Nitrogen and sulfur cycling driven by Campylobacterota in the sediment–water interface of deep-sea cold seep: a case in the South China Sea

ABSTRACT Chemoautotrophs within Campylobacterota, especially Sulfurovum and Sulfurimonas, are abundant in the seawater–sediment interface of the Formosa cold seep in the South China Sea. However, the in situ activity and function of Campylobacterota are unknown. In this study, the geochemical role of Campylobacterota in the Formosa cold seep was investigated with multiple means. Two members of Sulfurovum and Sulfurimonas were isolated for the first time from deep-sea cold seep. These isolates are new chemoautotrophic species that can use molecular hydrogen as an energy source and CO2 as a sole carbon source. Comparative genomics identified an important hydrogen-oxidizing cluster in Sulfurovum and Sulfurimonas. Metatranscriptomic analysis detected high expression of hydrogen-oxidizing gene in the RS, suggesting that H2 was likely an energy source in the cold seep. Genomic analysis indicated that the Sulfurovum and Sulfurimonas isolates possess a truncated sulfur-oxidizing system, and metatranscriptomic analysis revealed that Sulfurovum and Sulfurimonas with this genotype were active in the surface of RS and likely contributed to thiosulfate production. Furthermore, geochemical and in situ analyses revealed sharply decreased nitrate concentration in the sediment–water interface due to microbial consumption. Consistently, the denitrification genes of Sulfurimonas and Sulfurovum were highly expressed, suggesting an important contribution of these bacteria to nitrogen cycling. Overall, this study demonstrated that Campylobacterota played a significant role in the cycling of nitrogen and sulfur in a deep-sea cold seep. IMPORTANCE Chemoautotrophs within Campylobacterota, in particular Sulfurovum and Sulfurimonas, are ubiquitous in deep-sea cold seeps and hydrothermal vents. However, to date, no Sulfurovum or Sulfurimonas has been isolated from cold seeps, and the ecological roles of these bacteria in cold seeps remain to be investigated. In this study, we obtained two isolates of Sulfurovum and Sulfurimonas from Formosa cold seep, South China Sea. Comparative genomics, metatranscriptomics, geochemical analysis, and in situ experimental study indicated collectively that Campylobacterota played a significant part in nitrogen and sulfur cycling in cold seep and was the cause of thiosulfate accumulation and sharp reduction of nitrate level in the sediment–water interface. The findings of this study promoted our understanding of the in situ function and ecological role of deep-sea Campylobacterota.

Sulfurovum and Sulfurimonas, are ubiquitous in cold seeps and hydrothermal vents. These bacteria commonly inhabit redox boundaries, such as reduced sediments (RS), microbial mats, and chimney walls (2), which are deeply influenced by the seepage or vent. Sulfurovum spp. is also an episymbiont and can colonize the gills of shrimps (3). At the time of writing, five Sulfurovum species have been published, all of which were isolated from deep-sea hydrothermal systems (4)(5)(6)(7)(8). For Sulfurimonas, nine species have been published and six species have been proposed (https://lpsn.dsmz.de/genus/ sulfurimonas). Five of these species, that is, Sulfurimonas autotrophica OK10 T , Sulfurimo nas paralvinellae GO25 T , Sulfurimonas indica NW8N T , 'Sulfurimonas hydrogeniphila' NW10 and 'Sulfurimonas sediminis' S2-6 (9-13), were from hydrothermal fields, while the other species were from a brackish lake (14), a terrestrial mud volcano (15), seawater (16,17), and marine sediments (18)(19)(20)(21). No members of Sulfurovum and Sulfurimonas have been isolated from cold seeps. Both Sulfurovum spp. and Sulfurimonas spp. possess versatile energy metabolisms. They can use hydrogen sulfide, hydrogen, sulfur, and thiosulfate as electron donors and use nitrate, sulfur, thiosulfate, and oxygen as electron acceptors (12). Since it is challenging to obtain in situ undisturbed samples in deep-sea and extract high-quality RNA or protein, very few studies on the in situ metabolism of Campylobac terota in hydrothermal vents have been reported (22), and no such study on deep-sea cold seep Campylobacterota has been documented.
The Formosa cold seep is located in the South China Sea (SCS), where several active seeps have been found. In our previous cruises, a large number of macrobenthos were observed around the seepage, including crabs (Shinkaia crosnieri), mussels (Bathymodio lus platifrons), and shrimps (Alvinocaris longirostris), and a large area of black RS was also found (23). Our previous study demonstrated that Campylobacterota, especially Sulfurovum, was dominant in the macrobenthic area and the RS (23). The abundant distribution of Campylobacterota suggests that these bacteria play a critical role in the geochemical cycle of the cold seep. Therefore, the Formosa cold seep is an ideal place to investigate and understand the ecological function of Campylobacterota in cold seeps.
The aim of this study was to investigate the geochemical role and in situ function of Campylobacterota in deep-sea cold seep. For this purpose, we successfully isolated new species of Sulfurovum and Sulfurimonas from the Formosa cold seep and character ized their phenotypic and biochemical features. We then examined the ecological role of Campylobacterota on a comprehensive scale using multiple approaches, including comparative genomics, metatranscriptomics, geochemical analysis, and in situ experi ments.

