Polyamines: emerging players in bacteria-host interactions

Cell free supernatants of Bifidobacterium adolescentis and Bifidobacterium longum suppress the tumor growth in colorectal cancer organoid model

The probiotic gut microbiome and its metabolites are pivotal in regulating host metabolism, inflammation, and immunity. Host genetics, colonization at birth, the host lifestyle, and exposure to diseases and drugs determine microbial composition. Dysbiosis and disruption of homeostasis in the beneficial microbiome have been reported to be involved in the tumorigenesis and progression of colorectal cancer (CRC). However, the influence of bacteria-secreted metabolites on CRC growth is yet to be fully elucidated. In this study, we compared the microbial composition of CRC patients to healthy controls to identify distinct patterns of microbiota-derived metabolites in CRC patients. Metagenomic analysis demonstrated that beneficial bacteria strains; Blautia producta, Bifidobacterium adolescentis, and Bifidobacterium longum decreased, while Parabacteroides distasonis and Bacteroides ovatus were more prevalent in the CRC patient group. Treatment of cancer organoid lines with microbial culture supernatants from Blautia producta, Bifidobacterium adolescentis, and Bifidobacterium longum showed remarkable inhibition of cancer growth. This study demonstrates that the bacterial metabolites depleted in CRC patients may inhibit cancer growth and highlights the effects of microbiome-derived metabolites on CRC growth.

Gut microbiota as a modulator of type 1 diabetes: A molecular perspective

Type 1 diabetes (T1D) is defined as an autoimmune metabolic disorder, characterized by destruction of pancreatic β-cells and high blood sugar levels. If left untreated, T1D results in severe health complications, including cardiovascular and kidney disease, as well as nerve damage, with ultimately grave consequences. Besides the role of genetic and certain environmental factors in T1D development, in the last decade, one new player emerged to affect T1D pathology as well, and that is a gut microbiota. Dysbiosis of gut bacteria can contribute to T1D by gut barrier disruption and the activation of autoimmune response, leading to the destruction of insulin producing cells, causing the development and aggravation of T1D symptoms. The relationship between gut microbiota and diabetes is complex and varies between individuals and additional research is needed to fully understand the effects of gut microbiome alternations in T1D pathogenesis. Therefore, the goal of this review is to understand the current knowledge in underlying molecular mechanism of gut microbiota effects, which leads to the new approaches for further studies in the prevention and treatment of T1D.

Fibre & fermented foods: differential effects on the microbiota-gut-brain axis

The ability to manipulate brain function through the communication between the microorganisms in the gastrointestinal tract and the brain along the gut-brain axis has emerged as a potential option to improve cognitive and emotional health. Dietary composition and patterns have demonstrated a robust capacity to modulate the microbiota-gut-brain axis. With their potential to possess pre-, pro-, post-, and synbiotic properties, dietary fibre and fermented foods stand out as potent shapers of the gut microbiota and subsequent signalling to the brain. Despite this potential, few studies have directly examined the mechanisms that might explain the beneficial action of dietary fibre and fermented foods on the microbiota-gut-brain axis, thus limiting insight and treatments for brain dysfunction. Herein, we evaluate the differential effects of dietary fibre and fermented foods from whole food sources on cognitive and emotional functioning. Potential mediating effects of dietary fibre and fermented foods on brain health via the microbiota-gut-brain axis are described. Although more multimodal research that combines psychological assessments and biological sampling to compare each food type is needed, the evidence accumulated to date suggests that dietary fibre, fermented foods, and/or their combination within a psychobiotic diet can be a cost-effective and convenient approach to improve cognitive and emotional functioning across the lifespan.

Polyamines in Plant-Pathogen Interactions: Roles in Defense Mechanisms and Pathogenicity with Applications in Fungicide Development

Polyamines (PAs), which are aliphatic polycationic compounds with a low molecular weight, are found in all living organisms and play essential roles in plant-pathogen interactions. Putrescine, spermidine, and spermine, the most common PAs in nature, respond to and function differently in plants and pathogens during their interactions. While plants use certain PAs to enhance their immunity, pathogens exploit PAs to facilitate successful invasion. In this review, we compile recent studies on the roles of PAs in plant-pathogen interactions, providing a comprehensive overview of their roles in both plant defense and pathogen pathogenicity. A thorough understanding of the functions of PAs and conjugated PAs highlights their potential applications in fungicide development. The creation of new fungicides and compounds derived from PAs demonstrates their promising potential for further research and innovation in this field.

The telencephalon is a neuronal substrate for systemic inflammatory responses in teleosts via polyamine metabolism

Systemic inflammation elicits sickness behaviors and fever by engaging a complex neuronal circuitry that begins in the preoptic area of the hypothalamus. Ectotherms such as teleost fish display sickness behaviors in response to infection or inflammation, seeking warmer temperatures to enhance survival via behavioral fever responses. To date, the hypothalamus is the only brain region implicated in sickness behaviors and behavioral fever in teleosts. Yet, the complexity of neurobehavioral manifestations underlying sickness responses in teleosts suggests engagement of higher processing areas of the brain. Using in vivo models of systemic inflammation in rainbow trout, we find canonical pyrogenic cytokine responses in the hypothalamus whereas in the telencephalon and the optic tectum il-1b and tnfa expression is decoupled from il-6 expression. Polyamine metabolism changes, characterized by accumulation of putrescine and decreases in spermine and spermidine, are recorded in the telencephalon but not hypothalamus upon systemic injection of bacteria. While systemic inflammation causes canonical behavioral fever in trout, blockade of bacterial polyamine metabolism prior to injection abrogates behavioral fever, polyamine responses, and telencephalic but not hypothalamic cytokine responses. Combined, our work identifies the telencephalon as a neuronal substrate for brain responses to systemic inflammation in teleosts and uncovers the role of polyamines as critical chemical mediators in sickness behaviors.

The role of fiber in modulating plant protein-induced metabolic responses

The rising consumption of plant protein foods and the emergence of meat alternatives have prompted interest in the health benefits of such products, which contain fiber in addition to protein. This review investigates the effect of fiber on plant-based protein metabolism and evaluates its contribution to gut-derived health impacts. Plant proteins, which often come with added fiber, can have varying health outcomes. Factors such as processing and the presence of fiber and starch influence the digestibility of plant proteins, potentially leading to increased proteolytic fermentation in the gut and the production of harmful metabolites. However, fermentable fiber can counteract this effect by serving as a primary substrate for gut microbes, decreasing proteolytic activity. The increased amount of fiber, rather than the protein source itself, plays a significant role in the observed health benefits of plant-based diets in human studies. Differences between extrinsic and intrinsic fiber in the food matrix further impact protein fermentation and digestibility. Thus, in novel protein products without naturally occurring fiber, the health impact may differ from conventional plant protein sources. The influence of various fibers on plant-based protein metabolism throughout the gastrointestinal tract is not fully understood, necessitating further research.

Salmonella Typhimurium exploits host polyamines for assembly of the type 3 secretion machinery

Bacterial pathogens utilize the factors of their hosts to infect them, but which factors they exploit remain poorly defined. Here, we show that a pathogenic Salmonella enterica serovar Typhimurium (STm) exploits host polyamines for the functional expression of virulence factors. An STm mutant strain lacking principal genes required for polyamine synthesis and transport exhibited impaired infectivity in mice. A polyamine uptake-impaired strain of STm was unable to inject effectors of the type 3 secretion system into host cells due to a failure of needle assembly. STm infection stimulated host polyamine production by increasing arginase expression. The decline in polyamine levels caused by difluoromethylornithine, which inhibits host polyamine production, attenuated STm colonization, whereas polyamine supplementation augmented STm pathogenesis. Our work reveals that host polyamines are a key factor promoting STm infection, and therefore a promising therapeutic target for bacterial infection.

