Bacterial composition of murine fecal microflora is indigenous and genetically guided

The host genotype actively shapes its microbiome across generations in laboratory mice

BACKGROUND

The microbiome greatly affects health and wellbeing. Evolutionarily, it is doubtful that a host would rely on chance alone to pass on microbial colonization to its offspring. However, the literature currently offers only limited evidence regarding two alternative hypotheses: active microbial shaping by host genetic factors or transmission of a microbial maternal legacy.

RESULTS

To further dissect the influence of host genetics and maternal inheritance, we collected two-cell stage embryos from two representative wild types, C57BL6/J and BALB/c, and transferred a mixture of both genotype embryos into hybrid recipient mice to be inoculated by an identical microbiome at birth.

CONCLUSIONS

Observing the offspring for six generations unequivocally emphasizes the impact of host genetic factors over maternal legacy in constant environments, akin to murine laboratory experiments. Interestingly, maternal legacy solely controlled the microbiome in the first offspring generation. However, current evidence supporting maternal legacy has not extended beyond this initial generation, resolving the aforementioned debate. Video Abstract.

Microbiota transfer early after birth modulates genetic susceptibility to chronic arthritis in mice

Genetics is central to the susceptibility or resistance to autoimmunity, and mounting evidence indicates that the intestinal microbiota also plays an essential role. In murine arthritis models, short-chain fat acid supplementation reduces disease severity by modulating tryptophan-metabolizing bacteria. Common microbiota transfer methods modulate arthritis severity, however, they are not practical for chronic models such as pristane-induced arthritis (PIA). PIA-resistant (HIII) and PIA-susceptible (LIII) mice harbor diverse intestinal microbiomes, which might be implicated in their divergent susceptibility. To investigate this hypothesis, we used cross-fostering to stably transfer the microbiota. In this study, we show that extreme susceptibility to arthritis can be modulated by early microbiota transfer, with long-lasting effects. HIII and LIII pups were cross-fostered and injected with pristane after weaning. PIA severity in cross-fostered LIII mice was significantly reduced in the chronic phase. Metagenomic analyses showed that HIII and LIII microbiomes were partly shifted by cross-fostering. Microbial groups whose abundance was associated with either HIII or LIII mice presented similar composition in cross-fostered mice of the opposite strains, suggesting a role in PIA susceptibility. Identification of bacterial groups that modulate chronic arthritis will contribute novel insights on the pathogenesis of human rheumatoid arthritis and targets for replication and functional studies.

The fecal arsenic excretion, tissue arsenic accumulation, and metabolomics analysis in sub-chronic arsenic-exposed mice after in situ arsenic-induced fecal microbiota transplantation

Arsenic can be specifically enriched by rice, and the health hazards caused by high arsenic rice are gradually attracting attention. This study aimed to explore the potential of microbial detoxification via gut microbiome in the treatment of sub-chronic arsenic poisoning. We first exposed mice to high-dose arsenic feed (30 mg/kg, rice arsenic composition) for 60 days to promote arsenic-induced microbes in situ in the gastrointestinal tract, then transplanted their fecal microbiota (FMT) into another batch of healthy recipient mice, and dynamically monitored the microbial colonization by 16S rRNA sequencing and ITS sequencing. The results showed that in situ arsenic-induced fecal microbiome can stably colonized and interact with indigenous microbes in the recipient mice in two weeks, and established a more stable network of gut microbiome. Then, the recipient mice continued to receive high-dose arsenic exposure for 52 days. After above sub-chronic arsenic exposure, compared with the non-FMT group, fecal arsenic excretion, liver and plasma arsenic accumulation were significantly lower (P < 0.05), and that in kidney, hair, and thighbone present no significant differences. Metabolomics of feces- plasma-brain axis were also disturbed, some up-regulated metabolites in feces, plasma, and cerebral cortex may play positive roles for the host. Therefore, microbial detoxification has potential in the treatment of sub-chronic arsenic poisoning. However, gut flora is an extremely complex community with different microorganisms have different arsenic metabolizing abilities, and various microbial metabolites. Coupled with the matrix effects, these factors will have various effects on the efflux and accumulation of arsenic. The definite effects (detoxification or non-detoxification) could be not assured based on the current study, and more systematic and rigorous studies are needed in the future.

Mouse models for bacterial enteropathogen infections: insights into the role of colonization resistance

Globally, enteropathogenic bacteria are a major cause of morbidity and mortality.1-3 Campylobacter, Salmonella, Shiga-toxin-producing Escherichia coli, and Listeria are among the top five most commonly reported zoonotic pathogens in the European Union.4 However, not all individuals naturally exposed to enteropathogens go on to develop disease. This protection is attributable to colonization resistance (CR) conferred by the gut microbiota, as well as an array of physical, chemical, and immunological barriers that limit infection. Despite their importance for human health, a detailed understanding of gastrointestinal barriers to infection is lacking, and further research is required to investigate the mechanisms that underpin inter-individual differences in resistance to gastrointestinal infection. Here, we discuss the current mouse models available to study infections by non-typhoidal Salmonella strains, Citrobacter rodentium (as a model for enteropathogenic and enterohemorrhagic E. coli), Listeria monocytogenes, and Campylobacter jejuni. Clostridioides difficile is included as another important cause of enteric disease in which resistance is dependent upon CR. We outline which parameters of human infection are recapitulated in these mouse models, including the impact of CR, disease pathology, disease progression, and mucosal immune response. This will showcase common virulence strategies, highlight mechanistic differences, and help researchers from microbiology, infectiology, microbiome research, and mucosal immunology to select the optimal mouse model.

Individual variations and effects of birth facilities on the fecal microbiome of laboratory-bred marmosets (Callithrix jacchus) assessed by a longitudinal study

Laboratory animals are used for scientific research in various fields. In recent years, there has been a concern that the gut microbiota may differ among laboratory animals, which may yield different results in different laboratories where in-vivo experiments are performed. Our knowledge of the gut microbiota of laboratory-reared common marmosets (Callithrix jacchus) is limited; thus, in this study, we analyzed the daily changes in fecal microbiome composition, individual variations, and effects of the birth facility in healthy female laboratory-reared marmosets, supplied by three vendors. We showed that the marmoset fecal microbiome varied among animals from the same vendor and among animals from different vendors (birth facility), with daily changes of approximately 37%. The fecal microbiome per vendor is characterized by alpha diversity and specific bacteria, with Bifidobacterium for vendor A, Phascolarctobacterium for vendor B, and Megamonas for vendor C. Furthermore, we found that plasma progesterone concentrations and estrous cycles were not correlated with daily fecal microbiome changes. In contrast, animals with an anovulatory cycle lacked Megamonas and Desulfovibrio bacteria compared to normal estrous females. This study suggests that the source of the animal, such as breeding and housing facilities, is important for in-vivo experiments on the marmoset gut microbiota.

