Ocean plankton. Environmental characteristics of Agulhas rings affect interocean plankton transport

Multi-omics analysis reveals toxicity and gut-liver axis disruption induced by polychlorinated biphenyls exposure in Yellowfin Seabream (Acanthopagrus latus)

Polychlorinated biphenyls (PCBs) are persistent organic pollutants known for their environmental persistence and bioaccumulation, posing significant health risks. This study examines the toxic effects of a representative PCBs (Aroclor 1254) on yellowfin seabream (Acanthopagrus latus) exposured for 30 days through a multi-omics approach. Histopathological examinations revealed structural damage to the intestinal structure and hepatic steatosis, along with elevated serum lipopolysaccharide levels, indicating compromised intestinal barrier integrity and liver inflammation. Metabolomic profiling showed significant alterations in lipid metabolites, including elevated lysophosphatidylcholines and arachidonic acid derivatives. Transcriptomic analysis unveiled 2272 differentially expressed genes in the liver, with notable changes in immune response and metabolic pathways. Gut microbiome analysis showed dysbiosis characterized by an increase in Proteobacteria and a decrease in Firmicutes and Actinobacteria. Remarkably, Tetranor-12S-HETE and LPC 15:1 emerged as key biomarkers for the disruption of the gut-liver axis, correlating with immune gene expression and gut microbiota composition. The integration of transcriptomic, metabolomic, and microbiome data highlighted the complex interplay between A1254 exposure and the gut-liver axis, emphasizing the central role played by PPAR signaling in mediating these effects. Collectively, these results indicate that exposure to A1254 results in bioaccumulation in the liver and gut, leading to severe tissue injury, microbiota dysbiosis, and dysregulation of the gut-liver axis, ultimately disrupting lipid metabolism. These findings underscore the metabolic health risks posed by PCBs exposure in aquatic environments.

Microbial transitions and degradation pathways driven by butyrate concentration in mesophilic and thermophilic anaerobic digestion under low hydrogen partial pressure

Butyrate accumulation significantly affects the efficiency and stability of anaerobic digestion, while its specific impact on methane yield and butyrate degradation remains unclear. This study investigated how butyrate concentrations (2.0, 5.0, 10.0, and 20.0 g COD/L) affected methane production and butyrate degradation at 37 °C and 55 °C. Methane yield decreased when butyrate concentrations exceeded 10.0 g COD/L. Methanogenesis transitioned from the acetoclastic to the hydrogenotrophic pathway with butyrate concentration increasing at 37 °C, but this transition wasn't observed at 55 °C. Butyrate was fully degraded at butyrate concentrations of 2.0-20.0 g COD/L. Iso-butyrate production was observed at 37 °C, while it only occurred with 20 g COD/L butyrate at 55 °C. Metagenomic analysis identified distinct microbes responsible for butyrate degradation at each temperature, and revealed a novel iso-butyrate metabolic pathway. These insights significantly advance the comprehension of microbial and enzymatic mechanisms driving butyrate degradation and methane production.

Dissemination mechanisms of unique antibiotic resistance genes from flowback water to soil revealed by combined Illumina and Nanopore sequencing

As a byproduct of shale gas extraction, flowback water (FW) is produced in large quantities globally. Due to the unique interactions between pollutants and microorganisms, FW always harbor multiple antibiotic resistance genes (ARGs) that have been confirmed in our previous findings, potentially serving as a point source for ARGs released into the environment. However, whether ARGs in FW can disseminate or integrate into the environmental resistome remains unclear. In this study, unique ARGs from FW were identified, and the ARG profiles in soil and FW-spiked soil were compared using a combination of Illumina and Nanopore sequencing. The results indicated that the total abundance of the soil resistome increased by 30.8 % in soil contaminated with FW. Of this increase, 11.1 % was attributable to the integration of exogenous ARGs from FW into the soil resistome. Sequence alignment at the gene level further confirmed the successful integration of 20 unique ARG sequences classified as multidrug and vancomycin resistance genes into the soil resistome. These 20 ARG sequences were detected only in the FW. Multiple lines of evidence indicated that horizontal gene transfer dominated ARG dissemination in soil contaminated by FW. This conclusion is supported by the discrepancy between changes in mobile ARGs and host abundance, the upregulation of oxidative stress-related genes (SOD1 and SOD2) and the SOS response (lexA and recA), as well as the upregulation of genes related to quorum sensing (virD4, virB9, and virB3) and naked DNA uptake (pilD, pilT, and pilQ).

Analyses of the gut microbial composition of domestic pig louse Haematopinus suis

Haematopinus suis is an obligatory ectoparasite of the domestic pig, serving as a vector of several swine pathogens and posing great threats to the pig industry. The gut microbiome of lice is thought of an important mediator of their healthy physiology. However, there is a great paucity of lice-associated microbial communities' structure and function. The current study aimed to profile the gut microbiome and to understand the microbial functions of swine lice by metagenomic sequencing and bioinformatics analyses. In total, 102,358 (77.2 %) nonredundant genes were cataloged, by contrast, only a small proportion of genes were assigned to microbial taxa and functional assemblages. Bacteria of known or potential public health significance such as Anaplasma phagocytophilum, Chlamydia trachomatis, Waddlia chondrophila, Bacillus cereus, and Leptotrichia goodfellowii were observed in all samples. The integrated microbial profile further illustrated the evolutionary relevance of endosymbionts and detailed the functional composition, and findings suggested H. suis may acquire adenosylcobalamin by feeding due to an adenosylcobalamin synthesis defect and a lack of complete synthases of endosymbionts. Sucking lice contained fewer functional genes compared with ticks and fleas probably because of the obligate host specificity of parasitic lice. In addition, the genes from the intestines contained encompassed most of the microbial functional genes in sucking lice. A wide range of unknown taxonomic and functional assemblages were discovered, which improves our understanding related to microbial features and physiological activities of sucking lice. In general, this study increases the characterization of the microbiota of lice and offers clues for preventing and controlling lice infestation in swine production in the future.

Unraveling the determinants of antibiotic resistance evolution in farmland under fertilizations

Organic fertilization is a major driver potentiating soil antibiotic resistance in farmland. However, it remains unclear how bacterial antibiotic resistance evolves in fertilized soils and even spreads to crops. Compared with no fertilizer and commercial fertilizer treatments, organic fertilizers markedly increased the abundance of soil antibiotic resistance genes (ARGs) but the relatively weaker transfer of resistance genes from soil to crops. The introduction of organic fertilizers enriches the soil with nutrients, driving indigenous microorganisms towards a K-strategy. The pH, EC, and nutrients as key drivers influenced the ARGs abundance. The neutral (pH 7.2), low salt (TDS 1.4 %) and mesotrophic (carbon content 3.54 g/L) habitats similar to the soil environment conditioned by organic fertilizers. These environmental conditions clearly prolonged the persistence of resistant plasmids, and facilitated their dissemination to massive conjugators soil microbiome but not to plant endophytes. This suggested that organic fertilizers inhibited the spread of ARGs to crops. Moreover, the composition of conjugators showed differential selection of resistant plasmids by endophytes under these conditions. This study sheds light on the evolution and dissemination of antibiotic resistance in farmlands and can aid in the development of antimicrobial resistance control strategies in agriculture.

Breaking the Cycle: A Yeast Mannan-Rich Fraction Beneficially Modulates Egg Quality and the Antimicrobial Resistome Associated with Layer Hen Caecal Microbiomes under Commercial Conditions

Antibiotics and antibiotic growth promoters have been extensively employed in poultry farming to enhance growth performance, maintain bird health, improve nutrient uptake efficiency, and mitigate enteric diseases at both sub-therapeutic and therapeutic doses. However, the extensive use of antimicrobials in poultry farming has led to the emergence of antimicrobial resistance (AMR) in microbial reservoirs, representing a significant global public health concern. In response, non-antibiotic dietary interventions, such as yeast mannan-rich fraction (MRF), have emerged as a promising alternative to modulate the gut microbiota and combat the AMR crisis. This study investigated whether a yeast mannan-rich fraction containing feed supplement impacted the performance of laying hens, their microbiomes, and the associated carriage of antimicrobial resistance genes under commercial conditions. High-throughput DNA sequencing was utilised to profile the bacterial community and assess changes in the antibiotic resistance genomes detected in the metagenome, the "resistome", in response to MRF supplementation. It was found that supplementation favourably influenced laying hen performance and microbial composition. Notably, there was a compositional shift in the MRF supplemented group associated with a lower relative abundance of pathobionts, e.g., Escherichia, Brachyspira and Trueperella, and their AMR-encoded genes, relative to beneficial microbes. Overall, the findings further demonstrate the ability of prebiotics to improve laying hen performance through changes associated with their microbiome and resistome.

Vaginal microbiota are associated with in vitro fertilization during female infertility

The vaginal microbiome plays an essential role in the reproductive health of human females. As infertility increases worldwide, understanding the roles that the vaginal microbiome may have in infertility and in vitro fertilization (IVF) treatment outcomes is critical. To determine the vaginal microbiome composition of 1411 individuals (1255 undergoing embryo transplantation) and their associations with reproductive outcomes, clinical and biochemical features are measured, and vaginal samples are 16S rRNA sequenced. Our results suggest that both too high and too low abundance of Lactobacillus is not beneficial for pregnancy; a moderate abundance is more beneficial. A moderate abundance of Lactobacillus crispatus and Lactobacillus iners (~80%) (with a pregnancy rate of I-B: 54.35% and III-B: 57.73%) is found beneficial for pregnancy outcomes compared with a higher abundance (>90%) of Lactobacillus (I-A: 44.81% and III-A: 51.06%, respectively). The community state type (CST) IV-B (contains a high to moderate relative abundance of Gardnerella vaginalis) shows a similar pregnant ratio (48.09%) with I-A and III-A, and the pregnant women in this CST have a higher abundance of Lactobacillus species. Metagenome analysis of 71 samples shows that nonpregnant women are detected with more antibiotic-resistance genes, and Proteobacteria and Firmicutes are the main hosts. The inherent differences within and between women in different infertility groups suggest that vaginal microbes might be used to detect infertility and potentially improve IVF outcomes.

