13C-labeled DNA that are associated with partially serpentinized peridotite rocks from the equatorial Mid-Atlantic Ridge. The rock-hosted seafloor community was an order of magnitude more diverse compared to the seawater community directly above the rocks. With added H2, peridotite-associated taxa increased assimilation of 13C-bicarbonate and 13C-acetate into 16S rRNA genes of operational taxonomic units by 146% (±29%) and 55% (±34%), respectively, which correlated with enrichment of H2-oxidizing NiFe-hydrogenases encoded in peridotite-associated metagenomes. The effect of H2 on anabolism was phylogenetically organized, with taxa affiliated with Atribacteria, Nitrospira, and Thaumarchaeota exhibiting the most significant increases in 13C-substrate assimilation in the presence of H2. In SIP incubations with added H2, an order of magnitude higher number of peridotite rock-associated taxa assimilated 13C-bicarbonate, 13C-acetate, and 13C-formate compared to taxa that were not associated with peridotites. Collectively, these findings indicate that the unique geochemical nature of the peridotite-hosted ecosystem has selected for H2-metabolizing, rock-associated taxa that can increase anabolism under high H2 concentrations. Because ultramafic rocks are widespread in slow-, and ultraslow-spreading oceanic lithosphere, continental margins, and subduction zones where H2 is formed in copious amounts, the link between H2 and carbon assimilation demonstrated here may be widespread within these geological settings.

Carbon assimilating fungi from surface ocean to subseafloor revealed by coupled phylogenetic and stable isotope analysis.

Fungi are ubiquitous in the ocean and hypothesized to be important members of marine ecosystems, but their roles in the marine carbon cycle are poorly understood. Here, we use 13C DNA stable isotope probing coupled with phylogenetic analyses to investigate carbon assimilation within diverse communities of planktonic and benthic fungi in the Benguela Upwelling System (Namibia). Across the redox stratified water column and in the underlying sediments, assimilation of 13C-labeled carbon from diatom extracellular polymeric substances (13C-dEPS) by fungi correlated with the expression of fungal genes encoding carbohydrate-active enzymes. Phylogenetic analysis of genes from 13C-labeled metagenomes revealed saprotrophic lineages related to the facultative yeast Malassezia were the main fungal foragers of pelagic dEPS. In contrast, fungi living in the underlying sulfidic sediments assimilated more 13C-labeled carbon from chemosynthetic bacteria compared to dEPS. This coincided with a unique seafloor fungal community and dissolved organic matter composition compared to the water column, and a 100-fold increased fungal abundance within the subseafloor sulfide-nitrate transition zone. The subseafloor fungi feeding on 13C-labeled chemolithoautotrophs under anoxic conditions were affiliated with Chytridiomycota and Mucoromycota that encode cellulolytic and proteolytic enzymes, revealing polysaccharide and protein-degrading fungi that can anaerobically decompose chemosynthetic necromass. These subseafloor fungi, therefore, appear to be specialized in organic matter that is produced in the sediments. Our findings reveal that the phylogenetic diversity of fungi across redox stratified marine ecosystems translates into functionally relevant mechanisms helping to structure carbon flow from primary producers in marine microbiomes from the surface ocean to the subseafloor.

Genome Evolution in Bacteria Isolated from Million-Year-Old Subseafloor Sediment.

Beneath the seafloor, microbial life subsists in isolation from the surface world under persistent energy limitation. The nature and extent of genomic evolution in subseafloor microbes have been unknown. Here, we show that the genomes of Thalassospira bacterial populations cultured from million-year-old subseafloor sediments evolve in clonal populations by point mutation, with a relatively low rate of homologous recombination and elevated numbers of pseudogenes. Ratios of nonsynonymous to synonymous substitutions correlate with the accumulation of pseudogenes, consistent with a role for genetic drift in the subseafloor strains but not in type strains of Thalassospira isolated from the surface world. Consistent with this, pangenome analysis reveals that the subseafloor bacterial genomes have a significantly lower number of singleton genes than the type strains, indicating a reduction in recent gene acquisitions. Numerous insertion-deletion events and pseudogenes were present in a flagellar operon of the subseafloor bacteria, indicating that motility is nonessential in these million-year-old subseafloor sediments. This genomic evolution in subseafloor clonal populations coincided with a phenotypic difference: all subseafloor isolates have a lower rate of growth under laboratory conditions than the Thalassospira xiamenensis type strain. Our findings demonstrate that the long-term physical isolation of Thalassospira, in the absence of recombination, has resulted in clonal populations whereby reduced access to novel genetic material from neighbors has resulted in the fixation of new mutations that accumulate in genomes over millions of years. IMPORTANCE The nature and extent of genomic evolution in subseafloor microbial populations subsisting for millions of years below the seafloor are unknown. Subseafloor populations have ultralow metabolic rates that are hypothesized to restrict reproduction and, consequently, the spread of new traits. Our findings demonstrate that genomes of cultivated bacterial strains from the genus Thalassospira isolated from million-year-old abyssal sediment exhibit greatly reduced levels of homologous recombination, elevated numbers of pseudogenes, and genome-wide evidence of relaxed purifying selection. These substitutions and pseudogenes are fixed into the population, suggesting that the genome evolution of these bacteria has been dominated by genetic drift. Thus, reduced recombination, stemming from long-term physical isolation, resulted in small clonal populations of Thalassospira that have accumulated mutations in their genomes over millions of years.

