Publications

4774

Summary Large amounts of detrital organic matter and osmolytes accumulate in the sediments of hadal trenches (>6000 m depth) due to the funnelling effect. It is still unknown whether there are novel active microbes that depend on specific carbon sources in extreme and isolated environments. In this study, we present a novel active bacterial phylum, Candidatus Tianyabacteria in the FCB superphylum, which was enriched in sediments collected from the Challenger Deep. Genome binning resulted in high‐quality Ca . Tianyabacteria genomes representing two Ca . Tianyabacteria lineages (L1 and L2) in sediments 0–21 cm below the surface (cmbsf); L1 tends to be abundant in the upper layers (0–9 cmbsf), and L2 seems to be more prevalent in the deeper layers (12–21 cmbsf). Gene annotation and transcriptomics results indicate that the two lineages might import and catalyse amino acids and myo‐inositol into central carbon metabolism for a heterotrophic lifestyle. Probably due to differences in environmental oxygen levels, the L2 genomes harbour gene clusters responsible for denitrification and fermentation, while the L1 genomes encode octahaem cytochrome c and multicopper oxidase using unknown substrates. The Ca . Tianyabacteria are thus novel heterotrophic organisms that participate in processes of carbon, nitrogen and organic osmolyte cycling in hadal sediments.

Summary An anaerobic enrichment with CO from sediments of hypersaline soda lakes resulted in a methane‐forming binary culture, whereby CO was utilized by a bacterium and not the methanogenic partner. The bacterial isolate ANCO1 forms a deep‐branching phylogenetic lineage at the level of a new family within the class ‘ Natranaerobiia ’. It is an extreme haloalkaliphilic and moderate thermophilic acetogen utilizing CO, formate, pyruvate and lactate as electron donors and thiosulfate, nitrate (reduced to ammonia) and fumarate as electron acceptors. The genome of ANCO1 encodes a full Wood–Ljungdahl pathway allowing for CO oxidation and acetogenic conversion of pyruvate. A locus encoding Nap nitrate reductase/NrfA ammonifying nitrite reductase is also present. Thiosulfate respiration is encoded by a Phs/Psr‐like operon. The organism obviously relies on Na‐based bioenergetics, since the genome encodes for the Na + ‐Rnf complex, Na + ‐F1F0 ATPase and Na + ‐translocating decarboxylase. Glycine betaine serves as a compatible solute. ANCO1 has an unusual membrane polar lipid composition dominated by diethers, more common among archaea, probably a result of adaptation to multiple extremophilic conditions. Overall, ANCO1 represents a unique example of a triple extremophilic CO‐oxidizing anaerobe and is classified as a novel genus and species Natranaerofaba carboxydovora in a novel family Natranaerofabacea .

Summary Thermoplasmata is a widely distributed and ecologically important archaeal class in the phylum Euryarchaeota. Because few cultures and genomes are available, uncharacterized Thermoplasmata metabolisms remain unexplored. In this study, we obtained four medium‐ to high‐quality archaeal metagenome‐assembled genomes (MAGs) from the filamentous fragments of black‐odorous aquatic sediments (Foshan, Guangdong, China). Based on their 16S rRNA gene and ribosomal protein phylogenies, the four MAGs belong to the previously unnamed Thermoplasmata UBA10834 clade. We propose that this clade (five reference genomes from the Genome Taxonomy Database (GTDB) and four MAGs from this study) be considered a new order, Candidatus Gimiplasmatales. Metabolic pathway reconstructions indicated that the Ca . Gimiplasmatales MAGs can biosynthesize isoprenoids and nucleotides de novo . Additionally, some taxa have genes for formaldehyde and acetate assimilation, and the Wood–Ljungdahl CO 2 ‐fixation pathway, indicating a mixotrophic lifestyle. Sulfur reduction, hydrogen metabolism, and arsenic detoxification pathways were predicted, indicating sulfur‐, hydrogen‐, and arsenic‐transformation potentials. Comparative genomics indicated that the H 4 F Wood–Ljungdahl pathway of both Ca . Gimiplasmatales and Methanomassiliicoccales was likely obtained by the interdomain lateral gene transfer from the Firmicutes. Collectively, this study elucidates the taxonomic and potential metabolic diversity of the new order Ca . Gimiplasmatales and the evolution of this subgroup and its sister lineage Methanomassiliicoccales.

Abstract Na.no.ha.lo'bi.um. Gr. masc. n. nanos a dwarf; Gr. masc. n. hals , halos salt; Gr. masc. n. bios life; N.L. neut. n. Nanohalobium small organism living in salt. The genus Candidatus Nanohalobium was established based on a genome sequence found after the enrichment, cultivation, and characterization of a binary association with its chitinolytic host, obtained from a crystallizer pond brine collected in the marine solar saltern Saline della Laguna of Trapani, Italy. Ca . Nanohalobium is phylogenetically affiliated with members of the Ca . Nanohaloarchaeota ( Candidatus Haloredivivus, Candidatus Nanosalina, and Candidatus Nanosalinicola) of the archaeal DPANN superphylum. Cultivation experiments and analysis of the 0.97 Mb genome of Ca . Nanohalobium constans LC1Nh revealed that the organism has an organoheterotrophic, sugar‐fermenting lifestyle, lacking key anabolic machinery and any respiratory complexes. Additionally, the cultivation experiments revealed a remarkable mutualism of a nanohaloarchaeon–haloarchaeon association, namely the nanohaloarchaeon's ability to hydrolyze glycogen and starch to glucose, enabling the growth of Halomicrobium sp. LC1Hm in the absence of chitin. The low‐median isoelectric point for the predicted proteins suggests a “salt‐in” strategy used by the nanohaloarchaeon for osmotic balance. 16S rRNA gene sequences affiliated with Ca . Nanohalobium were recovered from other saltern ponds and hypersaline lakes worldwide. DNA G + C content (mol%) : 43.2 (genome). Type species : Candidatus Nanohalobium constans , La Cono et al. 2020. Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Candidatus Nanohalobium is: preferred name (not correct name) (last update, February 2025) * . LPSN classification: Archaea / Nanobdellati / Candidatus Nanohalarchaeota / Candidatus Nanohalobiia / Candidatus Nanohalobiales / Candidatus Nanohalobiaceae / Candidatus Nanohalobium The genus Candidatus Nanohalobium can also be recovered in the Genome Taxonomy Database (GTDB) as g__Nanohalobium (version v220) ** . GTDB classification: d__Archaea / p__Nanohaloarchaeota / c__Nanosalinia / o__Nanosalinales / f__Nanosalinaceae / g__Nanohalobium * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776

