High-quality Metagenome-assembled Genomes Research Articles

Chlamydiae as symbionts of photosynthetic dinoflagellates.

Chlamydiae are ubiquitous intracellular bacteria and infect a wide diversity of eukaryotes, including mammals. However, chlamydiae have never been reported to infect photosynthetic organisms. Here, we describe a novel chlamydial genus and species, Candidatus Algichlamydia australiensis, capable of infecting the photosynthetic dinoflagellate Cladocopium sp. (originally isolated from a scleractinian coral). A. australiensis was confirmed to be intracellular by fluorescence in situ hybridization and confocal laser scanning microscopy, and temporally stable at the population level by monitoring its relative abundance across four weeks of host growth. Using a combination of short- and long-read sequencing, we recovered a high-quality (completeness 91.73% and contamination 0.27%) metagenome-assembled genome of A. australiensis. Phylogenetic analyses show that this chlamydial taxon represents a new genus and species within the Simkaniaceae family. A. australiensis possesses all the hallmark genes for chlamydiae-host interactions, including a complete type III secretion system. In addition, a type IV secretion system is encoded on a plasmid and has previously been observed for only three other chlamydial species. Twenty orthologous groups of genes are unique to A. australiensis, one of which is structurally similar to a protein known from Cyanobacteria and Archaeplastida involved in thylakoid biogenesis and maintenance, hinting at potential chlamydiae interactions with the chloroplasts of Cladocopium cells. Our study shows that chlamydiae infect dinoflagellate symbionts of cnidarians, the first photosynthetic organism reported to harbor chlamydiae, thereby expanding the breadth of chlamydial hosts and providing a new contribution to the discussion around the role of chlamydiae in the establishment of the primary plastid.

Water-fertilizer regulation drives microorganisms to promote iron, nitrogen and manganese cycling: A solution for arsenic and cadmium pollution in paddy soils

The co-contamination of arsenic (As) and cadmium (Cd) in rice fields presents a global imperative for resolution. However, understanding the complex microbially driven geochemical processes and network connectivity crucial for As and Cd bioavailability under the frequent redox transitions in rice fields remains limited. Here, we conducted a series of microcosm experiments, using flooding and drainage, alongside fertilization treatments to emulate different redox environment in paddy soils. Soil As significantly reduced in drained conditions following applications of biochar or calcium-magnesium-phosphate (CMP) fertilizers by 26.3 % and 31.2 %, respectively, with concurrent decreases in Cd levels. Utilizing geochemical models, we identified the primary redox cycles dynamically altering during flooding (Fe and S cycles) and drainage (Fe, Mn, and N cycles). PLS-SEM elucidated 76 % and 61 % of the variation in Cd and As through Mn and N cycles. Functional genes implicated in multi-element cycles were analyzed, revealing a significantly higher abundance of assimilatory N reduction genes (nasA, nirA/B, narB) in drained soil, whereas an increase in ammonia-oxidizing genes (amoA/B) and a decrease in nitrate reduction to ammonium genes were observed after CMP fertilizer application. Biochar application led to significant enrichment of the substrate-binding protein of the Mn transport gene (mntC). Moreover, Fe transport genes were enriched after biochar or CMP application compared to drained soils. Among 40 high-quality metagenome-assembled genomes (MAGs), microbial predictors associated with low Cd and As contents across different treatments were examined. Bradyrhizobacea harbored abundant Mn and FeIII transport genes, while Nitrososphaeraceae carried nitrification-related genes. Two MAGs affiliated with Caulobacteraceae, carrying diverse Fe transport genes, were enriched in biochar-applied soils. Therefore, applying CMP fertilizer or biochar in aerobic rice fields can synergistically reduce the bioavailability of Cd and As by specifically enhancing the circulation of essential elements.

Construction of high-quality genomes and gene catalogue for culturable microbes of sugarcane (Saccharum spp.)

