Bacteriophage infections of microbiota can lead to leaky gut in an experimental rodent model

Microbiome-based therapeutics for Parkinson's disease

Recent experimental and clinical data demonstrate a significant dysregulation of the gut microbiome in individuals with Parkinson's disease (PD). With an immense influence on all aspects of physiology, this dysregulation has potential to directly or indirectly contribute to disease pathology. Experimental models have bridged these associations toward defined contributions, identifying various microbiome-dependent impacts to PD pathology. These studies have laid the foundation for human translation, examining whether certain members of the microbiome and/or whole restoration of the gut microbiome community can provide therapeutic benefit for people living with PD. Here, we review recent and ongoing clinically-focused studies that use microbiome-targeted therapies to limit the severity and progression of PD. Fecal microbiome transplants, prebiotic interventions, and probiotic supplementation are each emerging as viable methodologies to augment the gut microbiome and potentially limit PD symptoms. While still early, the data in the field to date support continued cross-talk between experimental systems and human studies to identify key microbial factors that contribute to PD pathologies.

Genetic recombination-mediated evolutionary interactions between phages of potential industrial importance and prophages of their hosts within or across the domains of Escherichia, Listeria, Salmonella, Campylobacter, and Staphylococcus

BACKGROUND

The in-depth understanding of the role of lateral genetic transfer (LGT) in phage-prophage interactions is essential to rationalizing phage applications for human and animal therapy, as well as for food and environmental safety. This in silico study aimed to detect LGT between phages of potential industrial importance and their hosts.

METHODS

A large array of genetic recombination detection algorithms, implemented in SplitsTree and RDP4, was applied to detect LGT between various Escherichia, Listeria, Salmonella, Campylobacter, Staphylococcus, Pseudomonas, and Vibrio phages and their hosts. PHASTER and RAST were employed respectively to identify prophages across the host genome and to annotate LGT-affected genes with unknown functions. PhageAI was used to gain deeper insights into the life cycle history of recombined phages.

RESULTS

The split decomposition inferences (bootstrap values: 91.3-100; fit: 91.433-100), coupled with the Phi (0.0-2.836E-12) and RDP4 (P being well below 0.05) statistics, provided strong evidence for LGT between certain Escherichia, Listeria, Salmonella, and Campylobacter virulent phages and prophages of their hosts. The LGT events entailed mainly the phage genes encoding for hypothetical proteins, while some of these genetic loci appeared to have been affected even by intergeneric recombination in specific E. coli and S. enterica virulent phages when interacting with their host prophages. Moreover, it is shown that certain L. monocytogenes virulent phages could serve at least as the donors of the gene loci, involved in encoding for the basal promoter specificity factor, for L. monocytogenes. In contrast, the large genetic clusters were determined to have been simultaneously exchanged by many S. aureus prophages and some Staphylococcus temperate phages proposed earlier as potential therapeutic candidates (in their native or modified state). The above genetic clusters were found to encompass multiple genes encoding for various proteins, such as e.g., phage tail proteins, the capsid and scaffold proteins, holins, and transcriptional terminator proteins.

CONCLUSIONS

It is suggested that phage-prophage interactions, mediated by LGT (including intergeneric recombination), can have a far-reaching impact on the co-evolutionary trajectories of industrial phages and their hosts especially when excessively present across microbially rich environments.

Effect of a multi-strain probiotic mixture consumption on anxiety and depression symptoms induced in adult mice by postnatal maternal separation

BACKGROUND

Intestinal microbial composition not only affects the health of the gut but also influences centrally mediated systems involved in mood, through the "gut-brain" axis, a bidirectional communication between gut microbiota and the brain. In this context, the modulation of intestinal microbiota and its metabolites through the administration of probiotics seems to represent a very promising approach in the treatment of the central nervous system alterations. Early postnatal life is a critical period during which the brain undergoes profound and essential modulations in terms of maturation and plasticity. Maternal separation (MS), i.e., the disruption of the mother-pup interaction, represents a pivotal paradigm in the study of stress-related mood disorders, by inducing persistent changes in the immune system, inflammatory processes, and emotional behavior in adult mammals.

RESULTS

We conducted experiments to investigate whether sustained consumption of a multi-strain probiotic formulation by adult male mice could mitigate the effects of maternal separation. Our data demonstrated that the treatment with probiotics was able to totally reverse the anxiety- and depressive-like behavior; normalize the neuro-inflammatory state, by restoring the resting state of microglia; and finally induce a proneurogenic effect. Mice subjected to maternal separation showed changes in microbiota composition compared to the control group that resulted in permissive colonization by the administered multi-strain probiotic product. As a consequence, the probiotic treatment also significantly affected the production of SCFA and in particular the level of butyrate.

CONCLUSION

Gut microbiota and its metabolites mediate the therapeutic action of the probiotic mix on MS-induced brain dysfunctions. Our findings extend the knowledge on the use of probiotics as a therapeutic tool in the presence of alterations of the emotional sphere that significantly impact on gut microbiota composition. Video Abstract.

Paving the way forward: Escherichia coli bacteriophages in a One Health approach

Escherichia coli is one of the most notorious pathogens for its ability to adapt, colonize, and proliferate in different habitats through a multitude of acquired virulence factors. Its presence affects the food-processing industry and causes food poisoning, being also a major economic burden for the food, agriculture, and health sectors. Bacteriophages are emerging as an appealing strategy to mitigate bacterial pathogens, including specific E. coli pathovars, without exerting a deleterious effect on humans and animals. This review globally analyzes the applied research on E. coli phages for veterinary, food, and human use. It starts by describing the pathogenic E. coli pathotypes and their relevance in human and animal context. The idea that phages can be used as a One Health approach to control and interrupt the transmission routes of pathogenic E. coli is sustained through an exhaustive revision of the recent literature. The emerging phage formulations, genetic engineering and encapsulation technologies are also discussed as a means of improving phage-based control strategies, with a particular focus on E. coli pathogens.

Role of bacteriophages in shaping gut microbial community

Phages are the most diversified and dominant members of the gut virobiota. They play a crucial role in shaping the structure and function of the gut microbial community and consequently the health of humans and animals. Phages are found mainly in the mucus, from where they can translocate to the intestinal organs and act as a modulator of gut microbiota. Understanding the vital role of phages in regulating the composition of intestinal microbiota and influencing human and animal health is an emerging area of research. The relevance of phages in the gut ecosystem is supported by substantial evidence, but the importance of phages in shaping the gut microbiota remains unclear. Although information regarding general phage ecology and development has accumulated, detailed knowledge on phage-gut microbe and phage-human interactions is lacking, and the information on the effects of phage therapy in humans remains ambiguous. In this review, we systematically assess the existing data on the structure and ecology of phages in the human and animal gut environments, their development, possible interaction, and subsequent impact on the gut ecosystem dynamics. We discuss the potential mechanisms of prophage activation and the subsequent modulation of gut bacteria. We also review the link between phages and the immune system to collect evidence on the effect of phages on shaping the gut microbial composition. Our review will improve understanding on the influence of phages in regulating the gut microbiota and the immune system and facilitate the development of phage-based therapies for maintaining a healthy and balanced gut microbiota.

