Changes in the gut microbiome community of nonhuman primates following radiation injury

Nicotinamide riboside alleviates ionizing radiation-induced intestinal senescence by alleviating oxidative damage and regulating intestinal metabolism

INTRODUCTION

The intestine, frequently subjected to pelvic or abdominal radiotherapy, is particularly vulnerable to delayed effects of acute radiation exposure (DEARE) owing to its high radiation sensitivity. Radiation-induced intestinal senescence, a result of DEARE, profoundly affects the well-being and quality of life of radiotherapy patients. However, targeted pharmaceutical interventions for radiation-induced senescence are currently scarce. Our findings showcase that nicotinamide riboside(NR) effectively alleviates radiation-induced intestinal senescence, offering crucial implications for utilizing NR as a pharmacological agent to combat intestinal DEARE.

OBJECTIVES

The aim of this study was to investigate the ability of NR to reduce radiation induced intestinal senescence and explore its related mechanisms.

METHODS

Male C57BL/6J mice were randomly divided into CON, IR, and IR + NR groups. The mice in the IR and IR + NR groups were subjected to a 6.0 Gy γ-ray total body exposure. After 8 weeks, the mice in the IR + NR group received NR via gavage at a dose of 400 mg/kg/d for 21 days. Then the mice were used for sample collection.

RESULTS

Our results demonstrate that NR can significantly mitigate radiation-induced intestinal senescence. Furthermore, our findings indicate that NR can mitigate oxidative damage, restore the normal function of intestinal stem cells, regulate the disruption of the intestinal symbiotic ecosystem and address metabolic abnormalities. In addition, the underlying mechanisms involve the activation of SIRT6, SIRT7 and the inhibition of the mTORC1 pathway by NR.

CONCLUSION

In conclusion, our results reveal the substantial inhibitory effects of NR on radiation-induced intestinal senescence. These findings offer valuable insights into the potential therapeutic use of NR as a pharmacological agent for alleviating intestinal DEARE.

A mechanistic understanding of the effect of Staphylococcus aureus VraS histidine kinase single point mutation on antibiotic resistance

Bacterial genomic mutations in Staphylococcus aureus (S. aureus) have been detected in isolated resistant clinical strains, yet their mechanistic effect on the development of antimicrobial resistance remains unclear. The resistance-associated regulatory systems acquire adaptive mutations under stress conditions that may lead to a gain of function effect and contribute to the resistance phenotype. Here, we investigate the effect of a single-point mutation (T331I) in VraS histidine kinase, part of the VraSR two-component system in S. aureus. VraSR senses and responds to environmental stress signals by upregulating gene expression for cell wall synthesis. A combination of enzyme kinetics, microbiological, and transcriptomic analysis revealed the mechanistic effect of the mutation on VraS and S. aureus . Michaelis Menten's kinetics show that the VraS mutation caused an increase in the autophosphorylation rate of VraS and enhanced its catalytic efficiency. The introduction of the mutation through recombineering coupled with CRISPR-Cas9 counterselection to the Newman strain wild-type (WT) genome doubled the minimum inhibitory concentration of three cell wall-targeting antibiotics. The mutation caused an enhanced S. aureus growth rate at sub-lethal doses of the antibiotics, confirming the causative effect of mutation on bacterial persistence. Transcriptomic analysis showed a genome-wide alteration in gene expression levels and protein-protein interaction network of the mutant compared to the WT strain after exposure to vancomycin. The results suggest that vraS mutation causes several mechanistic changes at the protein and cellular levels that favor bacterial survival under antibiotic stress and cause the mutation-harboring strains to become the dominant population during infection.

Importance

Rising antimicrobial resistance (AMR) is a global health problem. Mutations in the two- component system have been linked to drug- resistance in Staphylococcus aureus , yet the exact mechanism through which these mutations work is understudied. We investigated the T331I mutation in the vraS gene linked to sensing and responding to cell wall stress. The mutation caused changes at the protein level by increasing the catalytic efficiency of VraS kinase activity. Introducing the mutation to the genome of an S. aureus strain resulted in changes in the phenotypic antibiotic susceptibility, growth kinetics, and genome-wide transcriptomic alterations. By a combination of enzyme kinetics, microbiological, and transcriptomic approaches, we highlight how small genetic changes can significantly impact bacterial physiology and survival under antibiotic stress. Understanding the mechanistic basis of antibiotic resistance is crucial to guide the development of novel therapeutic agents to combat AMR.