Microbes living inside or around sugarcane (Saccharum spp.) are crucial for their resistance to abiotic and biotic stress, growth, and development. Sequences of microbial genomes and genes are helpful to understand the function of these microbes. However, there is currently a lack of such knowledge in sugarcane. Here, we combined Nanopore and Illumina sequencing technologies to successfully construct the first high-quality metagenome-assembled genomes (MAGs) and gene catalogues of sugarcane culturable microbes (GCSCMs), which contained 175 species-level genome bins (SGBs), and 7,771,501 non-redundant genes. The SGBs included 79 novel culturable bacteria genomes, and 3 bacterial genomes with nitrogen-fixing gene clusters. Four single scaffold near-complete circular MAGs (cMAGs) with 0% contamination were obtained from Nanopore sequencing data. In conclusion, we have filled a research gap in the genomes and gene catalogues of culturable microbes of sugarcane, providing a vital data resource for further understanding the genetic basis and functions of these microbes. In addition, our methodology and results can provide guidance and reference for other plant microbial genome and gene catalogue studies.

Microbial diversity and metabolic pathways linked to benzene degradation in petrochemical-polluted groundwater

The rapid advance in shotgun metagenome sequencing has enabled us to identify uncultivated functional microorganisms in polluted environments. While aerobic petrochemical-degrading pathways have been extensively studied, the anaerobic mechanisms remain less explored. Here, we conducted a study at a petrochemical-polluted groundwater site in Henan Province, Central China. A total of twelve groundwater monitoring wells were installed to collect groundwater samples. Benzene appeared to be the predominant pollutant, detected in 10 out of 12 samples, with concentrations ranging from 1.4 μg/L to 5,280 μg/L. Due to the low aquifer permeability, pollutant migration occurred slowly, resulting in relatively low benzene concentrations downstream within the heavily polluted area. Deep metagenome sequencing revealed Proteobacteria as the dominant phylum, accounting for over 63 % of total abundances. Microbial α-diversity was low in heavily polluted samples, with community compositions substantially differing from those in lightly polluted samples. dmpK encoding the phenol/toluene 2-monooxygenase was detected across all samples, while the dioxygenase bedC1 was not detected, suggesting that aerobic benzene degradation might occur through monooxygenation. Sequence assembly and binning yielded 350 high-quality metagenome-assembled genomes (MAGs), with 30 MAGs harboring functional genes associated with aerobic or anaerobic benzene degradation. About 80 % of MAGs harboring functional genes associated with anaerobic benzene degradation remained taxonomically unclassified at the genus level, suggesting that our current database coverage of anaerobic benzene-degrading microorganisms is very limited. Furthermore, two genes integral to anaerobic benzene metabolism, i.e, benzoyl-CoA reductase (bamB) and glutaryl-CoA dehydrogenase (acd), were not annotated by metagenome functional analyses but were identified within the MAGs, signifying the importance of integrating both contig-based and MAG-based approaches. Together, our efforts of functional annotation and metagenome binning generate a robust blueprint of microbial functional potentials in petrochemical-polluted groundwater, which is crucial for designing proficient bioremediation strategies.

Aerobic anoxygenic phototrophs play important roles in nutrient cycling within cyanobacterial Microcystis bloom microbiomes

BackgroundDuring the bloom season, the colonial cyanobacterium Microcystis forms complex aggregates which include a diverse microbiome within an exopolymer matrix. Early research postulated a simple mutualism existing with bacteria benefitting from the rich source of fixed carbon and Microcystis receiving recycled nutrients. Researchers have since hypothesized that Microcystis aggregates represent a community of synergistic and interacting species, an interactome, each with unique metabolic capabilities that are critical to the growth, maintenance, and demise of Microcystis blooms. Research has also shown that aggregate-associated bacteria are taxonomically different from free-living bacteria in the surrounding water. Moreover, research has identified little overlap in functional potential between Microcystis and members of its microbiome, further supporting the interactome concept. However, we still lack verification of general interaction and know little about the taxa and metabolic pathways supporting nutrient and metabolite cycling within Microcystis aggregates.ResultsDuring a 7-month study of bacterial communities comparing free-living and aggregate-associated bacteria in Lake Taihu, China, we found that aerobic anoxygenic phototrophic (AAP) bacteria were significantly more abundant within Microcystis aggregates than in free-living samples, suggesting a possible functional role for AAP bacteria in overall aggregate community function. We then analyzed gene composition in 102 high-quality metagenome-assembled genomes (MAGs) of bloom-microbiome bacteria from 10 lakes spanning four continents, compared with 12 complete Microcystis genomes which revealed that microbiome bacteria and Microcystis possessed complementary biochemical pathways that could serve in C, N, S, and P cycling. Mapping published transcripts from Microcystis blooms onto a comprehensive AAP and non-AAP bacteria MAG database (226 MAGs) indicated that observed high levels of expression of genes involved in nutrient cycling pathways were in AAP bacteria.ConclusionsOur results provide strong corroboration of the hypothesized Microcystis interactome and the first evidence that AAP bacteria may play an important role in nutrient cycling within Microcystis aggregate microbiomes.Bqr2Xubb8cMPqvNydLEaxMVideo