Microbiota and detrimental protein derived metabolites in colorectal cancer

Colorectal cancer (CRC) is the third leading cancer in incidence and the second leading cancer in mortality worldwide. There is growing scientific evidence to support the crucial role of the gut microbiota in the development of CRC. The gut microbiota is the complex community of microorganisms that inhabit the host gut in a symbiotic relationship. Diet plays a crucial role in modulating the risk of CRC, with a high intake of red and processed meat being a risk factor for the development of CRC. The production of metabolites derived from protein fermentation by the gut microbiota is considered a crucial element in the interaction between red and processed meat consumption and the development of CRC. This paper examines several metabolites derived from the bacterial fermentation of proteins associated with an increased risk of CRC. These metabolites include ammonia, polyamines, trimethylamine N-oxide (TMAO), N-nitroso compounds (NOC), hydrogen sulphide (H2S), phenolic compounds (p-cresol) and indole compounds (indolimines). These compounds are depicted and reviewed for their association with CRC risk, possible mechanisms promoting carcinogenesis and their relationship with the gut microbiota. Additionally, this paper analyses the evidence related to the role of red and processed meat intake and CRC risk and the factors and pathways involved in bacterial proteolytic fermentation in the large intestine.

Variation in the response to antibiotics and life-history across the major Pseudomonas aeruginosa clone type (mPact) panel

Pseudomonas aeruginosa is a ubiquitous, opportunistic human pathogen. Since it often expresses multidrug resistance, new treatment options are urgently required. Such new treatments are usually assessed with one of the canonical laboratory strains, PAO1 or PA14. However, these two strains are unlikely representative of the strains infecting patients, because they have adapted to laboratory conditions and do not capture the enormous genomic diversity of the species. Here, we characterized the major P. aeruginosa clone type (mPact) panel. This panel consists of 20 strains, which reflect the species' genomic diversity, cover all major clone types, and have both patient and environmental origins. We found significant strain variation in distinct responses toward antibiotics and general growth characteristics. Only few of the measured traits are related, suggesting independent trait optimization across strains. High resistance levels were only identified for clinical mPact isolates and could be linked to known antimicrobial resistance (AMR) genes. One strain, H01, produced highly unstable AMR combined with reduced growth under drug-free conditions, indicating an evolutionary cost to resistance. The expression of microcolonies was common among strains, especially for strain H15, which also showed reduced growth, possibly indicating another type of evolutionary trade-off. By linking isolation source, growth, and virulence to life history traits, we further identified specific adaptive strategies for individual mPact strains toward either host processes or degradation pathways. Overall, the mPact panel provides a reasonably sized set of distinct strains, enabling in-depth analysis of new treatment designs or evolutionary dynamics in consideration of the species' genomic diversity.

IMPORTANCE

New treatment strategies are urgently needed for high-risk pathogens such as the opportunistic and often multidrug-resistant pathogen Pseudomonas aeruginosa. Here, we characterize the major P. aeruginosa clone type (mPact) panel. It consists of 20 strains with different origins that cover the major clone types of the species as well as its genomic diversity. This mPact panel shows significant variation in (i) resistance against distinct antibiotics, including several last resort antibiotics; (ii) related traits associated with the response to antibiotics; and (iii) general growth characteristics. We further developed a novel approach that integrates information on resistance, growth, virulence, and life-history characteristics, allowing us to demonstrate the presence of distinct adaptive strategies of the strains that focus either on host interaction or resource processing. In conclusion, the mPact panel provides a manageable number of representative strains for this important pathogen for further in-depth analyses of treatment options and evolutionary dynamics.

Molecular mechanism of endophytic bacteria DX120E regulating polyamine metabolism and promoting plant growth in sugarcane

Introduction

Sugarcane endophytic nitrogen-fixing bacterium Klebsiella variícola DX120E displayed broad impact on growth, but the exact biological mechanism, especially polyamines (PAs) role, is still meager.

Methods

To reveal this relationship, the content of polyamine oxidase (PAO), PAs, reactive oxygen species (ROS)-scavenging antioxidative enzymes, phytohormones, 1-aminocyclopropane-1-carboxylic synthase (ACS), chlorophyll content, and biomass were determined in sugarcane incubated with the DX120E strain. In addition, expression levels of the genes associated with polyamine metabolism were measured by transcriptomic analysis.

Results

Genomic analysis of Klebsiella variícola DX120E revealed that 39 genes were involved in polyamine metabolism, transport, and the strain secrete PAs in vitro. Following a 7-day inoculation period, DX120E stimulated an increase in the polyamine oxidase (PAO) enzyme in sugarcane leaves, however, the overall PAs content was reduced. At 15 days, the levels of PAs, ROS-scavenging antioxidative enzymes, and phytohormones showed an upward trend, especially spermidine (Spd), putrescine (Put), catalase (CAT), auxin (IAA), gibberellin (GA), and ACS showed a significant up-regulation. The GO and KEGG enrichment analysis found a total of 73 differentially expressed genes, involving in the cell wall (9), stimulus response (13), peroxidase activity (33), hormone (14) and polyamine metabolism (4).

Discussion

This study demonstrated that endophytic nitrogen-fixing bacteria stimulated polyamine metabolism and phytohormones production in sugarcane plant tissues, resulting in enhanced growth. Dual RNA-seq analyses provided insight into the early-stage interaction between sugarcane seedlings and endophytic bacteria at the transcriptional level. It showed how diverse metabolic processes selectively use distinct molecules to complete the cell functions under present circumstances.

Current understandings of colibactin regulation

The biosynthetic machinery for the production of colibactin is encoded by 19 genes (clbA - S) within the pks pathogenicity island harboured by many E. coli of the B2-phylogroup. Colibactin is a potent genotoxic metabolite which causes DNA-damage and which has potential roles in microbial competition and fitness of pks+ bacteria. Colibactin has also been strongly implicated in the development of colorectal cancer. Given the genotoxicity of colibactin and the metabolic cost of its synthesis, the regulatory system governing the clb cluster is accordingly highly complex, and many of the mechanisms remain to be elucidated. In this review we summarise the current understanding of regulation of colibactin biosynthesis by internal molecular components and how these factors are modulated by signals from the external environment.

Antibiofilm and Antivirulence Properties of 6-Polyaminosteroid Derivatives against Antibiotic-Resistant Bacteria

The emergence of multi-drug resistant pathogens is a major public health problem, leading us to rethink and innovate our bacterial control strategies. Here, we explore the antibiofilm and antivirulence activities of nineteen 6-polyaminosterol derivatives (squalamine-based), presenting a modulation of their polyamine side chain on four major pathogens, i.e., carbapenem-resistant A. baumannii (CRAB) and P. aeruginosa (CRPA), methicillin-resistant S. aureus (MRSA), and vancomycin-resistant E. faecium (VRE) strains. We screened the effect of these derivatives on biofilm formation and eradication. Derivatives 4e (for CRAB, VRE, and MRSA) and 4f (for all the strains) were the most potent ones and displayed activities as good as those of conventional antibiotics. We also identified 11 compounds able to decrease by more than 40% the production of pyocyanin, a major virulence factor of P. aeruginosa. We demonstrated that 4f treatment acts against bacterial infections in Galleria mellonella and significantly prolonged larvae survival (from 50% to 80%) after 24 h of CRAB, VRE, and MRSA infections. As shown by proteomic studies, 4f triggered distinct cellular responses depending on the bacterial species but essentially linked to cell envelope. Its interesting antibiofilm and antivirulence properties make it a promising a candidate for use in therapeutics.