Human microbiota-transplanted C57BL/6 mice and offspring display reduced establishment of key bacteria and reduced immune stimulation compared to mouse microbiota-transplantation

Transplantation of germ-free (GF) mice with microbiota from mice or humans stimulates the intestinal immune system in disparate ways. We transplanted a human microbiota into GF C57BL/6 mice and a murine C57BL/6 microbiota into GF C57BL/6 mice and Swiss-Webster (SW) mice. Mice were bred to produce an offspring generation. 56% of the Operational Taxonomic Units (OTUs) present in the human donor microbiota established in the recipient mice, whereas 81% of the C57BL/6 OTUs established in the recipient C57BL/6 and SW mice. Anti-inflammatory bacteria such as Faecalibacterium and Bifidobacterium from humans were not transferred to mice. Expression of immune-related intestinal genes was lower in human microbiota-mice and not different between parent and offspring generation. Expression of intestinal barrier-related genes was slightly higher in human microbiota-mice. Cytokines and chemokines measured in plasma were differentially present in human and mouse microbiota-mice. Minor differences in microbiota and gene expression were found between transplanted mice of different genetics. It is concluded that important immune-regulating bacteria are lost when transplanting microbiota from humans to C57BL/6 mice, and that the established human microbiota is a weak stimulator of the murine immune system. The results are important for study design considerations in microbiota transplantation studies involving immunological parameters.

Development but not diet alters microbial communities in the Neotropical arboreal trap jaw ant Daceton armigerum: an exploratory study

To better understand the evolutionary significance of symbiotic interactions in nature, microbiome studies can help to identify the ecological factors that may shape host-associated microbial communities. In this study we explored both 16S and 18S rRNA microbial communities of D. armigerum from both wild caught individuals collected in the Amazon and individuals kept in the laboratory and fed on controlled diets. We also investigated the role of colony, sample type, development and caste on structuring microbial communities. Our bacterial results (16S rRNA) reveal that (1) there are colony level differences between bacterial communities; (2) castes do not structure communities; (3) immature stages (brood) have different bacterial communities than adults; and 4) individuals kept in the laboratory with a restricted diet showed no differences in their bacterial communities from their wild caught nest mates, which could indicate the presence of a stable and persistent resident bacterial community in this host species. The same categories were also tested for microbial eukaryote communities (18S rRNA), and (5) developmental stage has an influence on the diversity recovered; (6) the diversity of taxa recovered has shown this can be an important tool to understand additional aspects of host biology and species interactions.

Murine Genetic Background Overcomes Gut Microbiota Changes to Explain Metabolic Response to High-Fat Diet

Interactions of diet, gut microbiota, and host genetics play essential roles in the development of metabolic diseases. A/J and C57BL/6J (C57) are two mouse strains known to display different susceptibilities to metabolic disorders. In this context, we analyzed gut microbiota composition in A/J and C57 mice, and assessed its responses to high-fat diet (HFD) and antibiotic (AB) treatment. We also exchanged the gut microbiota between the two strains following AB treatment to evaluate its impact on the metabolism. We showed that A/J and C57 mice have different microbiome structure and composition at baseline. Moreover, A/J and C57 microbiomes responded differently to HFD and AB treatments. Exchange of the gut microbiota between the two strains was successful as recipients' microbiota resembled donor-strain microbiota. Seven weeks after inoculation, the differences between recipients persisted and were still closer from the donor-strain microbiota. Despite effective microbiota transplants, the response to HFD was not markedly modified in C57 and A/J mice. Particularly, body weight gain and glucose intolerance in response to HFD remained different in the two mouse strains whatever the changes in microbiome composition. This indicated that genetic background has a much stronger impact on metabolic responses to HFD than gut microbiome composition.

The links between the gut microbiome and non-alcoholic fatty liver disease (NAFLD)

NAFLD is currently the main cause of chronic liver disease in developed countries, and the number of NAFLD patients is growing worldwide. NAFLD often has similar symptoms to other metabolic disorders, including type 2 diabetes and obesity. Recently, the role of the gut microbiota in the pathophysiology of many diseases has been revealed. Regarding NAFLD, experiments using gut microbiota transplants to germ-free animal models showed that fatty liver disease development is determined by gut bacteria. Moreover, the perturbation of the composition of the gut microbiota has been observed in patients suffering from NAFLD. Numerous mechanisms relating the gut microbiome to NAFLD have been proposed, including the dysbiosis-induced dysregulation of gut endothelial barrier function that allows for the translocation of bacterial components and leads to hepatic inflammation. In addition, the various metabolites produced by the gut microbiota may impact the liver and thus modulate NAFLD susceptibility. Therefore, the manipulation of the gut microbiome by probiotics, prebiotics or synbiotics was shown to improve liver phenotype in NAFLD patients as well as in rodent models. Hence, further knowledge about the interactions among dysbiosis, environmental factors, and diet and their impacts on the gut-liver axis can improve the treatment of this life-threatening liver disease and its related disorders.

Selective colonization ability of human fecal microbes in different mouse gut environments

Mammalian hosts constantly interact with diverse exogenous microbes, but only a subset of the microbes manage to colonize due to selective colonization resistance exerted by host genetic factors as well as the native microbiota of the host. An important question in microbial ecology and medical science is if such colonization resistance can discriminate closely related microbial species, or even closely related strains of the same species. Using human-mouse fecal microbiota transplantation and metagenomic shotgun sequencing, we reconstructed colonization patterns of human fecal microbes in mice with different genotypes (C57BL6/J vs. NSG) and with or without an intact gut microbiota. We found that mouse genotypes and the native mouse gut microbiota both exerted different selective pressures on exogenous colonizers: human fecal Bacteroides successfully established in the mice gut, however, different species of Bacteroides selectively enriched under different gut conditions, potentially due to a multitude of functional differences, ranging from versatility in nutrient acquisition to stress responses. Additionally, different clades of Bacteroides cellulosilyticus strains were selectively enriched in different gut conditions, suggesting that the fitness of conspecific microbial strains in a novel host environment could differ.

Analyzing the innate immunity of NIH hairless mice and the impact of gut microbial polymorphisms on Listeria monocytogenes infection

Spontaneous mutant hairless (HL) mice are often used to study hair growth and hair follicle development, and they often exhibit immune dysfunctions. Listeria monocytogenes, an important food-borne bacterium, has been used in animal models to study immune responses to infection. Herein, we analyzed the innate immunity of HL mice and the impact of gut microbial polymorphisms on L. monocytogenes infection. Compared to NIH mice, NIH HL mice were more susceptible to L. monocytogenes, as weight losses, mortality, bacterial load, and histopathological lesions were more severe; the decrease in monocytes may be an important underlying reason. The degree of spleen damage was reduced after co-housing, indicating that the host guides the gut microbiota to alleviate infection. High-throughput pyrosequencing of 16S rRNA demonstrated that gut microbiota composition differed between NIH HL and NIH mice. Infection with L. monocytogenes induced an increase in the number of bacteria belonging to the Rikenellaceae family and Gammaproteobacteria class, and decreased bacteria belonging to the Clostridiales class and Lachnospiraceae family. A substantial reduction in Clostridiales bacteria in infected HL mice may cause a serious infection. The Mycoplasma genus was present only in NIH HL mice and was, thus, considered a biomarker. The results of this study improve our understanding of the use of NIH HL mice as a good animal model of innate immune dysfunction.

Suppression of Inflammatory Arthritis by Human Gut-Derived Prevotella histicola in Humanized Mice

OBJECTIVE

The gut microbiome regulates host immune homeostasis. Rheumatoid arthritis (RA) is associated with intestinal dysbiosis. This study was undertaken to test the ability of a human gut-derived commensal to modulate immune response and treat arthritis in a humanized mouse model.