Gut commensals and their metabolites in health and disease

Purpose of review

This review comprehensively discusses the role of the gut microbiome and its metabolites in health and disease and sheds light on the importance of a holistic approach in assessing the gut.

Recent findings

The gut microbiome consisting of the bacteriome, mycobiome, archaeome, and virome has a profound effect on human health. Gut dysbiosis which is characterized by perturbations in the microbial population not only results in gastrointestinal (GI) symptoms or conditions but can also give rise to extra-GI manifestations. Gut microorganisms also produce metabolites (short-chain fatty acids, trimethylamine, hydrogen sulfide, methane, and so on) that are important for several interkingdom microbial interactions and functions. They also participate in various host metabolic processes. An alteration in the microbial species can affect their respective metabolite concentrations which can have serious health implications. Effective assessment of the gut microbiome and its metabolites is crucial as it can provide insights into one's overall health.

Summary

Emerging evidence highlights the role of the gut microbiome and its metabolites in health and disease. As it is implicated in GI as well as extra-GI symptoms, the gut microbiome plays a crucial role in the overall well-being of the host. Effective assessment of the gut microbiome may provide insights into one's health status leading to more holistic care.

New Pieces for an Old Puzzle: Approaching Parkinson's Disease from Translatable Animal Models, Gut Microbiota Modulation, and Lipidomics

Parkinson's disease (PD) is a severe neurodegenerative disease characterized by disabling motor alterations that are diagnosed at a relatively late stage in its development, and non-motor symptoms, including those affecting the gastrointestinal tract (mainly constipation), which start much earlier than the motor symptoms. Remarkably, current treatments only reduce motor symptoms, not without important drawbacks (relatively low efficiency and impactful side effects). Thus, new approaches are needed to halt PD progression and, possibly, to prevent its development, including new therapeutic strategies that target PD etiopathogeny and new biomarkers. Our aim was to review some of these new approaches. Although PD is complex and heterogeneous, compelling evidence suggests it might have a gastrointestinal origin, at least in a significant number of patients, and findings in recently developed animal models strongly support this hypothesis. Furthermore, the modulation of the gut microbiome, mainly through probiotics, is being tested to improve motor and non-motor symptoms and even to prevent PD. Finally, lipidomics has emerged as a useful tool to identify lipid biomarkers that may help analyze PD progression and treatment efficacy in a personalized manner, although, as of today, it has only scarcely been applied to monitor gut motility, dysbiosis, and probiotic effects in PD. Altogether, these new pieces should be helpful in solving the old puzzle of PD.

The Novel Role of Phage Particles in Chronic Liver Diseases

The gut microbiome is made up of bacteria, fungi, viruses and archaea, all of which are closely related with human health. As the main component of enterovirus, the role of bacteriophages (phages) in chronic liver disease has been gradually recognized. Chronic liver diseases, including alcohol-related liver disease and nonalcoholic fatty liver disease, exhibit alterations of the enteric phages. Phages shape intestinal bacterial colonization and regulate bacterial metabolism. Phages adjoining to intestinal epithelial cells prevent bacteria from invading the intestinal barrier, and mediate intestinal inflammatory response. Phages are also observed increasing intestinal permeability and migrating to peripheral blood and organs, likely contributing to inflammatory injury in chronic liver diseases. By preying on harmful bacteria, phages can improve the gut microbiome of patients with chronic liver disease and thus act as an effective treatment method.

In Vitro Effect on Piglet Gut Microbiota and In Vivo Assessment of Newly Isolated Bacteriophages against F18 Enterotoxigenic Escherichia coli (ETEC)

Enterotoxigenic Escherichia coli (ETEC) causing post-weaning diarrhea (PWD) in piglets have a detrimental impact on animal health and economy in pig production. ETEC strains can adhere to the host's small intestinal epithelial cells using fimbriae such as F4 and F18. Phage therapy could represent an interesting alternative to antimicrobial resistance against ETEC infections. In this study, four bacteriophages, named vB_EcoS_ULIM2, vB_EcoM_ULIM3, vB_EcoM_ULIM8 and vB_EcoM_ULIM9, were isolated against an O8:F18 E. coli strain (A-I-210) and selected based on their host range. These phages were characterized in vitro, showing a lytic activity over a pH (4-10) and temperature (25-45 °C) range. According to genomic analysis, these bacteriophages belong to the Caudoviricetes class. No gene related to lysogeny was identified. The in vivo Galleria mellonella larvae model suggested the therapeutic potential of one selected phage, vB_EcoS_ULIM2, with a statistically significant increase in survival compared to non-treated larvae. To assess the effect of this phage on the piglet gut microbiota, vB_EcoS_ULIM2 was inoculated in a static model simulating the piglet intestinal microbial ecosystem for 72 h. This study shows that this phage replicates efficiently both in vitro and in vivo in a Galleria mellonella model and reveals the safety of the phage-based treatment on the piglet microbiota.

Impact Assessment of vB_KpnP_K1-ULIP33 Bacteriophage on the Human Gut Microbiota Using a Dynamic In Vitro Model

New control methods are needed to counter antimicrobial resistances and the use of bacteriophages as an alternative treatment seems promising. To that end, the effect of the phage vB_KpnP_K1-ULIP33, whose host is the hypervirulent Klebsiella pneumoniae SA12 (ST23 and capsular type K1), was assessed on intestinal microbiota, using an in vitro model: the SHIME® system (Simulator of the Human Intestinal Microbial Ecosystem). After stabilization of the system, the phage was inoculated for 7 days and its persistence in the different colons was studied until its disappearance from the system. The concentration of short chain fatty acids in the colons showed good colonization of the bioreactors by the microbiota and no significant effect related to the phage treatment. Diversity (α and β), the relative abundance of bacteria, and qPCR analysis targeting different genera of interest showed no significant variation following phage administration. Even if further in vitro studies are needed to assess the efficacy of this phage against its bacterial host within the human intestinal ecosystem, the phage ULIP33 exerted no significant change on the global colonic microbiota.

Human virome: Implications in cancer

In recent years, the human virome has gained importance, especially after the SARS-CoV-2 pandemic, due to its possible involvement in autoimmune, inflammatory diseases, and cancer. Characterization of the human virome can be carried out by shotgun next-generation sequencing (metagenomics), which allows the identification of all viral communities in an environmental sample and the discovery of new viral families not previously described. Variations in viral quantity and diversity have been associated with disease development, mainly due to their effect on gut bacterial microbiota. Phages can regulate bacterial flora through lysogeny; this is associated with increased susceptibility to infections, chronic inflammation, or cancer. The virome characterization in different human body ecological niches could help elucidate these particles' role in disease. Hence, it is important to understand the virome's influence on human health and disease. The present review highlights the significance of the human virome and how it is associated with disease, focusing on virome composition, characterization, and its association with cancer.