Multi-omics reveals the mechanism of rumen microbiome and its metabolome together with host metabolome participating in the regulation of milk production traits in dairy buffaloes

Recently, it has been discovered that certain dairy buffaloes can produce higher milk yield and milk fat yield under the same feeding management conditions, which is a potential new trait. It is unknown to what extent, the rumen microbiome and its metabolites, as well as the host metabolism, contribute to milk yield and milk fat yield. Therefore, we will analyze the rumen microbiome and host-level potential regulatory mechanisms on milk yield and milk fat yield through rumen metagenomics, rumen metabolomics, and serum metabolomics experiments. Microbial metagenomics analysis revealed a significantly higher abundance of several species in the rumen of high-yield dairy buffaloes, which mainly belonged to genera, such as Prevotella, Butyrivibrio, Barnesiella, Lachnospiraceae, Ruminococcus, and Bacteroides. These species contribute to the degradation of diets and improve functions related to fatty acid biosynthesis and lipid metabolism. Furthermore, the rumen of high-yield dairy buffaloes exhibited a lower abundance of methanogenic bacteria and functions, which may produce less methane. Rumen metabolome analysis showed that high-yield dairy buffaloes had significantly higher concentrations of metabolites, including lipids, carbohydrates, and organic acids, as well as volatile fatty acids (VFAs), such as acetic acid and butyric acid. Meanwhile, several Prevotella, Butyrivibrio, Barnesiella, and Bacteroides species were significantly positively correlated with these metabolites. Serum metabolome analysis showed that high-yield dairy buffaloes had significantly higher concentrations of metabolites, mainly lipids and organic acids. Meanwhile, several Prevotella, Bacteroides, Barnesiella, Ruminococcus, and Butyrivibrio species were significantly positively correlated with these metabolites. The combined analysis showed that several species were present, including Prevotella.sp.CAG1031, Prevotella.sp.HUN102, Prevotella.sp.KHD1, Prevotella.phocaeensis, Butyrivibrio.sp.AE3009, Barnesiella.sp.An22, Bacteroides.sp.CAG927, and Bacteroidales.bacterium.52-46, which may play a crucial role in rumen and host lipid metabolism, contributing to milk yield and milk fat yield. The "omics-explainability" analysis revealed that the rumen microbial composition, functions, metabolites, and serum metabolites contributed 34.04, 47.13, 39.09, and 50.14%, respectively, to milk yield and milk fat yield. These findings demonstrate how the rumen microbiota and host jointly affect milk production traits in dairy buffaloes. This information is essential for developing targeted feeding management strategies to improve the quality and yield of buffalo milk.

Arsenic biogeochemical cycling association with basin-scale dynamics of microbial functionality and organic matter molecular composition

Geogenic arsenic (As)-contaminated groundwater is a sustaining global health concern that is tightly constrained by multiple interrelated biogeochemical processes. However, a complete spectrum of the biogeochemical network of high-As groundwater remains to be established, concurrently neglecting systematic zonation of groundwater biogeochemistry on the regional scale. We uncovered the geomicrobial interaction network governing As biogeochemical pathways by merging in-field hydrogeochemical monitoring, metagenomic analyses, and ultrahigh resolution mass spectrometry (FT-ICR MS) characterization of dissolved organic matter. In oxidizing to weakly reducing environments, the nitrate-reduction and sulfate-reduction encoding genes (narGHI, sat) inhibited the dissolution of As-bearing iron minerals, leading to lower As levels in groundwater. In settings from weakly to moderately reducing, high abundances of sulfate-reduction and iron-transport encoding genes boosted iron mineral dissolution and consequent As release. As it evolved to strongly reducing stage, elevated abundance of methane cycle-related genes (fae, fwd, fmd) further enhanced As mobilization in part by triggering the formation of gaseous methylarsenic. During redox cycling of N, S, Fe, C and As in groundwater, As migration to groundwater and immobilization in mineral particles are geochemically constrained by basin-scale dynamics of microbial functionality and DOM molecular composition. The study constructs a theoretical model to summarize new perspectives on the biogeochemical network of As cycling.

GlcNac produced by the gut microbiome enhances host influenza resistance by modulating NK cells

Microbiota are known to modulate the host response to influenza infection, but the mechanisms remain largely unknown. Gut metabolites are the key mediators through which gut microbes play anti-influenza effect. Transferring fecal metabolites from mice with high influenza resistance into antibiotic-treated recipient mice conferred resistance to influenza infections. By comparing the metabolites of different individuals with high or low influenza resistance, we identified and validated N-acetyl-D-glucosamine (GlcNAc) and adenosine showed strong positive correlations with influenza resistance and exerted anti-influenza effects in vivo or in vitro, respectively. Especially, GlcNAc mediated the anti-influenza effect by increasing the proportion and activity of NK cells. Several gut microbes, including Clostridium sp., Phocaeicola sartorii, and Akkermansia muciniphila, were positively correlated with influenza resistance, and can upregulate the level of GlcNAc in the mouse gut by exogenous supplementation. Subsequent studies confirmed that administering a combination of the three bacteria to mice via gavage resulted in similar modulation of NK cell responses as observed with GlcNAc. This study demonstrates that gut microbe-produced GlcNAc protects the host against influenza by regulating NK cells, facilitating the elucidation of the action mechanism of gut microbes mediating host influenza resistance.

Study on the correlation between the dominant microflora and the main flavor substances in the fermentation process of cigar tobacco leaves

The flavor of cigar tobacco leaf determines the quality of finished cigar tobacco, and the enhancement of flavor generally relies on microbial fermentation. In this paper, the correlation between the dominant microorganisms and the main flavor substances of cigar tobacco leaves during fermentation and the correlation between the two were investigated to reveal the correlation between microorganisms and flavor and the metabolic pathways of microorganisms affecting the flavor substances. During the fermentation process, the main flavors of cigar tobacco leaves were sweet, light and grassy, with hexanal, 2,6-dimethylpyridine, nonanal, phenylacetaldehyde, naphthalene, and methyl benzoate as the main constituents, and the key microorganisms Haloferax mediterranei, Haloterrigena limicola, Candidatus Thorarchaeota archaeon SMTZ-45, the genera Methyloversatilis, Sphingomonas, Thauera, Pseudomonas, Penicillium, and Aspergillus. Correlation analysis revealed that fungi were negatively correlated with the main aroma and inhibited the main flavor substances, while bacteria were positively correlated with Benzoic acid, methyl ester in the main flavor substances, which was conducive to the accumulation of green aroma. Functional analysis revealed that the dominant bacterial population was producing aroma by metabolizing glycoside hydrolases and glycosyltransferases, performing amino acid metabolism, carbohydrate metabolism and film transport metabolism. The present study showed that the bacterial and fungal dominant microorganisms during the fermentation of cigar tobacco were influencing the production and degradation of the main flavor substances through the enzyme metabolism by the occurrence of the Merad reaction.

The composition and function of the gut microbiota of Francois' langurs (Trachypithecus francoisi) depend on the environment and diet

The microbiota is essential for the extraction of energy and nutrition from plant-based diets and may have facilitated primate adaptation to new dietary niches in response to rapid environmental shifts. In this study, metagenomic sequencing technology was used to analyze the compositional structure and functional differences of the gut microbial community of Francois' langurs (Trachypithecus francoisi) under different environmental and dietary conditions. The results showed that in terms of the composition of the gut microbial community, there were significant differences among the gut microbiota of Francois' langurs (anthropogenic disturbed populations, wild populations, and captive populations) under different environmental and dietary conditions. The microbial communities with the highest abundance in Francois' langurs were Firmicutes and Bacteroidetes. Firmicutes was the most abundant phylum in anthropogenic disturbed Francois' langurs and the least abundant in captive Francois' langurs. The abundance of Bacteroidetes was highest in captive Francois' langurs. In the analysis and comparison of alpha diversity, the diversity of the gut microbiota of Francois' langurs affected by anthropogenic disturbance was the highest. The significant differences in gut microbiota between Francois' langurs in different environments and different diets were further supported by principal coordinate analysis (PCoA), with the disturbance group having a gut microbiota more similar to the wild group. Kyoto Encyclopedia of Genes and Genomes (KEGG) functional annotation analysis indicated a high abundance of functional genes involved in carbohydrate metabolism, amino acid metabolism, replication and repair, cofactor and vitamin metabolism, and other amino acid metabolism pathways. Additionally, the functional genes involved in carbohydrate metabolism pathways were significantly enriched in the gut microbial community of Francois' langurs that were anthropogenic disturbed and captive. The gut microbiota of the Francois' langurs exhibited potential plasticity for dietary flexibility, and long-term food availability in captive populations leads to changes in gut microbiota composition and function. This study explored the composition and function of the gut microbiota of Francois' langurs and provided a scientific basis for understanding the physiological and health status of Francois' langurs, effectively protecting the population of wild Francois' langurs and reintroducing captive Francois' langurs into the wild.

