Indole Production Research Articles

Characterization and Evaluation of Native Rhizobium of Groundnut (Arachis hypogaea L.) and Soybean (Glycine max L.)

The present investigation was conducted to characterize and evaluate native Rhizobium isolates of groundnut and soybean to enhance the Legume-Rhizobium symbiosis as well as increase sustainable crop production. In this connection, all the native isolates under study were characterized biochemically and tested with N-free sand culture in the glasshouse to select effective native Rhizobium isolates through proper screening. 10 isolates of each crop were collected from the culture collection bank of the Department of Agricultural Microbiology, Indira Gandhi Krishi Vishwavidyalaya Raipur (Chhattisgarh). Out of 10 isolates, 3 isolates of each crop were selected on the basis of their growth performance and the purity of the culture. The biochemical studies of selected isolates include starch hydrolysis, catalase, urease, citrate utilization, indole production, gelatine iron, and methyl red tests, which were further evaluated for nodulation and biological nitrogen fixation in groundnut and soybean under controlled conditions with four treatments for each crop and five replications. The experiment result revealed that the evaluation of native Rhizobium isolate no. 1185 of groundnut and isolate no. 1076 of soybean was found to be superior among all the rhizobial isolates taken for study. These isolates accumulated 1.24, 1.44 mg/plant extra amount of atmospheric nitrogen over un-inoculated control plants, respectively. Further, it can be concluded that these native isolates may be the most effective nitrogen fixers for groundnut and soybean over the control.

Base-Mediated Synthesis of 2-Bromobenzoheterocycles

AbstractA base-mediated cyclization to synthesize 2-bromobenzoheterocycles is reported. This transformation was demonstrated with 16 examples to access a broad range of brominated benzoheterocycles. Mechanistic studies support the reaction proceeds through a bromoalkyne, and revealed an exchangeable proton at C3 of the indole products.

L-tryptophan anaerobic fermentation for indole acetic acid production: Bacterial enrichment and effects of zero valent iron

Indole acetic acid (IAA) as a plant hormone, was one of the valuable products of anaerobic fermentation. However, the enriching method remained unknown. Moreover, whether zero-valent iron (ZVI) could enhance IAA production was unexplored. In this work, IAA producing bacteria Klebsiella (63 %) was enriched successfully. IAA average production rate and concentration were up to 3 mg/L/h and 56 mg/L. With addition of 1 g/L ZVI, IAA average production rate and concentration was increased for 2 and 3 folds. Mechanisms indicated ZVI increased Na+K+-ATP activity and electron transport activity for 2 folds and 1 fold. Moreover, macro transcription determined indole pyruvate pathway activity like primary-amine oxidase, indole pyruvate decarboxylase and aldehyde dehydrogenase were increased for 146 %, 187 %, and 557 %, respectively. Therefore, ZVI was suitable for enhancement IAA production from mixed culture anaerobic fermentation.

Detection of Coliform Bacteria in Raw Milk Samples Collected from Industrial Cities of Pakistan

Antibiotics and heavy metals-resistant bacteria in livestock environments can result in economic losses and raise public health and environmental problems. There is a crisis in the world's access to and pipeline for antibiotics. Objective: To screen raw milk samples collected from three different industrial cities Gujranwala, Lahore, and Sheikhupura, situated in the province of Punjab, Pakistan. Methods: In this regard, a total of 26 samples were having 84 coliform strains. Separated coliform colonies were processed for Gram's staining, catalase, indole production, and Simmon's citrate and motility tests. Results: Metal resistance of bacterial strains was also checked and 39.5% and 45.23% of bacteria were found to be resistant to ZnCl2 1% and 0.5%. 69.045% and 77.38% bacteria were found to be resistant to CuSo4 salt solution1% and 0.5%. 17.85% and 27% bacteria were found to be resistant to Na2CrO4 salt solution1% and 0.5% respectively. 80% of bacteria were found to be resistant to Cefuroxime, 26.19% to Cephradine, 84.52% to Aztroeonam 41.67% to Erythromycin, 91.667% to Trimethoprim 89.28% to Lincomycins. Conclusions: The raw milk samples were not only contaminated with coliforms but the bacteria were also resistant to heavy metals and certain antibiotics which might be considered indicative of industrial and anthropogenic pollution. Cephradine, 84.52% to Aztroeonam 41.67% to Erythromycin, 91.667% to Trimethoprim 89.28% to Lincomycins. Conclusions: The raw milk samples were not only contaminated with coliforms but the bacteria were also resistant to heavy metals and certain antibiotics which might be considered indicative of industrial and anthropogenic pollution.

Inter- and intra-specific variations in phenotypic traits of Pectobacterium strains isolated from diverse eudicots and monocots in Taiwan.

