Chemoreceptors from the commensal gut Roseburia rectibacter bind to mucin and trigger chemotaxis.

Chemotaxis is crucial for bacterial adherence and colonization of the host gastrointestinal tract. Previous studies have demonstrated that chemotaxis affects the virulence of causative pathogens and the infection in the host. However, the chemotactic abilities of non-pathogenic and commensal gut bacteria have rarely been explored. We observed that Roseburia rectibacter NSJ-69 exhibited flagella-dependent motility and chemotaxis to a variety of molecules, including mucin and propionate. A genome-wide analysis revealed that NSJ-69 has 28 putative chemoreceptors, 15 of which have periplasmic ligand-binding domains (LBDs). These LBD-coding genes were chemically synthesized and expressed heterologously in Escherichia coli. Intensive screening of ligands revealed four chemoreceptors bound to mucin and two bound to propionate. When expressed in Comamonas testosteroni or E. coli, these chemoreceptors elicited chemotaxis toward mucin and propionate. Hybrid chemoreceptors were constructed, and results showed that the chemotactic responses to mucin and propionate were dependent on the LBDs of R. rectibacter chemoreceptors. Our study identified and characterized R. rectibacter chemoreceptors. These results will facilitate further investigations on the involvement of microbial chemotaxis in host colonization.

Alkaliphilus flagellatus sp. nov., Butyricicoccus intestinisimiae sp. nov., Clostridium mobile sp. nov., Clostridium simiarum sp. nov., Dysosmobacter acutus sp. nov., Paenibacillus brevis sp. nov., Peptoniphilus ovalis sp. nov. and Tissierella simiarum sp. nov., isolated from monkey faeces.

Non-human primates harbour diverse microbiomes in their guts. As a part of the China Microbiome Initiatives, we cultivated and characterized the gut microbiome of cynomolgus monkeys (Macaca fascicularis). In this report, we communicate the characterization and taxonomy of eight bacterial strains that were obtained from faecal samples of captive cynomolgus monkeys. The results revealed that they represented eight novel bacterial species. The proposed names of the eight novel species are Alkaliphilus flagellatus (type strain MSJ-5T=CGMCC 1.45007T=KCTC 15974T), Butyricicoccus intestinisimiae MSJd-7T (MSJd-7T=CGMCC 1.45013T=KCTC 25112T), Clostridium mobile (MSJ-11T=CGMCC 1.45009T=KCTC 25065T), Clostridium simiarum (MSJ-4T=CGMCC 1.45006T=KCTC 15975T), Dysosmobacter acutus (MSJ-2T=CGMCC 1.32896T=KCTC 15976T), Paenibacillus brevis MSJ-6T (MSJ-6T=CGMCC 1.45008T=KCTC 15973T), Peptoniphilus ovalis (MSJ-1T=CGMCC 1.31770T=KCTC 15977T) and Tissierella simiarum (MSJ-40T=CGMCC 1.45012T=KCTC 25071T).

PapA, a peptidoglycan-associated protein, interacts with OmpC and maintains cell envelope integrity.

The bacterial cell envelope is critical to support and maintain cellular life. In Gram-negative bacterial cells, the outer membrane and the peptidoglycan layer are two important parts of the cell envelope and they harbour abundant proteins. Here, we report the identification and characterization of a previously unknown peptidoglycan-associated protein, PapA, from the Gram-negative Comamonas testosteroni. PapA bound peptidoglycan with its C-terminal domain and interacted with the outer-membrane porin OmpC. The PapA-OmpC complex riveted the outer membrane and the peptidoglycan layer, and played a role in maintaining cell envelope integrity. When papA was disrupted, the mutant CNB-1ΔpapA apparently had an outer membrane partly separated from the peptidoglycan layer. Phenotypically, the mutant CNB-1ΔpapA lost chemotactic responses and had longer lag-phase of growth, less flagellation and higher sensitivity to harsh environments. Totally, 1093 functionally unknown PapA homologues were identified from the public NR protein database and they were mainly distributed in Burkholderiales of Betaproteobacteria. Our finding provides a clue that the PapA homologous proteins might function as a rivet to maintain cell envelope integrity in those Gram-negative bacteria.

N6-methyladenosine modification and METTL3 modulate enterovirus 71 replication.

N6-methyladenosine (m6A) constitutes one of the most abundant internal RNA modifications and is critical for RNA metabolism and function. It has been previously reported that viral RNA contains internal m6A modifications; however, only recently the function of m6A modification in viral RNAs has been elucidated during infections of HIV, hepatitis C virus and Zika virus. In the present study, we found that enterovirus 71 (EV71) RNA undergoes m6A modification during viral infection, which alters the expression and localization of the methyltransferase and demethylase of m6A, and its binding proteins. Moreover, knockdown of m6A methyltransferase resulted in decreased EV71 replication, whereas knockdown of the demethylase had the opposite effect. Further study showed that the m6A binding proteins also participate in the regulation of viral replication. In particular, two m6A modification sites were identified in the viral genome, of which mutations resulted in decreased virus replication, suggesting that m6A modification plays an important role in EV71 replication. Notably, we found that METTL3 interacted with viral RNA-dependent RNA polymerase 3D and induced enhanced sumoylation and ubiquitination of the 3D polymerase that boosted viral replication. Taken together, our findings demonstrated that the host m6A modification complex interacts with viral proteins to modulate EV71 replication.