Sampling and in situ incubation
Samples used in this study were collected from Formosa cold seep in the SCS during the scientific cruises of "Kexue" in 2020 and 2021. Sediment samples were obtained with a push core as previously reported (23). Porewater was collected from the sediment sample with a soil solution sampler (Rhizon, Holland). S. crosnieri was collected with a remotely operated vehicle. A gas-tight sampler based on a lander platform was used to collect seawater around the seepage. Raman probes were deployed near the sample inlet to detect the geochemical parameters in the gas-tight samples. Seepage-surround ing water was collected with the gas-tight sampler and placed in situ for 14 days and then used for analysis. As a control, the seepage-surrounding water was collected and analyzed without in situ incubation.

Geochemical analysis
Hydrogen sulfide in the porewater was measured by the methylene blue method (24). The concentration of nitrate (NO 3 − ) was analyzed colorimetrically with a Quaatro continuous flow analyzer (SEAL Analytical Ltd, Southampton, UK). Sulfate concentration was determined using a Dionex Ion Chromatograph (Thermo Fisher Scientific, Waltham, MA, USA). The ammonium concentration in the porewater was measured onboard via indophenol blue spectrophotometry (25).

Bacterial enrichment and isolation
To enrich the Campylobacterota in the upper RS and S. crosnieri setae, each sample was transferred to 10-mL of anaerobic MJ medium (DSMZ 1011) in a sterile 15-mL centrifuge tube. After vibrating for 3-5 minutes, 0.5 mL of suspension was transferred to 100 mL of MJ medium in a glass bottle tightly sealed with butyl rubber under the condition of 80% H 2 /20% CO 2 (200 kPa). The sample was maintained at 10℃ for 1 month. Bacteria was isolated by serial dilution. Two isolates were named CS14 T and CS47 T . The purity of the isolates was verified by 16S rRNA gene sequencing, microscopic observation, and heterotrophic cultivation. The type strain Sulfurovum denitrificans DSM 19611 T was obtained from Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH (DSMZ, Braunschweig, Germany). The type strains Sulfurovum lithotrophicum JCM 12117 T , Sulfurovum riftiae JCM 30810 T , Sulfurimonas autotrophica JCM 11897 T , and Sulfurimonas gotlandica JCM 16533 T were obtained from Japan Collection of Microorganisms (JCM, Ibaraki, Japan). These strains were used as reference strains for fatty acid methyl ester (FAME) analysis and phenotypic characterization.

Phenotypic, phylogenetic, and chemotaxonomic analysis
The cellular morphology of the strains was observed with a transmission electron microscope (HT7700; Hitachi, Tokyo, Japan). Gram staining was performed with Gram staining kit (Haibo, Qingdao, China). To examine the temperature range of growth, the bacterium was grown in MJ medium under 80% H 2 /20% CO 2 at 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 28°C, 30°C, 35°C, 37°C, 40°C, and 45°Cfor 2 weeks, and the OD 600 (optical density at 600 nm) value of the bacterial solution was measured. To examine the NaCl range of growth, the bacterium was grown in MJ medium containing different concentrations of NaCl (wt/vol, 0%-10%, with an interval of 1%) at the optimal temperature and under the condition of 80% H 2 /20% CO 2 . To examine the pH range of growth, the bacterium was grown in MJ medium under 80% H 2 /20% CO 2 at the optimal temperature with different buffers (12). Doubling time was assessed according to a previous report (26).
Phylogenetic analysis was conducted according to our previous report (27). The phylogenomic tree was reconstructed based on an up-to-date 92 bacterial core gene sets by UBCG version 3.0 (21). For the analysis of FAME, bacteria were grown at the optimum temperature and harvested after 7-10 days of growth. Data for FAME were analyzed as previously reported (28).