Revealing microbiota characteristics and predicting flavor-producing sub-communities in Nongxiangxing baijiu pit mud through metagenomic analysis and metabolic modeling

The microorganisms of the pit mud (PM) of Nongxiangxing baijiu (NXXB) have an important role in the synthesis of flavor substances, and they determine attributes and quality of baijiu. Herein, we utilize metagenomics and genome-scale metabolic models (GSMMs) to investigate the microbial composition, metabolic functions in PM microbiota, as well as to identify microorganisms and communities linked to flavor compounds. Metagenomic data revealed that the most prevalent assembly of bacteria and archaea was Proteiniphilum, Caproicibacterium, Petrimonas, Lactobacillus, Clostridium, Aminobacterium, Syntrophomonas, Methanobacterium, Methanoculleus, and Methanosarcina. The important enzymes ofPMwere in bothGH and GT familymetabolism. A total of 38 high-quality metagenome-assembled genomes (MAGs) were obtained, including those at the family level (n = 13), genus level (n = 17), and species level (n = 8). GSMMs of the 38 MAGs were then constructed. From the GSMMs, individual and community capabilities respectively were predicted to be able to produce 111 metabolites and 598 metabolites. Twenty-three predicted metabolites were consistent with the metabonomics detected flavors and served as targets. Twelve sub-community of were screened by cross-feeding of 38 GSMMs. Of them, Methanobacterium, Sphaerochaeta, Muricomes intestini, Methanobacteriaceae, Synergistaceae, and Caloramator were core microorganisms for targets in each sub-community. Overall, this study of metagenomic and target-community screening could help our understanding of the metabolite–microbiome association and further bioregulation of baijiu.

Effects of different assembly strategies on gene annotation in activated sludge

Activated sludge comprises diverse bacteria, fungi, and other microorganisms, featuring a rich repertoire of genes involved in antibiotic resistance, pollutant degradation, and elemental cycling. In this regard, hybrid assembly technology can revolutionize metagenomics by detecting greater gene diversity in environmental samples. Nonetheless, the optimal utilization and comparability of genomic information between hybrid assembly and short- or long-read technology remain unclear. To address this gap, we compared the performance of the hybrid assembly, short- and long-read technologies, abundance and diversity of annotated genes, and taxonomic diversity by analysing 46, 161, and 45 activated sludge metagenomic datasets, respectively. The results revealed that hybrid assembly technology exhibited the best performance, generating the most contiguous and longest contigs but with a lower proportion of high-quality metagenome-assembled genomes than short-read technology. Compared with short- or long-read technologies, hybrid assembly technology can detect a greater diversity of microbiota and antibiotic resistance genes, as well as a wider range of potential hosts. However, this approach may yield lower gene abundance and pathogen detection. Our study revealed the specific advantages and disadvantages of hybrid assembly and short- and long-read applications in wastewater treatment plants, and our approach could serve as a blueprint to be extended to terrestrial environments.

