Global transmission of broad-host-range plasmids derived from the human gut microbiome.

Broad-host-range (BHR) plasmids in human gut bacteria are of considerable interest for their ability to mediate horizontal gene transfer (HGT) across large phylogenetic distance. However, the human gut plasmids, especially the BHR plasmids, remain largely unknown. Here, we identified the plasmids in the draft genomes of gut bacterial isolates from Chinese and American donors, resulting in 5372 plasmid-like clusters (PLCs), of which, 820 PLCs (comPLCs) were estimated with > 60% completeness genomes and only 155 (18.9%) were classified to known replicon types (n = 37). We observed that 175 comPLCs had a broad host range across distinct bacterial genera, of which, 71 were detected in at least two human populations of Chinese, American, Spanish, and Danish, and 13 were highly prevalent (>10%) in at least one human population. Haplotype analyses of two widespread PLCs demonstrated their spreading and evolutionary trajectory, suggesting frequent and recent exchanges of the BHR plasmids in environments. In conclusion, we obtained a large collection of plasmid sequences in human gut bacteria and demonstrated that a subset of the BHR plasmids can be transmitted globally, thus facilitating extensive HGT (e.g. antibiotic resistance genes) events. This study highlights the potential implications of the plasmids for global human health.

A recently evolved diflavin-containing monomeric nitrate reductase is responsible for highly efficient bacterial nitrate assimilation.

Nitrate is one of the major inorganic nitrogen sources for microbes. Many bacterial and archaeal lineages have the capacity to express assimilatory nitrate reductase (NAS), which catalyzes the rate-limiting reduction of nitrate to nitrite. Although a nitrate assimilatory pathway in mycobacteria has been proposed and validated physiologically and genetically, the putative NAS enzyme has yet to be identified. Here, we report the characterization of a novel NAS encoded by Mycolicibacterium smegmatis Msmeg_4206, designated NasN, which differs from the canonical NASs in its structure, electron transfer mechanism, enzymatic properties, and phylogenetic distribution. Using sequence analysis and biochemical characterization, we found that NasN is an NADPH-dependent, diflavin-containing monomeric enzyme composed of a canonical molybdopterin cofactor-binding catalytic domain and an FMN-FAD/NAD-binding, electron-receiving/transferring domain, making it unique among all previously reported hetero-oligomeric NASs. Genetic studies revealed that NasN is essential for aerobic M. smegmatis growth on nitrate as the sole nitrogen source and that the global transcriptional regulator GlnR regulates nasN expression. Moreover, unlike the NADH-dependent heterodimeric NAS enzyme, NasN efficiently supports bacterial growth under nitrate-limiting conditions, likely due to its significantly greater catalytic activity and oxygen tolerance. Results from a phylogenetic analysis suggested that the nasN gene is more recently evolved than those encoding other NASs and that its distribution is limited mainly to Actinobacteria and Proteobacteria. We observed that among mycobacterial species, most fast-growing environmental mycobacteria carry nasN, but that it is largely lacking in slow-growing pathogenic mycobacteria because of multiple independent genomic deletion events along their evolution.

Alterations in Enteric Virome Are Associated With Colorectal Cancer and Survival Outcomes.