Global biogeography of the smallest plankton across ocean depths

Tiny ocean plankton (picoplankton) are fundamental for the functioning of the biosphere, but the ecological mechanisms shaping their biogeography were partially understood. Comprehending whether these microorganisms are structured by niche versus neutral processes is relevant in the context of global change. We investigate the ecological processes (selection, dispersal, and drift) structuring global-ocean picoplanktonic communities inhabiting the epipelagic (0 to 200 meters), mesopelagic (200 to 1000 meters), and bathypelagic (1000 to 4000 meters) zones. We found that selection decreased, while dispersal limitation increased with depth, possibly due to differences in habitat heterogeneity and dispersal barriers such as water masses and bottom topography. Picoplankton β-diversity positively correlated with environmental heterogeneity and water mass variability, but this relationship tended to be weaker for eukaryotes than for prokaryotes. Community patterns were more pronounced in the Mediterranean Sea, probably because of its cross-basin environmental heterogeneity and deep-water isolation. We conclude that different combinations of ecological mechanisms shape the biogeography of the ocean microbiome across depths.

A Gulf Stream frontal eddy harbors a distinct microbiome compared to adjacent waters

Mesoscale oceanographic features, including eddies, have the potential to alter productivity and other biogeochemical rates in the ocean. Here, we examine the microbiome of a cyclonic, Gulf Stream frontal eddy, with a distinct origin and environmental parameters compared to surrounding waters, in order to better understand the processes dominating microbial community assembly in the dynamic coastal ocean. Our microbiome-based approach identified the eddy as distinct from the surround Gulf Stream waters. The eddy-associated microbial community occupied a larger area than identified by temperature and salinity alone, increasing the predicted extent of eddy-associated biogeochemical processes. While the eddy formed on the continental shelf, after two weeks both environmental parameters and microbiome composition of the eddy were most similar to the Gulf Stream, suggesting the effect of environmental filtering on community assembly or physical mixing with adjacent Gulf Stream waters. In spite of the potential for eddy-driven upwelling to introduce nutrients and stimulate primary production, eddy surface waters exhibit lower chlorophyll a along with a distinct and less even microbial community, compared to the Gulf Stream. At the population level, the eddy microbiome exhibited differences among the cyanobacteria (e.g. lower Trichodesmium and higher Prochlorococcus) and in the heterotrophic alpha Proteobacteria (e.g. lower relative abundances of specific SAR11 phylotypes) versus the Gulf Stream. However, better delineation of the relative roles of processes driving eddy community assembly will likely require following the eddy and surrounding waters since inception. Additionally, sampling throughout the water column could better clarify the contribution of these mesoscale features to primary production and carbon export in the oceans.

Sanwei sandalwood decoction improves function of the gut microbiota in heart failure

Objective

To investigate the effects of Sanwei sandalwood decoction on improving function of the intestinal flora in doxorubicin-induced heart failure in rats.

Materials and methods

Thirty Sprague-Dawley rats were screened and randomly assigned into a blank group, a model group, and a Sanwei sandalwood decoction group (treatment group). The rat model of heart failure was prepared and established in the latter two groups. After successful model establishment, the treatment group received Sanwei sandalwood decoction by continuous gavage at 2 g/kg, once daily for 4 weeks. The other groups were given an equivalent volume of saline. After the final dose, fecal samples were collected from each group and analyzed by macrogenomics and nontargeted metabolomics to characterize the intestinal flora and associated metabolites.

Results

The composition of gut microbiota was significantly different between the three groups. There were 778,808 common genes between the blank and model groups, while 49,315 genes were lost and 521,008 were gained in the model group relative to the blank group. At the phylum level, all groups of rat fecal samples were dominated by Firmicutes, Bacteroidota, Actinobacteria, and Proteobacteria. At the genus level, the microbial community composition in all experimental groups of rat fecal samples was dominated by Lactobacillus, Bifidobacterium, Limosilactobacillus, Allobaculum, Prevotella, and Ligilactobacillus spp. Interestingly, cluster analysis was performed on the top 30 KEGG ontology (KO) terms displaying significant differences in relative abundance in the rat fecal microbiome among experimental groups. The relative frequency of posttranslational modification, coenzyme transport and metabolism, cell wall, membrane, and envelope biogenesis in the eggNOG and CAZy databases. In the nontargeted metabolomics, the group principal component analysis revealed that the groups were well distinguished from one another. The different metabolites were screened with VIP >1, and the KEGG different metabolite classification and enrichment analysis revealed that there includes 15 metabolites pathway, including loxoprofen, conifery-l-acetate, trichilin A, and others. The arachidonic acid pathway also accounted for a significant portion of the KEGG pathway classification analysis.

Conclusion

Sanwei sandalwood decoction positively affects the intestinal microbial environment of rats with heart failure, improving the gut dysbiosis that is caused by the condition. This treatment intervention inhibits the growth of pathogenic bacteria and promotes the growth of beneficial species.

A Preliminary Study of the Potential Molecular Mechanisms of Individual Growth and Rumen Development in Calves with Different Feeding Patterns

At present, it is common to feed calves with "Concentrate", "Concentrate + hay" and TMR "Total Mixed Rations" feeding patterns in China, which achieved well feeding efficiency, but the three feeding patterns molecular regulation mechanism in actual production is still unclear. The study aimed to explore the most suitable feeding pattern for Chinese Holstein calves to improve the rumen fermentation function and growth performance of calves. In this regard, the interactions between rumen microorganisms and host metabolism were investigated. The rumen volume and weight of calves in the GF group were significantly higher than those in the GFF and TMR groups (p < 0.05), and the rumen pH of calves in the GF group was 6.47~6.79. Metagenomics analysis revealed that the rumen microbiome of GF and GFF calves had higher relative abundances of Methanobrevibacter, Methanosphaera, and Methanolacinia (p < 0.05). Prevotella multisaccharivorax was significantly more abundant in the rumen of GF calves (p < 0.05), indicating that GF group calves had a stronger ability to ferment sugars. Notably, in the pyruvate metabolic pathway, phosphoenolpyruvate carboxylase was significantly up-regulated in GF calves compared with the TMR group, and pyruvate-phosphate dikinase was significantly down-regulated. Metabolomic results showed that Ursodeoxycholic acid was significantly up-regulated in GF calves, and most of the differential metabolites were enriched in Bile secretion pathways. The association analysis study found that the microorganisms of Prevotella and Ruminococcaceae might cooperate with the host, which was helpful for the digestion and absorption of lipids and made the calves have better growth. The three feeding modes had similar effects, but the 'GF' feeding pattern was more beneficial to the individual growth and ruminal development regarding ruminal morphology, contents physiology and microorganisms. Furthermore, the synergistic effect of rumen microorganisms and the host could more effectively hydrolyze lipid substances and promote the absorption of lipids, which was of great significance to the growth of calves.

The effects of differential feeding on ileum development, digestive ability and health status of newborn calves

Pre-weaning is the most important period for the growth and development of calves. Intestinal morphology, microbial community and immunity are initially constructed at this stage, and even have a lifelong impact on calves. Early feeding patterns have a significant impact on gastrointestinal development and microbial communities. This study mainly analyzed the effects of three feeding methods on the gastrointestinal development of calves, and provided a theoretical basis for further improving the feeding mode of calves. it is very important to develop a suitable feeding mode. In this study, we selected nine newborn healthy Holstein bull calves were randomly selected and divided into three groups (n = 3), which were fed with starter + hay + milk (SH group), starter + milk (SF group), total mixed ration + milk (TMR group). After 80 days of feeding Feeding to 80 days of age after, the ileum contents and blood samples were collected, and the differences were compared and analyzed by metagenomic analysis and serum metabolomics analysis. Results show that compared with the other two groups, the intestinal epithelium of the SH group was more complete and the goblet cells developed better. The feeding method of SH group was more conducive to the development of calves, with higher daily gain and no pathological inflammatory reaction. The intestinal microbial community was more conducive to digestion and absorption, and the immunity was stronger. These findings are helpful for us to explore better calf feeding patterns. In the next step, we will set up more biological replicates to study the deep-seated reasons for the differences in the development of pre-weaning calves. At the same time, the new discoveries of neuro microbiology broaden our horizons and are the focus of our future attention.

The effect of manure-borne doxycycline combined with different types of oversized microplastic contamination layers on carbon and nitrogen metabolism in sandy loam

The different forms and properties of microplastics (MPs) have different effects on the elemental cycles in soil ecosystems, and this is further complicated when the soil contains antibiotics; meanwhile, oversized microplastic (OMP) in soil is always ignored in studies of environmental behavior. In the context of antibiotic action, the effects of OMP on soil carbon (C) and nitrogen (N) cycling have rarely been explored. In this study, we created four types of oversized microplastic (thick fibers, thin fibers, large debris, and small debris) composite doxycycline (DOX) contamination layers (5-10 cm) in sandy loam, hoping to reveal the effects on soil C and N cycling and potential microbial mechanisms when exposed to the combination of manure-borne DOX and different types of OMP from the perspective of metagenomics in the longitudinal soil layer (0-30 cm). The results showed that all different forms of OMP, when combined with DOX, reduced the soil C content in each layer, but only reduced the soil N content in the upper layer of the OMP contamination layer. The microbial structure of the surface soil (0-10 cm) was more noteworthy than that of the deeper soil (10-30 cm). The genera Chryseolinea and Ohtaekwangia were key microbes involved in C and N cycling in the surface layer and regulated carbon fixation in photosynthetic organisms (K00134), carbon fixation pathways in prokaryotes (K00031), methane metabolism (K11212 and K14941), assimilatory nitrate reduction (K00367), and denitrification (K00376 and K04561). The present study is the first to reveal the potential microbial mechanism of C and N cycling under OMP combined with DOX in different layers, mainly the OMP contamination layer and its upper layer, and the OMP shape plays an important role in this process.