METHODS

We isolated a commensal bacterium, Prevotella histicola, that is native to the human gut and has systemic immune effects when administered enterally. Arthritis-susceptible HLA-DQ8 mice were immunized with type II collagen and treated with P histicola. Disease incidence, onset, and severity were monitored. Changes in gut epithelial proteins and immune response as well as systemic cellular and humoral immune responses were studied in treated mice.

RESULTS

When treated with P histicola in prophylactic or therapeutic protocols, DQ8 mice exhibited significantly decreased incidence and severity of arthritis compared to controls. The microbial mucosal modulation of arthritis was dependent on regulation by CD103+ dendritic cells and myeloid suppressors (CD11b+Gr-1+ cells) and by generation of Treg cells (CD4+CD25+FoxP3+) in the gut, resulting in suppression of antigen-specific Th17 responses and increased transcription of interleukin-10. Treatment with P histicola led to reduced intestinal permeability by increasing expression of enzymes that produce antimicrobial peptides as well as tight junction proteins (zonula occludens 1 and occludin). However, the innate immune response via Toll-like receptor 4 (TLR-4) and TLR-9 was not affected in treated mice.

CONCLUSION

Our results demonstrate that enteral exposure to P histicola suppresses arthritis via mucosal regulation. P histicola is a unique commensal that can be explored as a novel therapy for RA and may have few or no side effects.

Potential role of the gut microbiota in synthetic torpor and therapeutic hypothermia

Therapeutic hypothermia is today used in several clinical settings, among them the gut related diseases that are influenced by ischemia/reperfusion injury. This perspective paved the way to the study of hibernation physiology, in natural hibernators, highlighting an unexpected importance of the gut microbial ecosystem in hibernation and torpor. In natural hibernators, intestinal microbes adaptively reorganize their structural configuration during torpor, and maintain a mutualistic configuration regardless of long periods of fasting and cold temperatures. This allows the gut microbiome to provide the host with metabolites, which are essential to keep the host immunological and metabolic homeostasis during hibernation. The emerging role of the gut microbiota in the hibernation process suggests the importance of maintaining a mutualistic gut microbiota configuration in the application of therapeutic hypothermia as well as in the development of new strategy such as the use of synthetic torpor in humans. The possible utilization of tailored probiotics to mold the gut ecosystem during therapeutic hypothermia can also be taken into consideration as new therapeutic strategy.

A Review of Applied Aspects of Dealing with Gut Microbiota Impact on Rodent Models

The gut microbiota (GM) affects numerous human diseases, as well as rodent models for these. We will review this impact and summarize ways to handle this challenge in animal research. The GM is complex, with the largest fractions being the gram-positive phylum Firmicutes and the gram-negative phylum Bacteroidetes. Other important phyla are the gram-negative phyla Proteobacteria and Verrucomicrobia, and the gram-positive phylum Actinobacteria. GM members influence models for diseases, such as inflammatory bowel diseases, allergies, autoimmunity, cancer, and neuropsychiatric diseases. GM characterization of all individual animals and incorporation of their GM composition in data evaluation may therefore be considered in future protocols. Germfree isolator-housed rodents or rodents made virtually germ free by antibiotic cocktails can be used to study diverse microbial influences on disease expression. Through subsequent inoculation with selected strains or cocktails of microbes, new "defined flora" models can yield valuable knowledge on the impact of the GM, and of specific GM members and their interactions, on important disease phenotypes and mechanisms. Rodent husbandry and microbial quality assurance practices will be important to ensure and confirm appropriate and research relevant GM.

Head-to-head comparison of protocol modifications for the generation of collagen-induced arthritis in a specific-pathogen free facility using DBA/1 mice

Collagen-induced arthritis (CIA) is a widely used mouse model for studying inflammatory arthritis (IA). However, CIA induction protocols differ between laboratories, and direct comparison between protocol variations has not been reported. To address this issue, DBA/1 mice housed in conventional and specific-pathogen free (SPF) facilities were administered various combinations of two doses of collagen type II (CII) in complete (CFA) or incomplete Freund's adjuvant (IFA); some mice were also injected with lipopolysaccharide (LPS) and/or additional CII at specific intervals. Mice were evaluated for IA over the subsequent 2 months. Depending directly on the combination of CII, CFA, IFA, and LPS used, the incidence of IA ranged between 20%-100%, and severity extended from mild to severe even in an SPF environment. Our results demonstrate for the first time in head-to-head comparisons that specific variations in the use of CII, CFA, IFA, and LPS can induce a range of arthritic disease intensity and severity in an SPF facility. Thus, distinct experimental settings can be designed for robust assessment of factors that either exacerbate or inhibit arthritis pathogenesis. Furthermore, by achieving 100% incidence in an SPF facility, the protocols provide a practical and humane benefit by reducing the number of mice necessary for experimental assessment.

Mixed-strain housing for female C57BL/6, DBA/2, and BALB/c mice: validating a split-plot design that promotes refinement and reduction

Background

Inefficient experimental designs are common in animal-based biomedical research, wasting resources and potentially leading to unreplicable results. Here we illustrate the intrinsic statistical power of split-plot designs, wherein three or more sub-units (e.g. individual subjects) differing in a variable of interest (e.g. genotype) share an experimental unit (e.g. a cage or litter) to which a treatment is applied (e.g. a drug, diet, or cage manipulation). We also empirically validate one example of such a design, mixing different mouse strains -- C57BL/6, DBA/2, and BALB/c -- within cages varying in degree of enrichment. As well as boosting statistical power, no other manipulations are needed for individual identification if co-housed strains are differentially pigmented, so also sparing mice from stressful marking procedures.

Methods

The validation involved housing 240 females from weaning to 5 months of age in single- or mixed- strain trios, in cages allocated to enriched or standard treatments. Mice were screened for a range of 26 commonly-measured behavioural, physiological and haematological variables.

Results

Living in mixed-strain trios did not compromise mouse welfare (assessed via corticosterone metabolite output, stereotypic behaviour, signs of aggression, and other variables). It also did not alter the direction or magnitude of any strain- or enrichment-typical difference across the 26 measured variables, or increase variance in the data: indeed variance was significantly decreased by mixed- strain housing. Furthermore, using Monte Carlo simulations to quantify the statistical power benefits of this approach over a conventional design demonstrated that for our effect sizes, the split- plot design would require significantly fewer mice (under half in most cases) to achieve a power of 80 %.

Conclusions

Mixed-strain housing allows several strains to be tested at once, and potentially refines traditional marking practices for research mice. Furthermore, it dramatically illustrates the enhanced statistical power of split-plot designs, allowing many fewer animals to be used. More powerful designs can also increase the chances of replicable findings, and increase the ability of small-scale studies to yield significant results. Using mixed-strain housing for female C57BL/6, DBA/2 and BALB/c mice is therefore an effective, efficient way to promote both refinement and the reduction of animal-use in research.

Electronic supplementary material

The online version of this article (doi:10.1186/s12874-016-0113-7) contains supplementary material, which is available to authorized users.