Immunonutrients and intestinal microbiota: a gap in the literature

The human intestinal microbiota is composed of a wide variety of microorganisms that play an important role in intestinal permeability, digestion, and especially, in the maturation of host's immune system. At the same time, effectiveness of immunomodulatory nutrients is known, especially in situations of stress and in strengthening body's defenses. However, the influence of the use of immunonutrients on microbiota's composition and variability is still poorly investigated. Studies indicate that the use of immunomodulators such as omega 3, glutamine, and arginine, can play a role in its modulation, through the immunological enhancement of the hosts. Therefore, this article sought to concentrate the latest evidence on the influence of the use of the main immunonutrients used in clinical practice on human gut microbiota, and their potential benefits.

The Biosynthesis and Functions of Polyamines in the Interaction of Plant Growth-Promoting Rhizobacteria with Plants

Plant growth-promoting rhizobacteria (PGPR) are members of the plant rhizomicrobiome that enhance plant growth and stress resistance by increasing nutrient availability to the plant, producing phytohormones or other secondary metabolites, stimulating plant defense responses against abiotic stresses and pathogens, or fixing nitrogen. The use of PGPR to increase crop yield with minimal environmental impact is a sustainable and readily applicable replacement for a portion of chemical fertilizer and pesticides required for the growth of high-yielding varieties. Increased plant health and productivity have long been gained by applying PGPR as commercial inoculants to crops, although with uneven results. The establishment of plant-PGPR relationships requires the exchange of chemical signals and nutrients between the partners, and polyamines (PAs) are an important class of compounds that act as physiological effectors and signal molecules in plant-microbe interactions. In this review, we focus on the role of PAs in interactions between PGPR and plants. We describe the basic ecology of PGPR and the production and function of PAs in them and the plants with which they interact. We examine the metabolism and the roles of PAs in PGPR and plants individually and during their interaction with one another. Lastly, we describe some directions for future research.

Arginine Metabolism Powers Salmonella Resistance to Oxidative Stress

Salmonella invades host cells and replicates inside acidified, remodeled vacuoles that are exposed to reactive oxygen species (ROS) generated by the innate immune response. Oxidative products of the phagocyte NADPH oxidase mediate antimicrobial activity, in part, by collapsing the ΔpH of intracellular Salmonella. Given the role of arginine in bacterial resistance to acidic pH, we screened a library of 54 single-gene mutants in Salmonella that are each involved in, but do not entirely block, arginine metabolism. We identified several mutants that affected Salmonella virulence in mice. The triple mutant ΔargCBH, which is deficient in arginine biosynthesis, was attenuated in immunocompetent mice, but recovered virulence in phagocyte NADPH oxidase deficient Cybb-/- mice. Furthermore, ΔargCBH Salmonella was profoundly susceptible to the bacteriostatic and bactericidal effects of hydrogen peroxide. Peroxide stress led to a larger collapse of the ΔpH in ΔargCBH mutants than occurred in wild-type Salmonella. The addition of exogenous arginine rescued ΔargCBH Salmonella from peroxide-induced ΔpH collapse and killing. Combined, these observations suggest that arginine metabolism is a hitherto unknown determinant of virulence that contributes to the antioxidant defenses of Salmonella by preserving pH homeostasis. In the absence of phagocyte NADPH oxidase-produced ROS, host cell-derived l-arginine appears to satisfy the needs of intracellular Salmonella. However, under oxidative stress, Salmonella must additionally rely on de novo biosynthesis to maintain full virulence.

A polyamine acetyltransferase regulates the motility and biofilm formation of Acinetobacter baumannii

Acinetobacter baumannii is a nosocomial pathogen highly resistant to environmental changes and antimicrobial treatments. Regulation of cellular motility and biofilm formation is important for its virulence, although it is poorly described at the molecular level. It has been previously reported that Acinetobacter genus specifically produces a small positively charged metabolite, polyamine 1,3-diaminopropane, that has been associated with cell motility and virulence. Here we show that A. baumannii encodes novel acetyltransferase, Dpa, that acetylates 1,3-diaminopropane, directly affecting the bacterium motility. Expression of dpa increases in bacteria that form pellicle and adhere to eukaryotic cells as compared to planktonic bacterial cells, suggesting that cell motility is linked to the pool of non-modified 1,3-diaminopropane. Indeed, deletion of dpa hinders biofilm formation and increases twitching motion confirming the impact of balancing the levels of 1,3-diaminopropane on cell motility. The crystal structure of Dpa reveals topological and functional differences from other bacterial polyamine acetyltransferases, adopting a β-swapped quaternary arrangement similar to that of eukaryotic polyamine acetyltransferases with a central size exclusion channel that sieves through the cellular polyamine pool. The structure of catalytically impaired Dpa_Y128F in complex with the reaction product shows that binding and orientation of the polyamine substrates are conserved between different polyamine-acetyltransferases.

Polyamine-Drug Conjugates: Do They Boost Drug Activity?

Over the past two decades, the strategy of conjugating polyamine tails with bioactive molecules such as anticancer and antimicrobial agents, as well as antioxidant and neuroprotective scaffolds, has been widely exploited to enhance their pharmacological profile. Polyamine transport is elevated in many pathological conditions, suggesting that the polyamine portion could improve cellular and subcellular uptake of the conjugate via the polyamine transporter system. In this review, we have presented a glimpse on the polyamine conjugate scenario, classified by therapeutic area, of the last decade with the aim of highlighting achievements and fostering future developments.

Biodegradable Polymers and Polymer Composites with Antibacterial Properties

Antibiotic resistance is one of the greatest threats to global health and food security today. It becomes increasingly difficult to treat infectious disorders because antibiotics, even the newest ones, are becoming less and less effective. One of the ways taken in the Global Plan of Action announced at the World Health Assembly in May 2015 is to ensure the prevention and treatment of infectious diseases. In order to do so, attempts are made to develop new antimicrobial therapeutics, including biomaterials with antibacterial activity, such as polycationic polymers, polypeptides, and polymeric systems, to provide non-antibiotic therapeutic agents, such as selected biologically active nanoparticles and chemical compounds. Another key issue is preventing food from contamination by developing antibacterial packaging materials, particularly based on degradable polymers and biocomposites. This review, in a cross-sectional way, describes the most significant research activities conducted in recent years in the field of the development of polymeric materials and polymer composites with antibacterial properties. We particularly focus on natural polymers, i.e., polysaccharides and polypeptides, which present a mechanism for combating many highly pathogenic microorganisms. We also attempt to use this knowledge to obtain synthetic polymers with similar antibacterial activity.

Metabolite interactions between host and microbiota during health and disease: Which feeds the other?