Abstract Sil.va.ni.grel'la. N.L. fem. dim. n. Silvanigrella named after Silva nigra the Latin geographic name of the Schwarzwald (Black Forest) mountains located in the south‐west of Germany. The genus Silvanigrella accommodates heterotrophic freshwater bacteria isolated from the water column of circumneutral or slightly acidic (pH 5–7) lakes and ponds with low ion concentrations (conductivity < 30 μS/cm). So far, only the two species Silvanigrella aquatica and Silvanigrella paludirubra have been described. Cells of the type strains have in common red pigmentation, motility, and pleomorphic morphology. In both species, the cell morphology ranges from rod‐shaped cells to filamentous forms, the cell size is variable in length and width. The type strain of S. aquatica in addition forms, densely coiled spirals. The type strains of both species grow at temperatures above 30°C, but only the type strain of S. paludirubra grows at temperatures below 10°C. Growth occurred up to supplementary NaCl concentrations of 1.0–1.1% (w/v). Both type strains utilized various organic substrates including carbohydrates, amino acids, and short‐chain fatty acids; however, the substrate spectra of the two strains differed. The most abundant fatty acid was iso‐C 15:0 for both type strains, contributing 33% to the total fatty acid content. The major respiratory quinone of S. paludirubra is menaquinone MK‐8, while the quinones of S. aquatica remained unidentified. The type strains of S. aquatica and S. paludirubra were both characterized by medium‐sized genomes (3.5 and 3.9 Mb, respectively) with low G + C content (32.6 and 29.3 mol%, respectively). DNA G + C content (mol%) : 29–33 (genome sequencing). Type species : Silvanigrella aquatica Hahn et al. 2017 VP . Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Silvanigrella is: correct name (last update, February 2025) * . LPSN classification: Bacteria / Pseudomonadati / Pseudomonadota / Oligoflexia / Silvanigrellales / Silvanigrellaceae / Silvanigrella The genus Silvanigrella can also be recovered in the Genome Taxonomy Database (GTDB) as g__Silvanigrella (version v220) ** . GTDB classification: d__Bacteria / p__Bdellovibrionota / c__Oligoflexia / o__Silvanigrellales / f__Silvanigrellaceae / g__Silvanigrella * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776

Abstract Ni.tro.so.pe.la'gi.cus. N.L. masc. adj. nitrosus nitrous; L. masc. adj. pelagicus of the open sea; N.L. masc. n. Nitrosopelagicus a nitrite producer of the open sea. The genus Candidatus Nitrosopelagicus is composed of marine ammonia‐oxidizing archaea, almost all of which are uncultivated. They are found in shallow waters (<200 m depth) of the oligotrophic tropical, subtropical, and temperate open oceans. A single species has been described, Candidatus Nitrosopelagicus brevis, which couples growth with the oxidation of ammonia to nitrite. One described strain ( Ca . N. brevis U25) is capable of hydrolyzing urea to supply the ammonia required for growth. Cells are obligately aerobic, small, and nonmotile rods. They grow free‐living, not associated with surfaces. No growth enhancement has been observed in the presence of organic carbon compounds; a reduction in the lag phase of growth has been observed with addition of α‐ketoacids, potentially serving as radical oxygen scavengers. Organisms are mesophilic and obligately marine. Lipid composition distinguishes Ca . Nitrosopelagicus from Nitrosopumilus using glycerol dibiphytanyl glycerol tetraether (GDGT) distributions, with lower amounts of GDGT‐2 and higher amounts of GDGT‐0 and GDGT‐1 found in Ca . Nitrosopelagicus. Abundance of Ca . Nitrospelagicus‐like organisms is correlated with nitrification rates, suggesting that these organisms are the dominant ammonia oxidizers in epipelagic and upper mesopelagic environments of the low‐ and mid‐latitude open oceans. DNA G + C content (mol%) : 33.1. Type species : Candidatus Nitrosopelagicus brevis Santoro et al. 2015. Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Candidatus Nitrosopelagicus is: preferred name (not correct name) (last update, February 2025) * . LPSN classification: Archaea / Thermoproteati / Thermoproteota / Nitrososphaeria / Nitrosopumilales / incertae sedis / Candidatus Nitrosopelagicus The genus Candidatus Nitrosopelagicus can also be recovered in the Genome Taxonomy Database (GTDB) as g__Nitrosopelagicus (version v220) ** . GTDB classification: d__Archaea / p__Thermoproteota / c__Nitrososphaeria / o__Nitrososphaerales / f__Nitrosopumilaceae / g__Nitrosopelagicus * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776

Our results suggest that Midichloria mitochondrii , the intramitochondrial bacterium, does not invade mitochondria like predatory bacteria do but instead moves from mitochondrion to mitochondrion within the oocytes of Ixodes ricinus . A better understanding of the lifestyle of M. mitochondrii will allow us to better define the role of this bacterial symbiont in the host physiology.