Metagenomics of two aquifers with thermal anomalies in Mallorca Island, and proposal of new uncultivated taxa named following the rules of SeqCode

Groundwater offers an intriguing blend of distinctive physical and chemical conditions, constituting a challenge for microbial life. In Mallorca, the largest island of Balearic archipelago, harbours a variety of thermal anomalies (i.e., geothermal manifestation where surface aquifers exhibiting temperatures exceeding the regional average). The metagenomes of two aquifers in the centre and southern of the island showed Pseudomonadota to be the most represented phylum when using extracted 16S rRNA gene sequences. However, the microbial structures within and between aquifers were remarkably diverse but similar in their metabolic profiles as revealed by the metagenome-assembled genomes (MAGs) pointing to a prevalence of aerobic chemolithoautotrophic and heterotrophic metabolisms, especially in the Llucmajor aquifer. Also, some evidences of anaerobic lifestyles were detected, which would indicate that these environments either could suffer episodes of oxygen depletion or the anaerobes had been transported from deeper waters. We believe that the local environmental factors (temperature, external inputs or chemistry) seem to be more relevant than the connection and, eventually, transport of microbial cells within the aquifer in determining the highly divergent structures. Notably, most of the reconstructed genomes belonged to undescribed bacterial lineages and from them two high-quality MAGs could be classified as novel taxa named following the rules of the Code for Nomenclature of Prokaryotes Described from Sequence Data (SeqCode). Accordingly, we propose the new species and genus Costitxia debesea gen. nov., sp. nov., affiliated with the novel family Costitxiaceae fam. nov., order Costitxiales ord. nov. and class Costitxiia class. nov.; and the new new species and genus Lloretia debesea gen. nov. sp. nov. affiliated with the novel family Lloretiaceae fam. nov.

Biosynthetic potential of the sediment microbial subcommunities of an unexplored karst ecosystem and its ecological implications.

Microbial communities from various environments have been studied in the quest for new natural products with a broad range of applications in medicine and biotechnology. We employed an enrichment method and genome mining tools to examine the biosynthetic potential of microbial communities in the sediments of a coastal sinkhole within the karst ecosystem of the Yucatán Peninsula, Mexico. Our investigation led to the detection of 203 biosynthetic gene clusters (BGCs)and 55 secondary metabolites (SMs)within 35 high-quality metagenome-assembled genomes (MAGs)derived from these subcommunities. The most abundant types of BGCs were Terpene, Nonribosomal peptide-synthetase, and Type III polyketide synthase. Some of the in silico identified BGCs and SMs have been previously reported to exhibit biological activities against pathogenic bacteria and fungi. Others could play significant roles in the sinkhole ecosystem, such as iron solubilization and osmotic stress protection. Interestingly, 75% of the BGCs showed no sequence homology with bacterial BGCs previously reported in the MiBIG database. This suggests that the microbial communities in this environment could be an untapped source of genes encoding novel specialized compounds. The majority of the BGCs were identified in pathways found in the genus Virgibacillus, followed by Sporosarcina, Siminovitchia, Rhodococcus, and Halomonas. The latter, along with Paraclostridium and Lysinibacillus, had the highest number of identified BGC types. This study offers fresh insights into the potential ecological role of SMs from sediment microbial communities in an unexplored environment, underscoring their value as a source of novel natural products.

Oxygen mediated mobilization and co-occurrence of antibiotic resistance in lab-scale bioreactor using metagenomic binning.

Sub-lethal levels of antibiotic stimulate bacteria to generate reactive oxygen species (ROS) that promotes emergence and spread of antibiotic resistance mediated by mobile genetic elements (MGEs). Nevertheless, the influence of dissolved oxygen (DO) levels on mobility of antibiotic resistance genes (ARGs) in response to ROS-induced stress remains elusive. Thus, the study employs metagenomic assembly and binning approaches to decipher mobility potential and co-occurrence frequency of ARGs and MGEs under hyperoxic (5.5-7 mgL- 1), normoxic (2.5-4 mgL- 1), and hypoxic (0.5-1 mgL- 1) conditions in lab-scale bioreactor for 6 months. Among 163 high-quality metagenome-assembled genomes (MAGs) recovered from 13 metagenomes, 42 MAGs harboured multiple ARGs and were assigned to priority pathogen group. Total ARG count increased by 4.3 and 2.5% in hyperoxic and normoxic, but decreased by 0.53% in hypoxic conditions after 150 days. On contrary, MGE count increased by 7.3-1.3% in all the DO levels, with only two ARGs showed positive correlation with MGEs in hypoxic compared to 20 ARGs under hyperoxic conditions. Opportunistic pathogens (Escherichia, Klebsiella, Clostridium, and Proteus) were detected as potential hosts of ARGs wherein co-localisation of critical ARG gene cassette (sul1, dfr1,adeF, and qacC) were identified in class 1 integron/Tn1 family transposons. Thus, enhanced co-occurrence frequency of ARGs with MGEs in pathogens suggested promotion of ARGs mobility under oxidative stress. The study offers valuable insights into ARG dissemination and hosts dynamics that is essential for controlling oxygen-related stress for mitigating MGEs and ARGs in the environment.