Metabolites produced by the host and microbiota play a crucial role in how human bodies develop and remain healthy. Most of these metabolites are produced by microbiota and hosts in the digestive tract. Metabolites in the gut have important roles in energy metabolism, cellular communication, and host immunity, among other physiological activities. Although numerous host metabolites, such as free fatty acids, amino acids, and vitamins, are found in the intestine, metabolites generated by gut microbiota are equally vital for intestinal homeostasis. Furthermore, microbiota in the gut is the sole source of some metabolites, including short-chain fatty acids (SCFAs). Metabolites produced by microbiota, such as neurotransmitters and hormones, may modulate and significantly affect host metabolism. The gut microbiota is becoming recognized as a second endocrine system. A variety of chronic inflammatory disorders have been linked to aberrant host-microbiota interplays, but the precise mechanisms underpinning these disturbances and how they might lead to diseases remain to be fully elucidated. Microbiome-modulated metabolites are promising targets for new drug discovery due to their endocrine function in various complex disorders. In humans, metabolotherapy for the prevention or treatment of various disorders will be possible if we better understand the metabolic preferences of bacteria and the host in specific tissues and organs. Better disease treatments may be possible with the help of novel complementary therapies that target host or bacterial metabolism. The metabolites, their physiological consequences, and functional mechanisms of the host-microbiota interplays will be highlighted, summarized, and discussed in this overview.

The Interaction between Gut Microbiota and Host Amino Acids Metabolism in Multiple Myeloma

Although novel therapies have dramatically improved outcomes for multiple myeloma (MM) patients, relapse is inevitable and overall outcomes are heterogeneous. The gut microbiota is becoming increasingly recognized for its influence on host metabolism. To date, evidence has suggested that the gut microbiota contributes to MM, not only via the progressive activities of specific bacteria but also through the influence of the microbiota on host metabolism. Importantly, the abnormal amino acid metabolism, as well as the altered microbiome in MM, is becoming increasingly apparent, as is the influence on MM progression and the therapeutic response. Moreover, the gut-microbiota-host-amino-acid metabolism interaction in the progression of MM has been highlighted. Modulation of the gut microbiota (such as fecal microbiota transplantation, FMT) can be modified, representing a new angle in MM treatment that can improve outcomes. In this review, the relationship between gut microbiota, metabolism, and MM, together with strategies to modulate the microbiota, will be discussed, and some unanswered questions for ongoing and future research will be presented.

Probiotic induced synthesis of microbiota polyamine as a nutraceutical for metabolic syndrome and obesity-related type 2 diabetes

The gut microbiota regulates multiple facets of host metabolism and immunity through the production of signaling metabolites, such as polyamines which are small organic compounds that are essential to host cell growth and lymphocyte activation. Polyamines are most abundant in the intestinal lumen, where their synthesis by the gut microbiota is influenced by microbiome composition and host diet. Disruption of the host gut microbiome in metabolic syndrome and obesity-related type 2 diabetes (obesity/T2D) results in potential dysregulation of polyamine synthesis. A growing body of evidence suggests that restoration of the dysbiotic gut microbiota and polyamine synthesis is effective in ameliorating metabolic syndrome and strengthening the impaired immune responses of obesity/T2D. In this review, we discuss existing studies on gut microbiome determinants of polyamine synthesis, polyamine production in obesity/T2D, and evidence that demonstrates the potential of polyamines as a nutraceutical in obesity/T2D hosts.

Advances in Organoid Culture Research

Organoids are powerful systems to facilitate the study of individuals' disorders and personalized treatments because they mimic the structural and functional characteristics of organs. However, the full potential of organoids in research has remained unrealized and the clinical applications have been limited. One of the reasons is organoids are most efficient grown in reconstituted extracellular matrix hydrogels from mouse-derived, whose poorly defined, batch-to-batch variability and immunogenicity. Another reason is that organoids lack host conditions. As a component of the tumor microenvironment, microbiota and metabolites can regulate the development and treatment in several human malignancies. Here, we introduce several engineering matrix materials and review recent advances in the coculture of organoids with microbiota and their metabolites. Finally, we discuss current trends and future possibilities to build more complex cocultures.

Gut Microbiota Alterations in Trace Amine-Associated Receptor 9 (TAAR9) Knockout Rats

Trace amine-associated receptors (TAAR1-TAAR9) are a family of G-protein-coupled monoaminergic receptors which might have great pharmacological potential. It has now been well established that TAAR1 plays an important role in the central nervous system. Interestingly, deletion of TAAR9 in rats leads to alterations in the periphery. Previously, we found that knockout of TAAR9 in rats (TAAR9-KO rats) decreased low-density lipoprotein cholesterol levels in the blood. TAAR9 was also identified in intestinal tissues, and it is known that it responds to polyamines. To elucidate the role of TAAR9 in the intestinal epithelium, we analyzed TAAR9-co-expressed gene clusters in public data for cecum samples. As identified by gene ontology enrichment analysis, in the intestine, TAAR9 is co-expressed with genes involved in intestinal mucosa homeostasis and function, including cell organization, differentiation, and death. Additionally, TAAR9 was co-expressed with genes implicated in dopamine signaling, which may suggest a role for this receptor in the regulation of peripheral dopaminergic transmission. To further investigate how TAAR9 might be involved in colonic mucosal homeostasis, we analyzed the fecal microbiome composition in TAAR9-KO rats and their wild-type littermates. We identified a significant difference in the number of observed taxa between the microbiome of TAAR9-KO and wild-type rats. In TAAR9-KO rats, the gut microbial community became more variable compared with the wild-type rats. Furthermore, it was found that the family Saccharimonadaceae, which is one of the top 10 most abundant families in TAAR9-KO rat feces, is almost completely absent in wild-type animal fecal samples. Taken together, these data indicate a role of TAAR9 in intestinal function.

Underlying beneficial effects of Rhubarb on constipation-induced inflammation, disorder of gut microbiome and metabolism

Background: Constipation is a common syndrome and a worldwide healthy problem. Constipation patients are becoming younger, with a 29.6% overall prevalence in children, which has captured significant attention because of its epigenetic rejuvenation and recurrent episodes. Despite the usage of rhubarb extract to relieve constipation, novel targets and genes implicated in target-relevant pathways with remarkable functionalities should still be sought for. Materials and methods: We established a reliable constipation model in C57B/6N male mice using intragastric administration diphenoxylate, and the eligible subjects received 600 mg/25 g rhubarb extract to alleviate constipation. Resultant constipation was morphological and genetically compared with the specimen from different groups. Results: Constipation mice exhibited thicker muscle layers, higher levels of cytokines, including IL-17 and IL-23, and lower content of IL-22. Bacterial abundance and diversity varied tremendously. Notably, the alterations were reversed following rhubarb extract treatment. Additionally, Constipation also had a substantial impact on short-chain fatty acids (SCFAs), medium- and long-chain fatty acids (MLCFAs), and the expression of SCFA receptors, GPR41 and GPR43. Conclusion: This thesis has provided insight that rhubarb extract promoted the flexibility of collagen fiber, reduced pro-inflammatory cytokines, enhanced anti-inflammatory cytokines, and maintained gut microflora balance with potential impacts on the fatty acid and polyamine metabolism.

An observational investigation of the faical microbiota and metabonome of gastrostomy fed children, on blended and formula diets

Gastrostomy fed children traditionally have a Formulae diet (FD), which fulfills nutritional requirements; however, many families are adopting Blended diets (BD), which are what the whole family would eat. We undertook an observational investigation of the colonic microbiota and metabonome in a small group of gastrostomy fed children, who were either on an FD or BD, and compared, where possible to their siblings (17 FD, 28 BD, 19 HS). There was no increase in complications in tube blockage or infection rates, but a significant improvement in the prevalence of bowel problems, a reduction in medication and an increase in quality of life. Metataxonomic analysis showed that the FD group was significantly different to the Sibling group, and that families did not cluster together. Whole sample metabonomics showed no differences between groups; however, univariate analysis of biologically important metabolites did differ. Changing to a BD resulted in no increase in complications or risks, but improved the overall quality of life for the children and families.