Cryptic metabolisms in anoxic subseafloor sediment.

Microbial gene expression in anoxic subseafloor sediment was recently explored in the Baltic Sea and the Peru Margin. Our analysis of these data reveals diverse transcripts encoding proteins associated with neutralization of reactive oxygen species, including catalase, which may provide an in situ source of oxygen. We also detect transcripts associated with oxidation of iron and sulfur, and with reduction of arsenate, selenate and nitrate. Given limited input of electron acceptors from outside the system, these results suggest that the microbial communities use an unexpectedly diverse variety of electron acceptors. Products of water radiolysis and their interactions with sediment continuously provide diverse electron acceptors and hydrogen. Cryptic microbial utilization of these oxidized substrates and H2 may be an important mechanism for multi-million-year survival under the extreme energy limitation in subseafloor sediment.

Exploring the abundance, metabolic potential and gene expression of subseafloor Chloroflexi in million-year-old oxic and anoxic abyssal clay.

Chloroflexi are widespread in subsurface environments, and recent studies indicate that they represent a major fraction of the communities in subseafloor sediment. Here, we compare the abundance, diversity, metabolic potential and gene expression of Chloroflexi from three abyssal sediment cores from the western North Atlantic Gyre (water depth >5400 m) covering up to 15 million years of sediment deposition, where Chloroflexi were found to represent major components of the community at all sites. Chloroflexi communities die off in oxic red clay over 10-15 million years, and gene expression was below detection. In contrast, Chloroflexi abundance and gene expression at the anoxic abyssal clay site increase below the seafloor and peak in 2-3 million-year-old sediment, indicating a comparably higher activity. Metatranscriptomes from the anoxic site reveal increased expression of Chloroflexi genes involved in cell wall biogenesis, protein turnover, inorganic ion transport, defense mechanisms and prophages. Phylogenetic analysis shows that these Chloroflexi are closely related to homoacetogenic subseafloor clades and actively transcribe genes involved in sugar fermentations, gluconeogenesis and Wood-Ljungdahl pathway in the subseafloor. Concomitant expression of cell division genes indicates that these putative homoacetogenic Chloroflexi are actively growing in these million-year-old anoxic abyssal sediments.

Atribacteria Reproducing over Millions of Years in the Atlantic Abyssal Subseafloor.