Gene, environment, microbiome and mucosal immune tolerance in rheumatoid arthritis

RA is a complex multifactorial chronic disease that transitions through several stages. Multiple studies now support that there is a prolonged phase in early RA development during which there is serum elevation of RA-related autoantibodies including RF and ACPAs in the absence of clinically evident synovitis. This suggests that RA pathogenesis might originate in an extra-articular location, which we hypothesize is a mucosal site. In discussing this hypothesis, we will present herein the current understanding of mucosal immunology, including a discussion about the generation of autoimmune responses at these surfaces. We will also examine how other factors such as genes, microbes and other environmental toxins (including tobacco smoke) could influence the triggering of autoimmunity at mucosal sites and eventually systemic organ disease. We will also propose a research agenda to improve our understanding of the role of mucosal inflammation in the development of RA.

From lifetime to evolution: timescales of human gut microbiota adaptation

Human beings harbor gut microbial communities that are essential to preserve human health. Molded by the human genome, the gut microbiota (GM) is an adaptive component of the human superorganisms that allows host adaptation at different timescales, optimizing host physiology from daily life to lifespan scales and human evolutionary history. The GM continuously changes from birth up to the most extreme limits of human life, reconfiguring its metagenomic layout in response to daily variations in diet or specific host physiological and immunological needs at different ages. On the other hand, the microbiota plasticity was strategic to face changes in lifestyle and dietary habits along the course of the recent evolutionary history, that has driven the passage from Paleolithic hunter-gathering societies to Neolithic agricultural farmers to modern Westernized societies.

Intestinal dysbiosis and bacterial enteroinvasion in a murine model of Hirschsprung's disease

BACKGROUND/PURPOSE

Hirschsprung's disease (HSCR), characterized by the absence of ganglia in the distal colon, results in functional obstruction. Despite surgical resection of the aganglionic segment, around 40% of patients suffer recurrent life threatening Hirschsprung's-associated enterocolitis (HAEC). The aim of this study was to investigate whether gut microbiota and intestinal immunity changes contribute to the HAEC risk in an HSCR model.

METHODS

Mice with neural crest conditional deletion of Endothelin receptor B (EdnrB) and their littermate controls were used (EdnrB-null and EdnrB-het). Bacterial DNA was prepared from cecal contents of P16-18 and P21-24 animals and pyrosequencing employed for microbiome analysis. Ileal tissue was isolated and secretory phospholipase A2 (sPLA2) expression and activity determined. Enteroinvasion of Escherichia coli into ileal explants was measured using an ex vivo organ culture system.

RESULTS

EdnrB-het and EdnrB-nulls displayed similar flora, sPLA2 expression and activity at P16-18. However, by P21-24, EdnrB-hets demonstrated increased Lactobacillus and decreased Bacteroides and Clostridium, while EdnrB-nulls exhibited reciprocal changes. EdnrB-nulls also showed reduced sPLA2 expression and luminal activity at this stage. Functionally, EdnrB-nulls were more susceptible to enteroinvasion with E. coli ex vivo and released less sPLA2 than EdnrB-hets.

CONCLUSIONS

Initially, EdnrB-het and EdnrB-nulls contain similar cecal flora but then undergo reciprocal changes. EdnrB-nulls display dysbiosis, demonstrate impaired mucosal defense, decreased luminal sPLA2 and increased enteroinvasion of E. coli just prior to robust colonic inflammation and death. These findings suggest a role for the intestinal microbiome in the development of HAEC.

Transfer of gut microbiota from lean and obese mice to antibiotic-treated mice

Transferring gut microbiota from one individual to another may enable researchers to “humanize” the gut of animal models and transfer phenotypes between species. To date, most studies of gut microbiota transfer are performed in germ-free mice. In the studies presented, it was tested whether an antibiotic treatment approach could be used instead. C57BL/6 mice were treated with ampicillin prior to inoculation at weaning or eight weeks of age with gut microbiota from lean or obese donors. The gut microbiota and clinical parameters of the recipients was characterized one and six weeks after inoculation. The results demonstrate, that the donor gut microbiota was introduced, established, and changed the gut microbiota of the recipients. Six weeks after inoculation, the differences persisted, however alteration of the gut microbiota occurred with time within the groups. The clinical parameters of the donor phenotype were partly transmissible from obese to lean mice, in particularly β cell hyperactivity in the obese recipients. Thus, a successful inoculation of gut microbiota was not age dependent in order for the microbes to colonize, and transferring different microbial compositions to conventional antibiotic-treated mice was possible at least for a time period during which the microbiota may permanently modulate important host functions.

Gut microbial diversity in rat model induced by rhubarb

Rhubarb is often used to establish chronic diarrhea and spleen (Pi)-deficiency syndrome animal models in China. In this study, we utilized the enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) method to detect changes in bacterial diversity in feces and the bowel mucosa associated with this model. Total microbial genomic DNA from the small bowel (duodenum, jejunum, and ileum), large bowel (proximal colon, distal colon, and rectum), cecum, and feces of normal and rhubarb-exposed rats were used as templates for the ERIC-PCR analysis. We found that the fecal microbial composition did not correspond to the bowel bacteria mix. More bacterial diversity was observed in the ileum of rhubarb-exposed rats (P<0.05). Furthermore, a 380 bp product was found to be increased in rhubarb-exposed rats both in faces and the bowel mucosa. The product was cloned and sequenced and showed high similarity with regions of the Bacteroides genome. AS a result of discriminant analysis with the SPSS software, the Canonical Discriminant Function Formulae for model rats was established.

Mode of delivery shapes gut colonization pattern and modulates regulatory immunity in mice

Delivery mode has been associated with long-term changes in gut microbiota composition and more recently also with changes in the immune system. This has further been suggested to link Cesarean section (C-section) with an increased risk for development of immune-mediated diseases such as type 1 diabetes. In this study, we demonstrate that both C-section and cross-fostering with a genetically distinct strain influence the gut microbiota composition and immune key markers in mice. Gut microbiota profiling by denaturing gradient gel electrophoresis and 454/FLX-based 16S rRNA gene amplicon sequencing revealed that mice born by C-section had a distinct bacterial profile at weaning characterized by higher abundance of Bacteroides and Lachnospiraceae, and less Rikenellaceae and Ruminococcus. No clustering according to delivery method as determined by principal component analysis of denaturing gradient gel electrophoresis profiles was evident in adult mice. However, the adult C-section-born mice had lower proportions of Foxp3(+) regulatory T cells, tolerogenic CD103(+) dendritic cells, and less Il10 gene expression in mesenteric lymph nodes and spleens. This demonstrates long-term systemic effect on the regulatory immune system that was also evident in NOD mice, a model of type 1 diabetes, born by C-section. However, no effect of delivery mode was seen on diabetes incidence or insulitis development. In conclusion, the first exposure to microorganisms seems to be crucial for the early life gut microbiota and priming of regulatory immune system in mice, and mode of delivery strongly influences this.

Arthritis susceptibility and the gut microbiome

Rheumatoid arthritis (RA) is an autoimmune disease with unknown etiology though both genetic and environmental factors have been suggested to be involved in its pathogenesis. While infections and other environmental factors (e.g. smoking) have been studied extensively and show some association, a direct link between all the factors has been difficult to prove. With the recent advances in technology, it has become possible to sequence the commensals that are residing in our gut. The gut microbiome may provide the missing link to this puzzle and help solve the mystery of many leaky gut syndromes. The gut commensals are involved in maintaining host immune homeostasis and function suggesting that they might be critical in altering the immune system, which leads to autoimmune diseases like RA. Mouse models support the role of the gut microbiota in predisposition to RA. If that is true, the power of gut-derived commensal can be harnessed to our benefit by generating a biomarker profile along with genetic factors to define individuals at risk and by altering the gut microbial composition using various means.