BACKGROUND & AIMS: Patients with colorectal cancer (CRC) have a different gut microbiome signature than individuals without CRC. Little is known about the viral component of CRC-associated microbiome. We aimed to identify and validate viral taxonomic markers of CRC that might be used in detection of the disease or predicting outcome. METHODS: We performed shotgun metagenomic analyses of viromes of fecal samples from 74 patients with CRC (cases) and 92 individuals without CRC (controls) in Hong Kong (discovery cohort). Viral sequences were classified by taxonomic alignment against an integrated microbial reference genome database. Viral markers associated with CRC were validated using fecal samples from 3 separate cohorts: 111 patients with CRC and 112 controls in Hong Kong, 46 patients with CRC and 63 controls in Austria, and 91 patients with CRC and 66 controls in France and Germany. Using abundance profiles of CRC-associated virome genera, we constructed random survival forest models to identify those associated with patient survival times. RESULTS: The diversity of the gut bacteriophage community was significantly increased in patients with CRC compared with controls. Twenty-two viral taxa discriminated cases from controls with an area under the receiver operating characteristic curve of 0.802 in the discovery cohort. The viral markers were validated in 3 cohorts, with area under the receiver operating characteristic curves of 0.763, 0.736, and 0.715, respectively. Clinical subgroup analysis showed that dysbiosis of the gut virome was associated with early- and late-stage CRC. A combination of 4 taxonomic markers associated with reduced survival of patients with CRC (log-rank test, P = 8.1 × 10-6) independently of tumor stage, lymph node metastases, or clinical parameters. We found altered interactions between bacteriophages and oral bacterial commensals in fecal samples from patients with CRC compared with controls. CONCLUSIONS: In a metagenomic analysis of fecal samples from patients and controls, we identified virome signatures associated with CRC. These data might be used to develop tools to identify individuals with CRC or predict outcomes.

Comparative genomics of methicillin-resistant Staphylococcus aureus ST239: distinct geographical variants in Beijing and Hong Kong.

BACKGROUND: The ST239 lineage is a globally disseminated, multiply drug-resistant hospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA). We performed whole-genome sequencing of representative HA-MRSA isolates of the ST239 lineage from bacteremic patients in hospitals in Hong Kong (HK) and Beijing (BJ) and compared them with three published complete genomes of ST239, namely T0131, TW20 and JKD6008. Orthologous gene group (OGG) analyses of the Hong Kong and Beijing cluster strains were also undertaken. RESULTS: Homology analysis, based on highest-percentage nucleotide identity, indicated that HK isolates were closely related to TW20, whereas BJ isolates were more closely related to T0131 from Tianjin. Phylogenetic analysis, incorporating a total of 30 isolates from different continents, revealed that strains from HK clustered with TW20 into the 'Asian clade', whereas BJ isolates and T0131 clustered closely with strains of the 'Turkish clade' from Eastern Europe. HK isolates contained the typical φSPß-like prophage with the SasX gene similar to TW20. In contrast, BJ isolates contained a unique 15 kb PT1028-like prophage but lacked φSPß-like and φSA1 prophages. Besides distinct mobile genetic elements (MGE) in the two clusters, OGG analyses and whole-genome alignment of these clusters highlighted differences in genes located in the core genome, including the identification of single nucleotide deletions in several genes, resulting in frameshift mutations and the subsequent predicted truncation of encoded proteins involved in metabolism and antimicrobial resistance. CONCLUSIONS: Comparative genomics, based on de novo assembly and deep sequencing of HK and BJ strains, revealed different origins of the ST239 lineage in northern and southern China and identified differences between the two clades at single nucleotide polymorphism (SNP), core gene and MGE levels. The results suggest that ST239 strains isolated in Hong Kong since the 1990s belong to the Asian clade, present mainly in southern Asia, whereas those that emerged in northern China were of a distinct origin, reflecting the complexity of dissemination and the dynamic evolution of this ST239 lineage.

Direct detection and prediction of all pneumococcal serogroups by target enrichment-based next-generation sequencing.

Despite the availability of standard methods for pneumococcal serotyping, there is room for improvement in the available methods, in terms of throughput, multiplexing capacity, and the number of serotypes identified. We describe a target enrichment-based next-generation sequencing method applied to nasopharyngeal samples for direct detection and serogroup prediction of all known serotypes of Streptococcus pneumoniae, 32 to the serotype level and the rest to the closely related serogroup level. The method was applied to detect and to predict the serogroups of pneumococci directly in clinical samples and from sweeps of primary culture DNA, with increased detection rates versus culture-based identification and agreement with the serotypes/serogroups determined by conventional serotyping methods. We propose this method, in conjunction with traditional serotyping methods, as an alternative to rapid detection and serotyping of pneumococci.

Application of a target enrichment-based next-generation sequencing protocol for identification and sequence-based prediction of pneumococcal serotypes.