Amplicon analysis, genomics, and metatranscriptomics
Amplicon sequencing and analysis were performed as previously reported (23). Bacterial genome sequencing and analysis were performed according to our previous report (27). The functions of the genes were annotated with NCBI-NR and KEGG databases. For genome comparison, 18 Sulfurovum and Sulfurimonas genomes were obtained from NCBI (Table S1). Three S. crosnieri setae samples and one top surface sample of RS were used for metatranscriptomic sequencing. RNA was extracted with E.Z.N.A. Soil RNA Kit (Omega Bio-Tek, Norcross, GA, USA). The cDNA library of each sample was constructed and sequenced with the HiSeq 3000 platform (Illumina, San Diego, CA, USA). Adapters and low-quality reads (base quality ≤ 20) were trimmed with Cutadapt. The clean reads were assembled, and the genes were predicted with megahit (29) and MetaGeneMark (30). All predicted genes were filtered by 100-bp length cutoff, and the redundancies were removed by cd-hit. Transcript expression levels were quantified and expressed fragments per kilobase of transcript per million fragments mapped (FPKM) (31). Metatranscriptome catalogs were searched against the NR database to obtain the taxonomy and function of genes, and genes belonged to Sulfurovum and Sulfurimonas were used to conduct expression analyses.

Microbe-mediated nitrate consumption in the reduced sediment-water interface leads to a sharp decrease in the nitrate level
In the top surface of RS1-3, the hydrogen sulfide concentration ranged from 0.8 to 3.9 mM, the ammonia concentration ranged from 61 to 163 µM, and the sulfate concen tration ranged from 19.1 to 27.7 mM. In the top surface of OS, the hydrogen sulfide, ammonia, and sulfate concentrations were 0.02 mM, 26 µM, and 28.3 mM, respectively. Thiosulfate was also detected in the top surface of RS1-3 (26.7-705.4 µM) but not in that of OS. The nitrate concentration was 24.3 µM in the seawater close to the RS and plunged to very low levels in the sediments, such as a few hundred nanomoles in the subsurface and non-detectable in the deeper depths ( Fig. 2A). An in situ experiment with seawater collected from the seepage vicinity showed that when the water was placed in situ in a gas-tight container for 14 days, its nitrate level was reduced by nearly 100% (Fig. 2B). Because nitrate-reducing Sulfurovum is rich in these seawaters (23), these results suggest that nitrate consumption by microbes in the seawater close to the seepage led to a sharp reduction in the nitrate level.

Phylogenetic and phylogenomic analysis
The analysis of the 16S rRNA gene sequence indicated that strain CS14 T belongs to the genus Sulfurovum and shares the highest sequence identity with Sulfurovum aggregans Monchim33 T (96.3%). The identities between strain CS14 T and other close members of Sulfurovum are below 96.0%. These levels of identities are below the suggested threshold for bacterial species delineation (32). Based on the 16S rRNA gene sequence analysis, strain CS47 T belongs to the genus Sulfurimonas and shares the highest sequence identities with Sulfurimonas gotlandica GD1 T (96.2%) and Sulfurimonas hongkongensis AST-10 T (96.1%). The identities between strain CS47 T and other close members of Sulfurimonas are below 95.0%. Phylogenetic analysis showed that strain CS14 T formed a group with Sulfurovum spp. and represented a basal member of this group (Fig. 3). Strain CS47 T formed a group with Sulfurimonas spp., further supporting the proposal that strain CS47 T belongs to the genus Sulfurimonas (Fig. 3). Similar results were observed in the phylogenomic analysis (Fig. S2). Genomic analysis indicated that strain CS14 T contains a circular chromosome of 2,753,309 bp with 2,754 predicted genes, and strain CS47 T contains a circular chromosome of 2,596,819 bp with 2,531 predicted genes. The G + C contents of the CS14 T and CS47 T genomes are 37.6% and 32.1%, respectively (Tables 1 and 2). The average nucleotide identity (ANI) values and the digital DNA-DNA hybridization (DDH) values between strain CS14 T and its close members in Sulfurovum are listed in Table S3. The ANI values and the digital DDH values between strain CS47 T and its close members in Sulfurimonas are listed in Table S3. All of these ANI and DDH values are much lower than the threshold values for prokaryotic species delineation (95%-96% for ANI and 70% for DDH) (33,34). Together, these results indicate that strains CS14 T and CS47 T represent novel species of Sulfurovum and Sulfurimonas, respectively.