Salidroside ameliorates memory impairment following long-term ethanol intake in rats by modulating the altered intestinal microbiota content and hippocampal gene expression

Background

Salidroside (Sal), the main component of a famous herb Rhodiola rosea L, enhances memory performance and reduces fatigue. Therefore, this study assessed the effect of Sal on memory impairment induced by a long-term intake of ethanol (EtOH) in rats and investigated its relevant mechanisms using gut microbiota metagenomic analysis and hippocampal transcriptomic analysis.

Methods

Eighteen male SD rats were divided into the normal control group (CON group), EtOH model group (Model group), and Sal treatment group (Sal group). The rats in the Model and Sal groups intragastrically (i.g.) received 2 g/kg EtOH for 30 consecutive days, whereas the CON group was given an equal volume of distilled water. Meanwhile, the rats in the Sal group were administered i.g. 30 mg/kg Sal 60 min after EtOH intake. All rats were tested in the eight-arm maze for their memory function every 3 days. On the 30th day, metagenomic analyses of gut microbiota and transcriptomic analyses of the hippocampus were performed.

Results

Compared with the Model group, Sal treatment reduced the total time to complete the eight-arm maze task, decreased the number of arm entries, and abated the working memory error that was significant from the 9th day. Additionally, Sal intervention improved the gut microbiota composition, such as the increased abundance of Actinobacteria and Bifidobacterium, which was related to the metabolism of amino acids and terpenoid carbohydrate, endocrine function, and signal transduction by neurotransmitters. In the hippocampus, the EtOH intake differentially expressed 68 genes (54 genes increased, whereas 14 genes decreased), compared with the CON group, whereas Sal intervention affected these changes: 15 genes increased whereas 11 genes decreased. And, enrichment analyses revealed these genes were related to the structural components of the ribosome, mRNA splicing process, protein translation, mitochondria function, and immunological reaction. Finally, a correlation analysis found the memory impairment was positively correlated with the abnormal upregulation of Tomm7 but negatively correlated with decreased abundance of gut Alistipes_indistinctus, Lactobacillus_taiwanensis, Lactobacillus_paragasseri, and Lactobacillus johnsonii.

Conclusion

Sal improved memory impairment caused by long-term EtOH intake in rats, which may be related to its regulation of gut dysbiosis and hippocampal dysfunction.

Complete bacterial profile and potential pathogens of cat fleas Ctenocephalides felis

Fleas are important ectoparasites and vectors associated with a wide range of pathogenic diseases, posing threats to public health concerns, especially cat fleas that spread worldwide. Understanding the microbial components is essential due to cat fleas are capable of transmitting pathogens to humans, causing diseases like plague and murine typhus. In the present study, metagenomic next-generation sequencing was applied to obtain the complete microbiota and related functions in the gut of Ctenocephalides felis. A total of 1,870 species was taxonomically recognized including 1,407 bacteria, 365 eukaryotes, 69 viruses, and 29 archaea. Proteobacteria was the dominant phylum among the six samples. Pathogens Rickettsia felis, Acinetobacter baumannii, Coxiella burnetii, and Anaplasma phagocytophilum were taxonomically identified and had high abundances in all samples. The resistance gene MexD was predominant in microbial communities of all cat fleas. We also performed epidemiological surveys of pathogens R. felis, A. baumannii, C. burnetii, and A. phagocytophilum among 165 cat fleas collected from seven provinces in China, while only the DNAs of R. felis (38/165, 23.03%) and C. burnetii (2/165, 1.21%) were obtained. The data provide new insight and understanding of flea intestinal microbiota and provided novel information for preventing and controlling fleas and their transmitted diseases.

Differences in gut microbiota and its metabolic function among different fasting plasma glucose groups in Mongolian population of China

BACKGROUND

Many studies reported the association between gut microbiota and type 2 diabetes mellitus (T2D), but it is still unclear which bacterial genus plays a key role and how the metabolic function of gut microbiota changes in the occurrence and development of T2D. Besides, there is a high diabetic prevalence in Mongolian population, which may be partly affected by their high calorie diet. This study identified the main bacterial genus influencing T2D in Mongolian population, and analyzed the changes of metabolic function of gut microbiome. The association between dietary factors and the relative abundance of main bacterial genus and its metabolic function was also studied.

METHODS

Dietary surveys and gut microbiota test were performed on 24 Mongolian volunteers that were divided into T2D (6 cases), PRET2D (6 cases) and Control group (12 cases) according to fasting plasma glucose (FPG) values. The relative abundance and metabolic function of gut microbiome from their fecal samples were measured by metagenomic analysis. Statistic method was used to evaluate the association between dietary factors and the relative abundance of the main bacterial genus or its metabolic function.

RESULTS

This study found that the Clostridium genus may be one of the key bacterial genera affecting the process of T2D. First, the relative abundance of Clostridium genus was significantly different among the three groups. Second, there was a higher relative abundance of metabolic enzymes of gut bacteria in PRET2D and T2D group than that in Control group. Third, a strong correlation between Clostridium genus and many metabolic enzymes was uncovered, many of which may be produced by the Clostridium. Last, carotene intake daily was negatively correlated with the Clostridium but positively correlated with tagaturonate reductase catalyzing interconversions of pentose and glucuronate.

CONCLUSIONS

The gut Clostridium genus may play an important role in the development of T2D and it could be a potential biomarker for T2D in Mongolian population. Meanwhile, the metabolic function of gut bacteria has changed during the early stage of T2D and the changes in carbohydrate, amino acid, lipid or energy metabolism of Clostridium genus may play a critical role. In addition, the carotene intake may affect reproduction and metabolic function of Clostridium genus.

Coupling effects of nitrate reduction and sulfur oxidation in a subtropical marine mangrove ecosystem with Spartina alterniflora invasion

The mangrove ecosystem has a high nitrate reduction capacity, which significantly alleviates severe nitrogen pollution. However, current research on nitrate reduction mechanisms in the mangrove ecosystem is limited. Furthermore, Spartina alterniflora invasion has disrupted the balance of the mangrove ecosystem and the effect of S. alterniflora on nitrate reduction has not yet been fully elucidated. Nitrate reduction was comprehensively investigated in a subtropical mangrove ecosystem in this study, which has been invaded by S. alterniflora for 40 years. Results showed that S. alterniflora significantly increased the relative and absolute abundance of nitrate reduction genes, especially nirS (nitrite reductase), in the mangrove ecosystem. Dissimilatory nitrate reduction to ammonium was the main pathway of nitrate reduction in the mangrove ecosystem. Nitrate reduction was mainly performed by Desulfobacterales and occurred in the shallow layers (0-10 cm) of mangrove sediments. A strong positive correlation was found between nitrate reduction and sulfur oxidation (especially sulfide oxidation), and the sulfide content was significantly positively correlated with the relative abundance of nitrate reduction genes. Moreover, 207 metagenomic assembled genomes (MAGs) were constructed, including 50 MAGs with high numbers (≥ 10) of nitrate reduction genes. This finding indicates that the dominant microbes had strong nitrate reduction potential in mangrove sediments. Our findings highlight the impact of S. alterniflora invasion on nitrate reduction in a subtropical marine mangrove ecosystem. This study provides new insights into our understanding of nitrogen pollution control and contributes to the exploration of new nitrogen-degrading microbes in mangrove ecosystems.

Effects of levodopa on gut bacterial antibiotic resistance in Parkinson's disease rat

The second most prevalent neurodegenerative ailment, Parkinson's disease (PD), is characterized by both motor and non-motor symptoms. Levodopa is the backbone of treatment for PD at the moment. However, levodopa-induced side effects, such as dyskinesia, are commonly seen in PD patients. Recently, several antibiotics were found to present neuroprotective properties against neurodegenerative and neuro-inflammatory processes, which might be developed to effective therapies against PD. In this study, we aimed to identify if levodopa treatment could influence the gut bacterial antibiotic resistance in PD rat. Fecal samples were collected from healthy rats and 6-OHDA induced PD rats treated with different doses of levodopa, metagenomic sequencing data showed that levodopa resulted in gut bacteria composition change, the biomarkers of gut bacteria analyzed by LEfSe changed as well. More interestingly, compared with levodopa (5 mg/kg)-treated or no levodopa-treated PD rats, levodopa (10 mg/kg) caused a significant decrease in the abundance of tetW and vanTG genes in intestinal bacteria, which were related to tetracycline and vancomycin resistance, while the abundance of AAC6-lb-Suzhou gene increased apparently, which was related to aminoglycosides resistance, even though the total quantity of Antibiotic Resistance Gene (ARG) and Antibiotic Resistance Ontology (ARO) among all groups did not significantly differ. Consequently, our results imply that the combination of levodopa and antibiotics, such as tetracycline and vancomycin, in the treatment of PD may decrease the amount of corresponding antibiotic resistance genes in gut bacteria, which would give a theoretical basis for treating PD with levodopa combined with tetracycline and vancomycin in the future.