Novel endolithic bacteria of phylum Chloroflexota reveal a myriad of potential survival strategies in the Antarctic desert.

The ice-free McMurdo Dry Valleys of Antarctica are dominated by nutrient-poor mineral soil and rocky outcrops. The principal habitat for microorganisms is within rocks (endolithic). In this environment, microorganisms are provided with protection against sub-zero temperatures, rapid thermal fluctuations, extreme dryness, and ultraviolet and solar radiation. Endolithic communities include lichen, algae, fungi, and a diverse array of bacteria. Chloroflexota is among the most abundant bacterial phyla present in these communities. Among the Chloroflexota are four novel classes of bacteria, here named Candidatus Spiritibacteria class. nov. (=UBA5177), Candidatus Martimicrobia class. nov. (=UBA4733), Candidatus Tarhunnaeia class. nov. (=UBA6077), and Candidatus Uliximicrobia class. nov. (=UBA2235). We retrieved 17 high-quality metagenome-assembled genomes (MAGs) that represent these four classes. Based on genome predictions, all these bacteria are inferred to be aerobic heterotrophs that encode enzymes for the catabolism of diverse sugars. These and other organic substrates are likely derived from lichen, algae, and fungi, as metabolites (including photosynthate), cell wall components, and extracellular matrix components. The majority of MAGs encode the capacity for trace gas oxidation using high-affinity uptake hydrogenases, which could provide energy and metabolic water required for survival and persistence. Furthermore, some MAGs encode the capacity to couple the energy generated from H2 and CO oxidation to support carbon fixation (atmospheric chemosynthesis). All encode mechanisms for the detoxification and efflux of heavy metals. Certain MAGs encode features that indicate possible interactions with other organisms, such as Tc-type toxin complexes, hemolysins, and macroglobulins.IMPORTANCEThe ice-free McMurdo Dry Valleys of Antarctica are the coldest and most hyperarid desert on Earth. It is, therefore, the closest analog to the surface of the planet Mars. Bacteria and other microorganisms survive by inhabiting airspaces within rocks (endolithic). We identify four novel classes of phylum Chloroflexota, and, based on interrogation of 17 metagenome-assembled genomes, we predict specific metabolic and physiological adaptations that facilitate the survival of these bacteria in this harsh environment-including oxidation of trace gases and the utilization of nutrients (including sugars) derived from lichen, algae, and fungi. We propose that such adaptations allow these endolithic bacteria to eke out an existence in this cold and extremely dry habitat.

Microbiological risk assessment and resistome analysis from shotgun metagenomics of bovine colostrum microbiome

Colostrum is known for its nutraceutical qualities, probiotic attributes, and health benefits. The aim of this study was to profile colostrum microbiome from bovine in rural sites of a developing country. The focus was on microbiological safety assessments and antimicrobial resistance, taking into account the risks linked with the consumption of raw colostrum. Shotgun sequencing was employed to analyze microbiome in raw buffalo and cow colostrum. Alpha and beta diversity analyses revealed increased inter and intra-variability within colostrum samples' microbiome from both livestock species. The colostrum microbiome was mainly comprised of bacteria, with over 90% abundance, whereas fungi and viruses were found in minor abundance. Known probiotic species, such as Leuconostoc mesenteroides, Lactococcus lactis, Streptococcus thermophilus, and Lactobacillus paracasei, were found in the colostrum samples. A relatively higher number of pathogenic and opportunistic pathogenic bacteria were identified in colostrum from both animals, including clinically significant bacteria like Clostridium botulinum, Pseudomonas aeruginosa, Escherichia coli, and Listeria monocytogenes. Binning retrieved 11 high-quality metagenome-assembled genomes (MAGs), with three MAGs potentially representing novel species from the genera Psychrobacter and Pantoea. Notably, 175 antimicrobial resistance genes (ARGs) and variants were detected, with 55 of them common to both buffalo and cow colostrum metagenomes. These ARGs confer resistance against aminoglycoside, fluoroquinolone, tetracycline, sulfonamide, and peptide antibiotics. In conclusion, this study describes a thorough overview of microbial communities in buffalo and cow colostrum samples. It emphasizes the importance of hygienic processing and pasteurization in minimizing the potential transmission of harmful microorganisms linked to the consumption of colostrum.