The Potential Role of Microorganisms on Enteric Nervous System Development and Disease

The enteric nervous system (ENS), the inherent nervous system of the gastrointestinal (GI) tract is a vast nervous system that controls key GI functions, including motility. It functions at a critical interface between the gut luminal contents, including the diverse population of microorganisms deemed the microbiota, as well as the autonomic and central nervous systems. Critical development of this axis of interaction, a key determinant of human health and disease, appears to occur most significantly during early life and childhood, from the pre-natal through to the post-natal period. These factors that enable the ENS to function as a master regulator also make it vulnerable to damage and, in turn, a number of GI motility disorders. Increasing attention is now being paid to the potential of disruption of the microbiota and pathogenic microorganisms in the potential aetiopathogeneis of GI motility disorders in children. This article explores the evidence regarding the relationship between the development and integrity of the ENS and the potential for such factors, notably dysbiosis and pathogenic bacteria, viruses and parasites, to impact upon them in early life.

The Human Gut Virome and Its Relationship with Nontransmissible Chronic Diseases

The human gastrointestinal tract contains large communities of microorganisms that are in constant interaction with the host, playing an essential role in the regulation of several metabolic processes. Among the gut microbial communities, the gut bacteriome has been most widely studied in recent decades. However, in recent years, there has been increasing interest in studying the influences that other microbial groups can exert on the host. Among them, the gut virome is attracting great interest because viruses can interact with the host immune system and metabolic functions; this is also the case for phages, which interact with the bacterial microbiota. The antecedents of virome-rectification-based therapies among various diseases were also investigated. In the near future, stool metagenomic investigation should include the identification of bacteria and phages, as well as their correlation networks, to better understand gut microbiota activity in metabolic disease progression.

Targeting Staphylococcus aureus dominated skin dysbiosis in actinic keratosis to prevent the onset of cutaneous squamous cell carcinoma: Outlook for future therapies?

Cutaneous squamous cell carcinoma (cSCC) and its premalignant precursor, actinic keratosis (AK), present a global health burden that is continuously increasing despite extensive efforts to promote sun safety. Chronic UV exposure is a recognized risk factor for the development of AK and cSCC. However, increasing evidence suggests that AK and cSCC is also associated with skin microbiome dysbiosis and, in particular, an overabundance of the bacterium Staphylococcus aureus (S. aureus). Studies have shown that S. aureus-derived toxins can contribute to DNA damage and lead to chronic upregulation of proinflammatory cytokines that may affect carcinogenesis. Eradication of S. aureus from AK lesions and restoration of a healthy microbiome may therefore represent a therapeutic opportunity to alter disease progression. Whilst antibiotics can reduce the S. aureus load, antibiotic resistant S. aureus pose an increasing global public health threat. The use of specific topically delivered probiotics has been used experimentally in other skin conditions to restore eubiosis, and could therefore also present a non-invasive treatment approach to decrease S. aureus colonization and restore a healthy skin microbiome on AK lesions. This article reviews mechanisms by which S. aureus may contribute to cutaneous carcinogenesis, and discusses hypotheses and theories that explore the therapeutic potential of specific bacterial species which compete with S. aureus in an attempt to restore microbial eubiosis in skin.

Leaky Gut and the Ingredients That Help Treat It: A Review

The human body is in daily contact with potentially toxic and infectious substances in the gastrointestinal tract (GIT). The GIT has the most significant load of antigens. The GIT can protect the intestinal integrity by allowing the passage of beneficial agents and blocking the path of harmful substances. Under normal conditions, a healthy intestinal barrier prevents toxic elements from entering the blood stream. However, factors such as stress, an unhealthy diet, excessive alcohol, antibiotics, and drug consumption can compromise the composition of the intestinal microbiota and the homeostasis of the intestinal barrier function of the intestine, leading to increased intestinal permeability. Intestinal hyperpermeability can allow the entry of harmful agents through the junctions of the intestinal epithelium, which pass into the bloodstream and affect various organs and systems. Thus, leaky gut syndrome and intestinal barrier dysfunction are associated with intestinal diseases, such as inflammatory bowel disease and irritable bowel syndrome, as well as extra-intestinal diseases, including heart diseases, obesity, type 1 diabetes mellitus, and celiac disease. Given the relationship between intestinal permeability and numerous conditions, it is convenient to seek an excellent strategy to avoid or reduce the increase in intestinal permeability. The impact of dietary nutrients on barrier function can be crucial for designing new strategies for patients with the pathogenesis of leaky gut-related diseases associated with epithelial barrier dysfunctions. In this review article, the role of functional ingredients is suggested as mediators of leaky gut-related disorders.

Examining the effects of Salmonella phage on the caecal microbiota and metabolome features in Salmonella-free broilers

Bacteriophages selectively infect and kill their target bacterial host, being a promising approach to controlling zoonotic bacteria in poultry production. To ensure confidence in its use, fundamental questions of safety and toxicity monitoring of phage therapy should be raised. Due to its high specificity, a minimal impact on the gut ecology is expected; however, more in-depth research into key parameters that influence the success of phage interventions has been needed to reach a consensus on the impact of bacteriophage therapy in the gut. In this context, this study aimed to investigate the interaction of phages with animals; more specifically, we compared the caecum microbiome and metabolome after a Salmonella phage challenge in Salmonella-free broilers, evaluating the role of the phage administration route. To this end, we employed 45 caecum content samples from a previous study where Salmonella phages were administered via drinking water or feed for 24 h from 4, 5 to 6-weeks-old broilers. High-throughput 16S rRNA gene sequencing showed a high level of similarity (beta diversity) but revealed a significant change in alpha diversity between broilers with Salmonella-phage administered in the drinking water and control. Our results showed that the phages affected only a few genera of the microbiota's structure, regardless of the administration route. Among these, we found a significant increase in Streptococcus and Sellimonas in the drinking water and Lactobacillus, Anaeroplasma and Clostridia_vadinBB60_group in the feed. Nevertheless, the LC-HRMS-based metabolomics analyses revealed that despite few genera were significantly affected, a substantial number of metabolites, especially in the phage administered in the drinking water were significantly altered (64 and 14 in the drinking water and feed groups, respectively). Overall, our study shows that preventive therapy with bacteriophages minimally alters the caecal microbiota but significantly impacts their metabolites, regardless of the route of administration.

Highly different effects of phage therapy and antibiotic therapy on immunological responses of chickens infected with Salmonella enterica serovar Typhimurium

The appearance of bacteria resistant to most or even all known antibiotics has become a serious medical problem. One such promising and effective alternative form of therapy may be the use of phages, the administration of which is considered to be safe and highly effective, especially in animals with drug-resistant infections. Although there have been no reports to date suggesting that bacteriophages can cause any severe complications or adverse effects, we still know little about their interactions with animal organisms, especially in the context of the functioning of the immune system. Therefore, the aim of the present study was to compare the impact of the application of selected bacteriophages and antibiotics (enrofloxacin and colistin), commonly used in veterinary medicine, on immune functions in Salmonella enterica serovar Typhimurium-infected chickens. The birds were infected with S. Typhimurium and then treated with a phage cocktail (14 days), enrofloxacin (5 days), or colistin (5 days). The concentrations of a panel of pro-inflammatory cytokines (IL-1β, IL-6, IFN-γ, IL-8, and IL-12) and cytokines that reveal anti-inflammatory effects (IL-10 and IL-4), the percentage of lymphocytes, and the level of stress hormones (corticosterone and cortisol), which significantly modulate the immune responses, were determined in different variants of the experiment. The phage cocktail revealed anti-inflammatory effects when administered either 1 day after infection or 2 days after S. Typhimurium detection in feces, as measured by inhibition of the increase in levels of inflammatory response markers (IL-1β, IL-6, IFN-γ, IL-8, and IL-12). This was also confirmed by increased levels of cytokines that exert an anti-inflammatory action (IL-10 and IL-4) following phage therapy. Moreover, phages did not cause a negative effect on the number and activity of lymphocytes’ subpopulations crucial for normal immune system function. These results indicate for the first time that phage therapy not only is effective but also can be used in veterinary medicine without disturbing immune homeostasis, expressed as cytokine imbalance, disturbed percentage of key immune cell subpopulations, and stress axis hyperactivity, which were observed in our experiments as adverse effects accompanying the antibiotic therapy.