Gut microbiota facilitates adaptation of the plateau zokor (Myospalax baileyi) to the plateau living environment

Gut microbiota not only helps the hosts to perform many key physiological functions such as food digestion, energy harvesting and immune regulation, but also influences host ecology and facilitates adaptation of the host to extreme environments. Plateau zokors epitomize successful physiological adaptation to their living environment in the face of the harsh environment characterized by low temperature, low pressure and hypoxia in the Tibetan plateau region and high concentrations of CO₂ in their burrows. Therefore, here we used a metagenomic sequencing approach to explore how gut microbiota contributed to the adaptive evolution of the plateau zokor on the Qinghai-Tibet Plateau. Our metagenomic results show that the gut microbiota of plateau zokors on the Tibetan plateau is not only enriched in a large number of species related to energy metabolism and production of short-chain fatty acids (SCFAs), but also significantly enriched the KO terms that involve carbohydrate uptake pathways, which well address energy uptake in plateau zokors while also reducing inflammatory responses due to low pressure, hypoxia and high CO₂ concentrations. There was also a significant enrichment of tripeptidyl-peptidase II (TPPII) associated with antigen processing, apoptosis, DNA damage repair and cell division, which may facilitate the immune response and tissue damage repair in plateau zokors under extreme conditions. These results suggest that these gut microbiota and their metabolites together contribute to the physiological adaptation of plateau zokors, providing new insights into the contribution of the microbiome to the evolution of mammalian adaptation.

Diversity and ecological footprint of Global Ocean RNA viruses

DNA viruses are increasingly recognized as influencing marine microbes and microbe-mediated biogeochemical cycling. However, little is known about global marine RNA virus diversity, ecology, and ecosystem roles. In this study, we uncover patterns and predictors of marine RNA virus community- and "species"-level diversity and contextualize their ecological impacts from pole to pole. Our analyses revealed four ecological zones, latitudinal and depth diversity patterns, and environmental correlates for RNA viruses. Our findings only partially parallel those of cosampled plankton and show unexpectedly high polar ecological interactions. The influence of RNA viruses on ecosystems appears to be large, as predicted hosts are ecologically important. Moreover, the occurrence of auxiliary metabolic genes indicates that RNA viruses cause reprogramming of diverse host metabolisms, including photosynthesis and carbon cycling, and that RNA virus abundances predict ocean carbon export.

Metagenomics Reveals the Diversity and Taxonomy of Carbohydrate-Active Enzymes and Antibiotic Resistance Genes in Suancai Bacterial Communities

Suancai, as a traditional fermented food in China with reputed health benefits, has piqued global attention for many years. In some circumstances, the microbial-driven fermentation may confer health (e.g., probiotics) or harm (e.g., antibiotic resistance genes) to the consumers. To better utilize beneficial traits, a deeper comprehension of the composition and functionality of the bacterial species harboring enzymes of catalytically active is required. On the other hand, ingestion of fermented food increases the likelihood of microbial antibiotic resistance genes (ARGs) spreading in the human gastrointestinal tract. Besides, the diversity and taxonomic origin of ARGs in suancai are little known. In our study, a metagenomic approach was employed to investigate distribution structures of CAZymes and ARGs in main bacterial species in suancai. Functional annotation using the CAZy database identified a total of 8796 CAZymes in metagenomic data. A total of 83 ARGs were detected against the CARD database. The most predominant ARG category is multidrug-resistant genes. The ARGs of antibiotic efflux mechanism are mostly in Proteobacteria. The resistance mechanism of ARGs in Firmicutes is primarily antibiotic inactivation, followed by antibiotic efflux. Due to the abundance of species with different ARGs, strict quality control including microbial species, particularly those with lots of ARGs, is vital for decreasing the risk of ARG absorption via consumption. Ultimately, we significantly widen the understanding of suancai microbiomes by using metagenomic sequencing to offer comprehensive information on the microbial functional potential (including CAZymes and ARGs content) of household suancai.

Insights into carbon-fixation pathways through metagonomics in the sediments of deep-sea cold seeps

Carbon fixation by chemoautotrophic microorganisms in the dark ocean has a major impact on global carbon cycling and ecological relationships in the ocean's interior. At present, six pathways of autotrophic carbon fixation have been found: the Calvin cycle, the reductive Acetyl-CoA or Wood-Ljungdahl pathway (rAcCoA), the reductive tricarboxylic acid cycle (rTCA), the 3-hydroxypropionate bicycle (3HP), the 3-hydroxypropionate/4-hydroxybutyrate cycle (3HP/4HB), and the dicarboxylate/4-hydroxybutyrate cycle (DC/4HB). Although our knowledge about carbon fixation pathways in the ocean has increased significantly, carbon fixation pathways in the cold seeps are still unknown. In this study, we collected sediment samples from two cold seeps and one trough in the south China sea (SCS), and investigated with metagenomic and metagenome assembled genomes (MAGs). We found that six autotrophic carbon fixation pathways present in the cold seeps and trough with rTCA cycle was the most common pathway, whose genes were particularly high in the cold seeps and increased with sediment depths; the rAcCoA cycle mainly occurred in the cold seep regions, and the abundance of module genes increased with sediment depths. We also elucidated members of chemoautotrophic microorganisms involved in these six carbon-fixation pathways. The rAcCoA, rTCA and DC/4-HB cycles required significantly less energy probably play an important role in the deep-sea environments, especially in the cold seeps. This study provided metabolic insights into the carbon fixation pathways in the cold seeps, and laid the foundation for future detailed study on processes and rates of carbon fixation in the deep-sea ecosystems.

Metagenomics-based insights into the microbial community profiling and flavor development potentiality of baijiu Daqu and huangjiu wheat Qu

Daqu and wheat Qu are saccharification and fermenting agents in Chinese huangjiu and baijiu production. This study aimed to investigate the difference between Daqu and wheat Qu in physicochemical indices, microbial communities, functional genes, and the metabolic network of key microbes responsible for flavor synthesis by whole-metagenome sequencing and metabolite analysis. Herein, physicochemical indices indicated that compared with wheat Qu, Daqu exhibited higher protease and cellulase activity and acidity, and lower glucoamylase and amylase enzyme activity. Metagenomic sequencing reveals that although Daqu and wheat Qu community composition have significant differences at species level, they have similar functional genes. Daqu were enriched in Pediococcus pentosaceus, Weissella paramesenteroides, Rasamsonia emersonii and Byssochlamys spectabilis (22.48% of the total abundance), while wheat Qu harbored greater abundances of Saccharopolyspora (54.78%, Saccharopolyspora rectivirgula, Saccharopolyspora shandongensis, Saccharopolyspora hirsuta, Saccharopolyspora spinose, and Saccharopolyspora erythraea). From a functional perspective, the important functions of Daqu and wheat Qu are both amino acid metabolism and carbohydrate metabolism. Meanwhile, a combined analysis among microbiota, functional genes, and dominant flavors indicated S. shandongensis, S. rectivirgula, and S. spinose might be the main contributor to the synthesis of flavor compounds in wheat Qu, while R. emersonii, W. paramesenteroides, Leuconostoc citreum, Leuconostoc mesenteroides, Weissella cibaria and P. pentosaceus may make the greatest contribution to flavor compounds synthesis in Daqu. This study reveals the microbial and functional dissimilarities of Daqu and wheat Qu, and helps elucidating different metabolic roles of microbes during flavor formation.

Metagenomics of the midgut microbiome of Rhipicephalus microplus from China

Background

Ticks, which are ectoparasites of animals, may carry multiple pathogens. The cattle tick Rhipicephalus microplus is an important bovine parasite in China. However, the midgut microbiome of R. microplus from China has not been characterized via metagenomic methods.

Methods

Rhipicephalus microplus were collected from cattle in the city of Changsha in Hunan province, China. The DNA of the midgut contents was extracted from fully engorged adult female R. microplus. A DNA library was constructed and sequenced using an Illumina HiSeq sequencing platform. SOAPdenovo software was used to assemble and analyze the clean data. The latent class analysis algorithm applied to system classification by MEGAN software was used to annotate the information on the species’ sequences. DIAMOND software was used to compare unigenes with the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, and functional annotation was carried out based on the results of the comparison.

Results

The dominant phyla in the five samples were Firmicutes, Proteobacteria, and Actinobacteria. Streptococcus, Mycobacterium, Anaplasma, Enterococcus, Shigella, Lactobacillus, Brachyspira, Pseudomonas, Enterobacter, Bacillus, and Lactococcus were the dominant genera in the five samples. The endosymbiotic bacterium Wolbachia was also detected in all of the samples. Mycobacterium malmesburyense, Streptococcus pneumoniae, Anaplasma phagocytophilum, Enterococcus faecium, Shigella sonnei, Enterococcus faecalis, Lactobacillus casei, Brachyspira hampsonii, Pseudomonas syringae, Enterobacter cloacae, and Lactococcus garvieae were the dominant species in the five samples. In addition to these bacterial species, we also detected some eukaryotes, such as Rhizophagus irregularis, Enterospora canceri, Smittium culicis, Zancudomyces culisetae, Trachipleistophora hominis, and viruses such as orf virus, human endogenous retrovirus type W, enzootic nasal tumor virus of goats, bovine retrovirus CH15, and galidia endogenous retrovirus in all of the samples at the species level. The results of the annotated KEGG pathway predictions for the gene functions of the midgut microflora of R. microplus indicated genes involved in lipid and amino acid metabolism, infectious diseases (e.g., Streptococcuspneumonia infection, human granulocytic anaplasmosis, Shigellasonnei infection, Salmonella enterica infection, and pathogenic Escherichia coli infection), and cancer.

Conclusions

Our study revealed that the midgut microbiome of R. microplus is not only composed of a large number of bacteria, but that a portion also comprises eukaryotes and viruses. The data presented here enhance our understanding of this tick’s midgut microbiome and provide fundamental information for the control of ticks and tick-borne diseases.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05161-6.