Pectobacterium spp. are phytopathogenic bacteria whose phylogeny has been continuously revised throughout the years. Previous studies on Pectobacterium's phenotypic diversity often analyzed strains obtained from specific crops or adopted outdated Pectobacterium classification systems. Therefore, a current perspective on trait variations in Pectobacterium species or strains infecting more diverse plant species is limited. This study conducted phylogenetic and phenotypic analyses on strains isolated from 8 eudicot and 4 monocot families in Taiwan. Phylogenetic analysis on 78 strains identified 6 recognized species, namely P. brasiliense, P. aroidearum, P. actinidiae, P. colocasium, P. carotovorum, and P. versatile. Among these, the first two were the most predominant. Patterns suggesting varying host preferences among bacterial species were detected; most P. aroidearum strains were isolated from monocots, whereas P. brasiliense and P. actinidiae tended to exhibit preferences for eudicots. Physiological tests and Biolog analyses conducted on representative strains of each species revealed great within-species phenotypic variation. Despite these strain-level variations, a combination of indole production and phosphatase activity tests was capable of distinguishing all representative strains of P. brasiliense from those of other identified species. Inoculation assays on potato, bok choy, calla lily and onion showed inter- and intra-specific heterogeneities in the tested strains' maceration potentials. Virulence patterns across Pectobacterium species and strains differed depending on the inoculated host. Altogether the findings from this work expand the understanding of Pectobacterium's phenotypic diversity and provide implications for pathogen identification and management.

The regulatory effects of (p)ppGpp and indole on cAMP synthesis in Escherichia coli cells.

Bacterial stress adaptive response is formed due to changes in the cell gene expression profile in response to alterations in environmental conditions through the functioning of regulatory networks. The mutual influence of network signaling molecules represented by cells' natural metabolites, including indole and second messengers (p) ppGpp and cAMP, is hitherto not well understood, being the aim of this study. E. coli parent strain BW25141 ((p) ppGpp+) and deletion knockout BW25141ΔrelAΔspoT which is unable to synthesize (p)ppGpp ((p)ppGpp0) were cultivated in M9 medium supplemented with different glucose concentrations (5.6 and 22.2 mM) in the presence of tryptophan as a substrate for indole synthesis and in its absence. The glucose content was determined with the glucose oxidase method; the indole content, by means of HPLC; and the cAMP concentration, by ELISA. The onset of an increase in initially low intracellular cAMP content coincided with the depletion of glucose in the medium. Maximum cAMP accumulation in the cells was proportional to the concentration of initially added glucose. At the same time, the (p) ppGpp0 mutant showed a decrease in maximum cAMP levels compared to the (p)ppGpp+ parent, which was the most pronounced in the medium with 22.2 mM glucose. So, (p)ppGpp was able to positively regulate cAMP formation. The promoter of the tryptophanase operon responsible for indole biosynthesis is known to be under the positive control of catabolic repression. Therefore, in the cells of the (p)ppGpp+ strain grown in the tryptophan-free medium that were characterized by a low rate of spontaneous indole formation, its synthesis significantly increased in response to the rising cAMP level just after glucose depletion. However, this was not observed in the (p)ppGpp0 mutant cells with reduced cAMP accumulation. When tryptophan was added to the medium, both of these strains demonstrated high indole production, which was accompanied by a decrease in cAMP accumulation compared to the tryptophan-free control. Thus, under glucose depletion, (p)ppGpp can positively regulate the accumulation of both cAMP and indole, while the latter, in its turn, has a negative effect on cAMP formation.

N-Heterocyclic Carbene-Catalyzed Regio- and Enantioselective C7-Alkylation of 4-Aminoindoles with α-Bromoenals.

The first carbene-catalyzed regio- and enantioselective indole C7-alkylation reaction between 4-aminoindoles and α-bromoenals is disclosed. The corresponding indole products could be obtained in moderate to good yields with good to excellent enantioselectivities. The evaluation of antibacterial activity against Psa revealed that nine of the C7-functionalized indoles exhibited superior inhibitory activities compared to the positive controls TC and BT. Our approach provides an efficient strategy to introduce a chiral chain into the C7 position of indole compounds, with potential applications evaluated in pesticide development.

Accessing Highly Substituted Indoles via B(C6F5)3-Catalyzed Secondary Alkyl Group Transfer.

Herein, we report a synthetic method to access a range of highly substituted indoles via the B(C6F5)3-catalyzed transfer of 2° alkyl groups from amines. The transition-metal-free catalytic approach has been demonstrated across a broad range of indoles and amine 2° alkyl donors, including various substituents on both reacting components, to access useful C(3)-alkylated indole products. The alkyl transfer process can be performed using Schlenk line techniques in combination with commercially available B(C6F5)3·nH2O and solvents, which obviates the requirement for specialized equipment (e.g., glovebox).