BACKGROUND: The use of whole-genome sequencing in microbiology at a diagnostic level, although feasible, is still limited by the expenses associated and by the complex bioinformatics pipelines in data analyses. We describe the use of target enrichment-based next-generation sequencing for pneumococcal identification and serotyping as applied to the polysaccharide 23 valent vaccine serotypes as an affordable alternative to whole genome sequencing. RESULTS: Correct identification of Streptococcus pneumoniae and prediction of common vaccine serotypes: 12 to serotype level and the rest to serogroup levels were achieved for all serotypes with >500 reads mapped against serotypes sequences. A proportion-based criterion also enabled the identification of two serotypes present in the same sample, thus indicating the possibility of using this method in detecting co-colonizing serotypes. The results obtained were comparable to or an improvement on the currently existing molecular serotyping methods for S. pneumoniae in relation to the polysaccharide vaccine serotypes. CONCLUSION: We propose that this method has the potential to become an affordable and adaptable alternative to whole-genome sequencing for pneumococcal identification and serotyping.

Corynebacterium parakroppenstedtii secretes a novel glycolipid to promote the development of granulomatous lobular mastitis.

Granulomatous lobular mastitis (GLM) is a chronic idiopathic granulomatous mastitis of the mammary gland characterized by significant pain and a high propensity for recurrence, the incidence rate has gradually increased, and has become a serious breast disease that should not be ignored. GLM is highly suspected relative to microbial infections, especially those of Corynebacterium species; however, the mechanisms involved are unclear, and prevention and treatment are difficult. In this study, we demonstrated the pathogenicity of Corynebacterium parakroppenstedtii in GLM using Koch's postulates. Based on the drug sensitization results of C. parakroppenstedtii, and utilizing a retrospective study in conjunction with a comprehensive literature review, we suggested an efficacious, targeted antibiotic treatment strategy for GLM. Subsequently, we identified the pathogenic factor as a new type of glycolipid (named corynekropbactins) secreted by C. parakroppenstedtii. Corynekropbactins may chelate iron, cause the death of mammary cells and other mammary -gland-colonizing bacteria, and increase the levels of inflammatory cytokines. We further analyzed the prevalence of C. parakroppenstedtii infection in patients with GLM. Finally, we suggested that the lipophilicity of C. parakroppenstedtii may be associated with its infection route and proposed a possible model for the development of GLM. This research holds significant implications for the clinical diagnosis and therapeutic management of GLM, offering new insights into targeted treatment approaches.

Mycobacteriaceae Phenome Atlas (MPA): A Standardized Atlas for the Mycobacteriaceae Phenome Based on Heterogeneous Sources.

The bacterial family Mycobacteriaceae includes pathogenic and nonpathogenic bacteria, and systematic research on their genome and phenome can give comprehensive perspectives for exploring their disease mechanism. In this study, the phenotypes of Mycobacteriaceae were inferred from available phenomic data, and 82 microbial phenotypic traits were recruited as data elements of the microbial phenome. This Mycobacteriaceae phenome contains five categories and 20 subcategories of polyphasic phenotypes, and three categories and eight subcategories of functional phenotypes, all of which are complementary to the existing data standards of microbial phenotypes. The phenomic data of Mycobacteriaceae strains were compiled by literature mining, third-party database integration, and bioinformatics annotation. The phenotypes were searchable and comparable from the website of the Mycobacteriaceae Phenome Atlas (MPA, https://www.biosino.org/mpa/). A topological data analysis of MPA revealed the co-evolution between Mycobacterium tuberculosis and virulence factors, and uncovered potential pathogenicity-associated phenotypes. Two hundred and sixty potential pathogen-enriched pathways were found by Fisher's exact test. The application of MPA may provide novel insights into the pathogenicity mechanism and antimicrobial targets of Mycobacteriaceae. Supplementary Information: The online version contains supplementary material available at 10.1007/s43657-023-00101-5.

Analogous assembly mechanisms and functional guilds govern prokaryotic communities in mangrove ecosystems of China and South America.