Diatom Biogeography, Temporal Dynamics, and Links to Bacterioplankton across Seven Oceanographic Time-Series Sites Spanning the Australian Continent

Diatom communities significantly influence ocean primary productivity and carbon cycling, but their spatial and temporal dynamics are highly heterogeneous and are governed by a complex diverse suite of abiotic and biotic factors. We examined the seasonal and biogeographical dynamics of diatom communities in Australian coastal waters using amplicon sequencing data (18S-16S rRNA gene) derived from a network of oceanographic time-series spanning the Australian continent. We demonstrate that diatom community composition in this region displays significant biogeography, with each site harbouring distinct community structures. Temperature and nutrients were identified as the key environmental contributors to differences in diatom communities at all sites, collectively explaining 21% of the variability observed in diatoms assemblages. However, specific groups of bacteria previously implicated in mutualistic ecological interactions with diatoms (Rhodobacteraceae, Flavobacteriaceae and Alteromonadaceae) also explained a further 4% of the spatial dynamics observed in diatom community structure. We also demonstrate that the two most temperate sites (Port Hacking and Maria Island) exhibited strong seasonality in diatom community and that at these sites, winter diatom communities co-occurred with higher proportion of Alteromonadaceae. In addition, we identified significant co-occurrence between specific diatom and bacterial amplicon sequence variants (ASVs), with members of the Roseobacter and Flavobacteria clades strongly correlated with some of the most abundant diatom genera (Skeletonema, Thalassiosira, and Cylindrotheca). We propose that some of these co-occurrences might be indicative of ecologically important interactions between diatoms and bacteria. Our analyses reveal that in addition to physico-chemical conditions (i.e., temperature, nutrients), the relative abundance of specific groups of bacteria appear to play an important role in shaping the spatial and temporal dynamics of marine diatom communities.

Comparative metagenomics analysis reveals how the diet shapes the gut microbiota in several small mammals

The gut microbiomes of the host are large and complex communities, which helps to maintain homeostasis, improves digestive efficiency, and promotes the development of the immune system. The small mammals distributed in Sichuan Province are the most popular species for biodiversity research in Southwest China. However, the effects of different diets on the structure and function of the gut microbial community of these small mammals are poorly understood. In this study, whole-metagenome shotgun sequencing has been used to analyze the composition and functional structures of the gut microbiota of seven small mammals in Laojunshan National Nature Reserve, Sichuan Province, China. Taxonomic classification revealed that the most abundant phyla in the gut of seven small mammals were Bacteroides, Proteobacteria, and Firmicutes. Moreover, Hafnia, Lactobacillus, and Yersinia were the most abundant genus in the gut microbiomes of these seven species. At the functional level, we annotated a series of KEGG functional pathways, six Cazy categories, and 46,163 AROs in the gut microbiomes of the seven species. Comparative analysis found that the difference in the gut microbiomes between the Soricidea and Muridae concentrated on the increase in the F/B (Firmicutes/Bacteroides) ratio in the Soricidea group, probably driven by the high-fat and -calorie digestive requirements due to their insectivorous diet. The comparative functional profiling revealed that functions related to metabolism and carbohydrates were significantly more abundant in Muridae group, which may be attributed to their high carbohydrate digestion requirements caused by their herbivorous diet. These data suggested that different diets in the host may play an important role in shaping the gut microbiota, and lay the foundation for teasing apart the influences of heritable and environmental factors on the evolution of gut microbial communities.

Tianwang Buxin Granules Influence the Intestinal Flora in Perimenopausal Insomnia

Methods

The subjects included 13 PI patients from the Hubei Provincial Hospital of TCM, Hubei University of TCM, and Wuhan Traditional Chinese Medicine Hospital, and the corresponding noninsomniac spouses of the patients were selected as controls. TWBXG was continuously administered for 4 weeks. The feces of PI patients and their noninsomniac spouses before and after treatment with TWBXG were collected. The intestinal flora composition of each group was detected by metagenomic sequencing, and the efficacy of TWBXG was evaluated by the PSQI scale.

Results

Compared with the control group, the model group showed an increase in the abundance of Roseburia faecis, Ruminococcus, Prevotella copri, Fusicatenibacter saccharivorans, and Blautia obeum, while those of Bacteroides, fecal Bacteroidetes, and Faecalibacterium prausnitzii were decreased. Compared with pretreatment, the PSQI score was significantly reduced (P < 0.05), the abundance of Bacteroides, fecal Bacteroidetes, and Faecalibacterium prausnitzii increased, and that of Roseburia faecis, Ruminococcus, Prevotella copri, Fusicatenibacter saccharivorans, and Blautia obeum decreased after treatment. However, there was still a certain gap in the abundance of related flora in the treatment group compared with the control.

Conclusion

PI is associated with disturbances in the intestinal flora and is mainly related to the disorders of Roseburia faecis, Ruminococcus, Prevotella copri, Fusicatenibacter saccharivorans, Blautia obeum, Bacteroides, fecal Bacteroidetes, and Faecalibacterium prausnitzii. TWBXG can effectively treat PI, and its effect may be achieved by regulating the disordered intestinal flora. Clinical Trials. The study was registered in the Chinese clinical trial registry and approved by the World Health Organization clinical trial registration platform (Effects of the modified Tianwang Buxin granule and modified Tianwang Buxin decoction pieces on insomnia: a randomized, controlled trial, ChiCTR-IPR-17011549).

Effect of bioaugmentation on lignocellulose degradation and antibiotic resistance genes removal during biogas residues composting

In this study, six strains belonging to Alcaligenes, Enterobacter and Bacillus were employed to enhance the composting process of biogas residues and agricultural wastes. The dynamic changes of dissolved organic matter (DOM), microbial community and functional genes in composting was monitored. It was found bioaugmentation reduced the content of lignocellulose in the compost by 27.14-66.30%, and increased the seed germination index (GI) of the compost by 37.59%. Metagenomics analysis of the composting process indicated Proteobacteria (35.38%-64.19%), Actinobacteria (11.24%-28.93%) and Bacteroidetes (3.65%-9.57%) are the dominant microorganisms during the bioaugmented composting. The abundance of genes associated with glycoside hydrolase was obviously enhanced and the antibiotic resistance genes (ARGs) was significantly reduced during the bioaugmented composting. Following nursery investigation indicated the seedling substrates composed of bioaugmented compost increased the dry weight of tomato seedlings by 1.7 times, revealing obvious large-scale application potential in the resource utilization of agricultural wastes.

L-Cysteine Synthase Enhanced Sulfide Biotransformation in Subtropical Marine Mangrove Sediments as Revealed by Metagenomics Analysis

High sulfides concentrations can be poisonous to environment because of anthropogenic waste production or natural occurrences. How to elucidate the biological transformation mechanisms of sulfide pollutants in the subtropical marine mangrove ecosystem has gained increased interest. Thus, in the present study, the sulfide biotransformation in subtropical mangroves ecosystem was accurately evaluated using metagenomic sequencing and quantitative polymerase chain reaction analysis. Most abundant genes were related to the organic sulfur transformation. Furthermore, an ecological model of sulfide conversion was constructed. Total phosphorus was the dominant environmental factor that drove the sulfur cycle and microbial communities. We compared mangrove and non-mangrove soils and found that the former enhanced metabolism that was related to sulfate reduction when compared to the latter. Total organic carbon, total organic nitrogen, iron, and available sulfur were the key environmental factors that effectively influenced the dissimilatory sulfate reduction. The taxonomic assignment of dissimilatory sulfate-reducing genes revealed that Desulfobacterales and Chromatiales were mainly responsible for sulfate reduction. Chromatiales were most sensitive to environmental factors. The high abundance of cysE and cysK could contribute to the coping of the microbial community with the toxic sulfide produced by Desulfobacterales. Collectively, these findings provided a theoretical basis for the mechanism of the sulfur cycle in subtropical mangrove ecosystems.

Viruses infecting a warm water picoeukaryote shed light on spatial co-occurrence dynamics of marine viruses and their hosts

The marine picoeukaryote Bathycoccus prasinos has been considered a cosmopolitan alga, although recent studies indicate two ecotypes exist, Clade BI (B. prasinos) and Clade BII. Viruses that infect Bathycoccus Clade BI are known (BpVs), but not that infect BII. We isolated three dsDNA prasinoviruses from the Sargasso Sea against Clade BII isolate RCC716. The BII-Vs do not infect BI, and two (BII-V2 and BII-V3) have larger genomes (~210 kb) than BI-Viruses and BII-V1. BII-Vs share ~90% of their proteins, and between 65% to 83% of their proteins with sequenced BpVs. Phylogenomic reconstructions and PolB analyses establish close-relatedness of BII-V2 and BII-V3, yet BII-V2 has 10-fold higher infectivity and induces greater mortality on host isolate RCC716. BII-V1 is more distant, has a shorter latent period, and infects both available BII isolates, RCC716 and RCC715, while BII-V2 and BII-V3 do not exhibit productive infection of the latter in our experiments. Global metagenome analyses show Clade BI and BII algal relative abundances correlate positively with their respective viruses. The distributions delineate BI/BpVs as occupying lower temperature mesotrophic and coastal systems, whereas BII/BII-Vs occupy warmer temperature, higher salinity ecosystems. Accordingly, with molecular diagnostic support, we name Clade BII Bathycoccus calidus sp. nov. and propose that molecular diversity within this new species likely connects to the differentiated host-virus dynamics observed in our time course experiments. Overall, the tightly linked biogeography of Bathycoccus host and virus clades observed herein supports species-level host specificity, with strain-level variations in infection parameters.