An alternative splicing isoform of MITA antagonizes MITA-mediated induction of type I IFNs.

Mediator of IFN regulatory transcription factor 3 activation (MITA) is an important adaptor protein to mediate the induction of type I IFNs. In this study, we identified an alternatively spliced isoform of MITA lacking exon 7, termed MITA-related protein (MRP). MRP shares the N-terminal portion aa 1-253 with MITA but possesses a unique 30-aa sequence at the carboxyl terminal part, therefore lacking the conserved domains including TANK-binding kinase 1 (TBK1) and cyclic diguanylate binding domain. MRP is expressed in multiple tissues and distinct cell lines. Overexpression of MRP inhibited MITA-mediated activation of IFN-ß promoter by sendai virus infection and cyclic diguanylate treatment but enhanced that in HSV-1 infection. Interestingly, MRP expression was reduced after Sendai virus infection but was upregulated after HSV-1 infection. Overexpression of MRP inhibited MITA-mediated induction of IFN-ß via TBK1-IFN regulatory transcription factor 3 by disrupting the MITA-TBK1 interaction. However, NF-κB pathway was still activated by MRP, as MRP retained the ability to interact with inducible inhibitor of NF-κB (iκB) kinase. Thus, MRP acts as a dominant negative regulator of MITA-mediated induction of IFN production.

The monkey microbial biobank brings previously uncultivated bioresources for nonhuman primate and human gut microbiomes.

Nonhuman primates (NHPs) such as monkeys are the closest living relatives to humans and are the best available models for causative studies of human health and diseases. Gut microbiomes are intensively involved in host health. In this study, by large-scale cultivation of microbes from fecal samples of monkeys, we obtained previously uncultured bacterial species and constructed a Macaca fascicularis Gut Microbial Biobank (MfGMB). The MfGMB consisted of 250 strains that represent 97 species of 63 genera, 25 families, and 4 phyla. The information of the 250 strains and the genomes of 97 cultured species are publicly accessible. The MfGMB represented nearly 50% of core gut microbial compositions at the genus level and covered over 80% of the KO-based known gut microbiome functions of M. fascicularis. Data mining showed that the bacterial species in the MfGMB were prevalent not only in NHPs gut microbiomes but also in human gut microbiomes. This study will help the understanding and future investigations on how gut microbiomes interact with their mammalian hosts.

Hepatitis C virus infection induces the expression of amphiregulin, a factor related to the activation of cellular survival pathways and required for efficient viral assembly.

Amphiregulin (AREG) is a ligand of the epidermal growth factor (EGF) receptor and may play a role in the development of cirrhosis and hepatocellular carcinoma in patients infected with hepatitis C virus (HCV). AREG showed an enhanced expression in HCV-infected human hepatoma cells according to gene array analysis. Therefore, we addressed the question about the role of AREG in HCV infection. AREG expression level was elevated in hepatoma cells containing a subgenomic HCV replicon or infected by HCV. Using a reporter assay, AREG promoter activity was found to be upregulated upon HCV infection. The enhanced AREG expression in hepatoma cells was partly caused by dsRNAs, HCV NS3 protein and autocrine stimulation. AREG was able to activate cellular signalling pathways including ERK, Akt and p38, promote cell proliferation, and protect cells from HCV-induced cell death. Further, knockdown of AREG expression increased the efficiency of HCV entry, as proven by HCV pseudoparticles reporter assay. However, the formation and release of infectious HCV particles were reduced by AREG silencing with a concomitant accumulation of intracellular HCV RNA pool, indicating that the assembly and release of HCV progeny may require AREG expression. Blocking the MAPK-ERK pathway by U0126 in Huh7.5.1 cells had a similar effect on HCV replication. In conclusion, HCV infection leads to an increase in AREG expression in hepatocytes. AREG expression is essential for efficient HCV assembly and virion release. Due to the activation of the cellular survival pathways, AREG may counteract HCV-induced apoptosis of infected hepatocytes and facilitate the development of liver cirrhosis and hepatocellular carcinoma.

Enlightening the taxonomy darkness of human gut microbiomes with a cultured biobank.

