Manganese reduction and associated microbial communities in Antarctic surface sediments.

The polar regions are the fastest warming places on earth. Accelerated glacial melting causes increased supply of nutrients such as metal oxides (i.e.

Secondary production and priming reshape the organic matter composition in marine sediments.

Organic matter (OM) transformations in marine sediments play a crucial role in the global carbon cycle. However, secondary production and priming have been ignored in marine biogeochemistry. By incubating shelf sediments with various C-labeled algal substrates for 400 days, we show that ~65% of the lipids and ~20% of the proteins were mineralized by numerically minor heterotrophic bacteria as revealed by RNA stable isotope probing.

Physiological versatility of ANME-1 and Bathyarchaeotoa-8 archaea evidenced by inverse stable isotope labeling.

Background: The trophic strategy is one key principle to categorize microbial lifestyles, by broadly classifying microorganisms based on the combination of their preferred carbon sources, electron sources, and electron sinks. Recently, a novel trophic strategy, i.e.

Biogenic manganese oxides promote metal(loid) remediation by shaping microbial communities in biological aqua crust.

Biological aqua crust (biogenic aqua crust-BAC) is a potentially sustainable solution for metal(loid) bioremediation in global water using solar energy. However, the key geochemical factors and underlying mechanisms shaping microbial communities in BAC remain poorly understood. The current study aimed at determining the in situ metal(loid) distribution and the key geochemical factors related to microbial community structure and metal(loid)-related genes in BAC of a representative Pb/Zn tailing pond.

Unexpected carbon utilization activity of sulfate-reducing microorganisms in temperate and permanently cold marine sediments.

Significant amounts of organic carbon in marine sediments are degraded, coupled with sulfate reduction. However, the actual carbon and energy sources used in situ have not been assigned to each group of diverse sulfate-reducing microorganisms (SRM) owing to the microbial and environmental complexity in sediments. Here, we probed microbial activity in temperate and permanently cold marine sediments by using potential SRM substrates, organic fermentation products at very low concentrations (15-30 μM), with RNA-based stable isotope probing.

Chronic exposure to low concentrations of microplastics causing gut tissue damage but non-significant changes in the microbiota of marine medaka larvae (Oryzias melastigma).

Microplastics (MPs) have become a popular research topic due to their potential ramifications on aquatic organisms. To evaluate the ecotoxicological impacts of chronic exposure to different microplastics on marine medaka larvae, we exposed medaka larvae to 200 μg/L of polyethylene (PE-200) and polylactic acid (PLA-200) microplastics for 60 days, respectively. The results indicated that both exposures had no significant effect on fish length/weight and did not result in fish mortality.

Novel biological aqua crust enhances in situ metal(loid) bioremediation driven by phototrophic/diazotrophic biofilm.

Background: Understanding the ecological and environmental functions of phototrophic biofilms in the biological crust is crucial for improving metal(loid) (e.g. Cd, As) bioremediation in mining ecosystems.

Metal-Driven Anaerobic Oxidation of Methane as an Important Methane Sink in Methanic Cold Seep Sediments.

Anaerobic oxidation of methane (AOM) coupled with reduction of metal oxides is supposed to be a globally important bioprocess in marine sediments. However, the responsible microorganisms and their contributions to methane budget are not clear in deep sea cold seep sediments. Here, we combined geochemistry, muti-omics, and numerical modeling to study metal-dependent AOM in methanic cold seep sediments in the northern continental slope of the South China Sea.

The majority of microorganisms in gas hydrate-bearing subseafloor sediments ferment macromolecules.

Background: Gas hydrate-bearing subseafloor sediments harbor a large number of microorganisms. Within these sediments, organic matter and upward-migrating methane are important carbon and energy sources fueling a light-independent biosphere. However, the type of metabolism that dominates the deep subseafloor of the gas hydrate zone is poorly constrained.

Catabolic protein degradation in marine sediments confined to distinct archaea.

Metagenomic analysis has facilitated prediction of a variety of carbon utilization potentials by uncultivated archaea including degradation of protein, which is a wide-spread carbon polymer in marine sediments. However, the activity of detrital catabolic protein degradation is mostly unknown for the vast majority of archaea. Here, we show actively executed protein catabolism in three archaeal phyla (uncultivated Thermoplasmata, SG8-5; Bathyarchaeota subgroup 15; Lokiarchaeota subgroup 2c) by RNA- and lipid-stable isotope probing in incubations with different marine sediments.

