Review

Authors: Aimee Shen, Adrianne N Edwards, Mahfuzur R Sarker...

As obligate anaerobes, clostridial pathogens depend on their metabolically dormant, oxygen-tolerant spore form to transmit disease. However, the molecular mechanisms by which those spores germinate to initiate infection and then form new spores to transmit infection remain poorly understood. While sporulation and germination have been well characterized in and , striking differences in the regulation of these processes have been observed between the bacilli and the clostridia, with even some conserved proteins exhibiting differences in their requirements and functions. Here, we review our current understanding of how clostridial pathogens, specifically , , and , induce sporulation in response to environmental cues, assemble resistant spores, and germinate metabolically dormant spores in response to environmental cues. We also discuss the direct relationship between toxin production and spore formation in these pathogens.

Topics: Animals; Clostridium; Clostridium Infections; Humans; Spores, Bacterial

PubMed: 31858953
DOI: 10.1128/microbiolspec.GPP3-0017-2018

Review

Authors: Peter Dürre

Clostridia are Gram-positive, anaerobic, endospore-forming bacteria, incapable of dissimilatory sulfate reduction. Comprising approximately 180 species, the genus Clostridium is one of the largest bacterial genera. Physiology is mostly devoted to acid production. Numerous pathways are known, such as the homoacetate fermentation by acetogens, the propionate fermentation by Clostridium propionicum, and the butyrate/butanol fermentation by C. acetobutylicum, a well-known solvent producer. Clostridia degrade sugars, alcohols, amino acids, purines, pyrimidines, and polymers such as starch and cellulose. Energy conservation can be performed by substrate-level phosphorylation as well as by the generation of ion gradients. Endospore formation resembles the mechanism elucidated in Bacillus. Morphology, contents, and properties of spores are very similar to bacilli endospores. Sporulating clostridia usually form swollen mother cells and accumulate the storage substance granulose. However, clostridial sporulation differs by not employing the so-called phosphorelay. Initiation starts by direct phosphorylation of the master regulator Spo0A. The cascade of sporulation-specific sigma factors is again identical to what is known from Bacillus. The onset of sporulation is coupled in some species to either solvent (acetone, butanol) or toxin (e.g., C. perfringens enterotoxin) formation. The germination of spores is often induced by various amino acids, often in combination with phosphate and sodium ions. In medical applications, C. butyricum spores are used as a C. difficile prophylaxis and as treatment against diarrhea. Recombinant spores are currently under investigation and testing as antitumor agents, because they germinate only in hypoxic tissues (i.e., tumor tissue), allowing precise targeting and direct killing of tumor cells.

Topics: Anaerobiosis; Carboxylic Acids; Clostridium; Fermentation; Gene Expression Regulation, Bacterial; Spores, Bacterial

PubMed: 26104199
DOI: 10.1128/microbiolspec.TBS-0010-2012

Review

Authors: Raymond Kiu, Lindsay J Hall

Clostridium perfringens, a rapid-growing pathogen known to secrete an arsenal of >20 virulent toxins, has been associated with intestinal diseases in both animals and humans throughout the past century. Recent advances in genomic analysis and experimental systems make it timely to re-visit this clinically and veterinary important pathogen. This Review will summarise our understanding of the genomics and virulence-linked factors, including antimicrobial potentials and secreted toxins of this gut pathogen, and then its up-to-date clinical epidemiology and biological role in the pathogenesis of several important human and animal-associated intestinal diseases, including pre-term necrotising enterocolitis. Finally, we highlight some of the important unresolved questions in relation to C. perfringens-mediated infections, and implications for future research directions.

Topics: Animals; Bacterial Proteins; Bacterial Toxins; Clostridium Infections; Clostridium perfringens; Humans; Virulence

PubMed: 30082713
DOI: 10.1038/s41426-018-0144-8

Review

Authors: Bruno Bonnechère, Najaf Amin, Cornelia van Duijn...