BACKGROUND: In gut microbiome studies, the cultured gut microbial resource plays essential roles, such as helping to unravel gut microbial functions and host-microbe interactions. Although several major studies have been performed to elucidate the cultured human gut microbiota, up to 70% of the Unified Human Gastrointestinal Genome species have not been cultured to date. Large-scale gut microbial isolation and identification as well as availability to the public are imperative for gut microbial studies and further characterizing human gut microbial functions. RESULTS: In this study, we constructed a human Gut Microbial Biobank (hGMB; homepage: hgmb.nmdc.cn ) through the cultivation of 10,558 isolates from 31 sample mixtures of 239 fresh fecal samples from healthy Chinese volunteers, and deposited 1170 strains representing 400 different species in culture collections of the International Depository Authority for long-term preservation and public access worldwide. Following the rules of the International Code of Nomenclature of Prokaryotes, 102 new species were characterized and denominated, while 28 new genera and 3 new families were proposed. hGMB represented over 80% of the common and dominant human gut microbial genera and species characterized from global human gut 16S rRNA gene amplicon data (n = 11,647) and cultured 24 "most-wanted" and "medium priority" taxa proposed by the Human Microbiome Project. We in total sequenced 115 genomes representing 102 novel taxa and 13 previously known species. Further in silico analysis revealed that the newly sequenced hGMB genomes represented 22 previously uncultured species in the Unified Human Gastrointestinal Genome (UHGG) and contributed 24 representatives of potentially "dark taxa" that had not been discovered by UHGG. The nonredundant gene catalogs generated from the hGMB genomes covered over 50% of the functionally known genes (KEGG orthologs) in the largest global human gut gene catalogs and approximately 10% of the "most wanted" functionally unknown proteins in the FUnkFams database. CONCLUSIONS: A publicly accessible human Gut Microbial Biobank (hGMB) was established that contained 1170 strains and represents 400 human gut microbial species. hGMB expands the gut microbial resources and genomic repository by adding 102 novel species, 28 new genera, 3 new families, and 115 new genomes of human gut microbes. Video abstract.

Identification of an RNase that preferentially cleaves A/G nucleotides.

Ribonucleases play an important role in the RNA metabolism which is critical for the localization, stability and function of mature RNA transcripts. More and more ribonucleases were discovered in recent years with the progress of technology. In the present study, we found that the uncharacterized C19orf43, a novel interacting protein of human telomerase RNA (hTR), digested T7 transcribed RNA, total cellular RNA and RNA oligos but not DNA. Thus we named this new RNase as hTRIR (human telomerase RNA interacting RNase). Genetic analysis showed that hTRIR is conserved among eukaryotic species and widely expressed in different cell lines. The RNase activity of hTRIR works in a broad temperature and pH range while divalent cations are not required. The conserved C-terminus of C19orf43 is necessary for its activity. Finally, we found that hTRIR cleaves all four unpaired RNA nucleotides from 5' end or 3' end with higher efficiency for purine bases, which suggested that hTRIR is an exoribonuclease. Taken together, our study showed the first evidence of the novel function of hTRIR in vitro, which provides clue to study the regulatory mechanism of hTR homeostasis in vivo.

Persistent hepatitis C virus infections and hepatopathological manifestations in immune-competent humanized mice.

The majority of hepatitis C virus (HCV) infection develops chronic infection, which causes steatosis, cirrhosis and hepatocellular carcinoma. However, understanding HCV chronicity and pathogenesis is hampered by its narrow host range, mostly restricted to human and chimpanzee. Recent endeavour to infect a variety of humanized mice has not been able to achieve persistent HCV infection unless the essential innate immune responsive genes are knocked out. Nevertheless, such immune-compromised humanized mice still lacked HCV infection-induced hepatopathogenesis. Here we report that transgenic mice in ICR background harboring both human CD81 and occludin genes (C/O(Tg)) are permissive to HCV infection at a chronicity rate comparable to humans. In this mouse model, HCV accomplishes its replication cycle, leading to sustained viremia and infectivity for more than 12 months post infection with expected fibrotic and cirrhotic progression. Host factors favorable for HCV replication, and inadequate innate immune-response may contribute to the persistence. Lastly, NS3/4 protease inhibitor telaprevir can effectively inhibit de novo RNA synthesis and acute HCV infection of C/O(Tg) mice. Thus, chronic HCV infection with complete replication cycle and hepatopathologic manifestations is recapitulated, for the first time, in immune-competent mice. This model will open a new venue to study the mechanisms of chronic hepatitis C and develop better treatments.

Different responses of two highly permissive cell lines upon HCV infection.

The construction of the first infectious clone JFH-1 speeds up the research on hepatitis C virus (HCV). However, Huh7 cell line was the only highly permissive cell line for HCV infection and only a few clones were fully permissive. In this study, two different fully permissive clones of Huh7 cells, Huh7.5.1 and Huh7-Lunet-CD81 (Lunet-CD81) cells were compared for their responses upon HCV infection. The virus replication level was found slightly higher in Huh7.5.1 cells than that in Lunet-CD81 cells. Viability of Huh7.5.1 cells but not of Lunet-CD81 cells was reduced significantly after HCV infection. Further analysis showed that the cell cycle of infected Huh7.5.1 cells was arrested at G1 phase. The G1/S transition was blocked by HCV infection in Huh7.5.1 cells as shown by the cell cycle synchronization analysis. Genes related to cell cycle regulation was modified by HCV infection and gene interaction analysis in GeneSpring GX in Direct Interactions mode highlighted 31 genes. In conclusion, the responses of those two cell lines were different upon HCV infection. HCV infection blocked G1/S transition and cell cycle progress, thus reduced the cell viability in Huh7.5.1 cells but not in Lunet-CD81 cells. Lunet-CD81 cells might be suitable for long term infection studies of HCV.