Riboflavin Synthesis Research Articles

Anaerobic wastewater treatment containing sulfate enhanced by N-acyl homoserine lactones: Microbial insights as deciphered by metagenomics

Addressing the challenge of enhancing anaerobic wastewater treatment containing sulfate is a pressing concern. Adding quorum sensing signaling molecule N-acyl-homoserine lactones (AHLs) is beneficial for improving anaerobic treatment performances. Previous studies focused on the impact of AHL addition on microbial communities, the role of AHL addition in functional metabolism and interspecies electron transfer (IET) is poorly understood. This study delved into the roles of AHLs in anaerobic wastewater treatment containing sulfate. AHLs expedited COD degradation and improved methane production, with a 15.49 % increase in methane production with 20 μM AHL addition. AHL addition enhanced electron transport system activity by 28.02 % and specific methanogenic activity by 22.61 %, suggesting an enhancement in microbial activity and methanogenic capability. Taxonomic analysis revealed the facilitation of AHL addition on symbiotic relationships between acidifying bacteria and methanogens. KEGG annotations highlighted upregulation of genes associated with key enzymes in acidification, sulfate reduction, and methanogenesis with AHL addition. AHLs also bolstered syntrophic metabolism by upregulating genes involved in IET processes, including H2 production and utilization, riboflavin synthesis and secretion, and conductive pili assembly and synthesis. This study bridges gaps in understanding the influence of AHL addition on microbial metabolism and electron transfer.

Genome-centric metagenomic analysis reveals mechanisms of quorum sensing promoting anaerobic digestion under sulfide stress: Syntrophic metabolism and microbial self-adaptation

Sulfide stress is a common inhibition factor in anaerobic digestion systems with sulfur-rich feedstocks. Quorum sensing (QS) signaling molecule N-acyl-homoserine lactones (AHLs) possess positive effect on promoting anaerobic digestion. However, the micro-biological mechanisms of AHLs affecting syntrophic metabolism and microbial self-adaptation have not yet been deciphered in anaerobic digestion under sulfide stress. In this study, the CH4 production increased by 21.34 % at 20 μM AHLs addition in anaerobic digestion under sulfide stress. AHLs contributed to establishing potential syntrophic relationship between acidifying bacteria (unclassified_o__Bacteroidales, Lentimicrobium, Acetoanaerobium, Longilinea, and Sphaerochaetaa) and Methanothrix. AHLs promoted syntrophic metabolism by boosting microbial metabolic activity and interspecies electron transfer (IET) process under sulfide stress. For microbial metabolic activity, AHLs promoted the key enzyme synthesis in acidogenesis and methanogenesis. For IET process, AHLs promoted the assembly and synthesis of conductive pili, and synthesis and secretion of riboflavin. Furthermore, AHLs promoted microbial self-adaptation including two component system, lipopolysaccharide biosynthesis, and DNA repair, which were important evidences that microbial resistance to sulfide stress was enhanced by AHLs. Microbial self-adaptation provided favorable foundation and safeguard for syntrophic metabolisms under sulfide stress. These findings deciphered the micro-biological mechanisms of AHLs enhancing anaerobic digestion under sulfide stress.

Engineering Shewanella oneidensis-Carbon Felt Biohybrid Electrode Decorated with Bacterial Cellulose Aerogel-Electropolymerized Anthraquinone to Boost Energy and Chemicals Production.

Interfacial electron transfer between electroactive microorganisms (EAMs) and electrodes underlies a wide range of bio-electrochemical systems with diverse applications. However, the electron transfer rate at the biotic-electrode interface remains low due to high transmembrane and cell-electrode interfacial electron transfer resistance. Herein, a modular engineering strategy is adopted to construct a Shewanella oneidensis-carbon felt biohybrid electrode decorated with bacterial cellulose aerogel-electropolymerized anthraquinone to boost cell-electrode interfacial electron transfer. First, a heterologous riboflavin synthesis and secretion pathway is constructed to increase flavin-mediated transmembrane electron transfer. Second, outer membrane c-Cyts OmcF is screened and optimized via protein engineering strategy to accelerate contacted-based transmembrane electron transfer. Third, a S. oneidensis-carbon felt biohybrid electrode decorated with bacterial cellulose aerogel and electropolymerized anthraquinone is constructed to boost the interfacial electron transfer. As a result, the internal resistance decreased to 42 Ω, 480.8-fold lower than that of the wild-type (WT) S. oneidensis MR-1. The maximum power density reached 4286.6 ± 202.1mWm-2, 72.8-fold higher than that of WT. Lastly, the engineered biohybrid electrode exhibited superior abilities for bioelectricity harvest, Cr6+ reduction, and CO2 reduction. This study showed that enhancing transmembrane and cell-electrode interfacial electron transfer is a promising way to increase the extracellular electron transfer of EAMs.