There is a growing body of evidence highlighting there are significant changes in the gut microbiota composition and relative abundance in various neurological disorders. We performed a systematic review of the different microbiota altered in a wide range of neurological disorders (Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis, and stroke). Fifty-two studies were included representing 5496 patients. At the genus level, the most frequently involved microbiota are Akkermansia, Faecalibacterium, and Prevotella. The overlap between the pathologies was strongest for MS and PD, sharing eight genera (Akkermansia, Butyricicoccus, Bifidobacterium, Coprococcus, Dorea, Faecalibacterium, Parabacteroides, and Prevotella) and PD and stroke, sharing six genera (Enterococcus, Faecalibacterium, Lactobacillus, Parabacteroides, Prevotella, and Roseburia). The identification signatures overlapping for AD, PD, and MS raise the question of whether these reflect a common etiology or rather common consequence of these diseases. The interpretation is hampered by the low number and low power for AD, ALS, and stroke with ample opportunity for false positive and false negative findings.

Topics: Humans; Gastrointestinal Microbiome; Nervous System Diseases; Parkinson Disease; Microbiota; Akkermansia; Multiple Sclerosis; Prevotella; Clostridiaceae; Clostridiales; Stroke

PubMed: 36430144
DOI: 10.3390/ijms232213665

Authors: Hao Li, Haochen Xu, Youxiang Li...

Unruptured intracranial aneurysm (UIA) is a life-threatening cerebrovascular condition. Whether changes in gut microbial composition participate in the development of UIAs remains largely unknown. We perform a case-control metagenome-wide association study in two cohorts of Chinese UIA patients and control individuals and mice that receive fecal transplants from human donors. After fecal transplantation, the UIA microbiota is sufficient to induce UIAs in mice. We identify UIA-associated gut microbial species link to changes in circulating taurine. Specifically, the abundance of Hungatella hathewayi is markedly decreased and positively correlated with the circulating taurine concentration in both humans and mice. Consistently, gavage with H. hathewayi normalizes the taurine levels in serum and protects mice against the formation and rupture of intracranial aneurysms. Taurine supplementation also reverses the progression of intracranial aneurysms. Our findings provide insights into a potential role of H. hathewayi-associated taurine depletion as a key factor in the pathogenesis of UIAs.

Topics: Animals; Case-Control Studies; Clostridiaceae; Cohort Studies; Disease Progression; Fecal Microbiota Transplantation; Female; Gastrointestinal Microbiome; Humans; Intracranial Aneurysm; Male; Mice; Prognosis; Risk Factors; Taurine

PubMed: 32587239
DOI: 10.1038/s41467-020-16990-3

Authors: Pamela Vernocchi, Tommaso Gili, Federica Conte...

Several studies in recent times have linked gut microbiome (GM) diversity to the pathogenesis of cancer and its role in disease progression through immune response, inflammation and metabolism modulation. This study focused on the use of network analysis and weighted gene co-expression network analysis (WGCNA) to identify the biological interaction between the gut ecosystem and its metabolites that could impact the immunotherapy response in non-small cell lung cancer (NSCLC) patients undergoing second-line treatment with anti-PD1. Metabolomic data were merged with operational taxonomic units (OTUs) from 16S RNA-targeted metagenomics and classified by chemometric models. The traits considered for the analyses were: (i) condition: disease or control (CTRLs), and (ii) treatment: responder (R) or non-responder (NR). Network analysis indicated that indole and its derivatives, aldehydes and alcohols could play a signaling role in GM functionality. WGCNA generated, instead, strong correlations between short-chain fatty acids (SCFAs) and a healthy GM. Furthermore, commensal bacteria such as , Rikenellaceae, , Peptostreptococcaceae, Mogibacteriaceae and Clostridiaceae were found to be more abundant in CTRLs than in NSCLC patients. Our preliminary study demonstrates that the discovery of microbiota-linked biomarkers could provide an indication on the road towards personalized management of NSCLC patients.

Topics: Akkermansia; Alcohols; Aldehydes; Antineoplastic Agents, Immunological; Bacteroides; Carcinoma, Non-Small-Cell Lung; Clostridiaceae; Databases, Genetic; Disease Progression; Drug Monitoring; Fatty Acids, Volatile; Gastrointestinal Microbiome; Gene Expression Regulation, Neoplastic; Gene Regulatory Networks; Humans; Immunotherapy; Indoles; Lung Neoplasms; Metabolome; Metagenomics; Peptostreptococcus; Precision Medicine; Programmed Cell Death 1 Receptor; RNA, Ribosomal, 16S; Signal Transduction

PubMed: 33227982
DOI: 10.3390/ijms21228730

Authors: Masahiro Nagahama, Masaya Takehara, Julian I Rood...