Gut virome dysbiosis following focal cerebral ischemia in mice

Stroke leads to gut bacterial dysbiosis that impacts the post-stroke outcome. The gut microbiome also contains a high abundance of viruses which might play a crucial role in disease progression and recovery by modulating the metabolism of both host and host's gut bacteria. We presently analyzed the virome composition (viruses and phages) by shotgun metagenomics in the fecal samples obtained at 1 day of reperfusion following transient focal ischemia in adult mice. Viral genomes, viral auxiliary metabolic genes, and viral protein networks were compared between stroke and sham conditions (stroke vs sham, exclusive to sham and exclusive to stroke). Following focal ischemia, abundances of 2 viral taxa decreased, and 5 viral taxa increased compared with the sham. Furthermore, the abundance of Clostridia-like phages and Erysipelatoclostridiaceae-like phages were altered in the stroke compared with the sham cohorts. This is the first report to show that the gut virome responds acutely to stroke.

The gut virome: A new microbiome component in health and disease

The human gastrointestinal tract harbours an abundance of viruses, collectively known as the gut virome. The gut virome is highly heterogeneous across populations and is linked to geography, ethnicity, diet, lifestyle, and urbanisation. The currently known function of the gut virome varies greatly across human populations, and much remains unknown. We review current literature on the human gut virome, and the intricate trans-kingdom interplay among gut viruses, bacteria, and the mammalian host underlying health and diseases. We summarise evidence on the use of the gut virome as diagnostic markers and a therapeutic target. We shed light on novel avenues of microbiome-inspired diagnosis and therapies. We also review pre-clinical and clinical studies on gut virome-rectification-based therapies, including faecal microbiota transplantation, faecal virome transplantation, and refined phage therapy. Our review suggests that future research effort should focus on unravelling the mechanisms exerted by gut viruses/phages in human pathophysiology, and on developing phage-prompted precision therapies.

Loss of Gut Barrier Integrity In Lupus

Systemic Lupus Erythematosus is a complex autoimmune disease and its etiology remains unknown. Increased gut permeability has been reported in lupus patients, yet whether it promotes or results from lupus progression is unclear. Recent studies indicate that an impaired intestinal barrier allows the translocation of bacteria and bacterial components into systemic organs, increasing immune cell activation and autoantibody generation. Indeed, induced gut leakage in a mouse model of lupus enhanced disease characteristics, including the production of anti-dsDNA antibody, serum IL-6 as well as cell apoptosis. Gut microbiota dysbiosis has been suggested to be one of the factors that decreases gut barrier integrity by outgrowing harmful bacteria and their products, or by perturbation of gut immune homeostasis, which in turn affects gut barrier integrity. The restoration of microbial balance eliminates gut leakage in mice, further confirming the role of microbiota in maintaining gut barrier integrity. In this review, we discuss recent advances on the association between microbiota dysbiosis and leaky gut, as well as their influences on the progression of lupus. The modifications on host microbiota and gut integrity may offer insights into the development of new lupus treatment.

The role of virome in the gastrointestinal tract and beyond

The human gut virome is comprised of diverse commensal and pathogenic viruses. The colonization by these viruses begins right after birth through vaginal delivery, then continues through breastfeeding, and broader environmental exposure. Their constant interaction with their bacterial hosts in the body shapes not only our microbiomes but us. In addition, these viruses interact with the immune cells, trigger a broad range of immune responses, and influence different metabolic pathways. Besides its key role in regulating the human gut homeostasis, the intestinal virome contributes to disease development in distant organs, both directly and indirectly. In this review, we will describe the changes in the gut virome through life, health, and disease, followed by discussing the interactions between the virome, the microbiome, and the human host as well as providing an overview of their contribution to gut disease and disease of distant organs.

Rehabilitation of a misbehaving microbiome: phages for the remodeling of bacterial composition and function

The human gut microbiota is considered an adjunct metabolic organ owing to its health impact. Recent studies have shown correlations between gut phage composition and host health. Whereas phage therapy has popularized virulent phages as antimicrobials, both virulent and temperate phages have a natural ecological relationship with their cognate bacteria. Characterization of this evolutionary coadaptation has led to other emergent therapeutic phage applications that do not necessarily rely on bacterial eradication or target pathogens. Here, we present an overview of the tripartite relationship between phages, bacteria, and the mammalian host, and highlight applications of the wildtype and genetically engineered phage for gut microbiome remodeling. In light of new and varied strategies, we propose to categorize phage applications aiming to modulate bacterial composition or function as "phage rehabilitation." By delineating phage rehab from phage therapy, we believe it will enable greater nuance and understanding of these new phage-based technologies.

Metagenomic analysis of primary colorectal carcinomas and their metastases identifies potential microbial risk factors

The paucity of microbiome studies at intestinal tissues has contributed to a yet limited understanding of potential viral and bacterial cofactors of colorectal cancer (CRC) carcinogenesis or progression. We analysed whole-genome sequences of CRC primary tumours, their corresponding metastases and matched normal tissue for sequences of viral, phage and bacterial species. Bacteriome analysis showed Fusobacterium nucleatum, Streptococcus sanguinis, F. Hwasookii, Anaerococcus mediterraneensis and further species enriched in primary CRCs. The primary CRC of one patient was enriched for F. alocis, S. anginosus, Parvimonas micra and Gemella sp. 948. Enrichment of Escherichia coli strains IAI1, SE11, K-12 and M8 was observed in metastases together with coliphages enterobacteria phage φ80 and Escherichia phage VT2φ_272. Virome analysis showed that phages were the most preponderant viral species (46%), the main families being Myoviridae, Siphoviridae and Podoviridae. Primary CRCs were enriched for bacteriophages, showing five phages (Enterobacteria, Bacillus, Proteus, Streptococcus phages) together with their pathogenic hosts in contrast to normal tissues. The most frequently detected, and Blast-confirmed, viruses included human endogenous retrovirus K113, human herpesviruses 7 and 6B, Megavirus chilensis, cytomegalovirus (CMV) and Epstein-Barr virus (EBV), with one patient showing EBV enrichment in primary tumour and metastases. EBV was PCR-validated in 80 pairs of CRC primary tumour and their corresponding normal tissues; in 21 of these pairs (26.3%), it was detectable in primary tumours only. The number of viral species was increased and bacterial species decreased in CRCs compared with normal tissues, and we could discriminate primary CRCs from metastases and normal tissues by applying the Hutcheson t-test on the Shannon indices based on viral and bacterial species. Taken together, our results descriptively support hypotheses on microorganisms as potential (co)risk factors of CRC and extend putative suggestions on critical microbiome species in CRC metastasis.