Utilizing 5' UTR Engineering Enables Fine-Tuning of Multiple Genes within Operons to Balance Metabolic Flux in Bacillus subtilis.

The application of synthetic biology tools to modulate gene expression to increase yield has been thoroughly demonstrated as an effective and convenient approach in industrial production. In this study, we employed a high-throughput screening strategy to identify a 5' UTR sequence from the genome of B. subtilis 168. This sequence resulted in a 5.8-fold increase in the expression level of EGFP. By utilizing the 5' UTR sequence to overexpress individual genes within the rib operon, it was determined that the genes ribD and ribAB serve as rate-limiting enzymes in the riboflavin synthesis pathway. Constructing a 5' UTR library to regulate EGFP expression resulted in a variation range in gene expression levels exceeding 100-fold. Employing the same 5' UTR library to regulate the expression of EGFP and mCherry within the operon led to a change in the expression ratio of these two genes by over 10,000-fold. So, employing a 5' UTR library to modulate the expression of the rib operon gene and construct a synthetic rib operon resulted in a 2.09-fold increase in riboflavin production. These results indicate that the 5' UTR sequence identified and characterized in this study can serve as a versatile synthetic biology toolkit for achieving complex metabolic network reconstruction. This toolkit can facilitate the fine-tuning of gene expression to produce target products.

Signals that control MAIT cell function in healthy and inflamed human tissues.

Mucosal-associated invariant T (MAIT) cells have a semi-invariant T-cell receptor that allows recognition of antigen in the context of the MHC class I-related (MR1) protein. Metabolic intermediates of the riboflavin synthesis pathway have been identified as MR1-restricted antigens with agonist properties. As riboflavin synthesis occurs in many bacterial species, but not human cells, it has been proposed that the main purpose of MAIT cells is antibacterial surveillance and protection. The majority of human MAIT cells secrete interferon-gamma (IFNg) upon activation, while some MAIT cells in tissues can also express IL-17. Given that MAIT cells are present in human barrier tissues colonized by a microbiome, MAIT cells must somehow be able to distinguish colonization from infection to ensure effector functions are only elicited when necessary. Importantly, MAIT cells have additional functional properties, including the potential to contribute to restoring tissue homeostasis by expression of CTLA-4 and secretion of the cytokine IL-22. A recent study provided compelling data indicating that the range of human MAIT cell functional properties is explained by plasticity rather than distinct lineages. This further underscores the necessity to better understand how different signals regulate MAIT cell function. In this review, we highlight what is known in regards to activating and inhibitory signals for MAIT cells with a specific focus on signals relevant to healthy and inflamed tissues. We consider the quantity, quality, and the temporal order of these signals on MAIT cell function and discuss the current limitations of computational tools to extrapolate which signals are received by MAIT cells in human tissues. Using lessons learned from conventional CD8 T cells, we also discuss how TCR signals may integrate with cytokine signals in MAIT cells to elicit distinct functional states.

Effects of simulated microgravity on current generation of electrochemically active bacteria: Insights from case-control study using random positioning machine

Electrochemically active bacteria (EAB) exhibit promising prospects for space exploration and life support systems. However, the effects of the space environment on EAB are unclear. In this study, the effects of simulated microgravity on the current generation of mixed-culture EAB were illustrated, and the underlying mechanism was elucidated. The results demonstrated that the electrochemical activity of mixed-culture EAB was enhanced, which was mainly due to the enrichment of Geobacter and the increase in EAB biomass. Additionally, the genes and proteins of the biofilm changed obviously under simulated microgravity conditions, including: I) genes related to signal transfer, II) genes related to cell wall synthesis, and III) genes related to riboflavin synthesis. This study first revealed the enrichment in EAB abundance, the increase in EAB biomass, and the promotion of current generation under simulated microgravity.