L-Cysteine Synthase Enhanced Sulfide Biotransformation in Subtropical Marine Mangrove Sediments as Revealed by Metagenomics Analysis

High sulfides concentrations can be poisonous to environment because of anthropogenic waste production or natural occurrences. How to elucidate the biological transformation mechanisms of sulfide pollutants in the subtropical marine mangrove ecosystem has gained increased interest. Thus, in the present study, the sulfide biotransformation in subtropical mangroves ecosystem was accurately evaluated using metagenomic sequencing and quantitative polymerase chain reaction analysis. Most abundant genes were related to the organic sulfur transformation. Furthermore, an ecological model of sulfide conversion was constructed. Total phosphorus was the dominant environmental factor that drove the sulfur cycle and microbial communities. We compared mangrove and non-mangrove soils and found that the former enhanced metabolism that was related to sulfate reduction when compared to the latter. Total organic carbon, total organic nitrogen, iron, and available sulfur were the key environmental factors that effectively influenced the dissimilatory sulfate reduction. The taxonomic assignment of dissimilatory sulfate-reducing genes revealed that Desulfobacterales and Chromatiales were mainly responsible for sulfate reduction. Chromatiales were most sensitive to environmental factors. The high abundance of cysE and cysK could contribute to the coping of the microbial community with the toxic sulfide produced by Desulfobacterales. Collectively, these findings provided a theoretical basis for the mechanism of the sulfur cycle in subtropical mangrove ecosystems.

Identification of Tick-Borne Pathogens and Genotyping of Coxiella burnetii in Rhipicephalus microplus in Yunnan Province, China

Rhipicephalus microplus, a vector that can transmit many pathogens to humans and domestic animals, is widely distributed in Yunnan province, China. However, few reports on the prevalence of tick-borne pathogens (TBPs) in Rh. microplus in Yunnan are available. The aim of this study was to detect TBPs in Rh. microplus in Yunnan and to analyze the phylogenetic characterization of TBPs detected in these ticks. The adult Rh. microplus (n = 516) feeding on cattle were collected. The pooled DNA samples of these ticks were evaluated using metagenomic next-generation sequencing (mNGS) and then TBPs in individual ticks were identified using genus- or group-specific nested polymerase chain reaction (PCR) combined with DNA sequencing assay. As a result, Candidatus Rickettsia jingxinensis (24.61%, 127/516), Anaplasma marginale (13.18%, 68/516), Coxiella burnetii (3.10%, 16/516), and Coxiella-like endosymbiont (CLE) (8.33%, 43/516) were detected. The dual coinfection with Ca. R. jingxinensis and A. marginale and the triple coinfection with Ca. R. jingxinensis, A. marginale, and CLE were most frequent and detected in 3.68% (19/516) and 3.10% (16/516) of these ticks, respectively. The results provide insight into the diversity of TBPs and their coinfections in Rh. microplus in Yunnan province of China, reporting for the first time that C. burnetii had been found in Rh. microplus in China. Multilocus variable number tandem repeat analysis with 6 loci (MLVA-6) discriminated the C. burnetii detected in Rh. microplus in Yunnan into MLVA genotype 1, which is closely related to previously described genotypes found primarily in tick and human samples from different regions of the globe, indicating a potential public health threat posed by C. burnetii in Rh. microplus in Yunnan.

Major restructuring of marine plankton assemblages under global warming

Marine phytoplankton and zooplankton form the basis of the ocean’s food-web, yet the impacts of climate change on their biodiversity are poorly understood. Here, we use an ensemble of species distribution models for a total of 336 phytoplankton and 524 zooplankton species to determine their present and future habitat suitability patterns. For the end of this century, under a high emission scenario, we find an overall increase in plankton species richness driven by ocean warming, and a poleward shift of the species’ distributions at a median speed of 35 km/decade. Phytoplankton species richness is projected to increase by more than 16% over most regions except for the Arctic Ocean. In contrast, zooplankton richness is projected to slightly decline in the tropics, but to increase strongly in temperate to subpolar latitudes. In these latitudes, nearly 40% of the phytoplankton and zooplankton assemblages are replaced by poleward shifting species. This implies that climate change threatens the contribution of plankton communities to plankton-mediated ecosystem services such as biological carbon sequestration.

Warming will affect marine plankton biomass, but also its diversity and community composition in poorly understood ways. Here, the authors model the spatial distribution of 860 marine plankton species from 10 functional groups and identify the future hotspots of climate change impacts under RCP8.5.

Lagrangian betweenness as a measure of bottlenecks in dynamical systems with oceanographic examples

The study of connectivity patterns in networks has brought novel insights across diverse fields ranging from neurosciences to epidemic spreading or climate. In this context, betweenness centrality has demonstrated to be a very effective measure to identify nodes that act as focus of congestion, or bottlenecks, in the network. However, there is not a way to define betweenness outside the network framework. By analytically linking dynamical systems and network theory, we provide a trajectory-based formulation of betweenness, called Lagrangian betweenness, as a function of Lyapunov exponents. This extends the concept of betweenness beyond the context of network theory relating hyperbolic points and heteroclinic connections in any dynamical system to the structural bottlenecks of the network associated with it. Using modeled and observational velocity fields, we show that such bottlenecks are present and surprisingly persistent in the oceanic circulation across different spatio-temporal scales and we illustrate the role of these areas in driving fluid transport over vast oceanic regions. Analyzing plankton abundance data from the Kuroshio region of the Pacific Ocean, we find significant spatial correlations between measures of diversity and betweenness, suggesting promise for ecological applications.

Identification of tick-borne pathogens by metagenomic next-generation sequencing in Dermacentor nuttalli and Ixodes persulcatus in Inner Mongolia, China

Background

Hard ticks act as arthropod vectors in the transmission of human and animal pathogens and are widely distributed in northern China. The aim of this study is to screen the important tick-borne pathogens (TBPs) carried by hard ticks in Inner Mongolia using metagenomic next-generation sequencing (mNGS) and to estimate the risk of human infection imposed by tick bites.

Methods

The adult Dermacentor nuttalli (n = 203) and Ixodes persulcatus (n = 36) ticks feeding on cattle were collected. The pooled DNA samples prepared from these ticks were sequenced as the templates for mNGS to survey the presence of TBPs at the genus level. Individual tick DNA samples were detected by genus--specific or group-specific nested polymerase chain reaction (PCR) of these TBPs and combined with DNA sequencing assay to confirm the results of mNGS.

Results

R. raoultii (45.32%, 92/203), Candidatus R. tarasevichiae (5.42%, 11/203), Anaplasma sp. Mongolia (26.60%, 54/203), Coxiella-like endosymbiont (CLE) (53.69%, 109/203), and Babesia venatorum (7.88%, 16/203) were detected in D. nuttalli, while R. raoultii (30.56%, 11/36), Anaplasma sp. Mongolia (27.80%, 10/36), and CLE (27.80%, 10/36) were detected in I. persulcatus. The double- and triple-pathogen/endosymbiont co-infections were detected in 40.39% of D. nuttalli and 13.89% of I. persulcatus, respectively. The dual co-infection with R. raoultii and CLE (14.29%, 29/203) and triple co-infection with R. raoultii, Anaplasma sp. Mongolia, and CLE (13.79%, 28/203) were most frequent in D. nuttalli.

Conclusions

This study provides insight into the microbial diversity of D. nuttalli and I. persulcatus in Inner Mongolia, China, reporting for the first time that Candidatus R. tarasevichiae had been found in D. nuttalli in China, and for the first time in the world that Anaplasma sp. Mongolia has been detected in I. persulcatus. This study proves that various vertically transmitted pathogens co-inhabit D. nuttalli and I. persulcatus, and indicates that cattle in Inner Mongolia are exposed to several TBPs.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04740-3.

Desulfobacterales stimulates nitrate reduction in the mangrove ecosystem of a subtropical gulf

The amount of nitrogen compounds discharged into the natural environment has increased drastically due to frequent human activities and led to worsening pollution. The mangrove ecosystem can remove nitrogen pollution, in this regard, few studies had focused on the relationship among nitrogen cycling genes, environmental factors, and taxonomic composition. In this study, shotgun metagenomic sequencing and quantitative polymerase chain reaction were used to understand the nitrogen cycle in the subtropical mangrove ecosystem in the Beibu Gulf of China. Eight nitrogen cycling pathways were annotated. Nitrogen metabolism activities were significantly higher in the wet season than those in the dry season. The most abundant genes were those related to the synthesis and degradation of organic nitrogen, followed by the genes involved in nitrate reduction (denitrification, dissimilation/assimilation nitrate reduction). Furthermore, dissimilation nitrate reduction was the main nitrate reduction pathway. Desulfobacterales plays an important role in nitrogen cycling and contributes 12% of the genes of nitrogen pathways on average; as such, a strong coupling relationship exists among nitrogen cycling, sulfur cycling, and carbon cycling in the mangrove ecosystem. Nitrogen pollution in the mangrove wetland can be efficiently alleviated by nitrate reduction of Desulfobacterales. Nevertheless, only 50% of genes can be matched among the known species, suggesting that many unknown microorganisms in the mangrove ecosystem can perform nitrogen cycling. Total phosphorus, available iron, and total organic carbon are the key environmental factors that influence the distribution of nitrogen cycling genes, related pathways, and the taxonomic composition. Our study clearly illustrates how the mangrove ecosystem mitigates nitrogen pollution through Desulfobacterales. This finding could provide a research reference for the whole nitrogen cycling in the mangrove ecosystem.