Co-housing rodents with different coat colours as a simple, non-invasive means of individual identification: validating mixed-strain housing for C57BL/6 and DBA/2 mice

Standard practice typically requires the marking of laboratory mice so that they can be individually identified. However, many of the common methods compromise the welfare of the individuals being marked (as well as requiring time, effort, and/or resources on the part of researchers and technicians). Mixing strains of different colour within a cage would allow them to be readily visually identifiable, negating the need for more invasive marking techniques. Here we assess the impact that mixed strain housing has on the phenotypes of female C57BL/6 (black) and DBA/2 (brown) mice, and on the variability in the data obtained from them. Mice were housed in either mixed strain or single strain pairs for 19 weeks, and their phenotypes then assessed using 23 different behavioural, morphological, haematological and physiological measures widely used in research and/or important for assessing mouse welfare. No negative effects of mixed strain housing could be found on the phenotypes of either strain, including variables relevant to welfare. Differences and similarities between the two strains were almost all as expected from previously published studies, and none were affected by whether mice were housed in mixed- or single-strain pairs. Only one significant main effect of housing type was detected: mixed strain pairs had smaller red blood cell distribution widths, a measure suggesting better health (findings that now need replicating in case they were Type 1 errors resulting from our multiplicity of tests). Furthermore, mixed strain housing did not increase the variation in data obtained from the mice: the standard errors for all variables were essentially identical between the two housing conditions. Mixed strain housing also made animals very easy to distinguish while in the home cage. Female DBA/2 and C57BL/6 mice can thus be housed in mixed strain pairs for identification purposes, with no apparent negative effects on their welfare or the data they generate. This suggests that there is much value in exploring other combinations of strains.

Quantitatively different, yet qualitatively alike: a meta-analysis of the mouse core gut microbiome with a view towards the human gut microbiome

Background

A number of human diseases such as obesity and diabetes are associated with changes or imbalances in the gut microbiota (GM). Laboratory mice are commonly used as experimental models for such disorders. The introduction and dynamic development of next generation sequencing techniques have enabled detailed mapping of the GM of both humans and animal models. Nevertheless there is still a significant knowledge gap regarding the human and mouse common GM core and thus the applicability of the latter as an animal model. The aim of the present study was to identify inter- and intra-individual differences and similarities between the GM composition of particular mouse strains and humans.

Methodology/Principal Findings

A total of 1509428 high quality tag-encoded partial 16S rRNA gene sequences determined using 454/FLX Titanium (Roche) pyro-sequencing reflecting the GM composition of 32 human samples from 16 individuals and 88 mouse samples from three laboratory mouse strains commonly used in diabetes research were analyzed using Principal Coordinate Analysis (PCoA), nonparametric multivariate analysis of similarity (ANOSIM) and alpha diversity measures. A reliable cutoff threshold for low abundant taxa estimated on the basis of the present study is recommended for similar trials.

Conclusions/Significance

Distinctive quantitative differences in the relative abundance of most taxonomic groups between the examined categories were found. All investigated mouse strains clustered separately, but with a range of shared features when compared to the human GM. However, both mouse fecal, caecal and human fecal samples shared to a large extent not only representatives of the same phyla, but also a substantial fraction of common genera, where the number of shared genera increased with sequencing depth. In conclusion, the GM of mice and humans is quantitatively different (in terms of abundance of specific phyla and species) but share a large qualitatively similar core.

IL-1β-independent activation of lung immunity in male mice by female odor

In previous studies, we showed that long-term perception of female odor increases flu virus resistance in male mice. To expand on this finding, we examined the ability of female chemical cues to rapidly induce leukocyte mobilization into male lung tissue as a critical condition of signal-derived respiratory infection risk reduction, which is usually associated with sniffing scent marks. Here, we compared the immune and endocrine effects of female chemical cues and lipopolysaccharide (LPS) as common triggers of innate immunity. The number of leukocytes in the lung tissue, concentrations of IL-1β in lung and hypothalamus, and plasma corticosterone and testosterone levels were assessed in ICR male mice 2h after the intranasal application of female urine, LPS or urine and LPS. Both stimuli induced leukocyte mobilization but, in contrast to LPS, female urine alone did not stimulate increased IL-1β levels in lung and hypothalamus. Plasma corticosterone increased and plasma testosterone decreased in response to LPS, whereas the concentrations of these hormones did not change in response to female chemical cues. Thus, the present study gives additional evidence for an anticipatory adaptation of male mice to potential breeding risks. Appreciable mobilization of leukocytes to the lungs requires less than 2h and develops through an IL-1β-independent pathway.

The intestinal microbiota in the rat model: major breakthroughs from new technologies

The mammalian intestine harbors a large and diverse community of micro-organisms, known as the intestinal microbiota. Recent developments in molecular profiling methods, mainly based on microbial 16S ribosomal RNA gene sequencing, have provided unprecedented insights into the make-up and diversity of intestinal microbial communities. Using these culture-independent analyses, gut microbiota of several mammals including laboratory rodents, have been revisited. The laboratory rat is one of the major species bred and kept for scientific research. Although this animal is bred in confined environments and subjected to procedures for satisfying health requirements that hamper natural colonization, some major features of mammalian gut microbiota are conserved. However, the gut microbiota varies according to the breeding conditions of the rats and this could impact reproducibility of the experimental models. Determining the non-pathogenic microbial community might be relevant in standards of quality control of laboratory animals. Molecular profiling techniques could be applied to document this information.

Selective inbreeding does not increase gut microbiota similarity in BALB/c mice

Inflammatory diseases in mouse models are under strong impact from the gut microbiota. Therefore increased interindividual gut microbiota similarity may be seen as a way to reduce group sizes in mouse experiments. The composition of the gut microbiota is to a high extent defined by genetics, and it is known that selecting siblings as mothers even in inbred colonies may increase the gut microbiota similarity among the mice with 3-4%. We therefore hypothesized that selective breeding of mice aiming at a high similarity in the gut microbiota would increase the interindividual similarity of the gut microbiota. BALB/cCrl mice were, however, found to have a mean heterozygosity of only 0.8% in their genome, and selection of breeders with a high similarity in the gut microbiota for three generations did not change the overall gut microbiota similarity, which was 66% in the P generation and 66%, 64% and 63% in the F1, F2 and F3 generations, respectively. Increased gut microbiota similarity in closely related mice in inbred mouse colonies is, therefore, more likely to be caused by other factors, such as imprinting or different intrauterine conditions, rather than by residual heterozygosity.