Deciphering Microbial Community and Nitrogen Fixation in the Legume Rhizosphere.

Nitrogen is the most limiting factor in crop production. Legumes establish a symbiotic relationship with rhizobia and enhance nitrogen fixation. We analyzed 1,624 rhizosphere 16S rRNA gene samples and 113 rhizosphere metagenomic samples from three typical legumes and three non-legumes. The rhizosphere microbial community of the legumes had low diversity and was enriched with nitrogen-cycling bacteria (Sphingomonadaceae, Xanthobacteraceae, Rhizobiaceae, and Bacillaceae). Furthermore, the rhizosphere microbiota of legumes exhibited a high abundance of nitrogen-fixing genes, reflecting a stronger nitrogen-fixing potential, and Streptomycetaceae and Nocardioidaceae were the predominant nitrogen-fixing bacteria. We also identified helper bacteria and confirmed through metadata analysis and a pot experiment that the synthesis of riboflavin by helper bacteria is the key factor in promoting nitrogen fixation. Our study emphasizes that the construction of synthetic communities of nitrogen-fixing bacteria and helper bacteria is crucial for the development of efficient nitrogen-fixing microbial fertilizers.

Riboflavin Crystals with Extremely High Water Solubility.

New insights into the unique biochemical properties of riboflavin (Rf), also known as vitamin B2, are leading to the development of its use not only as a vitamin supplement but also as a potential anti-inflammatory, immunomodulatory, antioxidant, anticancer, and antiviral agent, where it may play a role as an inhibitor of viral proteinases. At the same time, the comparison of the pharmacoactivity of Rf with its known metabolites, namely, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), is very complicated due to its poor water solubility: 0.1-0.3 g/L versus 67 g/L for FMN and 50 g/L for FAD, which is the limiting factor for its administration in clinical practice. In this study, we report the recrystallization procedure of the type A Rf crystals into the slightly hydrophobic type B/C and a new hydrophilic crystal form that has been termed the P type. Our method of Rf crystal modification based on recrystallization from dilute alkaline solution provides an unprecedented extremely high water solubility of Rf, reaching 23.5 g/L. A comprehensive study of the physicochemical properties of type P riboflavin showed increased photodynamic therapeutic activity compared to the known types A and B/C against clinical isolates of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Salmonella typhimurium. Importantly, our work not only demonstrates a simple and inexpensive method for the synthesis of riboflavin with high solubility, which should lead to increased bioactivity, but also opens up opportunities for improving both known and new therapeutic applications of vitamin B2.

Riboflavin overproduction on lignocellulose hydrolysate by the engineered yeast Candida famata.

Lignocellulose (dry plant biomass) is an abundant cheap inedible residue of agriculture and wood industry with great potential as a feedstock for biotechnological processes. Lignocellulosic substrates can serve as valuable resources in fermentation processes, allowing the production of a wide array of chemicals, fuels, and food additives. The main obstacle for cost-effective conversion of lignocellulosic hydrolysates to target products is poor metabolism of the major pentoses, xylose and L-arabinose, which are the second and third most abundant sugars of lignocellulose after glucose. We study the oversynthesis of riboflavin in the flavinogenic yeast Candida famata and found that all major lignocellulosic sugars, including xylose and L-arabinose, support robust growth and riboflavin synthesis in the available strains of C. famata. To further increase riboflavin production from xylose and lignocellulose hydrolysate, genes XYL1 and XYL2 coding for xylose reductase and xylitol dehydrogenase were overexpressed. The resulting strains exhibited increased riboflavin production in both shake flasks and bioreactors using diluted hydrolysate, reaching 1.5g L-1.

Bifidobacterium longum subsp. iuvenis subsp. nov., a novel subspecies isolated from the faeces of weaning infants.