As an important coastal "blue carbon sink," mangrove ecosystems contain microbial communities with an as-yet-unknown high species diversity. Exploring the assemblage and structure of sediment microbial communities therein can aid in a better understanding of their ecosystem functioning, such as carbon sequestration and other biogeochemical cycles in mangrove wetlands. However, compared to other biomes, the study of mangrove sediment microbiomes is limited, especially in diverse mangrove ecosystems at a large spatial scale, which may harbor microbial communities with distinct compositions and functioning. Here, we analyzed 380 sediment samples from 13 and 8 representative mangrove ecosystems, respectively, in China and South America and compared their microbial features. Although the microbial community compositions exhibited strong distinctions, the community assemblage in the two locations followed analogous patterns: the assemblages of the entire community, abundant taxa, rare taxa, and generalists were predominantly driven by stochastic processes with significant distance-decay patterns, while the assembly of specialists was more likely related to the behaviors of other organisms in or surrounding the mangrove ecosystems. In addition, co-occurrence and topological network analysis of mangrove sediment microbiomes underlined the dominance of sulfate-reducing prokaryotes in both the regions. Moreover, we found that more than 70% of the keystone and hub taxa were sulfate-reducing prokaryotes, implying their important roles in maintaining the linkage and stability of the mangrove sediment microbial communities. This study fills a gap in the large-scale analysis of microbiome features covering distantly located and diverse mangrove ecosystems. Here, we propose a suggestion to the Mangrove Microbiome Initiative that 16S rRNA sequencing protocols should be standardized with a unified primer to facilitate the global-scale analysis of mangrove microbiomes and further comparisons with the reference data sets from other biomes.IMPORTANCEMangrove wetlands are important ecosystems possessing valuable ecological functions for carbon storage, species diversity maintenance, and coastline stabilization. These functions are greatly driven or supported by microorganisms that make essential contributions to biogeochemical cycles in mangrove ecosystems. The mechanisms governing the microbial community assembly, structure, and functions are vital to microbial ecology but remain unclear. Moreover, studying these mechanisms of mangrove microbiomes at a large spatial scale can provide a more comprehensive insight into their universal features and can help untangle microbial interaction patterns and microbiome functions. In this study, we compared the mangrove microbiomes in a large spatial range and found that the assembly patterns and key functional guilds of the Chinese and South American mangrove microbiomes were analogous. The entire communities exhibited significant distance-decay patterns and were strongly governed by stochastic processes, while the assemblage of specialists may be merely associated with the behaviors of the organisms in mangrove ecosystems. Furthermore, our results highlight the dominance of sulfate-reducing prokaryotes in mangrove microbiomes and their key roles in maintaining the stability of community structure and functions.

Natural products from plants and microorganisms: Novel therapeutics for chronic kidney disease via gut microbiota regulation.

Dysbiosis of gut microbiota plays a fundamental role in the pathogenesis and development of chronic kidney disease (CKD) and its complications. Natural products from plants and microorganisms can achieve recognizable improvement in renal function and serve as an alternative treatment for chronic kidney disease patients with a long history, yet less is known on its beneficial effects on kidney injury by targeting the intestinal microbiota. In this review, we summarize studies on the effects of natural products from plants and microorganisms, including herbal medicines and their bioactive extracts, polysaccharides from plants and microorganisms, and phytochemicals, on the prevention and treatment of chronic kidney disease through targeting gut microflora. We describe the strategies of these anti-CKD effects in animal experiments including remodulation of gut microbiota structure, reduction of uremic toxins, enhancement of short-chain fatty acid (SCFA) production, regulation of intestinal inflammatory signaling, and improvement in intestinal integrity. Meanwhile, the clinical trials of different natural products in chronic kidney disease clinical practice were also analyzed and discussed. These provide information to enable a better understanding of the renoprotective effects of these effective natural products from plants and microorganisms in the treatment of chronic kidney disease. Finally, we propose the steps to prove the causal role of the intestinal microflora in the treatment of chronic kidney disease by natural products from plants and microorganisms. We also assess the future perspective that natural active products from plants and microorganisms can beneficially delay the onset and progression of kidney disease by targeting the gut flora and highlight the remaining challenges in this area. With the continuous deepening of studies in recent years, it has been proved that gut microbiota is a potential target of natural active products derived from plants and microorganisms for chronic kidney disease treatment. Fully understanding the functions and mechanisms of gut microbiota in these natural active products from plants and microorganisms is conducive to their application as an alternative therapeutic in the treatment of chronic kidney disease.