Viruses in colorectal cancer

Increasing evidence suggests that microorganisms might represent at least highly interesting cofactors in colorectal cancer (CRC) oncogenesis and progression. Still, associated mechanisms, specifically in colonocytes and their microenvironmental interactions, are still poorly understood. Although, currently, at least seven viruses are being recognized as human carcinogens, only three of these – Epstein–Barr virus (EBV), human papillomavirus (HPV) and John Cunningham virus (JCV) – have been described, with varying levels of evidence, in CRC. In addition, cytomegalovirus (CMV) has been associated with CRC in some publications, albeit not being a fully acknowledged oncovirus. Moreover, recent microbiome studies set increasing grounds for new hypotheses on bacteriophages as interesting additional modulators in CRC carcinogenesis and progression. The present Review summarizes how particular groups of viruses, including bacteriophages, affect cells and the cellular and microbial microenvironment, thereby putatively contributing to foster CRC. This could be achieved, for example, by promoting several processes – such as DNA damage, chromosomal instability, or molecular aspects of cell proliferation, CRC progression and metastasis – not necessarily by direct infection of epithelial cells only, but also by interaction with the microenvironment of infected cells. In this context, there are striking common features of EBV, CMV, HPV and JCV that are able to promote oncogenesis, in terms of establishing latent infections and affecting p53‐/pRb‐driven, epithelial–mesenchymal transition (EMT)‐/EGFR‐associated and especially Wnt/β‐catenin‐driven pathways. We speculate that, at least in part, such viral impacts on particular pathways might be reflected in lasting (e.g. mutational or further genomic) fingerprints of viruses in cells. Also, the complex interplay between several species within the intestinal microbiome, involving a direct or indirect impact on colorectal and microenvironmental cells but also between, for example, phages and bacterial and viral pathogens, and further novel species certainly might, in part, explain ongoing difficulties to establish unequivocal monocausal links between specific viral infections and CRC.

Differences in Gut Virome Related to Barrett Esophagus and Esophageal Adenocarcinoma

The relationship between viruses (dominated by bacteriophages or phages) and lower gastrointestinal (GI) tract diseases has been investigated, whereas the relationship between gut bacteriophages and upper GI tract diseases, such as esophageal diseases, which mainly include Barrett’s esophagus (BE) and esophageal adenocarcinoma (EAC), remains poorly described. This study aimed to reveal the gut bacteriophage community and their behavior in the progression of esophageal diseases. In total, we analyzed the gut phage community of sixteen samples from patients with esophageal diseases (six BE patients and four EAC patients) as well as six healthy controls. Differences were found in the community composition of abundant and rare bacteriophages among three groups. In addition, the auxiliary metabolic genes (AMGs) related to bacterial exotoxin and virulence factors such as lipopolysaccharides (LPS) biosynthesis proteins were found to be more abundant in the genome of rare phages from BE and EAC samples compared to the controls. These results suggest that the community composition of gut phages and functional traits encoded by them were different in two stages of esophageal diseases. However, the findings from this study need to be validated with larger sample sizes in the future.

Potential roles of gut microbiota and microbial metabolites in Parkinson's disease

Parkinson's disease (PD) is a complicated neurodegenerative disease attributed to multifactorial changes. However, its pathological mechanism remains undetermined. Accumulating evidence has revealed the emerging functions of gut microbiota and microbial metabolites, which can affect both the enteric nervous system and the central nervous system via the microbiota-gut-brain axis. Accordingly, intestinal dysbiosis might be closely associated with PD. This review explores alterations to gut microbiota, correlations with clinical manifestations of PD, and briefly probes the underlying mechanisms. Next, the highly controversial roles of microbial metabolites including short-chain fatty acids (SCFAs), H₂ and H₂S are discussed. Finally, the pros and cons of the current treatments for PD, including those targeting microbiota, are assessed. Advancements in research techniques, further studies on levels of specific strains and longitudinal prospective clinical trials are urgently needed for the identification of early diagnostic markers and the development of novel therapeutic approaches for PD.

The Microbiota/Microbiome and the Gut-Brain Axis: How Much Do They Matter in Psychiatry?

The functioning of the central nervous system (CNS) is the result of the constant integration of bidirectional messages between the brain and peripheral organs, together with their connections with the environment. Despite the anatomical separation, gut microbiota, i.e., the microorganisms colonising the gastrointestinal tract, is highly related to the CNS through the so-called "gut-brain axis". The aim of this paper was to review and comment on the current literature on the role of the intestinal microbiota and the gut-brain axis in some common neuropsychiatric conditions. The recent literature indicates that the gut microbiota may affect brain functions through endocrine and metabolic pathways, antibody production and the enteric network while supporting its possible role in the onset and maintenance of several neuropsychiatric disorders, neurodevelopment and neurodegenerative disorders. Alterations in the gut microbiota composition were observed in mood disorders and autism spectrum disorders and, apparently to a lesser extent, even in obsessive-compulsive disorder (OCD) and related conditions, as well as in schizophrenia. Therefore, gut microbiota might represent an interesting field of research for a better understanding of the pathophysiology of common neuropsychiatric disorders and possibly as a target for the development of innovative treatments that some authors have already labelled "psychobiotics".

How to Train Your Phage: The Recent Efforts in Phage Training

Control of pathogenic bacteria by deliberate application of predatory phages has potential as a powerful therapy against antibiotic-resistant bacteria. The key advantages of phage biocontrol over antibacterial chemotherapy are: (1) an ability to self-propagate inside host bacteria, (2) targeted predation of specific species or strains of bacteria, (3) adaptive molecular machinery to overcome resistance in target bacteria. However, realizing the potential of phage biocontrol is dependent on harnessing or adapting these responses, as many phage species switch between lytic infection cycles (resulting in lysis) and lysogenic infection cycles (resulting in genomic integration) that increase the likelihood of survival of the phage in response to external stress or host depletion. Similarly, host range will need to be optimized to make phage therapy medically viable whilst avoiding the potential for deleteriously disturbing the commensal microbiota. Phage training is a new approach to produce efficient phages by capitalizing on the evolved response of wild-type phages to bacterial resistance. Here we will review recent studies reporting successful trials of training different strains of phages to switch into lytic replication mode, overcome bacterial resistance, and increase their host range. This review will also highlight the current knowledge of phage training and future implications in phage applications and phage therapy and summarize the recent pipeline of the magistral preparation to produce a customized phage for clinical trials and medical applications.