Longitudinal prevalence and co-carriage of pathogens associated with nursing home acquired pneumonia in three long-term care facilities

Nursing home acquired pneumonia (NHAP), and its subset - aspiration-associated pneumonia, is a leading cause of morbidity and mortality among residents in long-term care facilities (LTCFs). Understanding colonization dynamics of respiratory pathogens in LTCF residents is essential for effective infection control. This study examines the longitudinal trends in prevalence, persistence, bacterial load, and co-colonization patterns of five respiratory pathogens in three LTCFs in Phoenix, Arizona. Anterior nares and oral swabs were collected every other week and tested using qPCR for Haemophilus influenzae, Pseudomonas aeruginosa, Streptococcus pneumoniae, Staphylococcus aureus, and Chlamydia pneumoniae. Weekly average positivity rates were 17.75% for H. influenzae (0% - 39.39%), 9.95% for P. aeruginosa (0% - 37.74%), 31.89% for S. pneumoniae (1.79% - 41.67%), and for 28.00% for S. aureus (0% - 55.36%). C. pneumoniae was not detected. H. influenzae and S. pneumoniae predominantly colonized the oral cavity, while P. aeruginosa and S. aureus predominantly colonized the nasal cavity. S. pneumoniae and S. aureus colonizations were significantly more persistent than H. influenzae and P. aeruginosa, with persistence correlating with significantly higher bacterial loads. Co-colonization did occur in ~20% of positive samples, but appeared to be due to random chance. This study reveals distinct colonization patterns among respiratory pathogens in LTCF residents, highlighting differences in site-specific prevalence, persistence, and bacterial load. These findings underscore the importance of longitudinal monitoring to inform targeted infection control strategies in LTCFs.

Alterations in Gut Microbiota Correlate With Hematological Injuries Induced by Radiation in Beagles

Dynamics of gut microbiota and their associations with the corresponding hematological injuries postradiation remain to be elucidated. Using single whole-body exposure to 60Co-γ ray radiation at the sublethal dose of 2.5 Gy, we developed a beagle model of acute radiation syndrome (ARS) and then monitored the longitudinal changes of gut microbiome and hematology for 45 days. We found that the absolute counts of circulating lymphocytes, neutrophils, and platelets were sharply declined postradiation, accompanied by a largely shifted composition of gut microbiome that manifested as a significantly increased ratio of Firmicutes to Bacteroidetes. In irradiated beagles, alterations in hematological parameters reached a nadir on day 14, sustaining for 1 week, which were gradually returned to the normal levels thereafter. However, no structural recovery of gut microbiota was observed throughout the study. Fecal metagenomics revealed that irradiation increased the relative abundances of genus Streptococcus, species Lactobacillus animalis and Lactobacillus murinus, but decreased those of genera Prevotella and Bacteroides. Metagenomic functions prediction demonstrated that 26 altered KEGG pathways were significantly enriched on Day 14 and 35 postradiation. Furthermore, a total of 43 bacterial species were found to correlate well with hematological parameters by Spearman's analysis. Our results provide an insight into the longitudinal changes in intestinal microbiota at different clinical stages during ARS in canine. Several key microbes those tightly associated with the hematological alterations may serve as biomarkers to discriminate the different phases of host with ARS.