Ginsenoside Rb1 Improves Metabolic Disorder in High-Fat Diet-Induced Obese Mice Associated With Modulation of Gut Microbiota.

Gut microbiota plays an important role in metabolic homeostasis. Previous studies demonstrated that ginsenoside Rb1 might improve obesity-induced metabolic disorders through regulating glucose and lipid metabolism in the liver and adipose tissues. Due to low bioavailability and enrichment in the intestinal tract of Rb1, we hypothesized that modulation of the gut microbiota might account for its pharmacological effects as well. Here, we show that oral administration of Rb1 significantly decreased serum LDL-c, TG, insulin, and insulin resistance index (HOMA-IR) in mice with a high-fat diet (HFD). Dynamic profiling of the gut microbiota showed that this metabolic improvement was accompanied by restoring of relative abundance of some key bacterial genera. In addition, the free fatty acids profiles in feces were significantly different between the HFD-fed mice with or without Rb1. The content of eight long-chain fatty acids (LCFAs) was significantly increased in mice with Rb1, which was positively correlated with the increase of Akkermansia and Parasuttereller, and negatively correlated with the decrease of Oscillibacter and Intestinimonas. Among these eight increased LCFAs, eicosapentaenoic acid (EPA), octadecenoic acids, and myristic acid were positively correlated with metabolic improvement. Furthermore, the colonic expression of the free fatty acid receptors 4 (Ffar4) gene was significantly upregulated after Rb1 treatment, in response to a notable increase of LCFA in feces. These findings suggested that Rb1 likely modulated the gut microbiota and intestinal free fatty acids profiles, which should be beneficial for the improvement of metabolic disorders in HFD-fed mice. This study provides a novel mechanism of Rb1 for the treatment of metabolic disorders induced by obesity, which may provide a therapeutic avenue for the development of new nutraceutical-based remedies for treating metabolic diseases, such as hyperlipidemia, insulin resistance, and type 2 diabetes.

Symbiotic gut microbes modulate human metabolic phenotypes.

Humans have evolved intimate symbiotic relationships with a consortium of gut microbes (microbiome) and individual variations in the microbiome influence host health, may be implicated in disease etiology, and affect drug metabolism, toxicity, and efficacy. However, the molecular basis of these microbe-host interactions and the roles of individual bacterial species are obscure. We now demonstrate a"transgenomic" approach to link gut microbiome and metabolic phenotype (metabotype) variation. We have used a combination of spectroscopic, microbiomic, and multivariate statistical tools to analyze fecal and urinary samples from seven Chinese individuals (sampled twice) and to model the microbial-host metabolic connectivities. At the species level, we found structural differences in the Chinese family gut microbiomes and those reported for American volunteers, which is consistent with population microbial cometabolic differences reported in epidemiological studies. We also introduce the concept of functional metagenomics, defined as "the characterization of key functional members of the microbiome that most influence host metabolism and hence health." For example, Faecalibacterium prausnitzii population variation is associated with modulation of eight urinary metabolites of diverse structure, indicating that this species is a highly functionally active member of the microbiome, influencing numerous host pathways. Other species were identified showing different and varied metabolic interactions. Our approach for understanding the dynamic basis of host-microbiome symbiosis provides a foundation for the development of functional metagenomics as a probe of systemic effects of drugs and diet that are of relevance to personal and public health care solutions.

Genome recovery and metatranscriptomic confirmation of functional acetate-oxidizing bacteria from enriched anaerobic biogas digesters.