Metagenome-assembled genomes of two nitrifying microorganisms from the freshwater archaeal ammonia-oxidizing enrichment culture BO1.

Two metagenome-assembled genomes (MAGs) were recovered from the ammonia-oxidizing enrichment culture BO1 obtained from the sediment of the freshwater reservoir Lake Burr Oak, Ohio, USA. High quality MAGs were assembled for the archaeal ammonia oxidizer Nitrosarchaeum sp. BO1 and the canonical nitrite oxidizer Nitrospira sp. BO1.

Human-induced homogenization of microbial taxa and function in a subtropical river and its impacts on community stability

Combination of taxa and function can provide a more comprehensive picture on human-induced microbial homogenization. Here, we obtained 2.58 billion high-throughput sequencing reads and 479 high-quality metagenome-assembled genomes (MAGs) of planktonic microbial communities in a subtropical river for 5 years. We found the microbial taxa homogenization and functional homogenization were uncoupled. Although human activities in downstream sites significantly decreased the taxonomic diversity of non-abundant ASV communities (16S rRNA gene amplicon sequence variants), they did not significantly decrease the taxonomic diversity of abundant ASV and total observed MAG communities. However, the total observed MAG communities in downstream sites tended to homogenize into some specific taxa which encode human-activity-related functional genes, such as nutrient cycles, greenhouse gas emission, antibiotic and arsenic resistance. Those specific MAGs with high taxonomic diversity caused the weak heterogenization of total observed MAG communities in downstream sites. Moreover, functional homogenization promoted the synchrony among downstream MAGs, and these MAGs constructed some specific network modules might to synergistically execute or resist the human-activity-related functions. High synchrony also led to the tandem effects among MAGs and thus decreased community stability. Overall, our findings revealed the links of microbial taxa, functions and stability under human activity impacts, and provided a strong evidence to encourage us re-thinking biotic homogenization based on microbial taxa and their functional attributes.

Ecological significance of Candidatus ARS69 and Gemmatimonadota in the Arctic glacier foreland ecosystems.

The Gemmatimonadota phylum has been widely detected in diverse natural environments, yet their specific ecological roles in many habitats remain poorly investigated. Similarly, the Candidatus ARS69 phylum has been identified only in a few habitats, and literature on their metabolic functions is relatively scarce. In the present study, we investigated the ecological significance of phyla Ca. ARS69 and Gemmatimonadota in the Arctic glacier foreland (GF) ecosystems through genome-resolved metagenomics. We have reconstructed the first high-quality metagenome-assembled genome (MAG) belonging to Ca. ARS69 and 12 other MAGs belonging to phylum Gemmatimonadota from the three different Arctic GF samples. We further elucidated these two groups phylogenetic lineage and their metabolic function through phylogenomic and pangenomic analysis. The analysis showed that all the reconstructed MAGs potentially belonged to novel species. The MAGs belonged to Ca. ARS69 consist about 8296 gene clusters, of which only about 8% of single-copy core genes (n = 980) were shared among them. The study also revealed the potential ecological role of Ca. ARS69 is associated with carbon fixation, denitrification, sulfite oxidation, and reduction biochemical processes in the GF ecosystems. Similarly, the study demonstrates the widespread distribution of different classes of Gemmatimonadota across wide ranges of ecosystems and their metabolic functions, including in the polar region. KEY POINTS: • Glacier foreland ecosystems act as a natural laboratory to study microbial community structure. • We have reconstructed 13 metagenome-assembled genomes from the soil samples. • All the reconstructed MAGs belonged to novel species with different metabolic processes. • Ca. ARS69 and Gemmatimonadota MAGs were found to participate in carbon fixation and denitrification processes.

