Academic literature on the topic 'Microbial old friends'

A modern interpretation of the hygiene hypothesis proposes the so-called “old friends” to trigger tolerogenic responses through innate receptors of dendritic cells (DC). Tolerogenic DCs would drive regulatory T-cell polarization through induction of old-friend-specific Treg. In the tissues of the gut that are besieged by our old friends, these cells are held to produce a continuous bystander regulation. However, such local bystander regulation in the gut may be difficult to reconcile with suppression of responses to airway allergens or autoimmune antigens present in distant body tissues. Alternatively, the regulatory Tregs may be triggered through recognition of stress proteins or heat shock proteins (HSP). Microbial HSP are immunodominant and evolutionary conserved with homologs present in mammalian cells. Microbial HSP are now known to induce Tregs that cross-recognize mammalian HSP. In addition, microbial exposures, both friendly and nonfriendly, cause cell stress and, consequently, HSP upregulation in host cells. Also such upregulated HSP can activate HSP-specific Tregs that target the upregulated HSP at sites of inflammatory stress wherever in our body. Under inflammatory conditions, cell stress-associated HSP are abundant and therefore easy targets for cognate T-cell interactions. Herewith, they provide a molecular basis for the hygiene hypothesis.

AbstractTrichomonas vaginalisis an anaerobic protist, responsible for the most prevalent non-viral sexually transmitted infection in humans. One of the most intriguing aspects ofT. vaginalispathobiology is the complex relationship with intracellular microbial symbionts: a group of dsRNA viruses belonging to family ofTotiviridae(T. vaginalisvirus), and eubacteria belonging to theMycoplasmagenus, in particularMycoplasma hominis. Both microorganisms seem to strongly influence the lifestyle ofT. vaginalis, suggesting a role of the symbiosis in the high variability of clinical presentation and sequelae during trichomoniasis. In the last few years many aspects of this unique symbiotic relationship have been investigated:M. hominisresides and replicates in the protozoan cell, andT. vaginalisis able to pass the bacterial infection to both mycoplasma-free protozoan isolates and human epithelial cells;M. hominissynergistically upregulates the proinflammatory response of human monocytes toT. vaginalis. Furthermore, the influence ofM. hominisoverT. vaginalismetabolism and physiology has been characterized. The identification of a novel species belonging to the class ofMollicutes(CandidatusMycoplasma girerdii) exclusively associated toT. vaginalisopens new perspectives in the research of the complex series of events taking place in the multifaceted world of the vaginal microbiota, both under normal and pathological conditions.

Background: In the past, much of the scientific research on microbes focused on mechanisms of infection and disease. This was not in vain, as we gained valuable knowledge about our immune system, as well as the ability to develop vaccines and antibiotics. However, the relationship between humans and microbes is complex. These species have been co-evolving since multicellular organisms evolved on Earth. Summary: Recently, it is beginning to be appreciated that the majority of relationships between humans and microbes are beneficial. From this follows an understanding that beneficial microbes are vital to the normal physiological development of our gut and immune system. This beneficial relationship between the human host and the multitude of microbial communities is well established. However, currently in the developed world epidemiological studies are showing dramatic increases in autoimmunity, allergies, and obesity. It is thus suggested that within westernized societies hygiene is altering the relationship between the gut and the human host in a way that makes humans susceptible to conditions not seen in less developed countries. This understanding advanced the “hygiene hypothesis,” and more recently the, “old friends hypothesis” and “disappearing microbiota hypothesis” as possible explanations for the observed epidemiological phenomena. What follows is a review of the relationship between gut microbes and the host’s immune system, with a focus on how hygiene (antibiotics, chlorination of water, etc.) is beginning to alter this relationship. This review concludes that a further understanding of how hygiene affects the relationship between humans and microbes will be crucial for developing effective therapies considerate of our microbial friends.

Background: Alzheimer’s disease (AD) is an inflammatory neurodegenerative disease that may be associated with prior bacterial infections. Microbial “old friends” can suppress exaggerated inflammation in response to disease-causing infections or increase clearance of pathogens such as Mycobacterium tuberculosis, which causes tuberculosis (TB). One such “old friend” is Mycobacterium vaccae NCTC 11659, a soil-derived bacterium that has been proposed either as a vaccine for prevention of TB, or as immunotherapy for the treatment of TB when used alongside first line anti-TB drug treatment. Objective: The goal of this study was to use a hypothesis generating approach to explore the effects of M. vaccae on physiological changes in the plasma and cerebrospinal fluid (CSF). Methods: Liquid chromatography-tandem mass spectrometry-based proteomics were performed in plasma and CSF of adult male rats after immunization with a heat-killed preparation of M. vaccae NCTC 11659 or borate-buffered saline vehicle. Gene enrichment analysis and analysis of protein-protein interactions were performed to integrate physiological network changes in plasma and CSF. We used RT-qPCR to assess immune and metabolic gene expression changes in the hippocampus. Results: In both plasma and CSF, immunization with M. vaccae increased proteins associated with immune activation and downregulated proteins corresponding to lipid (including phospholipid and cholesterol) metabolism. Immunization with M. vaccae also increased hippocampal expression of interleukin-4 (IL-4) mRNA, implicating anti-inflammatory effects in the central nervous system. Conclusion: M. vaccae alters host immune activity and lipid metabolism. These data are consistent with the hypothesis that microbe-host interactions may protect against possible infection-induced, inflammation-related cognitive impairments.