Microbiota's role in health and diseases

The microbiome is a term that usually refers to the community of various microorganisms that inhabit/live inside human/animal bodies or on their skin. It forms a complex ecosystem that includes trillions of commensals, symbiotics, and even pathogenic microorganisms. The external environment, diet, and lifestyle are the major determinants influencing the microbiome's composition and vitality. Recent studies have indicated the tremendous influence of the microbiome on health and disease. Their number, constitution, variation, and viability are dynamic. All these elements are responsible for the induction, development, and treatment of many health disorders. Serious diseases such as cancer, metabolic disorders, cardiovascular diseases, and even psychological disorders such as schizophrenia are influenced directly or indirectly by microbiota. In addition, in the last few weeks, accumulating data about the link between COVID-19 and the microbiota were published. In the present work, the role of the microbiome in health and disease is discussed. A deep understanding of the exact role of microbiota in disease induction enables the prevention of diseases and the development of new therapeutic concepts for most diseases through the correction of diet and lifestyle. The present review brings together evidence from the most recent works and discusses suggested nutraceutical approaches for the management of COVID-19 pandemic.

Gut Microbiota: Critical Controller and Intervention Target in Brain Aging and Cognitive Impairment

The current trend for the rapid growth of the global aging population poses substantial challenges for society. The human aging process has been demonstrated to be closely associated with changes in gut microbiota composition, diversity, and functional features. During the first 2 years of life, the gut microbiota undergoes dramatic changes in composition and metabolic functions as it colonizes and develops in the body. Although the gut microbiota is nearly established by the age of three, it continues to mature until adulthood, when it comprises more stable and diverse microbial species. Meanwhile, as the physiological functions of the human body deteriorated with age, which may be a result of immunosenescence and "inflammaging," the guts of elderly people are generally characterized by an enrichment of pro-inflammatory microbes and a reduced abundance of beneficial species. The gut microbiota affects the development of the brain through a bidirectional communication system, called the brain-gut-microbiota (BGM) axis, and dysregulation of this communication is pivotal in aging-related cognitive impairment. Microbiota-targeted dietary interventions and the intake of probiotics/prebiotics can increase the abundance of beneficial species, boost host immunity, and prevent gut-related diseases. This review summarizes the age-related changes in the human gut microbiota based on recent research developments. Understanding these changes will likely facilitate the design of novel therapeutic strategies to achieve healthy aging.

The Human Gut Phageome: Origins and Roles in the Human Gut Microbiome

The investigation of the microbial populations of the human body, known as the microbiome, has led to a revolutionary field of science, and understanding of its impacts on human development and health. The majority of microbiome research to date has focussed on bacteria and other kingdoms of life, such as fungi. Trailing behind these is the interrogation of the gut viruses, specifically the phageome. Bacteriophages, viruses that infect bacterial hosts, are known to dictate the dynamics and diversity of bacterial populations in a number of ecosystems. However, the phageome of the human gut, while of apparent importance, remains an area of many unknowns. In this paper we discuss the role of bacteriophages within the human gut microbiome. We examine the methods used to study bacteriophage populations, how this evolved over time and what we now understand about the phageome. We review the phageome development in infancy, and factors that may influence phage populations in adult life. The role and action of the phageome is then discussed at both a biological-level, and in the broader context of human health and disease.

Bi- and Multi-directional Gene Transfer in the Natural Populations of Polyvalent Bacteriophages, and Their Host Species Spectrum Representing Foodborne Versus Other Human and/or Animal Pathogens

Unraveling the trends of phage-host versus phage-phage coevolution is critical for avoiding possible undesirable outcomes from the use of phage preparations intended for therapeutic, food safety or environmental safety purposes. We aimed to investigate a phenomenon of intergeneric recombination and its trajectories across the natural populations of phages predominantly linked to foodborne pathogens. The results from the recombination analyses, using a large array of the recombination detection algorithms imbedded in SplitsTree, RDP4, and Simplot software packages, provided strong evidence (fit: 100; P  ≤ 0.014) for both bi- and multi-directional intergeneric recombination of the genetic loci involved collectively in phage morphogenesis, host specificity, virulence, replication, and persistence. Intergeneric recombination was determined to occur not only among conspecifics of the virulent versus temperate phages but also between the phages with these different lifestyles. The recombining polyvalent phages were suggested to interact with fairly large host species networks, including sometimes genetically very distinct species, such as e.g., Salmonella enterica and/or Escherichia coli versus Staphylococcus aureus or Yersinia pestis. Further studies are needed to understand whether phage-driven intergeneric recombination can lead to undesirable changes of intestinal and other microbiota in humans and animals.

The Putative Antidepressant Mechanisms of Probiotic Bacteria: Relevant Genes and Proteins

Probiotic bacteria are widely accepted as therapeutic agents against inflammatory bowel diseases for their immunostimulating effects. In the last decade, more evidence has emerged supporting the positive effects of probiotics on the course of neurodegenerative and psychiatric diseases. This brief review summarizes the data from clinical studies of probiotics possessing antidepressant properties and focuses on the potential genes and proteins underlying these mechanisms. Data from small-sample placebo-controlled pilot studies indicate that certain strains of bacteria can significantly reduce the symptoms of depression, especially in depressed patients. Despite the disparity between studies attempting to pinpoint the bacterial putative genes and proteins accounting for these mechanisms, they ultimately show that bacteria are a potential source of metabiotics—microbial metabolites or structural components. Since the constituents of cells—namely, secreted proteins, peptides and cell wall components—are most likely to be entangled in the gut–brain axis, they can serve as starting point in the search for probiotics with concrete properties.

The Nerves to Conduct a Multiple Sclerosis Crime Investigation

Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative autoimmune disease characterized by the aberrant infiltration of immune cells into the central nervous system (CNS) and by the loss of myelin. Sclerotic lesions and various inhibitory factors hamper the remyelination processes within the CNS. MS patients typically experience gradual cognitive and physical disabilities as the disease progresses. The etiology of MS is still unclear and emerging evidence suggests that microbiome composition could play a much more significant role in disease pathogenesis than was initially thought. Initially believed to be isolated to the gut microenvironment, we now know that the microbiome plays a much broader role in various tissues and is essential in the development of the immune system. Here, we present some of the unexpected roles that the microbiome plays in MS and discuss approaches for the development of next-generation treatment strategies.

Phage Prevalence in the Human Urinary Tract-Current Knowledge and Therapeutic Implications

Recent metagenomic analyses imply an immense abundance of phages in the human body. Samples collected from different sites (lungs, skin, oral cavity, intestines, ascitic fluid, and urine) reveal a generally greater number of phage particles than that of eukaryotic viruses. The presence of phages in those tissues and fluids reflects the paths they must overcome in the human body, but may also relate to the health statuses of individuals. Besides shaping bacterial metabolism and community structure, the role of phages circulating in body fluids has not been fully understood yet. The lack of relevant reports is especially visible with regard to the human urobiome. Certainly, phage presence and the role they have to fulfill in the human urinary tract raises questions on potential therapeutic connotations. Urinary tract infections (UTIs) are among the most common bacterial infections in humans and their treatment poses a difficult therapeutic dilemma. Despite effective antibiotic therapy, these infections tend to recur. In this review, we summarized the recent data on phage presence in the human urinary tract and its possible implications for health and disease.