MICROBIOME AND INFLAMMASOME ALTERATIONS FOUND DURING RADIATION DOSE FINDING IN A SINCLAIR MINIPIG MODEL OF GASTROINTESTINAL ACUTE RADIATION SYNDROME

ABSTRACT

Both abdominal radiotherapy and a nuclear event can result in gastrointestinal symptoms, including acute radiation syndrome (GI-ARS). GI-ARS is characterized by compromised intestinal barrier integrity increasing the risk for infectious complications. Physiologically relevant animal models are crucial for elucidating host responses and therapeutic targets. We aimed to determine the radiation dose requirements for creating GI-ARS in the Sinclair minipig. Male, sexually mature swine were randomly divided into sham (n = 6) and three lower hemibody radiation dosage groups of 8, 10, and 12 Gy (n = 5/group) delivered using linear accelerator-derived x-rays (1.9 Gy/min). Animals were monitored for GI-ARS symptoms for 14 days with rectal swab and blood collection at days 0-3, 7, 10, and 14 followed by necropsy for western blotting and histology. Dose-dependent increases in weight loss, diarrhea severity, and mortality (log-rank test, P = 0.041) were seen. Villi length was significantly reduced in all irradiated animals compared to controls ( P < 0.001). Serum citrulline decreased and bacterial translocation increased after irradiation compared to controls. Increased NLRP3 levels in post-mortem jejunum were seen ( P = 0.0043) as well as increased IL-1β levels in the 12 Gy group ( P = 0.041). Radiation dose and survival were associated with significant gut microbial community shifts in beta diversity. Moreover, decedents had increased Porphyromonas, Campylobacter, Bacteroides , Parvimonas , and decreased Fusobacterium and decreased Aerococcus, Lactobacillus, Prevotella, and Streptococcus . Our novel Sinclair minipig model showed dose-dependent clinical symptoms of GI-ARS. These findings provide invaluable insights into the intricate interplay between GI-ARS, intestinal inflammation, and gut microbiota alterations offering potential targets for therapeutic and diagnostic interventions after radiation exposure.

Gastroprotective and microbiome-modulating effects of ubiquinol in rats with radiation-induced enteropathy

Radiation enteritis is a frequently encountered issue for patients receiving radiotherapy and has a significant impact on cancer patients' quality of life. The gut microbiota plays a pivotal role in intestinal function, yet the impact of irradiation on gut microorganisms is not fully understood. This study explores the gastroprotective effect and gut microbiome-modulating potential of ubiquinol (Ubq), the reduced form of the powerful antioxidant CoQ-10. For this purpose, male albino rats were randomly assigned to four groups: Control, IRR (acute 7 Gy γ-radiation), Ubq_Post (Ubq for 7 days post-irradiation), and Ubq_Pre/Post (Ubq for 7 days pre and 7 days post-irradiation). The fecal microbiomes of all groups were profiled by 16S rRNA amplicon sequencing followed by bioinformatics and statistical analysis. Histopathological examination of intestinal tissue indicated severe damage in the irradiated group, which was mitigated by ubiquinol with enhanced regeneration, goblet cells, and intestinal alkaline phosphatase expression. Compared to the irradiated group, the Ubq-treated groups had a significant recovery of intestinal interleukin-1β, caspase-3, nitric oxide metabolites, and thio-barbituric reactive substances to near-healthy levels. Ubq_Pre/Post group displayed elevated peroxisome proliferator-activated receptor (PPAR-γ) level, suggesting heightened benefits. Serum insulin reduction in irradiated rats improved post-Ubq treatment, with a possible anti-inflammatory effect on the pancreatic tissue. Fecal microbiota profiling revealed a dysbiosis state with a reduction of bacterial diversity post-irradiation, which was re-modulated in the Ubq treated groups to profiles that are indistinguishable from the control group. These findings underscore Ubq's gastroprotective effects against radiation-induced enteritis and its potential in restoring the gut microbiota's diversity and balance.

Early and long-term responses of intestinal microbiota and metabolites to 131I treatment in differentiated thyroid cancer patients

BACKGROUND

Multiple high doses of 131I therapy in patients with differentiated thyroid cancer (DTC) might disrupt the balance of gut microbiota and metabolites. This study aimed to investigate the alterations of intestinal bacteria and metabolism over two courses of 131I therapy, explore the interactions, and construct diagnostic models reflecting enteric microecology based on 131I therapy.

METHODS

A total of 81 patients were recruited for the first 131I therapy (131I-1st), among whom 16 received a second course (131I-2nd) after half a year. Fecal samples were collected 1 day before (Pre-131I-1st/2nd) and 3 days after (Post-131I-1st/2nd) 131I therapy for microbiome (16S rRNA gene sequencing) and metabolomic (LC-MS/MS) analyses.