Still rocking in the structural era: A molecular overview of the small multidrug resistance (SMR) transporter family

The small multidrug resistance (SMR) family is composed of widespread microbial membrane proteins that fulfill different transport functions. Four functional SMR subtypes have been identified, which variously transport the small, charged metabolite guanidinium, bulky hydrophobic drugs and antiseptics, polyamines, and glycolipids across the membrane bilayer. The transporters possess a minimalist architecture, with ∼100-residue subunits that require assembly into homodimers or heterodimers for transport. In part because of their simple construction, the SMRs are a tractable system for biochemical and biophysical analysis. Studies of SMR transporters over the last 25 years have yielded deep insights for diverse fields, including membrane protein topology and evolution, mechanisms of membrane transport, and bacterial multidrug resistance. Here, we review recent advances in understanding the structures and functions of SMR transporters. New molecular structures of SMRs representing two of the four functional subtypes reveal the conserved structural features that have permitted the emergence of disparate substrate transport functions in the SMR family and illuminate structural similarities with a distantly related membrane transporter family, SLC35/DMT.

Gut microbiota in systemic lupus erythematosus: A fuse and a solution

Gut commensals help shape and mold host immune system and deeply influence human health. The disease spectrum of mankind that gut microbiome may associate with is ever-growing, but the mechanisms are still enigmas. Characterized by loss of self-tolerance and sustained self-attack, systemic lupus erythematosus (SLE) is labeled with chronic inflammation, production of autoantibodies and multisystem injury, which so far are mostly incurable. Gut microbiota and their metabolites, now known as important environmental triggers of local/systemic immune responses, have been proposed to be involved in SLE development and progression probably through the following mechanisms: translocation beyond their niches; molecular mimicry to cross-activate immune response targeting self-antigens; epitope spreading to expand autoantibodies spectrum; and bystander activation to promote systemic inflammation. Gut microbiota which varies between individuals may also influence the metabolism and bio-transformation of disease-modifying anti-rheumatic drugs, thus associated with the efficacy and toxicity of these drugs, adding another explanation for heterogenic therapeutic responses. Modulation of gut microbiota via diet, probiotics/prebiotics, antibiotics/phages, fecal microbiota transplantation, or helminth to restore immune tolerance and homeostasis is expected to be a promising neoadjuvant therapy for SLE. We reviewed the advances in this territory and discussed the application prospect of modulating gut microbiota in controlling SLE.

Spermidine promotes lysozyme tolerance and acid stress resistance in Streptococcus pyogenes M3

Streptococcus pyogenes are Gram-positive opportunistic pathogens residing in the human nasopharynx and skin. Changes in environmental conditions, such as pH, temperature and availability of essential ions, can stimulate the expression of S. pyogenes virulence factors. One such factor could be the availability of an extracellular pool of polyamines. Polyamines are synthesized from amino acids, and are universally present in the environment. Polyamines have been implicated in the ecology of pathogenesis by modulating quorum sensing, host adaptation and virulence. Polyamines mediate pathogenesis and help the pathogen resist environmental stress. In this study, we investigated the ability of the polyamine, spermidine, to promote acid stress survival of S. pyogenes. S. pyogenes does not synthesize spermidine, but the extracellular pool of spermidine constituted by the host and microbiome could be utilized as a signalling molecule. We report that spermidine promotes acid stress resistance in S. pyogenes. Moreover, spermidine affects the morphology of S. pyogenes by decreasing the cell size and increasing the dltA gene expression. Along with dltA, spermidine upregulated the gene expression of cell wall-modifying genes such as mur, pgdA, pepO and srtA, which might help the bacteria to resist acidic stress.

Tumor microbiome metabolism: A game changer in cancer development and therapy

Accumulating recent evidence indicates that the human microbiome plays essential roles in pathophysiological states, including cancer. The tumor microbiome, an emerging concept that has not yet been clearly defined, has been proven to influence both cancer development and therapy through complex mechanisms. Small molecule metabolites produced by the tumor microbiome through unique biosynthetic pathways can easily diffuse into tissues and penetrate cell membranes through transporters or free diffusion, thus remodeling the signaling pathways of cancer and immune cells by interacting with biomacromolecules. Targeting tumor microbiome metabolism could offer a novel perspective for not only understanding cancer progression but also developing new strategies for the treatment of multiple cancer types. Here, we summarize recent advances regarding the role the tumor microbiome plays as a game changer in cancer biology. Specifically, the metabolites produced by the tumor microbiome and their potential effects on the cancer development therapy are discussed to understand the importance of the microbial metabolism in the tumor microenvironment. Finally, new anticancer therapeutic strategies that target tumor microbiome metabolism are reviewed and proposed to provide new insights in clinical applications.

Human Adult Microbiota in a Static Colon Model: AhR Transcriptional Activity at the Crossroads of Host–Microbe Interaction

Functional symbiotic intestinal microbiota regulates immune defense and the metabolic processing of xenobiotics in the host. The aryl hydrocarbon receptor (AhR) is one of the transcription factors mediating host–microbe interaction. An in vitro static simulation of the human colon was used in this work to analyze the evolution of bacterial populations, the microbial metabolic output, and the potential induction of AhR transcriptional activity in healthy gut ecosystems. Fifteen target taxa were explored by qPCR, and the metabolic content was chromatographically profiled using SPME-GC-MS and UPLC-FLD to quantify short-chain fatty acids (SCFA) and biogenic amines, respectively. Over 72 h of fermentation, the microbiota and most produced metabolites remained stable. Fermentation supernatant induced AhR transcription in two of the three reporter gene cell lines (T47D, HepG2, HT29) evaluated. Mammary and intestinal cells were more sensitive to microbiota metabolic production, which showed greater AhR agonism than the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) used as a positive control. Some of the SCFA and biogenic amines identified could crucially contribute to the potent AhR induction of the fermentation products. As a fundamental pathway mediating human intestinal homeostasis and as a sensor for several microbial metabolites, AhR activation might be a useful endpoint to include in studies of the gut microbiota.

Gut microbiota alternation under the intestinal epithelium-specific knockout of mouse Piga gene

Crosstalk between the gut microbiota and intestinal epithelium shapes the gut environment and profoundly influences the intestinal immune homeostasis. Glycosylphosphatidylinositol anchored proteins (GPI – APs) contribute to a variety of gut-associated immune functions, including microbial surveillance and defense, and epithelial cell polarity. Properly polarised epithelial cells are essential for the establishment of the barrier function of gut epithelia. The Piga gene is one among seven genes that encode for an enzyme which is involved in the first step of GPI-anchor biosynthesis. This is the first study reporting a knockout of the intestinal epithelial cell-specific Piga gene (Piga-/-) and its association with the gut microbiota in mice using a whole metagenome shotgun-based sequencing approach. An overall reduced microbiota diversity has been observed in the Piga-/- group as compared to the control group (ANOVA p = 0.34). The taxonomic biomarkers, namely: Gammaproteobacteria (class), Enterobacterales (order), Enterobacteriaceae (family), Escherichia (genus), Proteus (genus) and Escherichia coli (species), increased more in the Piga-/- mice as compared to in the control group. Further, the pathogenic E. coli strains, namely E. coli O157:H7 str. EDL 933 (EHEC), E. coli CFT073 (UPEC) and E. coli 536 (UPEC), were found in the Piga-/- mice which also harbored virulence factor transporters. In addition, the taxa responsible for short chain fatty acid production were decreased in the Piga-/- group. The Piga-/- mice gut harbored an increased number of microbial functions responsible for the survival of pathogens in the inflamed gut environment. Our observations clearly indicate that the Piga-/- mice gut might have an overall enhancement in pathogenic behaviour and reduced capabilities beneficial to health.