This study was conducted to investigate the effects of Boulardiiyeast wall polysaccharide (BRYP) on the intestinal micro-ecosystem of early-weaned lambs. A total of 60 early-weaned lambs (35-days-old, Kazak♂*Altay♀*Suffolk♂) were randomly assigned into two treatments: a control group with a basal diet, an experimental group with a basal diet and added 0.05% BRYP. The HiSeq high-throughput sequencing analysis of 16SrRNA was used to investigate the differences in intestinal microbial flora composition, diversity, relative abundance, principle coordination analysis, and the correlation between intestinal microbial flora composition and immune indices. After feeding for 40days, the addition of 0.5% BRYP in milk replacer significantly enhanced the species richness in the cecum and colon, but decreased the diversity of species in the colon (P <0.05); Compared with the control group, the relative abundance of Bacteroidetes in the experimental group was significantly enhanced, but the Proteobacteria was significantly decreased in all tested intestinal segments (P <0.05).In the jejunum, the relative abundance of Lactobacillus, Prevotella, and Fibrobacter of the experimental group were significantly enhanced than that of the control group, but the Ruminobacter was significantly decreased (P <0.05); In the cecum, the relative abundance of Bacteroides, Lactobacillus, Oscillospira and Bifidobacterium of the experimental group were significantly enhanced than that of the control group, but the Blautia were significantly decreased (P <0.05); In the colon, the relative abundance of Akkermansia, Bifidobacterium, Lactobacillus and Faecalibacteriumof the experimental group were significantly enhanced than that of the control group, but the Prevotella, Streptococcus, and Escherichia were significantly decreased (P <0.05). There were significant correlations between intestinal immune indices (IL-6, IL-10, TNF-α) and intestinal microbial composition in the colon (P <0.05). These results indicated that BRYP may contribute to the promotion of the proportion of helpful microbial populations and enhancing the balance of intestinal; Besides, BRYP may indirectly improve the intestinal immune function by changes of intestinal microflora composition, but suppress the inflammatory response in the bottom of intestinal mucosa of early-weaned lambs.© 2021 Friends Science Publishers

Diminished exposure to harmless micro-organisms, such as lactobacilli, has been suggested to play a role in the increased prevalence of allergic disorders in Westernized communities. The development of allergies depends on both environmental factors and genetic variations, including polymorphisms in genes encoding pattern recognition receptors. The present study examines the effects of both colonization with specific Lactobacillus species and genetic variations in DC-SIGN, a pattern recognition receptor on dendritic cells that recognizes lactobacilli, on the development of atopic dermatitis (AD) and sensitization in infancy. Within the KOALA Birth Cohort Study, faecal samples of 681 one-month-old infants were collected and quantitatively screened for five Lactobacillus species: L. casei, L. paracasei, L. rhamnosus, L. acidophilus and L. reuteri. Eleven haplotype-tagging polymorphisms in the DC-SIGN gene were genotyped in these children. Allergic outcomes were a clinical diagnosis of AD and sensitization (specific IgE) at age 2 years. L. rhamnosus (31.5 %), L. paracasei (31.3 %) and L. acidophilus (14.4 %) were frequently detected in the faecal samples of one-month-old infants, whereas L. casei (2.5 %) and L. reuteri (<1 %) were rare. Colonization with L. paracasei decreased the risk of AD significantly (odds ratio 0.57, 95 % confidence interval 0.32–0.99), whereas effects of L. acidophilus were of borderline statistical significance (0.46, 0.20–1.04). Two DC-SIGN polymorphisms, rs11465413 and rs8112555, were statistically significantly associated with atopic sensitization. The present study supports the ‘old friends’ hypothesis suggesting that certain health-beneficial micro-organisms protect us from developing allergies and that these protective effects are species-dependent. Firm conclusions on the potential interaction between lactobacillus colonization and genetic variations in DC-SIGN in association with the development of allergic disorders cannot be drawn, given the limited power of our study. Therefore, incorporation of consecutive faecal sampling in newly started (birth) cohort studies would be a first requisite to further increase our understanding of host–microbial interactions in health and disease.