RESULTS

A total of six microbial genera and 11 fecal metabolites enriched in three pathways were identified to show significant differences between Pre-131I-1st and other groups throughout the two courses of 131I treatment. In the Post-131I-1st group, the beneficial bacteria Bifidobacterium, Lachnoclostridium, uncultured_bacterium_f_Lachnospiraceae, and Lachnospiraceae_UCG004 were abundant and the radiation-sensitive pathways of linoleic acid (LA), arachidonic acid, and tryptophan metabolism were inhibited compared with the Pre-131I-1st group. Compared with the Pre-131I-1st group, the Pre-131I-2nd group exhibited a reduced diversity of flora and differentially expressed metabolites, with a low abundance of beneficial bacteria and dysregulated radiation-sensitive pathways. However, less significant differences in microbiota and metabolites were found between the Pre/Post-131I-2nd groups compared with those between the Pre/Post-131I-1st groups. A complex co-occurrence was observed between 6 genera and 11 metabolites, with Lachnoclostridium, Lachnospiraceae_UCG004, Escherichia-Shigella, and LA-related metabolites contributing the most. Furthermore, combined diagnostic models of charactered bacteria and metabolites answered well in the early, long-term, and dose-dependent responses for 131I therapy.

CONCLUSIONS

Different stages of 131I therapy exert various effects on gut microecology, which play an essential role in regulating radiotoxicity and predicting the therapeutic response.

Human gut microbiota interactions shape the long-term growth dynamics and evolutionary adaptations of Clostridioides difficile

Clostridioides difficile can transiently or persistently colonize the human gut, posing a risk factor for infections. This colonization is influenced by complex molecular and ecological interactions with human gut microbiota. By investigating C. difficile dynamics in human gut communities over hundreds of generations, we show patterns of stable coexistence, instability, or competitive exclusion. Lowering carbohydrate concentration shifted a community containing C. difficile and the prevalent human gut symbiont Phocaeicola vulgatus from competitive exclusion to coexistence, facilitated by increased cross-feeding. In this environment, C. difficile adapted via single-point mutations in key metabolic genes, altering its metabolic niche from proline to glucose utilization. These metabolic changes substantially impacted inter-species interactions and reduced disease severity in the mammalian gut. In sum, human gut microbiota interactions are crucial in shaping the long-term growth dynamics and evolutionary adaptations of C. difficile, offering key insights for developing anti-C. difficile strategies.

Effects of combined ciprofloxacin and Neulasta therapy on intestinal pathology and gut microbiota after high-dose irradiation in mice

Introduction

Treatments that currently exist in the strategic national stockpile for acute radiation syndrome (ARS) focus on the hematopoietic subsyndrome, with no treatments on gastrointestinal (GI)-ARS. While the gut microbiota helps maintain host homeostasis by mediating GI epithelial and mucosal integrity, radiation exposure can alter gut commensal microbiota which may leave the host susceptible to opportunistic pathogens and serious sequelae such as sepsis. To mitigate the effects of hematopoietic ARS irradiation, currently approved treatments exist in the form of colony stimulating factors and antibiotics: however, there are few studies examining how these therapeutics affect GI-ARS and the gut microbiota. The aim of our study was to examine the longitudinal effects of Neulasta and/or ciprofloxacin treatment on the gut microbiota after exposure to 9.5 Gy 60Co gamma-radiation in mice.

Methods

The gut microbiota of vehicle and drug-treated mice exposed to sham or gamma-radiation was characterized by shotgun sequencing with alpha diversity, beta diversity, and taxonomy analyzed on days 2, 4, 9, and 15 post-irradiation.

Results

No significant alpha diversity differences were observed following radiation, while beta diversity shifts and taxonomic profiles revealed significant alterations in Akkermansia, Bacteroides, and Lactobacillus. Ciprofloxacin generally led to lower Shannon diversity and Bacteroides prevalence with increases in Akkermansia and Lactobacillus compared to vehicle treated and irradiated mice. While Neulasta increased Shannon diversity and by day 9 had more similar taxonomic profiles to sham than ciprofloxacin-or vehicle-treated irradiated animals. Combined therapy of Neulasta and ciprofloxacin induced a decrease in Shannon diversity and resulted in unique taxonomic profiles early post-irradiation, returning closer to vehicle-treated levels over time, but persistent increases in Akkermansia and Bacteroides compared to Neulasta alone.