Metatranscriptomics reveals different features of methanogenic archaea among global vegetated coastal ecosystems.

Vegetated coastal ecosystems (VCEs; i.e., mangroves, saltmarshes, and seagrasses) represent important sources of natural methane emission.

Iron and sulfate reduction structure microbial communities in (sub-)Antarctic sediments.

Permanently cold marine sediments are heavily influenced by increased input of iron as a result of accelerated glacial melt, weathering, and erosion. The impact of such environmental changes on microbial communities in coastal sediments is poorly understood. We investigated geochemical parameters that shape microbial community compositions in anoxic surface sediments of four geochemically differing sites (Annenkov Trough, Church Trough, Cumberland Bay, Drygalski Trough) around South Georgia, Southern Ocean.

Crystalline iron oxides stimulate methanogenic benzoate degradation in marine sediment-derived enrichment cultures.

Elevated dissolved iron concentrations in the methanic zone are typical geochemical signatures of rapidly accumulating marine sediments. These sediments are often characterized by co-burial of iron oxides with recalcitrant aromatic organic matter of terrigenous origin. Thus far, iron oxides are predicted to either impede organic matter degradation, aiding its preservation, or identified to enhance organic carbon oxidation via direct electron transfer.

Subgroup level differences of physiological activities in marine Lokiarchaeota.

Asgard is a recently discovered archaeal superphylum, closely linked to the emergence of eukaryotes. Among Asgard archaea, Lokiarchaeota are abundant in marine sediments, but their in situ activities are largely unknown except for Candidatus 'Prometheoarchaeum syntrophicum'. Here, we tracked the activity of Lokiarchaeota in incubations with Helgoland mud area sediments (North Sea) by stable isotope probing (SIP) with organic polymers, C-labelled inorganic carbon, fermentation intermediates and proteins.

Diverse Asgard archaea including the novel phylum Gerdarchaeota participate in organic matter degradation.

Asgard is an archaeal superphylum that might hold the key to understand the origin of eukaryotes, but its diversity and ecological roles remain poorly understood. Here, we reconstructed 15 metagenomic-assembled genomes from coastal sediments covering most known Asgard archaea and a novel group, which is proposed as a new Asgard phylum named as the "Gerdarchaeota". Genomic analyses predict that Gerdarchaeota are facultative anaerobes in utilizing both organic and inorganic carbon.

Rates and Microbial Players of Iron-Driven Anaerobic Oxidation of Methane in Methanic Marine Sediments.

The flux of methane, a potent greenhouse gas, from the seabed is largely controlled by anaerobic oxidation of methane (AOM) coupled to sulfate reduction (S-AOM) in the sulfate methane transition (SMT). S-AOM is estimated to oxidize 90% of the methane produced in marine sediments and is mediated by a consortium of anaerobic methanotrophic archaea (ANME) and sulfate reducing bacteria. An additional methane sink, i.

DNA and RNA Stable Isotope Probing of Methylotrophic Methanogenic Archaea.

Methylotrophic methanogenic archaea are an integral part of the carbon cycle in various anaerobic environments. Different from methylotrophic bacteria, methylotrophic methanogens assimilate both, the methyl compound and dissolved inorganic carbon. Here, we present DNA- and RNA-stable isotope probing (SIP) methods involving an effective labeling strategy using C-labeled dissolved inorganic carbon (DIC) as carbon source along with methanol as dissimilatory substrate.

CO conversion to methane and biomass in obligate methylotrophic methanogens in marine sediments.

Methyl substrates are important compounds for methanogenesis in marine sediments but diversity and carbon utilization by methylotrophic methanogenic archaea have not been clarified. Here, we demonstrate that RNA-stable isotope probing (SIP) requires C-labeled bicarbonate as co-substrate for identification of methylotrophic methanogens in sediment samples of the Helgoland mud area, North Sea. Using lipid-SIP, we found that methylotrophic methanogens incorporate 60-86% of dissolved inorganic carbon (DIC) into lipids, and thus considerably more than what can be predicted from known metabolic pathways (~40% contribution).

Temperature Controls Crystalline Iron Oxide Utilization by Microbial Communities in Methanic Ferruginous Marine Sediment Incubations.

Microorganisms can use crystalline iron minerals for iron reduction linked to organic matter degradation or as conduits for direct interspecies electron transfer (mDIET) to syntrophic partners, e.g., methanogens.