Elevated plasma phage load as a marker for intestinal permeability in leukemic patients

Microbial translocation (MT) and altered gut microbiota have been described in acute leukemic patients and contribute to immune activation and inflammation. However, phage translocation has not been investigated in leukemia patients yet. We recruited 44 leukemic patients and 52 healthy adults and quantified the levels of 3 phages in peripheral blood, which were the most positive phages screened from fecal samples. The content of 16S rRNA in plasma was detected by qPCR to assess the intestinal mucosa of these patients. Spearman's rank correlation was used to analyze the relationship between phage load and the relevant clinical data. We found the most prevalent phages in fecal samples were λ phage, Wphi phage, and P22 phage, and λ phage had the highest detection rate in plasma (68%). Phage content was affected by chemotherapy and course of disease and correlated with the levels of CRP (r = 0.43, p = 0.003), sCD14 (r = 0.37, p = 0.014), and sCD163 (r = 0.44, p = 0.003). Our data indicate that plasma phage load is a promising marker for gut barrier damage and that gut phage translocation correlates with monocyte/macrophage activation and systemic inflammatory response in leukemic patients.

Phages and their potential to modulate the microbiome and immunity

Bacteriophages (hence termed phages) are viruses that target bacteria and have long been considered as potential future treatments against antibiotic-resistant bacterial infection. However, the molecular nature of phage interactions with bacteria and the human host has remained elusive for decades, limiting their therapeutic application. While many phages and their functional repertoires remain unknown, the advent of next-generation sequencing has increasingly enabled researchers to decode new lytic and lysogenic mechanisms by which they attack and destroy bacteria. Furthermore, the last decade has witnessed a renewed interest in the utilization of phages as therapeutic vectors and as a means of targeting pathogenic or commensal bacteria or inducing immunomodulation. Importantly, the narrow host range, immense antibacterial repertoire, and ease of manipulating phages may potentially allow for their use as targeted modulators of pathogenic, commensal and pathobiont members of the microbiome, thereby impacting mammalian physiology and immunity along mucosal surfaces in health and in microbiome-associated diseases. In this review, we aim to highlight recent advances in phage biology and how a mechanistic understanding of phage-bacteria-host interactions may facilitate the development of novel phage-based therapeutics. We provide an overview of the challenges of the therapeutic use of phages and how these could be addressed for future use of phages as specific modulators of the human microbiome in a variety of infectious and noncommunicable human diseases.

An exegesis of bacteriophage therapy: An emerging player in the fight against anti-microbial resistance

Bacteriophages (simply referred to as Phages) are a class of viruses with the ability to infect and kill prokaryotic cells (bacteria), but are unable to infect mammalian cells. This unique ability to achieve specific infectiousness by bacteriophages has been harnessed in antibacterial treatments dating back almost a decade before the antibiotic era began. Bacteriophages were used as therapeutic agents in treatment of dysentery caused by Shigella dysenteriae as far back as 1919 and in the experimental treatment of a wide variety of other bacterial infections caused by Vibriocholerae, Staphylococcussp., Pseudomonas sp. etc, with varying degrees of success. Phage therapy and its many prospects soon fell out of favour in western medicine after the Second World War, with the discovery of penicillin. The Soviet Union and other countries in Eastern Europe however mastered the craft of bacteriophage isolation, purification and cocktail preparation, with phage-based therapeutics becoming widely available over-the-counter. With the recent rise in cases of multi-drug resistant bacterial infections, the clamour for a return to phage therapy, as a potential solution to the anti-microbial resistance (AMR) crisis has grown louder. This review provides an extensive exposé on phage therapy, addressing its historical use, evidences of its safety and efficacy, its pros and cons when compared with antibiotics, cases of compassionate use for treating life-threatening antibiotic-resistant infections, the limitations to its acceptance and how these may be circumvented.

Pharmacological Interventions for Bacterial Prostatitis

Prostatitis is a common urinary tract condition but bring innumerable trouble to clinicians in treatment, as well as great financial burden to patients and the society. Bacterial prostatitis (acute bacterial prostatitis plus chronic bacterial prostatitis) accounting for approximately 20% among all prostatitis have made the urological clinics complain about the genital and urinary systems all over the world. The international challenges of antibacterial treatment (emergence of multidrug-resistant bacteria, extended-spectrum beta-lactamase-producing bacteria, bacterial biofilms production and the shift in bacterial etiology) and the transformation of therapeutic strategy for classic therapy have attracted worldwide attention. To the best of our knowledge currently, there is not a single comprehensive review, which can completely elaborate these important topics and the corresponding treatment strategy in an effective way. This review summarizes the general treatment choices for bacterial prostatitis also provides the alternative pharmacological therapies for those patients resistant or intolerant to general treatment.

Probiotic Bacillus Spores Protect Against Acetaminophen Induced Acute Liver Injury in Rats

Acetaminophen (APAP) is one of the most used analgesics and antipyretic agents in the world. Intoxication with APAP is the main cause of acute liver toxicity in both the US and Europe. Spore-forming probiotic bacteria have the ability to resist harsh gastric and intestinal conditions. The aim of this study was to investigate the possible protective effect of Bacillus (B) species (sp) spores (B. licheniformis, B. indicus, B. subtilis, B. clausii, B. coagulans) against hepatotoxicity induced by APAP in rats. A total of 35 rats were randomly divided into seven groups: group I served as control; group II received silymarin; group III received MegaSporeBiotic^TM (MSB); group IV received APAP and served as the model of hepatotoxicity; group V received APAP and silymarin; group VI received APAP and MSB; group VII received APAP, silymarin and MSB. The livers for histopathological examination and blood samples were collected on the last day of the experiment. We determined aspartate aminotransferase (AST), alanine aminotransferase (ALT) and total antioxidant capacity (TAC) levels and zonula occludens (ZO-1), tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β) expression. APAP overdose increased AST and ALT. It slowly decreased TAC compared to the control group, but pretreatment with silymarin and MSB increased TAC levels. Elevated plasma concentrations were identified for ZO-1 in groups treated with APAP overdose compared with those without APAP or receiving APAP in combination with silymarin, MSB or both. The changes were positively correlated with the levels of other proinflammatory cytokines (TNF-α, IL-1β). In addition, histopathological hepatic injury was improved by preadministration of MSB or silymarin versus the disease model group. Bacillus sp spores had a protective effect on acute hepatic injury induced by APAP. Pretreatment with MSB resulted in a significant reduction in serum AST, ALT, TNF-α, IL-1β, ZO-1, TAC and also hepatocyte necrosis, similar to the well-known hepatoprotective agent—silymarin.

A new biological definition of life

Here we have proposed a new biological definition of life based on the function and reproduction of existing genes and creation of new ones, which is applicable to both unicellular and multicellular organisms. First, we coined a new term "genetic information metabolism" comprising functioning, reproduction, and creation of genes and their distribution among living and non-living carriers of genetic information. Encompassing this concept, life is defined as organized matter that provides genetic information metabolism. Additionally, we have articulated the general biological function of life as Tetz biological law: "General biological function of life is to provide genetic information metabolism" and formulated novel definition of life: "Life is an organized matter that provides genetic information metabolism". New definition of life and Tetz biological law allow to distinguish in a new way living and non-living objects on Earth and other planets based on providing genetic information metabolism.