The species Bifidobacterium longum currently comprises four subspecies: B. longum subsp. longum , B. longum subsp. infantis , B. longum subsp. suis and B. longum subsp. suillum . Recently, several studies on B. longum suggested the presence of a separate clade containing four strains isolated from infants and one from rhesus macaque. These strains shared a phylogenetic similarity to B. longum subsp. suis DSM 20210T and B. longum subsp. suillum JCM1995T [average nucleotide identity (ANI) of 98.1 %) while showed an ANI of 96.5 % with both B. longum subsp. infantis and B. longum subsp. longum . The current work describes five novel additional B. longum strains isolated from Bangladeshi weaning infants and demonstrates their common phylogenetic origin with those of the previously proposed separated clade. Based on polyphasic taxonomic approach comprising loci multilocus sequence analysis and whole genome multilocus sequence typing, all ten examined strains have been confirmed as a distinct lineage within the species B. longum with B. longum subsp. suis and B. longum subsp. suillum as closest subspecies. Interestingly, these strains are present in weaning infants and primates as opposed to their closest relatives which have been typically isolated from pig and calves. These strains, similarly to B. longum subsp. infantis , show a common capacity to metabolize the human milk oligosaccharide 3-fucosyllactose. Moreover, they harbour a riboflavin synthesis operon, which differentiate them from their closest subspecies, B. longum subsp. suis and B. longum subsp. suillum . Based on the consistent results from genotypical, ecological and phenotypical analyses, a novel subspecies with the name Bifidobacterium longum subsp. iuvenis, with type strain NCC 5000T (=LMG 32752T=CCOS 2034T), is proposed.

Molecular docking studies of principal components and in vitro inhibitory activities of Rosmarinus officinalis essential oil against Aspergillus flavus, Aspergillus fumigatus and Mucor indicus

BackgroundEssential oil from Rosmarinus officinalis (REO) is endowed with innumerable pharmacological biological activities such as antibacterial, antioxidant, anti-inflammatory, anti-cancer, anti-diabetic, and immunostimulant hence used as complementary and traditional medicine worldwide. This study aimed at molecular docking studies of principal components and in vitro inhibitory activities of REO against Aspergillus flavus, Aspergillus fumigatus and Mucor indicus. MethodsThis was followed by molecular docking of major bioactive compounds from REO against fungal enzymes involved in riboflavin synthesis pathway and cell wall synthesis as pertinent sites for drug designing against spp of the Aspergillus and Mucor genera. Finally, in vitro confirmation was conducted to determine the antifungal potential of REO using food poisoning technique. ResultsDrug-likeness and toxicity profile of REO components were also calculated. GC-FID analyses revealed the presence of diverse phytocomponents including cis-3-hexanol (18 %), vertocitral C (16 %), camphene (9 %), α-pinene (8 %), humulene oxide (7.6 %), α-caryophyllene (6.6 %), cumenol (4.4 %), 1,8-cineole (4.1 %), β-caryophyllene (3.8 %) as major components in REO, hence used for docking analysis. For the most predominating phytochemicals present in the REO molecular docking analysis revealed active binding of all bioactive compounds to all targets involved in riboflavin synthesis pathway and cell wall synthesis fungal enzymes. All the ligands obeyed the LIPINSKY rule and exhibited adequate bioactivity. Wet-lab confirmation was achieved against three fungal strains Aspergillus fumigatus, Aspergillus flavus, and Mucor indicus. Wet lab results indicated that REO were able to inhibit fungal growth of these fungal spp, thus indicating its role as effective antifungal drug. ConclusionsThese results support the fungicidal abilities of REO essential oil as potential substitutes for artificial antifungals.

MAIT cells altered phenotype and cytotoxicity in lupus patients are linked to renal disease severity and outcome.

Systemic lupus erythematosus (SLE) is an autoimmune disease in which circulating immune complexes can cause different types of glomerulonephritis, according to immune deposits and to the type of glomerular cell injury. Proliferative lesions represent the most severe form of lupus nephritis (LN) and often lead to kidney failure and death. Mucosal-associated invariant T (MAIT) cells are a subset of innate-like T cells that recognize microbial-derived ligands from the riboflavin synthesis pathway. Although abundant in peripheral blood, MAIT cells are enriched in mucosal and inflamed tissues. While previous studies have reported concordant results concerning lower MAIT cell frequencies in the blood of SLE patients, no information is known about MAIT cell function and LN severity and outcome. In the current study, we analyzed the baseline phenotype and function of peripheral blood MAIT cells by flow cytometry in 26 patients with LN and in a control group of 16 healthy individuals. We observe that MAIT cell frequencies are markedly reduced in blood of LN patients. MAIT cells from patients have an altered phenotype in terms of migration, proliferation and differentiation markers, notably in most severe forms of LN. Frequencies of PMA/ionomycin stimulated MAIT cells secreting effector molecules, such as proinflammatory IL-17 and cytotoxic protein granzyme B, are higher in LN patients. Patients undergoing a complete renal remission after immunosuppressive therapy had higher MAIT cell frequency, lower expression of proliferation marker Ki-67 and granzyme B (GzB) at inclusion. Remarkably, GzB production defines a predictive model for complete remission. We report here that blood MAIT cells display proinflammatory and cytotoxic function in severe lupus nephritis which may play a pathogenesis role, but without association with systemic lupus activity. Finally, low cytotoxic profile of MAIT cells may represent a promising prognostic factor of lupus nephritis remission one year after induction therapy.