Ecology and evolution of chlamydial symbionts of arthropods

The phylum Chlamydiae consists of obligate intracellular bacteria including major human pathogens and diverse environmental representatives. Here we investigated the Rhabdochlamydiaceae, which is predicted to be the largest and most diverse chlamydial family, with the few described members known to infect arthropod hosts. Using published 16 S rRNA gene sequence data we identified at least 388 genus-level lineages containing about 14 051 putative species within this family. We show that rhabdochlamydiae are mainly found in freshwater and soil environments, suggesting the existence of diverse, yet unknown hosts. Next, we used a comprehensive genome dataset including metagenome assembled genomes classified as members of the family Rhabdochlamydiaceae, and we added novel complete genome sequences of Rhabdochlamydia porcellionis infecting the woodlouse Porcellio scaber, and of 'Candidatus R. oedothoracis' associated with the linyphiid dwarf spider Oedothorax gibbosus. Comparative analysis of basic genome features and gene content with reference genomes of well-studied chlamydial families with known host ranges, namely Parachlamydiaceae (protist hosts) and Chlamydiaceae (human and other vertebrate hosts) suggested distinct niches for members of the Rhabdochlamydiaceae. We propose that members of the family represent intermediate stages of adaptation of chlamydiae from protists to vertebrate hosts. Within the genus Rhabdochlamydia, pronounced genome size reduction could be observed (1.49-1.93 Mb). The abundance and genomic distribution of transposases suggests transposable element expansion and subsequent gene inactivation as a mechanism of genome streamlining during adaptation to new hosts. This type of genome reduction has never been described before for any member of the phylum Chlamydiae. This study provides new insights into the molecular ecology, genomic diversity, and evolution of representatives of one of the most divergent chlamydial families.

How do plants defend themselves against pathogens-Biochemical mechanisms and genetic interventions

In agro-ecosystem, plant pathogens hamper food quality, crop yield, and global food security. Manipulation of naturally occurring defense mechanisms in host plants is an effective and sustainable approach for plant disease management. Various natural compounds, ranging from cell wall components to metabolic enzymes have been reported to protect plants from infection by pathogens and hence provide specific resistance to hosts against pathogens, termed as induced resistance. It involves various biochemical components, that play an important role in molecular and cellular signaling events occurring either before (elicitation) or after pathogen infection. The induction of reactive oxygen species, activation of defensive machinery of plants comprising of enzymatic and non-enzymatic antioxidative components, secondary metabolites, pathogenesis-related protein expression (e.g. chitinases and glucanases), phytoalexin production, modification in cell wall composition, melatonin production, carotenoids accumulation, and altered activity of polyamines are major induced changes in host plants during pathogen infection. Hence, the altered concentration of biochemical components in host plants restricts disease development. Such biochemical or metabolic markers can be harnessed for the development of "pathogen-proof" plants. Effective utilization of the key metabolites-based metabolic markers can pave the path for candidate gene identification. This present review discusses the valuable information for understanding the biochemical response mechanism of plants to cope with pathogens and genomics-metabolomics-based sustainable development of pathogen proof cultivars along with knowledge gaps and future perspectives to enhance sustainable agricultural production.

Spermidine enhances the survival of Streptococcus pyogenes M3 under oxidative stress

Streptococcus pyogenes, a host-restricted gram-positive pathogen during infection, initially adheres to the epithelia of the nasopharynx and respiratory tract of the human host, followed by disseminating to other organs and evading the host immune system. Upon phagocytosis, S. pyogenes encounters oxidative stress inside the macrophages. The role of polyamines in regulating various physiological functions including stress resistance in bacteria has been reported widely. Since S. pyogenes lacks the machinery for the biosynthesis of polyamines, the study aimed to understand the role of extracellular polyamines in the survival of S. pyogenes under oxidative stress environments. S. pyogenes being a catalase-negative organism, we report that its survival within the macrophages and H₂ O₂ is enhanced by the presence of spermidine. The increased survival can be attributed to the upregulation of oxidative stress response genes such as sodM, npx, and mtsABC. In addition, spermidine influences the upregulation of virulence factors such as sagA, slo, and hasA. Also, spermidine leads to a decrease in hydrophobicity of the cell membrane and an increase in hyaluronic acid. This study suggests a role for extracellular spermidine in the survival of S. pyogenes under oxidative stress environments. Recognizing the factors that modulate S. pyogenes survival and virulence under stress will assist in understanding its interactions with the host.

Host microbiomes in tumor precision medicine: how far are we?

The human gut microbiome has received a crescendo of attention in recent years, due to the countless influences on human pathophysiology, including cancer. Research on cancer and anticancer therapy is constantly looking for new hints to improve the response to therapy while reducing the risk of relapse. In this scenario, the gut microbiome and the plethora of microbial-derived metabolites are considered a new opening in the development of innovative anticancer treatments for a better prognosis. This narrative review summarizes the current knowledge on the role of the gut microbiome in the onset and progression of cancer, as well as in response to chemo-immunotherapy. Recent findings regarding the tumor microbiome and its implications for clinical practice are also commented on. Current microbiome-based intervention strategies (i.e., prebiotics, probiotics, live biotherapeutics and fecal microbiota transplantation) are then discussed, along with key shortcomings, including a lack of long-term safety information in patients who are already severely compromised by standard treatments. The implementation of bioinformatic tools applied to microbiomics and other omics data, such as machine learning, has an enormous potential to push research in the field, enabling the prediction of health risk and therapeutic outcomes, for a truly personalized precision medicine.

Effect of Quorum Sensing Inducers and Inhibitors on Cytoplasmic Incompatibility Induced by Wolbachia (Rickettsiales: Anaplasmataceae) in American Serpentine Leafminer (Diptera: Agromyzidae): Potential Tool for the Incompatible Insect Technique

Agricultural crops around the world are attacked by approximately 3,000-10,000 species of pest insect. There is increasing interest in resolving this problem using environmentally friendly approaches. Wolbachia (Hertig), an insect endosymbiont, can modulate host reproduction and offspring sex through cytoplasmic incompatibility (CI). The incompatible insect technique (IIT) based on CI-Wolbachia is a promising biological control method. Previous studies have reported an association between CI and Wolbachia density, which may involve a quorum sensing (QS) mechanism. In this study, we investigated the effect of manipulating QS in Wolbachia using several chemicals including 3O-C12-HSL; C2HSL; spermidine (QS inducers), 4-phenylbutanoyl; and 4-NPO (QS inhibitors) on American serpentine leafminer (Liriomyza trifolii [Burgess]), an agricultural pest. The results showed that inducing QS with 3O-C12-HSL decreased the proportion of hatched eggs and increased Wolbachia density, whereas QS inhibition with 4-phenylbutanoyl had the opposite effects. Thus, manipulating QS in Wolbachia can alter cell density and the proportion of hatched eggs in the host L. trifolii, thereby reducing the number of insect progeny. These findings provide evidence supporting the potential efficacy of the IIT based on CI-Wolbachia for the environmentally friendly control of insect pest populations.