Metatranscriptomic analysis unveils the in situ metabolic activities of Sulfurovum and Sulfurimonas
To understand the in situ metabolism of Sulfurovum and Sulfurimonas, metatranscrip tomic analysis was conducted. Given the difficulty of using seepage seawater for metatranscriptomics and the fact that Sulfurovum is abundant in the setae of the shrimp (S. crosnieri) inhabiting the seepage surroundings (23), we included three samples of shrimp setae (SC-1 to 3) in the metatranscriptomic analysis. The results showed that the hydrogen oxidization-associated gene hydB of Sulfurimonas and Sulfurovum was expressed at high levels in the surface of RS (153.5 and 111.6 in FPKM, respectively), but hydrogen oxidization-associated gene expression was not found in SC-1 to 3 ( Fig.  5; Table S5 and S6). The sulfide-oxidizing gene sqr of Sulfurovum was expressed at high levels in SC-1 to 3, especially in SC-3 (4061.6 in FPKM), and on the surface of RS (302.9 in FPKM) ( Fig. 5; Table S5). The expression of Sulfurimonas sqr was also high in the surface of RS (214.6 in FPKM) but very low or undetectable in S. crosnieri setae ( Fig. 5; Table  S6). The soxABCDXYZ genes of Sulfurovum were expressed at a high level in S. crosnieri setae (especially in SC-2 and SC-3) ( Fig. 5; Table S5), indicating that two sulfur-oxidizing systems (soxABXYZ and soxCDYZ) were operating in S. crosnieri setae. On the surface of RS, only soxC of Sulfurovum was expressed at a high level (63.7 in FPKM) ( Fig. 5; Table  S5). For Sulfurimonas, soxCD genes were expressed at a high level in S. crosnieri setae, especially in SC-2 and SC-3 (FPKM > 1,000), soxC was expressed at a high level in the surface of RS (529.9 in FPKM), and soxABX was not expressed or was expressed at an extremely low level (FPKM < 1.0) in S. crosnieri setae and on the surface of RS ( Fig.  5; Table S6). These results indicated that only one sulfur-oxidizing system (soxCDYZ) of Sulfurimonas was working in the RS and S. crosnieri setae. All of the denitrification-associated genes of Sulfurovum were expressed at high levels in shrimp setae and on the surface of RS ( Fig. 5; Table S5), except for norC, which was not detected on the surface of RS. For Sulfurimonas, all of the denitrification-associated genes were expressed at high levels on the surface of RS, except for nosZ, whose expression was not detected (Fig. 5; Table S6). NapA and norB were expressed at high levels in S. crosnieri setae, while other denitrification genes were not expressed or were expressed at low levels ( Fig. 5; Table S6). For carbon fixation, previous reports indicated that Campylobacterota could fix carbon via the reductive tricarboxylic acid pathway (35). Indeed, all of the genes of the reductive tricarboxylic acid pathway were found in the genomes of CS14 T and CS47 T . The key enzyme of this cycle, ATP-dependent citrate lyase, was also found in all of the analyzed genomes of Sulfurovum and Sulfurimonas. Metatranscriptome analyses indicated that ATP-dependent citrate lyase of Sulfurovum was expressed at high levels in all samples (Table S5). In addition, two transcripts encoding nitrogenase belonging to anaerobic methane-oxidizing archaea (ANME) and methanogenic archaea were expressed at high levels in the RS (Table S7).