In many cases, it is difficult to isolate the key microbial organisms from their communities present in natural environments. Metagenomic methods can recover near-complete genomes of the dominant microbial organisms in communities, and metatrancriptomic data could further reveal important genes and pathways related to their functions. In this study, three draft genomes of Clostridium ultunense-like bacteria were recovered based on metagenomic analyses, which is an essential syntrophic acetate-oxidizing bacteria (SAOB) member for maintaining high methane production in high-ammonium biogas digesters but difficult to isolate from its syntrophic partners. Firstly, syntrophic acetate-oxidizing bacteria in a microbial community series were enriched from a biogas digester by adding sodium acetate in the medium. Global analyses of C. ultunense suggested that it would combine the pyruvate-serine-glycine pathway and part of the Wood-Ljungdahl pathway for syntrophic acetate oxidization. Moreover, metatranscriptomic analyses showed that all of the genes of the proposed syntrophic acetate-oxidizing pathway present in the genome were actively transcribed in the microbiota. The functional bacterial enrichment and refined assembly method identify rare microbial genome in complex natural microbiota, which help to recover the syntrophic acetate-oxidizing pathway in C. ultunense strains in this study.

Integrated metabolomics and gut microbiome to the effects and mechanisms of naoxintong capsule on type 2 diabetes in rats.

Naoxintong Capsule (NXT) is a Traditional Chinese Medicine formulation which has been widely applied in treating cardiovascular and cerebrovascular diseases. Previous studies also reported the potential effects of NXT against diabetes and certain complications, yet its mechanisms remain largely obscured. Herein, in this study, we investigated the anti-diabetic effects of NXT as well as its potential mechanisms. Type 2 diabetes (T2D) was induced in rats by 10-week high-fat diet in companion with a low-dose streptozotocin injection. NXT was administrated for additional 8 weeks. The results showed that NXT exerted potent efficacy against T2D by alleviating hyperglycemia and hyperlipidemia, ameliorating insulin resistance, mitigating inflammation, relieving hypertension, and reducing myocardial injuries. To investigate its mechanisms, by integrating sequencing of gut microbiota and serum untargeted metabolomics, we showed that NXT could significantly recover the disturbances of gut microbiota and metabolic phenotypes in T2D rats. Several feature pathways, such as arachidonic acid metabolism, fatty acid ß-oxidation and glycerophospholipid metabolism, were identified as the potential mechanisms of NXT in vivo. In summary, our study has comprehensively revealed the anti-diabetic effects of NXT which could be considered as a promising strategy for treating metabolic disorders, T2D and diabetic related complications in clinical practice.

Distinct Responses of Gut Microbiota to Jian-Pi-Yi-Shen Decoction Are Associated With Improved Clinical Outcomes in 5/6 Nephrectomized Rats.

Gut dysbiosis contributes to the development and progression of chronic kidney disease (CKD) and its complications. However, the effect of drugs on the gut microbiota of CKD patients and its influence on treatment outcomes remains to be explored. Here, we assessed whether the response of gut microbiota to the traditional Chinese medicine Jian-Pi-Yi-Shen (JPYS) decoction differed from that to piperazine ferulate (PF), a kidney-targeted drug, by 16S rDNA sequencing, and whether the difference could be linked with drug-specific clinical outcomes. We showed that both JPYS and PF improved renal function, but only JPYS was able to restore the blood reticulocyte counting and serum calcium level in CKD rats. We also found that weighted UniFrac beta-diversity of the gut microbiome of the JPYS treated rats was significantly different from that of PF. Microbiome markers of drug-specific response were identified and subjected to correlation network analysis, together with clinical parameters and KEGG pathways. Among the microbiome markers of CKD, Corynebacterium was found to form a network hub that was closely correlated with the JPYS responder Enterococcus, suggesting a potential indirect impact of JPYS on Corynebacterium via interspecies interactions. We also identified two network hubs of the PF responder Blautia and the JPYS-only marker Coprococcus, which were connected with many genera and clinical parameters. They might serve as keystone taxa driving the response of gut microbiota to the drugs and influence host outcomes. Moreover, the JPYS-only marker Clostridium_XIVb was found to be connected to many pathways that are associated with CKD progression and might account for the improved outcomes in the JPYS treated rats. At last, the identified keystone markers of drug response were validated by qPCR for their differential abundance between CKD and the two drugs. Taken together, our study revealed that the responses of gut microbiota to JPYS were distinct from that to PF, and pinpointed drug-specific keystone microbiome markers closely correlated to clinical parameters, which could serve as candidate microbiome targets for further studies on their roles in medicating the drug efficacy of TCM in CKD.