Faecal and caecal microbiota profiles of mice do not cluster in the same way

Polymerase chain reaction (PCR)-based denaturation gradient gel electrophoresis (DGGE) is currently being used for characterizing the composition of the gut microbiota (GM) of mice in order to better control the study variation arising from the GM. At present, faeces are commonly sampled from live animals, while caecum is most commonly sampled from terminated animals. However, there is no knowledge whether the composition at the one site is representative for the other. In this study C57BL/6 mice were observed from the age of four weeks until the age of 10 weeks. Faeces were sampled weekly. Caecum was sampled surgically under anaesthesia and with subsequent ampicillin treatment at the age of six weeks and again after euthanasia at the age of 10 weeks. Faecal and caecal microbiota profiles were determined using DGGE and subjected to subsequent cluster analysis. The mice subjected to surgical caecal sampling clustered separately for two weeks after termination of antibiotics after which they again clustered with the non-surgically sampled mice. Faecal and caecal profiles clustered separately at the age of six weeks, but not at the age of 10 weeks. There were no correlations between faecal or caecal profiles at six or 10 weeks of age, respectively. It is concluded that faecal and caecal microbiota profiles are not representative of each other in mice. Therefore, it is recommendable in studies to sample from several sites specifically decided in relation to the specific model of a study.

Environmental and gene-environment interactions and risk of rheumatoid arthritis

Multiple environmental factors including hormones, dietary factors, infections, and exposure to tobacco smoke, as well as gene-environment interactions, have been associated with increased risk for rheumatoid arthritis (RA). The growing understanding of the prolonged period before the first onset of symptoms of RA suggests that these environmental and genetic factors are likely acting to drive the development of RA-related autoimmunity long before the appearance of the first joint symptoms and clinical findings that are characteristic of RA. This article reviews these factors and interactions, especially those that have been investigated in a prospective fashion before the symptomatic onset of RA.

Amixicile, a novel inhibitor of pyruvate: ferredoxin oxidoreductase, shows efficacy against Clostridium difficile in a mouse infection model

Clostridium difficile infection (CDI) is a serious diarrheal disease that often develops following prior antibiotic usage. One of the major problems with current therapies (oral vancomycin and metronidazole) is the high rate of recurrence. Nitazoxanide (NTZ), an inhibitor of pyruvate:ferredoxin oxidoreductase (PFOR) in anaerobic bacteria, parasites, Helicobacter pylori, and Campylobacter jejuni, also shows clinical efficacy against CDI. From a library of ∼250 analogues of NTZ, we identified leads with increased potency for PFOR. MIC screens indicated in vitro activity in the 0.05- to 2-μg/ml range against C. difficile. To improve solubility, we replaced the 2-acetoxy group with propylamine, producing amixicile, a soluble (10 mg/ml), nontoxic (cell-based assay) lead that produced no adverse effects in mice by oral or intraperitoneal (i.p.) routes at 200 mg/kg of body weight/day. In initial efficacy testing in mice treated (20 mg/kg/day, 5 days each) 1 day after receiving a lethal inoculum of C. difficile, amixicile showed slightly less protection than did vancomycin by day 5. However, in an optimized CDI model, amixicile showed equivalence to vancomycin and fidaxomicin at day 5 and there was significantly greater survival produced by amixicile than by the other drugs on day 12. All three drugs were comparable by measures of weight loss/gain and severity of disease. Recurrence of CDI was common for mice treated with vancomycin or fidaxomicin but not for mice receiving amixicile or NTZ. These results suggest that gut repopulation with beneficial (non-PFOR) bacteria, considered essential for protection against CDI, rebounds much sooner with amixicile therapy than with vancomycin or fidaxomicin. If the mouse model is indeed predictive of human CDI disease, then amixicile, a novel PFOR inhibitor, appears to be a very promising new candidate for treatment of CDI.

Loss of sex and age driven differences in the gut microbiome characterize arthritis-susceptible 0401 mice but not arthritis-resistant 0402 mice

Background

HLA-DRB1*0401 is associated with susceptibility, while HLA-DRB1*0402 is associated with resistance to developing rheumatoid arthritis (RA) and collagen-induced arthritis in humans and transgenic mice respectively. The influence of gut-joint axis has been suggested in RA, though not yet proven.

Methodology/Principal Findings

We have used HLA transgenic mice carrying arthritis susceptible and -resistant HLA-DR genes to explore if genetic factors and their interaction with gut flora gut can be used to predict susceptibility to develop arthritis. Pyrosequencing of the 16S rRNA gene from the fecal microbiomes of DRB1*0401 and DRB1*0402 transgenic mice revealed that the guts of *0401 mice is dominated by a Clostridium-like bacterium, whereas the guts of *0402 mice are enriched for members of the Porphyromonadaceae family and Bifidobacteria. DRB1*0402 mice harbor a dynamic sex and age-influenced gut microbiome while DRB1*0401 mice did not show age and sex differences in gut microbiome even though they had altered gut permeability. Cytokine transcripts, measured by rtPCR, in jejuna showed differential TH17 regulatory network gene transcripts in *0401 and *0402 mice.

Conclusions/Significance

We have demonstrated for the first time that HLA genes in association with the gut microbiome may determine the immune environment and that the gut microbiome might be a potential biomarker as well as contributor for susceptibility to arthritis. Identification of pathogenic commensal bacteria would provide new understanding of disease pathogenesis, thereby leading to novel approaches for therapy.

Time to include the gut microbiota in the hygienic standardisation of laboratory rodents

The gut microbiota (GM) composition and its impact on animal experiments has become currently dramatically relevant in our days: (1) recent progress in metagenomic technologies, (2) the availability of large scale quantitative analyses to characterize even subtle phenotypes, (3) the limited diversity of laboratory rodent GM due to strict barriers at laboratory animal vendors, and (4) the availability of up to 300.000 different transgenic mouse strains from different sources displaying a huge variety in their GM composition. In this review the GM is described as a variable in animal experiments which need to be reduced for scientific as well as ethical reasons, and strategies how to implement this in routine diagnostic procedures are proposed. We conclude that we have both enough information available to state that the GM has an essential impact on animal models, as well as the methods available to start dealing with these impacts.

Altering host resistance to infections through microbial transplantation

Host resistance to bacterial infections is thought to be dictated by host genetic factors. Infections by the natural murine enteric pathogen Citrobacter rodentium (used as a model of human enteropathogenic and enterohaemorrhagic E. coli infections) vary between mice strains, from mild self-resolving colonization in NIH Swiss mice to lethality in C3H/HeJ mice. However, no clear genetic component had been shown to be responsible for the differences observed with C. rodentium infections. Because the intestinal microbiota is important in regulating resistance to infection, and microbial composition is dependent on host genotype, it was tested whether variations in microbial composition between mouse strains contributed to differences in “host” susceptibility by transferring the microbiota of resistant mice to lethally susceptible mice prior to infection. Successful transfer of the microbiota from resistant to susceptible mice resulted in delayed pathogen colonization and mortality. Delayed mortality was associated with increased IL-22 mediated innate defense including antimicrobial peptides Reg3γ and Reg3β, and immunono-neutralization of IL-22 abrogated the beneficial effect of microbiota transfer. Conversely, depletion of the native microbiota in resistant mice by antibiotics and transfer of the susceptible mouse microbiota resulted in reduced innate defenses and greater pathology upon infection. This work demonstrates the importance of the microbiota and how it regulates mucosal immunity, providing an important factor in susceptibility to enteric infection. Transfer of resistance through microbial transplantation (bacteriotherapy) provides additional mechanisms to alter “host” resistance, and a novel means to alter enteric infection and to study host-pathogen interactions.