Discussion

This study provides a framework for the identification of microbial elements that may influence radiosensitivity, biodosimetry and the efficacy of potential therapeutics. Moreover, increased survival from H-ARS using these therapeutics may affect the symptoms and appearance of what may have been subclinical GI-ARS.

Ferroptosis, Inflammation, and Microbiome Alterations in the Intestine in the Göttingen Minipig Model of Hematopoietic-Acute Radiation Syndrome

Hematopoietic acute radiation syndrome (H-ARS) involves injury to multiple organ systems following total body irradiation (TBI). Our laboratory demonstrated that captopril, an angiotensin-converting enzyme inhibitor, mitigates H-ARS in Göttingen minipigs, with improved survival and hematopoietic recovery, as well as the suppression of acute inflammation. However, the effects of captopril on the gastrointestinal (GI) system after TBI are not well known. We used a Göttingen minipig H-ARS model to investigate captopril's effects on the GI following TBI (60Co 1.79 or 1.80 Gy, 0.42-0.48 Gy/min), with endpoints at 6 or 35 days. The vehicle or captopril (0.96 mg/kg) was administered orally twice daily for 12 days, starting 4 h post-irradiation. Ilea were harvested for histological, protein, and RNA analyses. TBI increased congestion and mucosa erosion and hemorrhage, which were modulated by captopril. GPX-4 and SLC7A11 were downregulated post-irradiation, consistent with ferroptosis at 6 and 35 days post-irradiation in all groups. Interestingly, p21/waf1 increased at 6 days in vehicle-treated but not captopril-treated animals. An RT-qPCR analysis showed that radiation increased the gene expression of inflammatory cytokines IL1B, TNFA, CCL2, IL18, and CXCL8, and the inflammasome component NLRP3. Captopril suppressed radiation-induced IL1B and TNFA. Rectal microbiome analysis showed that 1 day of captopril treatment with radiation decreased overall diversity, with increased Proteobacteria phyla and Escherichia genera. By 6 days, captopril increased the relative abundance of Enterococcus, previously associated with improved H-ARS survival in mice. Our data suggest that captopril mitigates senescence, some inflammation, and microbiome alterations, but not ferroptosis markers in the intestine following TBI.

Microbiota as the unifying factor behind the hallmarks of cancer

The human microbiota is a complex ecosystem that colonizes body surfaces and interacts with host organ systems, especially the immune system. Since the composition of this ecosystem depends on a variety of internal and external factors, each individual harbors a unique set of microbes. These differences in microbiota composition make individuals either more or less susceptible to various diseases, including cancer. Specific microbes are associated with cancer etiology and pathogenesis and several mechanisms of how they drive the typical hallmarks of cancer were recently identified. Although most microbes reside in the distal gut, they can influence cancer initiation and progression in distant tissues, as well as modulate the outcomes of established cancer therapies. Here, we describe the mechanisms by which microbes influence carcinogenesis and discuss their current and potential future applications in cancer diagnostics and management.

Novel biomarkers for acute radiation injury and countermeasures using large and small animal models and multi-omics approach

Threats of radiological or nuclear disasters are of serious concern and a top priority for government agencies involved in domestic security and public health preparedness. There is a need for sensitive bioassays for biodosimetric assessments of radiation exposures originating from unanticipated nuclear/radiological events. The Food and Drug Administration Animal Rule approval pathway requires an in-depth understanding of the mechanisms of radiation injury, drug efficacy and biomarkers for radiation medical countermeasure approval. Biomarkers can be helpful for extrapolating the efficacious countermeasure dose in animals to humans. We summarised here our studies to identify candidate biomarkers for the acute radiation injury using various omic platforms (metabolomics/lipidomics, proteomics, microbiome and transcriptomics/microRNA) using murine and non-human primate models conducted in our laboratory. Multi-omic platforms appear to be highly useful in assessing radiation exposure levels and for identifying biomarkers of radiation injury and countermeasure efficacy, which can expedite the regulatory approval of countermeasures.