Synthetic 5-amino-6-D-ribitylaminouracil paired with inflammatory stimuli facilitates MAIT cell expansion in vivo.

Mucosal-associated invariant T (MAIT) cells are a population of innate-like T cells, which mediate host immunity to microbial infection by recognizing metabolite antigens derived from microbial riboflavin synthesis presented by the MHC-I-related protein 1 (MR1). Namely, the potent MAIT cell antigens, 5-(2-oxopropylideneamino)-6-D-ribitylaminouracil (5-OP-RU) and 5-(2-oxoethylideneamino)-6-D-ribitylaminouracil (5-OE-RU), form via the condensation of the riboflavin precursor 5-amino-6-D-ribitylaminouracil (5-A-RU) with the reactive carbonyl species (RCS) methylglyoxal (MG) and glyoxal (G), respectively. Although MAIT cells are abundant in humans, they are rare in mice, and increasing their abundance using expansion protocols with antigen and adjuvant has been shown to facilitate their study in mouse models of infection and disease. Here, we outline three methods to increase the abundance of MAIT cells in C57BL/6 mice using a combination of inflammatory stimuli, 5-A-RU and MG. Our data demonstrate that the administration of synthetic 5-A-RU in combination with one of three different inflammatory stimuli is sufficient to increase the frequency and absolute numbers of MAIT cells in C57BL/6 mice. The resultant boosted MAIT cells are functional and can provide protection against a lethal infection of Legionella longbeachae. These results provide alternative methods for expanding MAIT cells with high doses of commercially available 5-A-RU (± MG) in the presence of various danger signals.

Complete De Novo Assembly of Wolbachia Endosymbiont of Frankliniella intonsa.

As an endosymbiont, Wolbachia exerts significant effects on the host, including on reproduction, immunity, and metabolism. However, the study of Wolbachia in Thysanopteran insects, such as flower thrips Frankliniella intonsa, remains limited. Here, we assembled a gap-free looped genome assembly of Wolbachia strain wFI in a length of 1,463,884 bp (GC content 33.80%), using Nanopore long reads and Illumina short reads. The annotation of wFI identified a total of 1838 protein-coding genes (including 85 pseudogenes), 3 ribosomal RNAs (rRNAs), 35 transfer RNAs (tRNAs), and 1 transfer-messenger RNA (tmRNA). Beyond this basic description, we identified mobile genetic elements, such as prophage and insertion sequences (ISs), which make up 17% of the entire wFI genome, as well as genes involved in riboflavin and biotin synthesis and metabolism. This research lays the foundation for understanding the nutritional mutualism between Wolbachia and flower thrips. It also serves as a valuable resource for future studies delving into the intricate interactions between Wolbachia and its host.

Type I interferons drive MAIT cell functions against bacterial pneumonia.

Mucosal-associated invariant T (MAIT) cells are abundant in the lung and contribute to host defense against infections. During bacterial infections, MAIT cell activation has been proposed to require T cell receptor (TCR)-mediated recognition of antigens derived from the riboflavin synthesis pathway presented by the antigen-presenting molecule MR1. MAIT cells can also be activated by cytokines in an MR1-independent manner, yet the contribution of MR1-dependent vs. -independent signals to MAIT cell functions in vivo remains unclear. Here, we use Klebsiella pneumoniae as a model of bacterial pneumonia and demonstrate that MAIT cell activation is independent of MR1 and primarily driven by type I interferons (IFNs). During Klebsiella infection, type I IFNs stimulate activation of murine and human MAIT cells, induce a Th1/cytotoxic transcriptional program, and modulate MAIT cell location within the lungs. Consequently, adoptive transfer or boosting of pulmonary MAIT cells protect mice from Klebsiella infection, with protection being dependent on direct type I IFN signaling on MAIT cells. These findings reveal type I IFNs as new molecular targets to manipulate MAIT cell functions during bacterial infections.