Implications of Gut Microbiota in Complex Human Diseases

Humans, throughout the life cycle, from birth to death, are accompanied by the presence of gut microbes. Environmental factors, lifestyle, age and other factors can affect the balance of intestinal microbiota and their impact on human health. A large amount of data show that dietary, prebiotics, antibiotics can regulate various diseases through gut microbes. In this review, we focus on the role of gut microbes in the development of metabolic, gastrointestinal, neurological, immune diseases and, cancer. We also discuss the interaction between gut microbes and the host with respect to their beneficial and harmful effects, including their metabolites, microbial enzymes, small molecules and inflammatory molecules. More specifically, we evaluate the potential ability of gut microbes to cure diseases through Fecal Microbial Transplantation (FMT), which is expected to become a new type of clinical strategy for the treatment of various diseases.

Understanding the Effects of Metabolites on the Gut Microbiome and Severe Acute Pancreatitis

Acute pancreatitis (AP) is an inflammatory disease of the pancreas. The severity is classified as mild (MAP), moderately severe (MSAP), or severe (SAP). In patients with SAP, organ dysfunction can occur in the early stage of the disease course, accompanied by secondary infection, with a mortality rate of 36%-50%. In the late stage SAP, infection-related complications caused by pancreatic necrotic tissue and peripancreatic effusion are the main causes of death in patients. Dysbacteriosis of intestinal microflora, barrier dysfunction of intestinal mucosa, and translocation of enteric bacteria are considered to be the main causes of infection of pancreatic necrotic tissue and peripancreatic effusion. During the past few years, increasing attention has been paid to the metabolic activities of intestinal microflora in SAP, which plays an important role in the metabolic activities of the human body. This review is aimed at bringing together the most recent findings and advances regarding the gut microbial community and associated gut microbial community metabolites and illustrating the role of these metabolites in disease progression in severe acute pancreatitis. We hope that this review will provide new ideas and schemes for the treatment of SAP in the clinical settings.

Polyamines: double agents in disease and plant immunity

Polyamines (PAs) are ubiquitous amine molecules found in all living organisms. In plants, beside their role in signaling and protection against abiotic stresses, there is increasing evidence that PAs have a major role in the interaction between plants and pathogens. Plant PAs are involved in immunity against pathogens, notably by amplifying pattern-triggered immunity (PTI) responses through the production of reactive oxygen species (ROS). In response, pathogens use phytotoxins and effectors to manipulate the levels of PAs in the plant, most likely to their own benefit. It also appears that pathogenic microorganisms produce PAs during infection, sometimes in large quantities. This may reflect different infectious strategies based on the selective exploitation of these molecules and the functions they perform in the cell.

Crosstalk Between Intestinal Microbiota Derived Metabolites and Tissues in Allogeneic Hematopoietic Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an evidence based- cellular immunotherapy for hematological malignancies. Immune reactions not only promote graft-versus-tumor effects that kill hematological malignant cells but also graft-versus-host disease (GVHD) that is the primary complication characterized by systemic organ damages consisting of T-cells and antigen presenting cells (APCs) activation. GVHD has long been recognized as an immunological reaction that requires an immunosuppressive treatment targeting immune cells. However immune suppression cannot always prevent GVHD or effectively treat it once it has developed. Recent studies using high-throughput sequencing technology investigated the impact of microbial flora on GVHD and provided profound insights of the mechanism of GVHD other than immune cells. Allo-HSCT affects the intestinal microbiota and microbiome-metabolome axis that can alter intestinal homeostasis and the severity of experimental GVHD. This axis can potentially be manipulated via dietary intervention or metabolites produced by intestinal bacteria affected post-allo-HSCT. In this review, we discuss the mechanism of experimental GVHD regulation by the complex microbial community-metabolites-host tissue axis. Furthermore, we summarize the major findings of microbiome-based immunotherapeutic approaches that protect tissues from experimental GVHD. Understanding the complex relationships between gut microbiota-metabolites-host tissues axis provides crucial insight into the pathogenesis of GVHD and advances the development of new therapeutic approaches.

Molecular Mechanism of Microbiota Metabolites in Preterm Birth: Pathological and Therapeutic Insights

Preterm birth (PTB) refers to the birth of infants before 37 weeks of gestation and is a challenging issue worldwide. Evidence reveals that PTB is a multifactorial dysregulation mediated by a complex molecular mechanism. Thus, a better understanding of the complex molecular mechanisms underlying PTB is a prerequisite to explore effective therapeutic approaches. During early pregnancy, various physiological and metabolic changes occur as a result of endocrine and immune metabolism. The microbiota controls the physiological and metabolic mechanism of the host homeostasis, and dysbiosis of maternal microbial homeostasis dysregulates the mechanistic of fetal developmental processes and directly affects the birth outcome. Accumulating evidence indicates that metabolic dysregulation in the maternal or fetal membranes stimulates the inflammatory cytokines, which may positively progress the PTB. Although labour is regarded as an inflammatory process, it is still unclear how microbial dysbiosis could regulate the molecular mechanism of PTB. In this review based on recent research, we focused on both the pathological and therapeutic contribution of microbiota-generated metabolites to PTB and the possible molecular mechanisms.

Micro- and Mycobiota Dysbiosis in Pancreatic Ductal Adenocarcinoma Development

BACKGROUND

Dysbiosis of the intestinal flora has emerged as an oncogenic contributor in different malignancies. Recent findings suggest a crucial tumor-promoting role of micro- and mycobiome alterations also in the development of pancreatic ductal adenocarcinoma (PDAC).

METHODS

To summarize the current knowledge about this topic, a systematic literature search of articles published until October 2020 was performed in MEDLINE (PubMed).

RESULTS

An increasing number of publications describe associations between bacterial and fungal species and PDAC development. Despite the high inter-individual variability of the commensal flora, some studies identify specific microbial signatures in PDAC patients, including oral commensals like Porphyromonas gingivalis and Fusobacterium nucleatum or Gram-negative bacteria like Proteobacteria. The role of Helicobacter spp. remains unclear. Recent isolation of Malassezia globosa from PDAC tissue suggest also the mycobiota as a crucial player of tumorigenesis. Based on described molecular mechanisms and interactions between the pancreatic tissue and the immune system this review proposes a model of how the micro- and the mycobial dysbiosis could contribute to tumorigenesis in PDAC.

CONCLUSIONS

The presence of micro- and mycobial dysbiosis in pancreatic tumor tissue opens a fascinating perspective on PDAC oncogenesis. Further studies will pave the way for novel tumor markers and treatment strategies.

Role of microbial dysbiosis in carcinogenesis & cancer therapies

The human body supports a heterogeneous population of microorganisms. Every microorganism has the ability to contribute to the unique microenvironment around it. The aim of this review is to discuss the changes in the microbial population and their relative abundance across different ecosystems of the human body, the interactions within the microbial communities, metabolites they secrete to their external environment, their immunomodulatory functions, their signal transduction pathways and how these respond to environmental stimuli such as various diets, alcohol and drug consumption, smoking and finally suggest new therapeutic approaches. The microbiota may leads to cancer through inflammation mediated mechanisms which modulate immune responses, or produce carcinogenic metabolites and genotoxins, or deregulate cell proliferative signalling pathways. The identification of these molecular mechanisms in carcinogenesis may lead to better treatment strategies. In this review we have tried to explore the changes in microbial composition between cancer and normal tissues and what molecular mechanisms provide a connecting link between microbial dysbiosis and cancer.