The Effects of Ionizing Radiation on Gut Microbiota: What Can Animal Models Tell Us?-A Systematic Review

BACKGROUND

The gut microbiota is relatively stable; however, various factors can precipitate an imbalance that is known to be associated with various diseases. We aimed to conduct a systematic literature review of studies reporting the effects of ionizing radiation on the composition, richness, and diversity of the gut microbiota of animals.

METHODS

A systematic literature search was performed in PubMed, EMBASE, and Cochrane library databases. The standard methodologies expected by Cochrane were utilized.

RESULTS

We identified 3531 non-duplicated records and selected twenty-nine studies after considering the defined inclusion criteria. The studies were found to be heterogeneous, with significant differences in the chosen populations, methodologies, and outcomes. Overall, we found evidence of an association between ionizing radiation exposure and dysbiosis, with a reduction of microbiota diversity and richness and alterations in the taxonomic composition. Although differences in taxonomic composition varied across studies, Proteobacteria, Verrucomicrobia, Alistipes, and Akkermancia most consistently reported to be relatively more abundant after ionizing radiation exposure, whereas Bacteroidetes, Firmicutes, and Lactobacillus were relatively reduced.

CONCLUSIONS

This review highlights the effect of ionizing exposure on gut microbiota diversity, richness, and composition. It paves the way for further studies on human subjects regarding gastrointestinal side effects in patients submitted to treatments with ionizing radiation and the development of potential preventive, therapeutic approaches.

Gut microbiota and ionizing radiation-induced damage: Is there a link?

According to observational findings, ionizing radiation (IR) triggers dysbiosis of the intestinal microbiota, affecting the structural composition, function, and species of the gut microbiome and its metabolites. These modifications can further exacerbate IR-induced damage and amplify proinflammatory immune responses. Conversely, commensal bacteria and favorable metabolites can remodel the IR-disturbed gut microbial structure, promote a balance between anti-inflammatory and proinflammatory mechanisms in the body, and mitigate IR toxicity. The discovery of effective and safe remedies to prevent and treat radiation-induced injuries is vitally needed because of the proliferation of radiation toxicity threats produced by recent radiological public health disasters and increasing medical exposures. This review examines how the gut microbiota and its metabolites are linked to the processes of IR-induced harm. We highlight protective measures based on interventions with gut microbes to optimize the distress caused by IR damage to human health. We offer prospects for research in emerging and promising areas targeting the prevention and treatment of IR-induced damage.

A Review of Radiation-Induced Alterations of Multi-Omic Profiles, Radiation Injury Biomarkers, and Countermeasures

Increasing utilization of nuclear power enhances the risks associated with industrial accidents, occupational hazards, and the threat of nuclear terrorism. Exposure to ionizing radiation interferes with genomic stability and gene expression resulting in the disruption of normal metabolic processes in cells and organs by inducing complex biological responses. Exposure to high-dose radiation causes acute radiation syndrome, which leads to hematopoietic, gastrointestinal, cerebrovascular, and many other organ-specific injuries. Altered genomic variations, gene expression, metabolite concentrations, and microbiota profiles in blood plasma or tissue samples reflect the whole-body radiation injuries. Hence, multi-omic profiles obtained from high-resolution omics platforms offer a holistic approach for identifying reliable biomarkers to predict the radiation injury of organs and tissues resulting from radiation exposures. In this review, we performed a literature search to systematically catalog the radiation-induced alterations from multi-omic studies and radiation countermeasures. We covered radiation-induced changes in the genomic, transcriptomic, proteomic, metabolomic, lipidomic, and microbiome profiles. Furthermore, we have covered promising multi-omic biomarkers, FDA-approved countermeasure drugs, and other radiation countermeasures that include radioprotectors and radiomitigators. This review presents an overview of radiation-induced alterations of multi-omics profiles and biomarkers, and associated radiation countermeasures.