Untargeted metabolomics reveal sex-specific and non-specific redox-modulating metabolites in kidneys following binge drinking

Graphical abstract Abstract Binge drinking is a growing health concern among all age groups. The ability of individuals to handle ethanol in their systems differs not due to differences in enzyme expression but also due to other factors. Vital organs including brain, liver, heart, and kidneys are at high risk following repeated exposure to high concentrations of ethanol from binge drinking. The impact of chronic binge drinking on kidneys is not well studied. Using a mouse model of chronic binge drinking, we have identified major metabolic alterations that could set the stage for detrimental effects in the kidneys of male and female mice. We have deciphered that even though there are pathway overlaps, the different sexes exhibited unique and divergent metabolic pathway dysregulations as per the metabolite panels following binge drinking. We have reported that binge drinking could negatively influence renal redox homeostasis in both sexes through the regulation of different metabolite clusters. In male mice by downregulation of pantothenic acid and riboflavin synthesis, and in female mice by upregulation of α-aminoadipic acid and formyl kynurenine level. Interestingly, the uric acid biosynthesis pathway has been upregulated independent of the sex-specific effects, portraying the significance of uric acid as a potential marker for binge drinking-induced injury in both sexes. Thus, by altering renal metabolome, binge drinking sets the stage for renal damage by disturbing renal redox balance. Our data has high translational potential and will aid in finding ideal therapeutics in a sex-specific manner for subjects exposed to binge drinking- induced renal injury.

Mucosal-associated invariant T cells in digestive tract: Local guardians or destroyers?

Mucosa-associated invariant T cells (MAIT) are a class of innate-like T lymphocytes mainly presenting CD8+ phenotype with a semi-invariant αβ T-cell receptor, which specifically recognises MR1-presented biosynthetic derivatives of riboflavin synthesis produced by various types of microbiomes. As innate-like T lymphocytes, MAIT can be activated by a variety of cytokines, leading to immediate immune responses to infection and tumour cues. As an organ that communicates with the external environment, the digestive tract, especially the gastrointestinal tract, contains abundant microbial populations. Communication between MAIT and local microbiomes is important for the homeostasis of mucosal immunity. In addition, accumulating evidence suggests changes in the abundance and structure of the microbial community during inflammation and tumorigenesis plays a critical role in disease progress partly through their impact on MAIT development and function. Therefore, it is essential for the understanding of MAIT response and their interaction with microbiomes in the digestive tract. Here, we summarised MAIT characteristics in the digestive tract and its alteration facing inflammation and tumour, raising that targeting MAIT can be a candidate for treatment of gastrointestinal diseases.

Subtractive sequence-mediated therapeutic targets from the conserved gene clusters of Campylobacter hyointestinalis and computational inhibition assessment

Campylobacter hyointestinalis is a causative agent of enteritis, proctitis, human gastroenteritis, and diarrhea. Reported transmission is from pigs to humans. Link with gastrointestinal carcinoma has also been established in non-Helicobacter pylori patients carrying this strain. The genome size of the strain LMG9260 is 1.8 MB with 1785 chromosomal and seven plasmid proteins. No therapeutic targets have been identified and reported in this bacterium. Therefore, subtractive computational screening of its genome was carried out for the purpose. In total, 31 such targets were mined and riboflavin synthase was utilized for screening natural product inhibitors against it. Among more than 30,000 screened natural compounds from the NPASS library, three (NPC472060, NPC33653, and NPC313886) were prioritized to have the potential to be developed into new antimicrobial drugs. Dynamics simulation assay along with other relevant parameters like absorption, toxicity, and distribution of the inhibiting compounds were also predicted and NPC33653 was identified as having the best drug-like properties among the prioritized compounds. Thus, it has potential to be pursued further for the inhibition of riboflavin synthesis in C. hyointestinalis for subsequent obstruction of its growth and survival. Communicated by Ramaswamy H. Sarma

Anti-aspergillosis and anti-mucormycosis potential of essential oils from two Cymbopogon spp. targeting riboflavin synthesis pathway