Predominant effect of host genetics on levels of Lactobacillus johnsonii bacteria in the mouse gut

The gut microbiota is strongly associated with the well-being of the host. Its composition is affected by environmental factors, such as food and maternal inoculation, while the relative impact of the host's genetics have been recently uncovered. Here, we studied the effect of the host genetic background on the composition of intestinal bacteria in a murine model, focusing on lactic acid bacteria (LAB) as an important group that includes many probiotic strains. Based on 16S rRNA gene genotyping, variation was observed in fecal LAB populations of BALB/c and C57BL/6J mouse lines. Lactobacillus johnsonii, a potentially probiotic bacterium, appeared at significantly higher levels in C57BL/6J versus BALB/c mouse feces. In the BALB/c gut, the L. johnsonii level decreased rapidly after oral administration, suggesting that some selective force does not allow its persistence at higher levels. The genetic inheritance of L. johnsonii levels was further tested in reciprocal crosses between the two mouse lines. The resultant F1 offspring presented similar L. johnsonii levels, confirming that mouse genetics plays a major role in determining these levels compared to the smaller maternal effect. Our findings suggest that mouse genetics has a major effect on the composition of the LAB population in general and on the persistence of L. johnsonii in the gut in particular. Concentrating on a narrow spectrum of culturable LAB enables the isolation and characterization of such potentially probiotic bacterial strains, which might be specifically oriented to the genetic background of the host as part of a personalized-medicine approach.

Unravelling the effects of the environment and host genotype on the gut microbiome

To what extent do host genetics control the composition of the gut microbiome? Studies comparing the gut microbiota in human twins and across inbred mouse lines have yielded inconsistent answers to this question. However, candidate gene approaches, in which one gene is deleted or added to a model host organism, show that a single host gene can have a tremendous effect on the diversity and population structure of the gut microbiota. Now, quantitative genetics is emerging as a highly promising approach that can be used to better understand the overall architecture of host genetic influence on the microbiota, and to discover additional host genes controlling microbial diversity in the gut. In this Review, we describe how host genetics and the environment shape the microbiota, and how these three factors may interact in the context of chronic disease.

Manipulation of the gut microbiota in C57BL/6 mice changes glucose tolerance without affecting weight development and gut mucosal immunity

Inflammatory diseases such as type 2 diabetes (T2D) in humans and mice are under the influence of the composition of the gut microbiota (GM). It was previously demonstrated that treating Lep(ob) mice with antibiotics improved glucose tolerance. However, wild type C57BL/6J mice may also exhibit plasma glucose intolerance reminiscent of human T2D. We hypothesized that antibiotic treatment in C57BL/6 mice would have an impact on glucose tolerance without affecting weight and gut immunology. When compared to mice treated with erythromycin or the controls, treatment for five weeks with ampicillin improved glucose tolerance without significantly affecting the weight or the number of gut mucosal regulatory T cells, tolerogenic dendritic cells or T helper cells type 1. 16S rRNA gene based denaturing gradient gel electrophoresis profiles clearly clustered according to treatment and showed that antibiotic treatment reduced GM diversity. It is concluded that antibiotic treatment changes glucose metabolism as well as the composition of the GM in C57BL/6 mice, and that this does not seem to be correlated to weight development in the mice.

Diversity of caecal bacteria is altered in interleukin-10 gene-deficient mice before and after colitis onset and when fed polyunsaturated fatty acids

Interleukin-10 gene-deficient (Il10(-/-)) mice show a hyper-reaction to normal intestinal bacteria and develop spontaneous colitis similar to that of human Crohn's disease when raised under conventional (but not germ-free) conditions. The lack of IL10 protein in these mice leads to changes in intestinal metabolic and signalling processes. The first aim of this study was to identify changes in the bacterial community of the caeca at 7 weeks of age (preclinical colitis) and at 12 weeks of age (when clinical signs of colitis are present), and establish if there were any changes that could be associated with the mouse genotype. We have previously shown that dietary n-3 and n-6 polyunsaturated fatty acids (PUFA) have anti-inflammatory effects and affect colonic gene expression profiles in Il10(-/-) mice; therefore, we also aimed to test the effect of the n-3 PUFA eicosapentaenoic acid (EPA) and the n-6 PUFA arachidonic acid (AA) on the bacterial community of caeca in both Il10(-/-) and C57 mice fed these diets. The lower number of caecal bacteria observed before colitis (7 weeks of age) in Il10(-/-) compared to C57 mice suggests differences in the intestinal bacteria that might be associated with the genotype, and this could contribute to the development of colitis in this mouse model. The number and diversity of caecal bacteria increased after the onset of colitis (12 weeks of age). The increase in caecal Escherichia coli numbers in both inflamed Il10(-/-) and healthy C57 mice might be attributed to the dietary PUFA (especially dietary AA), and thus not be a cause of colitis development. A possible protective effect of E. coli mediated by PUFA supplementation and associated changes in the bacterial environment could be a subject for further investigation to define the mode of action of PUFA in colitis.

Family relationship of female breeders reduce the systematic inter-individual variation in the gut microbiota of inbred laboratory mice

The gut microbiota (GM) may influence disease expression in several animal models for inflammatory diseases. It may therefore seem reasonable to pursue reduction in the number of animals used for individual studies by reducing the variation in the GM. Previous studies have shown that the composition of the GM is related to genetics to a certain extent. We hypothesized that the GM similarity in a group of mice born by mothers not being sisters would be lower than that in a group born by mothers being sisters. The lower similarity could lead to clustering of the GM of mice born by non-sisters according to their mothers, while such clustering would not be visible if the mothers were sisters. We used 16S rRNA gene (V3 region) polymerase chain reaction-derived amplicon profiling by denaturing gradient gel electrophoresis (DGGE) to study the GM composition in caecum samples of 33 eight-week-old C57BL/6Sca mice from a breeding set-up with dam breeders that were sisters, as well as caecum samples of 35 eight-week-old C57BL/6Sca mice from a breeding set-up with dam breeders that were not sisters. Principal component analysis revealed a significant difference between the litters from the breeding set-up with dam breeders that were not sisters, whereas no significant difference between the litters based on the breeding set-up with dam breeders that were sisters was observed. The results obtained indicate that the systematic variation in the GM of inbred mice can be reduced by increasing the family relatedness of the breeding pairs.

Female scent signals enhance the resistance of male mice to influenza

Background

The scent from receptive female mice functions as a signal, which stimulates male mice to search for potential mating partners. This searching behavior is coupled with infection risk due to sniffing both scent marks as well as nasal and anogenital areas of females, which harbor bacteria and viruses. Consideration of host evolution under unavoidable parasitic pressures, including helminthes, bacteria, viruses, etc., predicts adaptations that help protect hosts against the parasites associated with mating.

Methods and Findings

We propose that the perception of female signals by BALB/c male mice leads to adaptive redistribution of the immune defense directed to protection against respiratory infection risks. Our results demonstrate migration of macrophages and neutrophils to the upper airways upon exposure to female odor stimuli, which results in an increased resistance of the males to experimental influenza virus infection. This moderate leukocyte intervention had no negative effect on the aerobic performance in male mice.

Conclusions

Our data provide the first demonstration of the adaptive immunological response to female odor stimuli through induction of nonspecific immune responses in the upper respiratory tract.

Intestinal microflora molecular markers of spleen-deficient rats and evaluation of traditional Chinese drugs

AIM: To find a rapid and efficient analysis method of gastrointestinal microflora in Pi-deficient (spleen-deficient) rats and to evaluate traditional Chinese drugs.