Unveiling the hidden diversity and functional role of Chloroflexota in full-scale wastewater treatment plants through genome-centric analyses

Abstract The phylum Chloroflexota has been found to exhibit high abundance in the microbial communities from wastewater treatment plants (WWTPs) in both aerobic and anaerobic systems. However, its metabolic role has not been fully explored due to the lack of cultured isolates. To address this gap, we use publicly available metagenome datasets from both activated sludge (AS) and methanogenic (MET) full-scale wastewater treatment reactors to assembled genomes. Using this strategy, 264 dereplicated, medium- and high-quality metagenome-assembled genomes (MAGs) classified within Chloroflexota were obtained. Taxonomic classification revealed that AS and MET reactors harbored distinct Chloroflexota families. Nonetheless, the majority of the annotated MAGs (166 MAGs with >85% completeness and < 5% contamination) shared most of the metabolic potential features, including the ability to degrade simple sugars and complex polysaccharides, fatty acids and amino acids, as well as perform fermentation of different products. While Chloroflexota MAGs from MET reactors showed the potential for strict fermentation, MAGs from AS harbored the potential for facultatively aerobic metabolism. Metabolic reconstruction of Chloroflexota members from AS unveiled their versatile metabolism and suggested a primary role in hydrolysis, carbon removal and involvement in nitrogen cycling, thus establishing them as fundamental components of the ecosystem. Microbial reference genomes are essential resources for understanding the potential functional role of uncultured organisms in WWTPs. Our study provides a comprehensive genome catalog of Chloroflexota for future analyses aimed at elucidating their role in these ecosystems.

Ecological niches and assembly dynamics of diverse microbial consortia in the gastrointestine of goat kids.

Goats are globally invaluable ruminants that balance food security and environmental impacts, and their commensal microbiome residing in the gastrointestinal tract (GIT) is associated with animal health and productivity. However, the reference genomes and functional repertoires of GIT microbes in goat kids have not been fully elucidated. Herein, we performed a comprehensive landscape survey of the GIT microbiome of goat kids using metagenomic sequencing and binning, spanning a dense sampling regime covering three gastrointestinal compartments spatially and five developmental ages temporally. We recovered 1002 high-quality metagenome-assembled genomes (termed the goat kid GIT microbial catalog [GKGMC]), 618 of which were novel. They encode more than 2.3 million nonredundant proteins, and represent a variety of carbohydrate-degrading enzymes and metabolic gene clusters. The GKGMC-enriched microbial taxa, particularly Sodaliphilus, expanded the microbial tree of life in goat kids. Using this GKGMC, we first deciphered the prevalence of fiber-degrading bacteria for carbohydrate decomposition in the rumen and colon, while the ileal microbiota specialized in the uptake and conversion of simple sugars. Moreover, GIT microorganisms were rapidly assembled after birth, and their carbohydrate metabolic adaptation occurred in three phases of progression. Finally, phytobiotics modified the metabolic cascades of the ileal microbiome, underpinned by the enrichment of Sharpea azabuensis and Olsenella spp. implicated in lactate formation and utilization. This GKGMC reference provides novel insights into the early-life microbial developmental dynamics in distinct compartments, and offers expanded resources for GIT microbiota-related research in goat kids.

PH selects for distinct N2O-reducing microbiomes in tropical soil microcosms.

Nitrous oxide (N2O), a greenhouse gas with ozone destruction potential, is mitigated by the microbial reduction to dinitrogen catalyzed by N2O reductase (NosZ). Bacteria with NosZ activity have been studied at circumneutral pH but the microbiology of low pH N2O reduction has remained elusive. Acidic (pH < 5) tropical forest soils were collected in the Luquillo Experimental Forest in Puerto Rico, and microcosms maintained with low (0.02mM) and high (2mM) N2O assessed N2O reduction at pH4.5 and 7.3. All microcosms consumed N2O, with lag times of up to 7months observed in microcosms with 2mM N2O. Comparative metagenome analysis revealed that Rhodocyclaceae dominated in circumneutral microcosms under both N2O feeding regimes. At pH4.5, Peptococcaceae dominated in high-N2O, and Hyphomicrobiaceae in low-N2O microcosms. Seventeen high-quality metagenome-assembled genomes (MAGs) recovered from the N2O-reducing microcosms harbored nos operons, with all eight MAGs derived from acidic microcosms carrying the Clade II type nosZ and lacking nitrite reductase genes (nirS/K). Five of the eight MAGs recovered from pH4.5 microcosms represent novel taxa indicating an unexplored N2O-reducing diversity exists in acidic tropical soils. A survey of pH3.5-5.7 soil metagenome datasets revealed that nosZ genes commonly occur, suggesting broad distribution of N2O reduction potential in acidic soils.