Gut Microbiome Alterations Precede Cerebral Amyloidosis and Microglial Pathology in a Mouse Model of Alzheimer's Disease.

Emerging evidence suggests that the gut microbiome actively regulates cognitive functions and that gut microbiome imbalance is associated with Alzheimer's disease (AD), the most prevalent neurodegenerative disorder. However, the changes in gut microbiome composition in AD and their association with disease pathology, especially in the early stages, are unclear. Here, we compared the profiles of gut microbiota between APP/PS1 transgenic mice (an AD mouse model) and their wild-type littermates at different ages by amplicon-based sequencing of 16S ribosomal RNA genes. Microbiota composition started diverging between the APP/PS1 and wild-type mice at young ages (i.e., 1-3 months), before obvious amyloid deposition and plaque-localized microglial activation in the cerebral cortex in APP/PS1 mice. At later ages (i.e., 6 and 9 months), there were distinct changes in the abundance of inflammation-related bacterial taxa including Escherichia-Shigella, Desulfovibrio, Akkermansia, and Blautia in APP/PS1 mice. These findings suggest that gut microbiota alterations precede the development of key pathological features of AD, including amyloidosis and plaque-localized neuroinflammation. Thus, the investigation of gut microbiota might provide new avenues for developing diagnostic biomarkers and therapeutic targets for AD.

Molecular diversity of Bacteroides spp. in human fecal microbiota as determined by group-specific 16S rRNA gene clone library analysis.

Bacteroides spp. represent a prominent bacterial group in human intestinal microbiota with roles in symbiosis and pathogenicity; however, the detailed composition of this group in human feces has yet to be comprehensively characterized. In this study, the molecular diversity of Bacteroides spp. in human fecal microbiota was analyzed from a seven-member, four-generation Chinese family using Bacteroides spp. group-specific 16S rRNA gene clone library analysis. A total of 549 partial 16S rRNA sequences amplified by Bacteroides spp.-specific primers were classified into 52 operational taxonomic units (OTUs) with a 99% sequence identity cut-off. Twenty-three OTUs, representing 83% of all clones, were related to 11 validly described Bacteroides species, dominated by Bacteroides coprocola, B. uniformis, and B. vulgatus. Most of the OTUs did not correspond to known species and represented hitherto uncharacterized bacteria. Relative to 16S rRNA gene universal libraries, the diversity of Bacteroides spp. detected by the group-specific libraries was much higher than previously described. Remarkable inter-individual differences were also observed in the composition of Bacteroides spp. in this family cohort. The comprehensive observation of molecular diversity of Bacteroides spp. provides new insights into potential contributions of various species in this group to human health and disease.

tmap: an integrative framework based on topological data analysis for population-scale microbiome stratification and association studies.

Untangling the complex variations of microbiome associated with large-scale host phenotypes or environment types challenges the currently available analytic methods. Here, we present tmap, an integrative framework based on topological data analysis for population-scale microbiome stratification and association studies. The performance of tmap in detecting nonlinear patterns is validated by different scenarios of simulation, which clearly demonstrate its superiority over the most commonly used methods. Application of tmap to several population-scale microbiomes extensively demonstrates its strength in revealing microbiome-associated host or environmental features and in understanding the systematic interrelations among their association patterns. tmap is available at https://github.com/GPZ-Bioinfo/tmap.

Role of Two-Component System Response Regulator bceR in the Antimicrobial Resistance, Virulence, Biofilm Formation, and Stress Response of Group B Streptococcus.