Bacteriophage and the Innate Immune System: Access and Signaling

Bacteriophage and the bacteria they infect are the dominant members of the gastrointestinal microbiome. While bacteria are known to be central to maintenance of the structure, function, and health of the microbiome, it has only recently been recognized that phage too might serve a critical function. Along these lines, bacteria are not the only cells that are influenced by bacteriophage, and there is growing evidence of bacteriophage effects on epithelial, endothelial, and immune cells. The innate immune system is essential to protecting the Eukaryotic host from invading microorganisms, and bacteriophage have been demonstrated to interact with innate immune cells regularly. Here, we conduct a systematic review of the varying mechanisms allowing bacteriophage to access and interact with cells of the innate immune system and propose the potential importance of these interactions.

The Microbiota-Gut-Brain Axis

The importance of the gut-brain axis in maintaining homeostasis has long been appreciated. However, the past 15 yr have seen the emergence of the microbiota (the trillions of microorganisms within and on our bodies) as one of the key regulators of gut-brain function and has led to the appreciation of the importance of a distinct microbiota-gut-brain axis. This axis is gaining ever more traction in fields investigating the biological and physiological basis of psychiatric, neurodevelopmental, age-related, and neurodegenerative disorders. The microbiota and the brain communicate with each other via various routes including the immune system, tryptophan metabolism, the vagus nerve and the enteric nervous system, involving microbial metabolites such as short-chain fatty acids, branched chain amino acids, and peptidoglycans. Many factors can influence microbiota composition in early life, including infection, mode of birth delivery, use of antibiotic medications, the nature of nutritional provision, environmental stressors, and host genetics. At the other extreme of life, microbial diversity diminishes with aging. Stress, in particular, can significantly impact the microbiota-gut-brain axis at all stages of life. Much recent work has implicated the gut microbiota in many conditions including autism, anxiety, obesity, schizophrenia, Parkinson’s disease, and Alzheimer’s disease. Animal models have been paramount in linking the regulation of fundamental neural processes, such as neurogenesis and myelination, to microbiome activation of microglia. Moreover, translational human studies are ongoing and will greatly enhance the field. Future studies will focus on understanding the mechanisms underlying the microbiota-gut-brain axis and attempt to elucidate microbial-based intervention and therapeutic strategies for neuropsychiatric disorders.

Bacteriophages: Uncharacterized and Dynamic Regulators of the Immune System

The human gut is an extremely active immunological site interfacing with the densest microbial community known to colonize the human body, the gut microbiota. Despite tremendous advances in our comprehension of how the gut microbiota is involved in human health and interacts with the mammalian immune system, most studies are incomplete as they typically do not consider bacteriophages. These bacterial viruses are estimated to be as numerous as their bacterial hosts, with tremendous and mostly uncharacterized genetic diversity. In addition, bacteriophages are not passive members of the gut microbiota, as highlighted by the recent evidence for their active involvement in human health. Yet, how bacteriophages interact with their bacterial hosts and the immune system in the human gut remains poorly described. Here, we aim to fill this gap by providing an overview of bacteriophage communities in the gut during human development, detailing recent findings for their bacterial-mediated effects on the immune response and summarizing the latest evidence for direct interactions between them and the immune system. The dramatic increase in antibiotic-resistant bacterial pathogens has spurred a renewed interest in using bacteriophages for therapy, despite the many unknowns about bacteriophages in the human body. Going forward, more studies encompassing the communities of bacteria, bacteriophages, and the immune system in diverse health and disease settings will provide invaluable insight into this dynamic trio essential for human health.

Phage therapy administered noninvasively could be effective in thin tubes subject to episodic flow despite washout: a simulation study

Bacteriophages (phages) have been proposed as candidates for the treatment of bacterial infections in light of emerging antibiotic-resistant microorganisms. Bacterial growth within thin tubes is a particular concern, such as in urinary tract infections and colonization of catheters. However, it is not clear whether phage administration to the urinary tract or in catheters could be effective in the context of flow to the outside (i.e. voiding or saline flush). Here, we adapt a previous model of phage infection to a thin tube geometry mimicking the spatial organization of the urinary tract, including bacterial motility and episodic flow during which phages are washed out of the system. We show that density-dependent dynamics permit propagation of the phage infection and that washout has little effect on the timing of bacterial clearance. In addition, instillation of phage at the bottom ~0.1 mm of the tract is effective in our computational model, suggesting that therapeutic phage introduced non-invasively could be efficacious in such situations.

Alpha-Synuclein Pathology and the Role of the Microbiota in Parkinson's Disease

There is a principle in science, known as Occam’s razor, that says the correct solution is usually the one with the simplest explanation. The microbiota-gut-brain axis, an interdependent series of communication loops between the enteric nervous system (ENS), the microbiota, the gut, and the brain, offers important insight into how changes in our gut affect distant organs like our brains. The inherent complexity of this axis with the crosstalk between the immune system, inflammatory states, and the thousands of bacteria, viral, and fungal species that together make up the microbiota make studying the interactions that govern this axis difficult and far from parsimonious. It is becoming increasingly clear that the microbiota is integral to this axis. Disruption of the healthy flora, a phenomenon collectively referred to as dysbiosis, has been implicated as a driver for several diseases such as irritable bowel syndrome, rheumatoid arthritis, obesity, diabetes, liver disease, and neurological disorders such as depression, anxiety, and Parkinson’s disease (PD). Teasing apart these complex interactions as they pertain to PD is critical for our understanding of this debilitating disease, but more importantly, for the development of future treatments. So far, treatments have been unable to stop this neurodegenerative disease, succeeding only in briefly dampening symptoms and buying patients time before the inevitable loss of function ensues. Given that the 10 years prognosis for death or life-limiting disability with someone diagnosed with PD is upwards of 80%, there is a desperate need for curative treatments that go beyond symptom management. If PD does begin in the periphery with bidirectional communication between the microbiota and the immune system, as recent literature suggests, there is an exciting possibility that progression could be stopped before it reaches the brain. This systematic review assesses the current literature surrounding the role of the microbiota in the pathogenesis of alpha-synucleinopathies and explores the hypothesis that alpha-synuclein folding is modulated by the microbiota. Furthermore, we discuss how changes in the gut environment can lead to pathology and outline the implications that advances in understanding the interactions between host and microbiota will have on future research and the development of potential biomarkers.

Parkinson's disease and bacteriophages as its overlooked contributors

Recent studies suggest that alterations in the gut phagobiota may contribute to pathophysiological processes in mammals; however, the association of bacteriophage community structure with Parkinson's disease (PD) has not been yet characterized. Towards this end, we used a published dataset to analyse bacteriophage composition and determine the phage/bacteria ratio in faecal samples from drug-naive PD patients and healthy participants. Our analyses revealed significant alterations in the representation of certain bacteriophages in the phagobiota of PD patients. We identified shifts of the phage/bacteria ratio in lactic acid bacteria known to produce dopamine and regulate intestinal permeability, which are major factors implicated in PD pathogenesis. Furthermore, we observed the depletion of Lactococcus spp. in the PD group, which was most likely due to the increase of lytic c2-like and 936-like lactococcal phages frequently present in dairy products. Our findings add bacteriophages to the list of possible factors associated with the development of PD, suggesting that gut phagobiota composition may serve as a diagnostic tool as well as a target for therapeutic intervention, which should be confirmed in further studies. Our results open a discussion on the role of environmental phages and phagobiota composition in health and disease.