Abstract Rumen, a pregastric anaerobic gut ecosystem, inhabits arguably the most diverse and complex microbial community, with a mutualistic relationship with the host. The relationship is best exemplified in the utilization of lignocellulosic material and non-protein nitrogen to provide energy and protein to the host. The microbial community of the rumen is composed of bacteria, archaea, protozoa, fungi and bacteriophages. Culture- or microscopy-based procedures have identified over 200 species of bacteria, methanogens, ciliated protozoa and zoosporic fungi. The community analysis based on the genetic material of all microbial cells, called microbiome, has vastly expanded our understanding of the ruminal ecosystem. Microbiome analysis is based on sequencing of the targeted amplicons (16S rDNA variable regions for bacteria and archaea, 18S rDNA for protozoa or Internal Transcribed Regions for fungi) or whole genome shotgun metagenomics analysis. Rapid advancements in nucleic acid sequencing technologies and bioinformatics pipelines have provided unprecedented opportunities to delineate the diversity and complexity of the microbial community in relation ruminal function and dysfunctions and link ruminal microbes to host nutrition and productivity. Culture-independent methods have identified thousands of microbial species in the rumen, suggesting that a major fraction of the microbiome has not been cultured and functionally identified. A core microbiome in bacterial and archaeal populations of the rumen has been identified across a wide geographical regions, but significant variations in diversity, abundance, and individual taxa do exist because of diet and host genetics. However, there is evidence of signature microbiome among individual animals on the same diet and environment. Microbiome-wide association studies in relation to dietary changes, ruminal function and dysfunctions have begun to link and define the complexity of the host-microbe relationships. Translation of the potential of the microbiome analysis is supported by emerging evidences that specific microbiota can be linked to ruminal activity and productivity.

Emerging evidence suggests that exposure to microbial diversity and key species (Old Friends) from biodiverse, natural environments may provide critical immune training and regulation. Conversely, reduced contact with the right kind of environmental microbial communities (microbiota) and their genetic material (microbiomes) may contribute to the modern growth in immunoregulatory disorders with potential to impact both infectious and non-communicable diseases. However, possible connections between biodiversity, environmental microbiomes and human health remain understudied due to their multidisciplinary nature. There is limited knowledge of the composition, modes of action, and environmental distribution of Old Friends. We do not know if it is microbial diversity per se, key species, or a combination of both, that may have protective effects. Yet, importantly, the environment-host microbiota pathway offers promise for cost-effective population health interventions (e.g. through restoring biodiverse green space in cities) at a time when health care systems around the world are seeing unsustainable growth in utilisation and budget demands. Therefore, a primary goal of this thesis was to build knowledge of potential connections, with a view to informing policy. Specifically, the aims were to: 1. Test whether the notion of beneficial biodiversity-health relationships are supported in existing Australia-wide datasets 2. Examine what types or attributes of environments might be most associated with health benefits, to focus more detailed study 3. Identify microbial taxa that associate with natural vs. degraded environments and potential links to human health 4. Gather controlled experimental evidence of microbiota transfer from biodiverse environments to hosts, to explore potential mechanistic links. I employed multidisciplinary methods reflecting the nature of the research topic. From continent-wide environmental mapping and hospital admission datasets, I found that landscape-scale measures of biodiversity correlated with reduced rates of respiratory disease and ranked highly among known predictors. Also, I found that populations living near soils with high cation exchange capacity—a proxy for soil microbial diversity—experienced lower rates of infectious and parasitic disease. I developed a new merged-sample bootstrap resampling technique enabling deep analysis of soil bacterial 16S rRNA microbiome data from a grassy woodland restoration chronosequence, from which key indicator groups were identified. Human-associated opportunistic and pathogen-containing taxa were found to be favoured in disturbed environments, yet reduced in mature, biodiverse environments. Finally, in a randomised controlled experiment with mice exposed to airborne dust from soil spanning a biodiversity gradient, I found changes to gut microbiota and reduced anxiety-like behaviour in females corresponding to the high biodiversity treatment. Among bacterial taxa that increased in the gut of high treatment mice, I identified a putative sporeforming, anaerobic environmental microbe capable of producing a key metabolite, butyrate, linked to mammalian gut health and mental health. These findings suggest naturally-diverse soil microbial communities may provide a health protecting role due to: ecological controls on potential opportunistic pathogens, increased immunomodulatory microbial diversity, and enhanced capacity to support beneficial key species and metabolite production pathways, for example via the gut-brain-microbiome axis. Implications of this work include opportunities to improve public health through increased exposure to biodiverse green space and soils.
Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 2019