Group B Streptococcus (GBS; Streptococcus agalactiae) is a leading cause of sepsis in neonates and pregnant mothers worldwide. Whereas the hyper-virulent serogroup III clonal cluster 17 has been associated with neonatal disease and meningitis, serogroup III ST283 was recently implicated in invasive disease among non-pregnant adults in Asia. Here, through comparative genome analyses of invasive and non-invasive ST283 strains, we identified a truncated DNA-binding regulator of a two-component system in a non-invasive strain that was homologous to Bacillus subtilis bceR, encoding the bceRSAB response regulator, which was conserved among GBS strains. Using isogenic knockout and complementation mutants of the ST283 strain, we demonstrated that resistance to bacitracin and the human antimicrobial peptide cathelicidin LL-37 was reduced in the ΔbceR strain with MICs changing from 64 and 256 µg/ml to 0.25 and 64 µg/ml, respectively. Further, the ATP-binding cassette transporter was upregulated by sub-inhibitory concentrations of bacitracin in the wild-type strain. Upregulation of dltA in the wild-type strain was also observed and thought to explain the increased resistance to antimicrobial peptides. DltA, an enzyme involved in D-alanylation during the synthesis of wall teichoic acids, which mediates reduced antimicrobial susceptibility, was previously shown to be regulated by the bceR-type regulator in Staphylococcus aureus. In a murine infection model, we found that the ΔbceR mutation significantly reduced the mortality rate compared to that with the wild-type strain (p < 0.01). Moreover, this mutant was more susceptible to oxidative stress compared to the wild-type strain (p < 0.001) and was associated with reduced biofilm formation (p < 0.0001). Based on 2-DGE and mass spectrometry, we showed that downregulation of alkyl hydroperoxide reductase (AhpC), a Gls24 family stress protein, and alcohol dehydrogenase (Adh) in the ΔbceR strain might explain the attenuated virulence and compromised stress response. Together, we showed for the first time that the bceR regulator in GBS plays an important role in bacitracin and antimicrobial peptide resistance, virulence, survival under oxidative stress, and biofilm formation.

Functional metagenomics reveals abundant polysaccharide-degrading gene clusters and cellobiose utilization pathways within gut microbiota of a wood-feeding higher termite.

Plant cell-wall polysaccharides constitute the most abundant but recalcitrant organic carbon source in nature. Microbes residing in the digestive tract of herbivorous bilaterians are particularly efficient at depolymerizing polysaccharides into fermentable sugars and play a significant support role towards their host's lifestyle. Here, we combine large-scale functional screening of fosmid libraries, shotgun sequencing, and biochemical assays to interrogate the gut microbiota of the wood-feeding "higher" termite Globitermes brachycerastes. A number of putative polysaccharide utilization gene clusters were identified with multiple fibrolytic genes. Our large-scale functional screening of 50,000 fosmid clones resulted in 464 clones demonstrating plant polysaccharide-degrading activities, including 267 endoglucanase-, 24 exoglucanase-, 72 ß-glucosidase-, and 101 endoxylanase-positive clones. We sequenced 173 functionally active clones and identified ~219 genes encoding putative carbohydrate-active enzymes (CAZymes) targeting cellulose, hemicellulose and pectin. Further analyses revealed that 68 of 154 contigs encode one or more CAZyme, which includes 35 examples of putative saccharolytic operons, suggesting that clustering of CAZymes is common in termite gut microbial inhabitants. Biochemical characterization of a representative xylanase cluster demonstrated that constituent enzymes exhibited complementary physicochemical properties and saccharolytic capabilities. Furthermore, diverse cellobiose-metabolizing enzymes include ß-glucosidases, cellobiose phosphorylases, and phopho-6-ß-glucosidases were identified and functionally verified, indicating that the termite gut micro-ecosystem utilizes diverse metabolic pathways to interconnect hydrolysis and central metabolism. Collectively, these results provide an in-depth view of the adaptation and digestive strategies employed by gut microbiota within this tiny-yet-efficient host-associated ecosystem.