The pathogenesis of clostridial myonecrosis or gas gangrene involves an interruption to the blood supply to the infected tissues, often via a traumatic wound, anaerobic growth of the infecting clostridial cells, the production of extracellular toxins, and toxin-mediated cell and tissue damage. This review focuses on host-pathogen interactions in -mediated and -mediated myonecrosis. The major toxins involved are α-toxin, which has phospholipase C and sphingomyelinase activity, and α-toxin, a β-pore-forming toxin that belongs to the aerolysin family. Although these toxins are cytotoxic, their effects on host cells are quite complex, with a range of intracellular cell signaling pathways induced by their action on host cell membranes.

Topics: Anaerobiosis; Bacterial Toxins; Clostridium perfringens; Clostridium septicum; Gas Gangrene; Host-Pathogen Interactions; Humans; Wounds and Injuries

PubMed: 31350831
DOI: 10.1128/microbiolspec.GPP3-0024-2018

Review

Authors: Joachim Frey, Laurent Falquet

The genomic sequence of Clostridium chauvoei, the etiological agent of blackleg, a severe disease of ruminants with high mortality specified by a myonecrosis reveals a chromosome of 2.8 million base-pairs and a cryptic plasmid of 5.5 kilo base-pairs. The chromosome contains the main pathways like glycolysis/gluconeogenesis, sugar metabolism, purine and pyrimidine metabolisms, but the notable absence of genes of the citric acid cycle and deficient or partially deficient amino acid metabolism for Histidine, Tyrosine, Phenylalanine, and Tryptophan. These essential amino acids might be acquired from host tissue damage caused by various toxins and by protein metabolism that includes 57 genes for peptidases, and several ABC transporters for amino acids import.

Topics: Animals; Clostridium Infections; Clostridium chauvoei; Metabolic Networks and Pathways; Virulence; Virulence Factors

PubMed: 25445013
DOI: 10.1016/j.resmic.2014.10.013

Review

Authors: Ana Sousa Gerós, Alison Simmons, Hal Drakesmith...

Iron is an essential element for almost all living organisms, but can be extremely toxic in high concentrations. All organisms must therefore employ homeostatic mechanisms to finely regulate iron uptake, usage and storage in the face of dynamic environmental conditions. The critical step in mammalian systemic iron homeostasis is the fine regulation of dietary iron absorption. However, as the gastrointestinal system is also home to >10 bacteria, all of which engage in their own programmes of iron homeostasis, the gut represents an anatomical location where the inter-kingdom fight for iron is never-ending. Here, we explore the molecular mechanisms of, and interactions between, host and bacterial iron homeostasis in the gastrointestinal tract. We first detail how mammalian systemic and cellular iron homeostasis influences gastrointestinal iron availability. We then focus on two important human pathogens, Salmonella and Clostridia; despite their differences, they exemplify how a bacterial pathogen must navigate and exploit this web of iron homeostasis interactions to avoid host nutritional immunity and replicate successfully. We then reciprocally explore how iron availability interacts with the gastrointestinal microbiota, and the consequences of this on mammalian physiology and pathogen iron acquisition. Finally, we address how understanding the battle for iron in the gastrointestinal tract might inform clinical practice and inspire new treatments for important diseases.

Topics: Animals; Clostridiaceae; Gastrointestinal Diseases; Gram-Positive Bacterial Infections; Homeostasis; Humans; Iron; Microbiota; Salmonella; Salmonella Infections

PubMed: 32639029
DOI: 10.1111/imm.13236

Review

Authors: Kaori Ohtani, Tohru Shimizu

The Gram-positive anaerobic bacterium Clostridium perfringens is widely distributed in nature, especially in soil and the gastrointestinal tracts of humans and animals. C. perfringens causes gas gangrene and food poisoning, and it produces extracellular enzymes and toxins that are thought to act synergistically and contribute to its pathogenesis. A complicated regulatory network of toxin genes has been reported that includes a two-component system for regulatory RNA and cell-cell communication. It is necessary to clarify the global regulatory system of these genes in order to understand and treat the virulence of C. perfringens. We summarize the existing knowledge about the regulatory mechanisms here.

Topics: Bacterial Proteins; Bacterial Toxins; Clostridium perfringens; Gene Expression Regulation, Bacterial; Host-Pathogen Interactions; Virulence

PubMed: 27399773
DOI: 10.3390/toxins8070207