DISCUSSION
Although Sulfurimonas and Sulfurovum are typical autotrophic bacteria dominant in both deep-sea hydrothermal vents and cold seeps, they have been isolated only from hydrothermal vents. In this study, two members of Sulfurovum and Sulfurimonas were isolated for the first time from a cold seep. Like most cultivable Sulfurovum spp. and Sulfurimonas spp. from other environments, the two cold seep isolates can use hydrogen as an electron donor and possess a hydrogen-oxidizing cluster in their genomes. Comparative genomic analysis indicated that this cluster is complete in all but one examined Sulfurovum spp. and Sulfurimonas spp. that can oxidize hydrogen and is incomplete in Sulfurovum spp. and Sulfurimonas spp. that cannot use hydrogen. These results indicated that this gene cluster is probably essential to hydrogen oxida tion. A previous study has reported that hydrogen can serve as an energy source in hydrothermal vents (36). It is unknown whether hydrogen can also be an energy source in deep-sea cold seeps. In this study, both strain CS14 T and strain CS47 T isolated from a cold seep used hydrogen as the electron donor, and metatranscriptomic analysis demonstrated the high expression of hydrogen-oxidizing genes in the RS. These results suggest that hydrogen is likely to serve as an energy source in deep-sea cold seeps. In addition to hydrogen, hydrogen sulfide is an important energy source in deepsea hydrothermal vents as well as cold seeps. Previous studies have shown that most Sulfurimonas spp. and one Sulfurovum can use sulfide as the electron donor (4,12). In this study, it was found that all Sulfurimonas and Sulfurovum sp. possess the sulfide-oxidizing gene (sqr). Although the isolates CS14 T and CS47 T could not use sulfide under laboratory conditions, the sqr gene of Sulfurovum and Sulfurimonas was expressed at high levels in RS, suggesting that Sulfurovum and Sulfurimonas used sulfide as an electron donor in situ. Further, comparative genome analysis indicated that most Sulfurovum and Sulfurimonas have two sulfur-oxidizing systems (soxABXYZ and soxCDYZ), and only a small number of these bacteria, including CS14 T and CS47 T isolated in this study, have one sulfur-oxidizing system (soxCDYZ). Differences in the number of the sulfur-oxidizing system can cause differences in metabolic features. When sulfide was the sole electron donor, Sulfurimonas with soxABXYZ and soxCDYZ could completely oxidize sulfide to sulfate, while Sulfurimo nas with soxCDYZ alone could only partially oxidize sulfide to form thiosulfate and sulfate (37). In this study, high concentrations of sulfide and thiosulfate were detected in RS, in  Table S5 and S6.
Research Article mBio which only the soxCDYZ system was expressed at a high level, suggesting that partial oxidation of sulfide in the RS contributed to thiosulfate accumulation. In contrast, both soxABXYZ and soxCDYZ of Sulfurovum were expressed at high levels in the microbial community of shrimp setae, implying complete oxidation of sulfide to sulfate. Previous studies have demonstrated that the denitrification pathway is common in Sulfurovum and Sulfurimonas (12), and a recent study has shown that two Sulfurimonas species are capable of nitrogen fixation (17). In the present study, we systematically examined the nitrogen metabolism pathways of Sulfurovum spp. and Sulfurimonas spp. via comparative genomic analysis. We found that all examined Sulfurovum spp. have the denitrification pathway, while Sulfurimonas spp. have versatile nitrogen metabolisms, including denitrification, dissimilatory denitrification reduction, assimilation denitrification reduction, and nitrogen fixation pathway, of which, the last three were identified for the first time in Sulfurimonas genomes. In the metatranscriptome, denitrificationassociated genes of Sulfurovum and Sulfurimonas were expressed at high levels in RS and shrimp seta microbiota, indicating an active denitrification process. Furthermore, compared to the nitrate level in the seawater, the nitrate level at the surface of the sediment decreased dramatically to barely detectable level. This is the first record of nitrate exhaustion in the sediment-water interface of a cold seep. Given the dominance of Campylobacterota observed in the present and previous studies, this result suggested nitrate consumption by Sulfurovum and Sulfurimonas in the interface. Indeed, the in situ experiment showed nitrate expenditure occurring in the seawater around the seepage. Altogether, these results demonstrated that Campylobacterota played an important biogeochemical role in the nitrogen cycle of cold seeps by reducing nitrate to nitrogen. It is interesting that although CS47 T isolated from this study and a few other Sulfuri monas spp. possess nitrogen fixation genes, the expression of these genes was not detected, suggesting that Sulfurimonas did not perform nitrogen fixation in the cold seep. In contrast, nitrogen fixation genes belonging to ANME and methanogens, which are known to be capable of nitrogen fixation (38,39), were expressed at high levels. Consistently, high concentrations of ammonia were detected in the RS. Based on these results, we propose that in the Formosa cold seep, Campylobacterota reduces nitrate to nitrogen, which is then transformed to ammonium by ANME and methanogens.