BackgroundCymbopogon martinii (palmrose essential oil, PEO) and Cymbopogon citratus (lemon grass essential oil, (LEO) are used as complementary and traditional medicine worldwide. PEO and LEO from Cymbopogon genus, contains a diversity of pharmacologically active compounds. Due to the complex nature of essential oils, their antifungal mechanism of action against aspergillosis and mucormycosis is still not completely understood. PurposeHence, the present study aimed at determining the chemical profile of each PEO and LEO and performing a molecular docking of two of their components geraniol and geranial against fungal enzymes involved in riboflavin synthesis pathway viz: riboflavin synthase (RS), riboflavin biosynthesis protein RibD domain-containing protein (RibD), and 3,4-dihydroxy-2-butanone 4-phosphate synthase (DBPS) as opposite sites for drug designing against aspergillosis and mucormycosis and in vitro confirmation. Study design and methodChemical profile of PEO and LEO was performed by GC-FID analysis. For molecular docking, patch-dock tool was conducted. Ligand-enzyme 3-D interactions were also calculated. ADMET properties (absorption, distribution, metabolism, excretion and toxicity) were also calculated. Antifungal activity was evaluated agaist three test pathogens Aspergillus niger, Aspergillus oryzae and Mucor indicus using poisoned food technique. ResultsGC-FID showed geraniol/geranial as the major components in PEO/LEO, thus, they were selected for docking analysis. Docking analysis specified active binding of geraniol and geranial to riboflavin synthase (RS), riboflavin biosynthesis protein RibD domain-containing protein (RibD), and 3,4-dihydroxy-2-butanone 4-phosphate synthase (DBPS) fungal enzymes. Wet-lab authentication was achieved by three fungal strains A. niger, A. oryzae and M. indicus. Docking studies revealed that the ligands geraniol/geranial exhibited interactions with RS, RibD, and DBPS fungal enzymes by H- bond and hydrophobic interactions. Geraniol and geranial obeyed LIPINSKY rule, and exhibited adequate bioactivity. Wet lab results indicated that PEO/LEO was able to inhibit fungal growth against test pathogens. ConclusionsThese findings confirm the fungicidal properties PEO/LEO essential oils as possible alternatives to synthetic fungicides.

MAIT cells and the microbiome.

Mucosal associated invariant T (MAIT) cells are innate-like T lymphocytes, strikingly enriched at mucosal surfaces and characterized by a semi-invariant αβ T cell receptor (TCR) recognizing microbial derived intermediates of riboflavin synthesis presented by the MHC-Ib molecule MR1. At barrier sites MAIT cells occupy a prime position for interaction with commensal microorganisms, comprising the microbiota. The microbiota is a rich source of riboflavin derived antigens required in early life to promote intra-thymic MAIT cell development and sustain a life-long population of tissue resident cells. A symbiotic relationship is thought to be maintained in health whereby microbes promote maturation and homeostasis, and in turn MAIT cells can engage a TCR-dependent "tissue repair" program in the presence of commensal organisms conducive to sustaining barrier function and integrity of the microbial community. MAIT cell activation can be induced in a MR1-TCR dependent manner or through MR1-TCR independent mechanisms via pro-inflammatory cytokines interleukin (IL)-12/-15/-18 and type I interferon. MAIT cells provide immunity against bacterial, fungal and viral pathogens. However, MAIT cells may have deleterious effects through insufficient or exacerbated effector activity and have been implicated in autoimmune, inflammatory and allergic conditions in which microbial dysbiosis is a shared feature. In this review we summarize the current knowledge on the role of the microbiota in the development and maintenance of circulating and tissue resident MAIT cells. We also explore how microbial dysbiosis, alongside changes in intestinal permeability and imbalance between pro- and anti-inflammatory components of the immune response are together involved in the potential pathogenicity of MAIT cells. Whilst there have been significant improvements in our understanding of how the microbiota shapes MAIT cell function, human data are relatively lacking, and it remains unknown if MAIT cells can conversely influence the composition of the microbiota. We speculate whether, in a human population, differences in microbiomes might account for the heterogeneity observed in MAIT cell frequency across mucosal sites or between individuals, and response to therapies targeting T cells. Moreover, we speculate whether manipulation of the microbiota, or harnessing MAIT cell ligands within the gut or disease-specific sites could offer novel therapeutic strategies.