Armed Forces Radiobiology Research Institute/Uniformed Services University of the Health Sciences perspective on space radiation countermeasure discovery

There is a need to develop and deploy medical countermeasures (MCMs) in order to support astronauts during space missions against excessive exposures to ionizing radiation exposure. The radiation environment of extraterrestrial space is complex and is characterized by nearly constant fluences of elemental atomic particles (protons being a dominant particle type) with widely different energies and ionization potentials. Chronic exposure to such ionizing radiation carries both near- and long-term health risks, which are generally related to the relative intensity and duration of exposure. These radiation-associated health risks can be managed only to a limited extent by physical means, but perhaps they might be more effectively managed biomedically. The Armed Forces Radiobiology Research Institute/Uniformed Services University of the Health Sciences has a long history of researching and developing MCMs specifically designed to support terrestrial-based military missions involving a radiation-threat component. The development of MCMs for both low and high doses of radiation are major aims of current research, and as such can provide lessons learned for the development of countermeasures applicable to future space missions and its extraterrestrial radiation environment.

Anthropogenic Disturbance Impacts Gut Microbiome Homeostasis in a Malagasy Primate

Increasing anthropogenic disturbances in Madagascar are exerting constrains on endemic Malagasy lemurs and their habitats, with possible effects on their health and survival. An important component of health is the gut microbiome, which might be disrupted by various stressors associated with environmental change. We have studied the gut microbiome of gray-brown mouse lemurs (Microcebus griseorufus), one of the smallest Malagasy primates and an important model of the convergent evolution of diseases. We sampled two sites: one situated in a national park and the other consisting of a more disturbed site around human settlement. We found that more intense anthropogenic disturbances indeed disrupted the gut microbiome of this lemur species marked by a reduction in bacterial diversity and a shift in microbial community composition. Interestingly, we noted a decrease in beneficial bacteria (i.e., members of the Bacteroidaceae family) together with a slight increase in disease-associated bacteria (i.e., members of the Veillonellaceae family), and alterations in microbial metabolic functions. Because of the crucial services provided by the microbiome to pathogen resistance and host health, such negative alterations in the gut microbiome of mouse lemurs inhabiting anthropogenically disturbed habitats might render them susceptible to diseases and ultimately affecting their survival in the shrinking biodiversity seen in Madagascar. Gut microbiome analyses might thus serve as an early warning signal for pending threats to lemur populations.

Differences in the Establishment of Gut Microbiota and Metabolome Characteristics Between Balb/c and C57BL/6J Mice After Proton Irradiation

Although proton irradiation is ubiquitous in outer space as well as in the treatment of human diseases, its effects remain largely unclear. This work aimed to investigate and compare the composition of gut microbiota composition of mice in different species exposed to high-dose radiation. Male Balb/c mice and C57BL/6J mice were irradiated at a high dose (5Gy). Fecal specimens before and after irradiation were subjected to high-throughput sequencing (HTS) for the amplification of 16S rRNA gene sequences. We observed substantial changes in gut microbial composition among mice irradiated at high doses compared to non-irradiated controls. The changes included both the alpha and beta diversities. Furthermore, there were 11 distinct alterations in the irradiation group compared to the non-radiation control, including the families Muribaculaceae, Ruminococcaceae, Lactobacillus, Lachnospiraceae_NK4A136, Bacteroides, Alistipes, Clostridiales, Muribaculum, and Alloprevotella. Such alterations in the gut microbiome were accompanied by alterations in metabolite abundances, while at the metabolic level, 32 metabolites were likely to be potential biomarkers. Some alterations may have a positive effect on the repair of intestinal damage. Simultaneously, metabolites were predicted to involve multiple signal pathways, such as Urea Cycle, Ammonia Recycling, Alpha Linolenic Acid and Linoleic Acid Metabolism, Ketone Body Metabolism, Aspartate Metabolism, Phenylacetate Metabolism, Malate-Aspartate Shuttle, Arginine and Proline Metabolism and Carnitine Synthesis. Metabolites produced by proton irradiation in the microbial region play a positive role in repairing damage, making this area worthy of further experimental exploration. The present work offers an analytical and theoretical foundation to investigate how proton radiation affects the treatment of human diseases and identifies potential biomarkers to address the adverse effects of radiation.