How microbial metabolism is translated into cellular reproduction under energy-limited settings below the seafloor over long timescales is poorly understood. Here, we show that microbial abundance increases an order of magnitude over a 5 million-year-long sequence in anoxic subseafloor clay of the abyssal North Atlantic Ocean. This increase in biomass correlated with an increased number of transcribed protein-encoding genes that included those involved in cytokinesis, demonstrating that active microbial reproduction outpaces cell death in these ancient sediments. Metagenomes, metatranscriptomes, and 16S rRNA gene sequencing all show that the actively reproducing community was dominated by the candidate phylum "Candidatus Atribacteria," which exhibited patterns of gene expression consistent with fermentative, and potentially acetogenic, metabolism. "Ca. Atribacteria" dominated throughout the 8 million-year-old cored sequence, despite the detection limit for gene expression being reached in 5 million-year-old sediments. The subseafloor reproducing "Ca. Atribacteria" also expressed genes encoding a bacterial microcompartment that has potential to assist in secondary fermentation by recycling aldehydes and, thereby, harness additional power to reduce ferredoxin and NAD+ Expression of genes encoding the Rnf complex for generation of chemiosmotic ATP synthesis were also detected from the subseafloor "Ca Atribacteria," as well as the Wood-Ljungdahl pathway that could potentially have an anabolic or catabolic function. The correlation of this metabolism with cytokinesis gene expression and a net increase in biomass over the million-year-old sampled interval indicates that the "Ca Atribacteria" can perform the necessary catabolic and anabolic functions necessary for cellular reproduction, even under energy limitation in millions-of-years-old anoxic sediments.IMPORTANCE The deep subseafloor sedimentary biosphere is one of the largest ecosystems on Earth, where microbes subsist under energy-limited conditions over long timescales. It remains poorly understood how mechanisms of microbial metabolism promote increased fitness in these settings. We discovered that the candidate bacterial phylum "Candidatus Atribacteria" dominated a deep-sea subseafloor ecosystem, where it exhibited increased transcription of genes associated with acetogenic fermentation and reproduction in million-year-old sediment. We attribute its improved fitness after burial in the seabed to its capabilities to derive energy from increasingly oxidized metabolites via a bacterial microcompartment and utilize a potentially reversible Wood-Ljungdahl pathway to help meet anabolic and catabolic requirements for growth. Our findings show that "Ca Atribacteria" can perform all the necessary catabolic and anabolic functions necessary for cellular reproduction, even under energy limitation in anoxic sediments that are millions of years old.

Anaerobic metabolism of Foraminifera thriving below the seafloor.

Foraminifera are single-celled eukaryotes (protists) of large ecological importance, as well as environmental and paleoenvironmental indicators and biostratigraphic tools. In addition, they are capable of surviving in anoxic marine environments where they represent a major component of the benthic community. However, the cellular adaptations of Foraminifera to the anoxic environment remain poorly constrained. We sampled an oxic-anoxic transition zone in marine sediments from the Namibian shelf, where the genera Bolivina and Stainforthia dominated the Foraminifera community, and use metatranscriptomics to characterize Foraminifera metabolism across the different geochemical conditions. Relative Foraminifera gene expression in anoxic sediment increased an order of magnitude, which was confirmed in a 10-day incubation experiment where the development of anoxia coincided with a 20-40-fold increase in the relative abundance of Foraminifera protein encoding transcripts, attributed primarily to those involved in protein synthesis, intracellular protein trafficking, and modification of the cytoskeleton. This indicated that many Foraminifera were not only surviving but thriving, under the anoxic conditions. The anaerobic energy metabolism of these active Foraminifera was characterized by fermentation of sugars and amino acids, fumarate reduction, and potentially dissimilatory nitrate reduction. Moreover, the gene expression data indicate that under anoxia Foraminifera use the phosphogen creatine phosphate as an ATP store, allowing reserves of high-energy phosphate pool to be maintained for sudden demands of increased energy during anaerobic metabolism. This was co-expressed alongside genes involved in phagocytosis and clathrin-mediated endocytosis (CME). Foraminifera may use CME to utilize dissolved organic matter as a carbon and energy source, in addition to ingestion of prey cells via phagocytosis. These anaerobic metabolic mechanisms help to explain the ecological success of Foraminifera documented in the fossil record since the Cambrian period more than 500 million years ago.

Biodegradation of textile waste by marine bacterial communities enhanced by light.

Knowledge of biofilm formation on pollutants in the marine realm is expanding, but how communities respond to substrates during colonization remains poorly understood. Here, we assess community assembly and respiration in response to two different micropollutants, virgin high-density polyethylene (HDPE) microbeads and textile fibres under different light settings. Raman characterization, high-throughput DNA sequencing data, quantitative PCR, and respiration measurements reveal how a stimulation of aerobic respiration by micropollutants is translated into selection for significantly different communities colonizing the substrates. Despite the lack of evidence for biodegradation of HDPE, an increased abundance and respiration of bacterial taxa closely related to hydrocarbonoclastic Kordiimonas spp. and Alteromonas spp. in the presence of textile waste highlights their biodegradation potential. Incubations with textile fibres exhibited significantly higher respiration rates in the presence of light, which could be partially explained by photochemical dissolution of the textile waste into smaller bioavailable compounds. Our results suggest that the development and increased respiration of these unique microbial communities may potentially play a role in the bioremediation of the relatively long-lived textile pollutants in marine habitats, and that the respiration of heterotrophic hydrocarbon-degrading bacteria colonizing marine pollutants can be stimulated by light.

Author Correction: Metabolic activity analyses demonstrate that Lokiarchaeon exhibits homoacetogenesis in sulfidic marine sediments.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.