Metagenomic insights into jellyfish-associated microbiome dynamics during strobilation.

Host-associated microbiomes can play key roles in the metamorphosis of animals. Most scyphozoan jellyfish undergo strobilation in their life cycles, similar to metamorphosis in classic bilaterians. The exploration of jellyfish microbiomes may elucidate the ancestral mechanisms and evolutionary trajectories of metazoan-microbe associations and interactions during metamorphosis. However, current knowledge of the functional features of jellyfish microbiomes remains limited. Here, we performed a genome-centric analysis of associated microbiota across four successive life stages (polyp, early strobila, advanced strobila, and ephyra) during strobilation in the common jellyfish Aurelia coerulea. We observed shifts in taxonomic and functional diversity of microbiomes across distinct stages and proposed that the low microbial diversity in ephyra stage may be correlated with the high expression of the host-derived antimicrobial peptide aurelin. Furthermore, we recovered 43 high-quality metagenome-assembled genomes and determined the nutritional potential of the dominant Vibrio members. Interestingly, we observed increased abundances of genes related to the biosynthesis of amino acids, vitamins, and cofactors, as well as carbon fixation during the loss of host feeding ability, indicating the functional potential of Aurelia-associated microbiota to support the synthesis of essential nutrients. We also identified several potential mechanisms by which jellyfish-associated microbes establish stage-specific community structures and maintain stable colonization in dynamic host environments, including eukaryotic-like protein production, bacterial secretion systems, restriction-modification systems, and clustered regularly interspaced short palindromic repeats-Cas systems. Our study characterizes unique taxonomic and functional changes in jellyfish microbiomes during strobilation and provides foundations for uncovering the ancestral mechanism of host-microbe interactions during metamorphosis.

Functional traits and health implications of the global household drinking-water microbiome retrieved using an integrative genome-centric approach

The biological safety of drinking water plays a crucial role in public health protection. However, research on the drinking water microbiome remains in its infancy, especially little is known about the potentially pathogenic bacteria in and functional characteristics of the microbiome in household tap water that people are directly exposed to. In this study, we used a genomic-centric approach to construct a genetic catalogue of the drinking water microbiome by analysing 116 metagenomic datasets of household tap water worldwide, spanning nine countries/regions on five continents. We reconstructed 859 high-quality metagenome-assembled genomes (MAGs) spanning 27 bacterial and 2 archaeal phyla, and found that the core MAGs belonging to the phylum Proteobacteria encoded the highest metabolic functional diversity of the 33 key complete metabolic modules. In particular, we found that two core MAGs of Brevibacillus and Methylomona encoded genes for methane metabolism, which may support the growth of heterotrophic organisms observed in the oligotrophic ecosystem. Four MAGs of complete ammonia oxidation (comammox) Nitrospira were identified and functional metabolic analysis suggested these may enable mixotrophic growth and encode genes for reactive oxygen stress defence and arsenite reduction that could aid survival in the environment of oligotrophic drinking water systems. Four MAGs were annotated as potentially pathogenic bacteria (PPB) and thus represented a possible public health concern. They belonged to the genera Acinetobacter (n = 3) and Mycobacterium (n = 1), with a total relative abundance of 1.06 % in all samples. The genomes of PPB A. junii and A. ursingii were discovered to contain antibiotic resistance genes and mobile genetic elements that could contribute to antimicrobial dissemination in drinking water. Further network analysis suggested that symbiotic microbes which support the growth of pathogenic bacteria can be targets for future surveillance and removal.