Phytoplankton taxonomic and functional diversity patterns across a coastal tidal front

Oceanic physics at fine scale; e.g. eddies, fronts, filaments; are notoriously difficult to sample. However, an increasing number of theoretical approaches hypothesize that these processes affect phytoplankton diversity which have cascading effects on regional ecosystems. In 2015, we targeted the Iroise Sea (France) and evidenced the setting up of the Ushant tidal front from the beginning of spring to late summer. Seawater samples were taken during three sampling cruises and DNA-barcoding allowed us to investigate patterns of eukaryotic phytoplankton diversity across this front. First focusing on patterns of taxonomic richness, we evidenced that the front harbored a hotspot of eukaryotic phytoplankton diversity sustained throughout summer. We then detail the ecological processes leading to the formation of this hotspot by studying shifts in community composition across the Iroise Sea. Physical mixing mingled the communities surrounding the front, allowing the formation of a local ecotone, but it was cycles of disturbances and nutrient inputs over the front that allowed a decrease in competitive exclusion, which maintained a higher diversity of rare phytoplankton taxa. These processes did not select a specific ecological strategy as inferred by a trait approach coupled to our taxonomic approach. Instead the front favored higher richness within widespread strategies, resulting in functional redundancy. We detail how fine-scale ocean physics affect phytoplankton diversity and suppose that this interplay is a major control on regional ecosystems.

Cyanorak v2.1: a scalable information system dedicated to the visualization and expert curation of marine and brackish picocyanobacteria genomes

Cyanorak v2.1 (http://www.sb-roscoff.fr/cyanorak) is an information system dedicated to visualizing, comparing and curating the genomes of Prochlorococcus, Synechococcus and Cyanobium, the most abundant photosynthetic microorganisms on Earth. The database encompasses sequences from 97 genomes, covering most of the wide genetic diversity known so far within these groups, and which were split into 25,834 clusters of likely orthologous groups (CLOGs). The user interface gives access to genomic characteristics, accession numbers as well as an interactive map showing strain isolation sites. The main entry to the database is through search for a term (gene name, product, etc.), resulting in a list of CLOGs and individual genes. Each CLOG benefits from a rich functional annotation including EggNOG, EC/K numbers, GO terms, TIGR Roles, custom-designed Cyanorak Roles as well as several protein motif predictions. Cyanorak also displays a phyletic profile, indicating the genotype and pigment type for each CLOG, and a genome viewer (Jbrowse) to visualize additional data on each genome such as predicted operons, genomic islands or transcriptomic data, when available. This information system also includes a BLAST search tool, comparative genomic context as well as various data export options. Altogether, Cyanorak v2.1 constitutes an invaluable, scalable tool for comparative genomics of ecologically relevant marine microorganisms.

Metagenomic insights into Chinese northeast suancai: Predominance and diversity of genes associated with nitrogen metabolism in traditional household suancai fermentation

Chinese northeast suancai represents a typical and valuable food product that has been handed down by traditional household procedures over centuries. Nitrite is formed and accumulated during the suancai fermentation process and commonly causes food safety problems. The biogeochemical cycle of nitrite may provide a reference and guidance for the enzymatic degradation of nitrite in fermented food. The potential nitrogen metabolic pathways in the microbially driven suancai fermentation were reasonably inferred through monitoring nitrogen conversions and detecting the genes of different functional enzymes. Complex microbial metabolism is responsible for the unique nitrogen conversions during suancai fermentation. The metagenomic results showed that Pseudomonas with nitrate reductase genes (narG, narH, narI) and nitrite reductase genes (nirB, nirD) contributed the most to both nitrite reduction and nitrate reduction. The majority of the sequences of nitrate reductase and nitrite reductase were derived from the families of Pseudomonadaceae, Erwiniaceae and Yersiniaceae. According to the physicochemical analysis, the nitrite concentration of the fermentation broth reached the peak value (0.48 mM) and gradually decreased to the minimum (0.02 mM). The downward trend of the pH and nitrite concentration were closely associated with the nitrite enzymatic degradation period before the acid degradation period. Our results indicated that nitrite removal in suancai fermentation involved the reduction of nitrite to ammonia and denitrification, which were mainly contributed by the reduction of nitrite to ammonia mediated by the nirB/nirD enzyme (Indentified ECs: 1.7.1.15). This research offers new insights into the metagenome-based bioinformatic roles of the previously unstudied microorganisms in spontaneous suancai fermentation for the enzymatic degradation of nitrite. It provides helpful basis for the detection and even elimination of nitrite in suancai and for improving the safety level of suancai.

Evolutionary origin of the Atlantic Cabo Verde nibbler (Girella stuebeli), a member of a primarily Pacific Ocean family of antitropical herbivorous reef fishes

Nibblers (family Girellidae) are reef fishes that are mostly distributed in the Indo-Pacific, with one exception: Girella stuebeli, which is found in the Cabo Verde Archipelago, in the Atlantic Ocean. We capitalized on this unusual distribution to study the evolutionary history of the girellids, and determine the relationship between G. stuebeli and the remaining nibbler taxa. Based on thousands of genomic markers (RAD sequences), we identified the closest relatives of G. stuebeli as being a clade of three species endemic to the northwestern Pacific, restricted to the Sea of Japan and vicinity. This clade diverged from G. stuebeli approximately 2.2 Mya. Two alternative potential routes of migration may explain this affinity: a western route, from the Tropical Eastern Pacific and the Tropical Western Atlantic, and an eastern route via the Indian Ocean and Southern Africa. The geological history and oceanography of the regions combined with molecular data presented here, suggest that the eastern route of invasion (via the Indian Ocean and Southern Africa) is a more likely scenario.

Analysis of the vaginal microbiome of giant pandas using metagenomics sequencing

In this study, a total of 14 vaginal samples (GPV1‐14) from giant pandas were analyzed. These vaginal samples were divided into two groups as per the region and age of giant pandas. All the vaginal samples were analyzed using metagenomic sequencing. As per the outcomes of metagenomic analysis, Proteobacteria (39.04%), Firmicutes (5.27%), Actinobacteria (2.94%), and Basidiomycota (2.77%) were found to be the dominant phyla in the microbiome of the vaginal samples. At the genus level, Pseudomonas (21.90%) was found to be the most dominant genus, followed by Streptococcus (3.47%), Psychrobacter (1.89%), and Proteus (1.38%). Metastats analysis of the microbial species in the vaginal samples of giant pandas from Wolong Nature Reserve, Dujiangyan and Ningbo Youngor Zoo, and Ya'an Bifengxia Nature Reserve was found to be significantly different (p < 0.05). Age groups, that is, AGE1 (5‐10 years old) and AGE2 (11‐16 years old), also demonstrated significantly different inter‐group microbial species (p < 0.05). For the first time, Chlamydia and Neisseria gonorrhoeae were detected in giant pandas’ reproductive tract. GPV3 vaginal sample (2.63%) showed highest Chlamydia content followed by GPV14 (0.91%), and GPV7 (0.62%). GPV5 vaginal sample (7.17%) showed the highest Neisseria gonorrhoeae content, followed by GPV14 (7.02%), and GPV8 (6.50%). Furthermore, we employed eggNOG, CAZy, KEGG, and NCBI databases to investigate the functional significance of giant panda's vaginal microbial community. The outcomes indicated that giant panda's vaginal microbes were involved in biological processes. The data from this study will help in improving the reproductive health of giant pandas.

Harnessing the strategy of metagenomics for exploring the intestinal microecology of sable (Martes zibellina), the national first-level protected animal

Sable (Martes zibellina), a member of family Mustelidae, order Carnivora, is primarily distributed in the cold northern zone of Eurasia. The purpose of this study was to explore the intestinal flora of the sable by metagenomic library-based techniques. Libraries were sequenced on an Illumina HiSeq 4000 instrument. The effective sequencing data of each sample was above 6000 M, and the ratio of clean reads to raw reads was over 98%. The total ORF length was approximately 603,031, equivalent to 347.36 Mbp. We investigated gene functions with the KEGG database and identified 7140 KEGG ortholog (KO) groups comprising 129,788 genes across all of the samples. We selected a subset of genes with the highest abundances to construct cluster heat maps. From the results of the KEGG metabolic pathway annotations, we acquired information on gene functions, as represented by the categories of metabolism, environmental information processing, genetic information processing, cellular processes and organismal systems. We then investigated gene function with the CAZy database and identified functional carbohydrate hydrolases corresponding to genes in the intestinal microorganisms of sable. This finding is consistent with the fact that the sable is adapted to cold environments and requires a large amount of energy to maintain its metabolic activity. We also investigated gene functions with the eggNOG database; the main functions of genes included gene duplication, recombination and repair, transport and metabolism of amino acids, and transport and metabolism of carbohydrates. In this study, we attempted to identify the complex structure of the microbial population of sable based on metagenomic sequencing methods, which use whole metagenomic data, and to map the obtained sequences to known genes or pathways in existing databases, such as CAZy, KEGG, and eggNOG. We then explored the genetic composition and functional diversity of the microbial community based on the mapped functional categories.

SimkaMin: fast and resource frugal de novo comparative metagenomics

MOTIVATION

De novo comparative metagenomics is one of the most straightforward ways to analyze large sets of metagenomic data. Latest methods use the fraction of shared k-mers to estimate genomic similarity between read sets. However, those methods, while extremely efficient, are still limited by computational needs for practical usage outside of large computing facilities.

RESULTS

We present SimkaMin, a quick comparative metagenomics tool with low disk and memory footprints, thanks to an efficient data subsampling scheme used to estimate Bray-Curtis and Jaccard dissimilarities. One billion metagenomic reads can be analyzed in <3 min, with tiny memory (1.09 GB) and disk (≈0.3 GB) requirements and without altering the quality of the downstream comparative analyses, making of SimkaMin a tool perfectly tailored for very large-scale metagenomic projects.

AVAILABILITY AND IMPLEMENTATION

https://github.com/GATB/simka.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.