METHODS: Enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR) based assay was performed to examine changes of intestinal microflora in two Pi-deficienct animal models and to evaluate the efficacy of four traditional Chinese drugs as well as a probiotic recipe and another therapy in Pi-deficient rats.

RESULTS: A molecular marker was identified for Pi-deficiency in rats. The pharmacodynamic evaluation system, including identified molecular markers (net integral area and abundance of DNA bands), Shannon’s index for diversity of intestinal microflora, and Sorenson’s pairwise similarity coefficient, was established. The four major clinical recipes of traditional Chinese drugs for Pi-deficiency in rats, especially at their medium dose (equivalence to the clinical dose), produced more pronounced recovery activities in Pi-deficient rats, while higher doses of these recipes did not show a better therapeutic effect but some toxic effects such as perturbation deterioration of intestinal microflora.

CONCLUSION: Both fingerprint analysis and identified marker can show Pi-deficiency in rats and its difference after treatment. The identified molecular marker may be applied in screening for the active compounds both in relative traditional Chinese drugs and in pharmacodynamic study of Pi-deficiency in rats.

Orthogonal array design in optimizing ERIC-PCR system for fingerprinting rat's intestinal microflora

AIMS

The aim of the present study was to rapidly optimize enterobacterial repetitive intergenic consensus (ERIC)-PCR amplification systems for fingerprinting rat's intestinal microflora.

METHODS AND RESULTS

Orthogonal array design and statistic analysis methods were attempted to rapidly optimize ERIC-PCR reaction system for fingerprinting intestinal microflora. The results showed that variations of the four factors (Mg(2+), dNTP, primer and HotstarTaq polymerase concentrations) changed the fingerprinting patterns significantly. The order of effects of those factors on fingerprinting patterns was primers (F = 274.000, P = 0.000), Hotstar Taq polymerase (F = 197.000, P = 0.001), Mg(2+) (F = 181.000, P = 0.001) and dNTP (F = 27.000, P = 0.011). The optimal ERIC-PCR condition was containing 200 micromol l(-1) dNTP, 2.5 mmol l(-1) Mg(2+), 0.4 micromol l(-1) primer, 1 U HotstarTaq DNA polymerase namely 25 microl reaction system, which is proved to be a simple, fast and reliable method suitable for fingerprinting rat's intestinal microflora.

CONCLUSIONS

The results suggest that Mg(2+), dNTP, primer and HotstarTaq polymerase concentrations play important roles on ERIC-PCR fingerprinting patterns. Orthogonal array design is a considerable method to optimize ERIC-PCR reaction system for its rapidness, simplicity, potential to investigate mutual effects of parameters.

SIGNIFICANCE AND IMPACT OF THE STUDY

It is the first report on optimization of ERIC-PCR amplification systems for fingerprinting intestinal microflora using orthogonal array design or statistic analysis methods and systematically observing the effects of variables of reaction conditions.

Effects of host plant environment and Ustilago maydis infection on the fungal endophyte community of maize (Zea mays)

The focus of many fungal endophyte studies has been how plants benefit from endophyte infection. Few studies have investigated the role of the host plant as an environment in shaping endophyte community diversity and composition. The effects that different attributes of the host plant, that is, host genetic variation, host variation in resistance to the fungal pathogen Ustilago maydis and U. maydis infection, have on the fungal endophyte communities in maize (Zea mays) was examined. The internal transcribed spacer (ITS) region of the rDNA was sequenced to identify fungi and the endophyte communities were compared in six maize lines that varied in their resistance to U. maydis. It was found that host genetic variation, as determined by maize line, had significant effects on species richness, while the interactions between line and U. maydis infection and line and field plot had significant effects on endophyte community composition. However, the effects of maize line were not dependent on whether lines were resistant or susceptible to U. maydis. Almost 3000 clones obtained from 58 plants were sequenced to characterize the maize endophyte community. These results suggest that the endophyte community is shaped by complex interactions and factors, such as inoculum pool and microclimate, may be important.

Murine scent mark microbial communities are genetically determined

Scent marking in mice allows males to communicate information such as territory ownership, male competitive ability and current reproductive, nutritional, social and health status. It has been suggested that female mice eavesdrop on these olfactory cues, using them as a means of selecting mates with dissimilar major histocompatibility complex (MHC) genes, known as H2 in mice. The mechanisms underpinning MHC-dependent olfactory communication remain unresolved. Using congenic mouse strains and molecular methods we explore the involvement of the microbial communities, a known source of odourants, in scent marks to test the hypothesis that the microbial communities and hence the olfactory signals are genetically determined. Here we show that the indigenous microbial community of murine scent marks is genetically determined. Both background genotype and H2 haplotype influence the community structure of the scent mark flora, removing the possibility that community composition is solely orchestrated by the MHC. Qualitative and quantitative components of the bacterial community associated with MHC haplotype and background genotype were identified. The analyses confirm that the four groups of congenic mice tested are distinguishable on basis of the microbiology of their scent marks alone, strengthening the role of microorganisms in the development of MHC-dependent odours.

Lectin binding profile of the small intestine of five-week-old pigs in response to the use of chlortetracycline as a growth promotant and under gnotobiotic conditions

Antibiotics have traditionally been used for growth promotion in the pork industry; however, their use in animal feed has recently been limited because of human health concerns. The intestinal microbiota plays an important role in mediating many physiological functions such as digestion and animal growth. It was hypothesized that use of antibiotics as growth promotants and subsequent variations in intestinal microbiota induce significant changes in the intestinal glycoconjugate composition, which ultimately affects animal growth and disease susceptibility. The aim of this study was to characterize the lectin binding profiles of the ileum of weanling pigs in response to the absence of intestinal microbiota and to the use of the antibiotic chlortetracycline as growth promotant. Eighteen half-sib piglets obtained by cesarean section were divided into 3 treatment groups (n = 6) and maintained as control, antibiotic-fed, and gnotobiotic piglets until 5 wk of age. The glycoconjugate composition of the ileal tissues was examined by lectin histochemistry. Lycopersicon esculentum lectin, Jacalin, Pisum sativum agglutinin, Lens culinaris agglutinin (LCA), and Sambucus nigra lectin showed significant differences (P < 0.05) in binding intensities on the dome and villous epithelium between the treatment groups. Griffonia simplicifolia lectin I, Glycine maxi agglutinin, and Arachis hypogea agglutinin exhibited differences (P < 0.05) between treatment groups in lectin binding on goblet cells. Triticum vulgaris agglutinin, Pisum sativum agglutinin, and LCA showed significant differences (P < 0.05) in binding intensities on dome, corona, and follicular regions of the ileum among treatment groups of animals. Overall, ileal tissues from gnotobiotic piglets expressed significantly weaker (P < 0.05) lectin binding for many lectins compared with control and antibiotic groups. This suggests that the intestinal microbiota plays an important role in the expression of sugar moieties in the intestine. Lectins LCA, Phaseolus vulgaris Leucoagglutinin, and Maackia amurensis lectin II showed significant differences (P < 0.05) in lectin bindings between control and antibiotic-fed piglets. This indicates that chlortetracycline as a growth promotant induces biologically relevant changes in the lectin binding profile of the ileum. These findings will help in further understanding the role of the gut microbiota and the mechanisms of action of antibiotics as growth promotants in pigs.