Metabolic regulation in the immune response to cancer

Metabolic reprogramming in tumor‐immune interactions is emerging as a key factor affecting pro‐inflammatory carcinogenic effects and anticancer immune responses. Therefore, dysregulated metabolites and their regulators affect both cancer progression and therapeutic response. Here, we describe the molecular mechanisms through which microenvironmental, systemic, and microbial metabolites potentially influence the host immune response to mediate malignant progression and therapeutic intervention. We summarized the primary interplaying factors that constitute metabolism, immunological reactions, and cancer with a focus on mechanistic aspects. Finally, we discussed the possibility of metabolic interventions at multiple levels to enhance the efficacy of immunotherapeutic and conventional approaches for future anticancer treatments.

Exogenous Polyamines Influence In Vitro Microbial Adhesion to Human Mucus According to the Age of Mucus Donor

Adhesion to intestinal mucus is the first step for microbiota colonization in early life. Polyamines are polycations with important physiological functions in both procaryotic and eucaryotic cells. However, their role in intestinal mucus adhesion is not known. The objective of the present study was to evaluate whether exogenous polyamines (putrescine, spermidine, spermine, and their combination) would alter the adhesive properties of Lacticaseibacillus rhamnosus GG (LGG), Bifidobacterium animalis subs. lactis Bb12, Cronobacter sakazakii, and Escherichia coli. Human intestinal mucus was isolated from healthy infants (0-6-month-old and 6-12-month-old) and healthy adults (25-52 years old). Spermidine significantly increased Bb12 adhesion (p < 0.05) in the mucus of infants (0-6 months) but reduced the adhesion of LGG in adult mucus (p < 0.05) with no significant effect in any of the infant groups. Spermine was more effective than polyamine combinations in reducing C. sakazakii (p < 0.05) adhesion in early infant mucus (0-6 months). The adhesion ability of E. coli remained unaffected by exogenous polyamines at any age in the concentrations tested. Our data suggest that polyamines may modulate the bacterial adhesion to mucus depending on the bacterial strain and depending at what age the mucus has been generated.

Crystal structure of Z-DNA in complex with the polyamine putrescine and potassium cations at ultra-high resolution

The X-ray crystal structure of the d(CGCGCG)2/putrescine(2+)/K+ complex has been determined at 0.60 Å resolution. Stereochemical restraints were used only for the putrescinium dication, and 23 bonds and 18 angles of the Z-DNA nucleotides with dual conformation. The N atoms of the putrescine(2+) dication form three direct hydrogen bonds with the N7_G atoms of three different Z-DNA molecules, plus three water-mediated hydrogen bonds with cytosine, guanine and phosphate acceptors. A unique potassium cation was also unambiguously identified in the structure, albeit at a ∼0.5 occupation site shared with a water molecule, providing the first example of such a complex with Z-DNA. The K+ cation has coordination number of eight and an irregular coordination sphere, formed by four water molecules and four O atoms from two phosphate groups of the Z-DNA, including ligands present at fractional occupancy. The structural disorder of the Z-DNA duplex is manifested by the presence of alternate conformations along the DNA backbone. Comparison of the position and interactions of putrescine(2+) in the present structure with other ultra-high-resolution structures of Z-DNA in complexes with Mn2+ and Zn2+ ions shows that the dicationic putrescinium moiety can effectively substitute these metal ions for stabilization of Z-type DNA duplexes. Furthermore, this comparison also suggests that the spermine(4+) tetracation has a higher affinity for Z-DNA than K+.

Polyamines are Required for tRNA Anticodon Modification in Escherichia coli

Biogenic polyamines are natural aliphatic polycations formed from amino acids by biochemical pathways that are highly conserved from bacteria to humans. Their cellular concentrations are carefully regulated and dysregulation causes severe cell growth defects. Polyamines have high affinity for nucleic acids and are known to interact with mRNA, tRNA and rRNA to stimulate the translational machinery, but the exact molecular mechanism(s) for this stimulus is still unknown. Here we exploit that Escherichia coli is viable in the absence of polyamines, including the universally conserved putrescine and spermidine. Using global macromolecule labelling approaches we find that ribosome efficiency is reduced by 50-70% in the absence of polyamines and this reduction is caused by slow translation elongation speed. The low efficiency causes rRNA and multiple tRNA species to be overproduced in the absence of polyamines, suggesting an impact on the feedback regulation of stable RNA transcription. Importantly, we find that polyamine deficiency affects both tRNA levels and tRNA modification patterns. Specifically, a large fraction of tRNA^his, tRNA^tyr and tRNA^asn lack the queuosine modification in the anticodon "wobble" base, which can be reversed by addition of polyamines to the growth medium. In conclusion, we demonstrate that polyamines are needed for modification of specific tRNA, possibly by facilitating the interaction with modification enzymes.

Gut microbiota-derived metabolites in the regulation of host immune responses and immune-related inflammatory diseases

The gut microbiota has a critical role in the maintenance of immune homeostasis. Alterations in the intestinal microbiota and gut microbiota-derived metabolites have been recognized in many immune-related inflammatory disorders. These metabolites can be produced by gut microbiota from dietary components or by the host and can be modified by gut bacteria or synthesized de novo by gut bacteria. Gut microbiota-derived metabolites influence a plethora of immune cell responses, including T cells, B cells, dendritic cells, and macrophages. Some of these metabolites are involved in the pathogenesis of immune-related inflammatory diseases, such as inflammatory bowel diseases, diabetes, rheumatoid arthritis, and systemic lupus erythematosus. Here, we review the role of microbiota-derived metabolites in regulating the functions of different immune cells and the pathogenesis of chronic immune-related inflammatory diseases.

Bacterial infection reinforces host metabolic flux from arginine to spermine for NLRP3 inflammasome evasion

Hosts recognize cytosolic microbial infection via the nucleotide-binding domain-like receptor (NLR) protein family, triggering inflammasome complex assembly to provoke pyroptosis or cytokine-related caspase-1-dependent antimicrobial responses. Pathogens have evolved diverse strategies to antagonize inflammasome activation. Here, Edwardsiella piscicida gene-defined transposon library screening for lactate dehydrogenase (LDH) release in nlrc4^-/- bone marrow-derived macrophages (BMDMs) demonstrates that genes clustered in the bacterial arginine metabolism pathway participate in NLRP3 inflammasome inhibition. Blocking arginine uptake or putrescine export significantly relieves NLRP3 inflammasome inhibition, indicating that this bacterium rewires its arginine metabolism network during infection. Moreover, intracellular E. piscicida recruits the host arginine importer (mCAT-1) and putrescine exporter (Oct-2) to bacterium-containing vacuoles, accompanied by reduced arginine and accumulated cytosolic spermine. Neutralizing E. piscicida-induced cytosolic spermine enhancement by spermine synthetase or extracellular spermine significantly alters NLRP3 inflammasome activation. Importantly, accumulated cytosolic spermine inhibits K⁺ efflux-dependent NLRP3 inflammasome activation. These data highlight the mechanism of bacterial gene-mediated arginine metabolism control for NLRP3 inflammasome evasion.