In this study, high concentrations of sulfide were detected in the top surface of RS, suggesting the existence of active anaerobic oxidation of methane in this region that led to the production of H 2 S. The H 2 S thus generated would diffuse into the surrounding water and reach the nearby macrobenthic area. Indeed, a previous study of the Formosa cold seep showed that the H 2 S concentration was up to 20 µM in the seawater of the animal community but could not be detected farther away from the seepage (23). The abundance of Sulfurovum closely correlated with the H 2 S level and was very high in the seawater in the animal community and very low or undetectable in the seawater farther away from the seepage (23). These observations indicated that H 2 S was an important factor affecting the distribution of Campylobacterota in the seawater. In the RS, Campylobacterota was mainly distributed in the upper areas, mostly the top surface. It is of note that the abundance/scarcity pattern of Campylobacterota appeared to be similar to that of nitrate, which had a high concentration in the seawater close to the top surface but dropped sharply in the subsurface and deeper regions of the sediments. These results suggested that nitrate was likely a key factor in determining the distribution of Campylobacterota in the RS.
In conclusion, in this study, we systematically analyzed the in situ activity and function of Campylobacterota in the Formosa cold seep. We found that Campylobacterota plays an important geochemical role in the sediment-water interface as illustrated in Fig.  6. The ANME and sulfate-reducing bacteria (SRB) probably oxidize anaerobically the methane in the upper RS, leading to the production of a large amount of sulfide. The sulfide then diffuses into the water and is utilized by Campylobacterota as an electron donor, producing thiosulfate and sulfate during the process. At the same time, nitrate as an electron donor is consumed heavily by Campylobacterota at the sediment-water interface, resulting in a sharp decline of the nitrate concentration in the upper sediments. Campylobacterota transforms nitrate into nitrogen, which is then fixed by ANME and methanogen to form ammonium, providing a sufficient nitrogen source for the local microbial community. Additionally, the carbon dioxide generated by the anaerobic oxidation of methane (AOM) can be used by Campylobacterota to form organic matter, providing nutrients for organisms in the cold seep.
The type strain, CS14 T (=CGMCC 1.18034 T =MCCC 1K08662 T ) was isolated from the deep-sea cold seep in the SCS. The genomic DNA G + C content is 37.6 mol%.
Cells are Gram-stain-negative, curved, 1.5-2.5 µm long, and 0.3-0.5 µm wide, motile by a polar flagellum. Anaerobic to microaerobic. Grows occurs at 0°C-37°C (optimum 25°C-28°C), pH 6.5-7.5 (optimum 6.5), and 1%-6% (wt/vol) NaCl (optimum 2%-3% [wt/ vol]). Obligate chemolithoautotrophic growth occurs with H 2 or S 0 as electron donors and nitrate or molecular oxygen as electron acceptor. Organic substrates are not utilized as carbon sources. anaerobic methane-oxidizing archaea (ANME) and sulfate-reducing bacteria (SRB) perform AOM in the upper sediments, producing sulfide, which diffuses into the water and supports Campylobacterota as an electron donor, where the sulfide is completely or partially oxidized to form thiosulfate and sulfate. At the same time, nitrate at the sediment-water interface is consumed by Campylobacterota as an electron acceptor and is transformed into nitrogen, which is then fixed by ANME and methanogens to form ammonium, providing a nitrogen source for the local microbial community. Additionally, the carbon dioxide generated by the AOM reaction can be fixed by Campylobacterota to form organic matter, which serves as nutrients for the organisms in the cold seep.

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The type strain, CS47 T (=CGMCC 1.18035 T =MCCC 1K08663 T ) was isolated from the deep-sea cold seep in the SCS. The genomic DNA G + C content is 32.1 mol%.

DATA AVAILABILITY STATEMENT
The amplicon sequencing data were deposited in the Sequence Read Archive (National Center for Biotechnology Information) under the accession number PRJNA917276. The 16S rRNA gene sequences of strain CS14 T and CS47 T were deposited in GenBank under the accession numbers OQ152601 and OQ152602, respectively. The complete genome sequences of strain CS14 T and CS47 T were deposited in GenBank under the accession numbers PRJNA917258 and PRJNA917262, respectively. Metatranscriptomic sequences were deposited in the Sequence Read Archive under the accession number PRJNA917539.

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