First Report of Pantoea anthophila Causing Shoot Dieback Disease of Ceylon Ironwood (Mesua ferrea) in Malaysia

Ceylon ironwood (Mesua ferrea Linn.) or Penaga lilin is one of Asia's most popular tropical herbal plants, including Malaysia (Sharma et al., 2017). The trees are cultivated for their aesthetic value and pharmacological properties, especially as traditional remedies for asthma, dermatopathy, inflammation, and rheumatic conditions (Adib et al., 2019). In August 2022, a disease survey was conducted on Ceylon ironwood trees ranging from 5 to 12 years old in Botanical Park, Putrajaya, Malaysia, with 80% exhibiting shoot dieback disease of the 15 trees exhibiting shoot dieback disease. Symptoms include irregular, water-soaked with brown lesions on young leaves and shoots, where the small lesion coalesced and formed broad necrotic regions, subsequently causing dieback and gradual defoliation. Three infected shoots were collected from each tree, excised into small pieces (10 to 20 mm), immersed with 75% ethanol for 3 min, washed with 2% NaOCl solution for 1 min, and rinsed twice for 1 min in sterilized distilled water. A 10 µl aliquot of the sample suspension was streaked onto nutrient agar (NA) and incubated for 24 h to 48 h at 35 °C. A total of 15 isolates with similar morphology were obtained, and each isolate was re-streaked three times to obtain pure colonies that were round, smooth, with irregular edges, and produced yellow pigment in culture. All isolates were Gram-negative, negative for indole production, and utilized glucose, maltose, trehalose, sucrose, D-lactose, and pectin. Three representative isolates (C001, C002, and C003) with similar morphology were selected for further characterization. The total genomic DNA of all isolates was extracted from overnight cultures using Geneaid™ DNA Isolation Kit (Geneaid Biotech Ltd., Taiwan). PCR amplification of 16S rDNA (Zhou et al., 2015) and species-specific infB (Brady et al., 2008) genes was performed, and each of the ~1500 bp and ~900 bp amplicons were sequenced. BLASTn and phylogenetic analyses revealed all isolates were 100% identical to Pantoea anthophila (P. anthophila) LGM 2558 strains (Accession Nos. NR_116749 and NR_116113) for the 16S rDNA gene. They were 99% identical to P. anthophila CL1 strain (Accession Number CP110473) for infB gene. These sequences were later deposited in the GenBank (Accession Nos. OQ772233, OQ772234, and OQ772235 for 16S rDNA gene, and OQ803527, OQ803528, and OQ803529 for infB gene). For the pathogenicity test, healthy Ceylon ironwood seedlings' shoots were inoculated with 10 mL of each isolate suspension (1 x 108 CFU/ml) by spraying the inoculum on the young shoots using a sterilized spray bottle. Control seedlings were inoculated with sterile water. The inoculated shoots were covered with a sealed plastic bag to maintain the moisture and were kept in the greenhouse with temperatures ranging from 26 to 35 °C. The experiments were repeated twice, with three replicates for each treatment. Inoculated shoots showed dieback symptoms like natural infection, including irregular, water-soaked, and brown lesions on leaves and young shoots at 10 days post-inoculation. Control seedlings remained asymptomatic. The pathogen was re-isolated and identified via sequencing of the 16S rDNA and infB genes, thus fulfilling Koch’s postulates. Previously, P. anthophila has been reported to cause soft rot in wampee plants in China (Zhou et al., 2015) and leaf blight of cotton in Pakistan (Tufail et al., 2020). To our knowledge, this is the first report of P. anthophila causing shoot dieback disease of Ceylon ironwood trees in Malaysia. Plant disease management strategies need to be established to reduce losses due to P. anthophila infection since the pathogen could limit Ceylon ironwood tree production in Malaysia.

The Microbial Community Structure in the Rhizosphere of Theobroma cacao L. and Euterpe oleracea Mart. Is Influenced by Agriculture System in the Brazilian Amazon.

This study tested the hypothesis that cocoa monoculture (MS) and cocoa-açai agroforestry systems (AFS) may influence the microbial community structure and populations of plant growth-promoting bacteria (PGPR). Accordingly, the aim was to analyze the microbial community structure and PGPR populations in different agroecosystems in the Brazilian Amazon. To achieve this, the rhizosphere microbial community of cocoa and açai plants in both Amazonian seasons (dry and rainy) was analyzed using culture-dependent (PGPR screening) and -independent methods [PCR-DGGE based on rrs, alp, nifH gene, and intergenic region (ITS) of fungi]. Concerning PGPR screening, out of 48 isolated bacterial strains, 25% were capable of siderophore production, 29% of mineralized organic phosphate, 8% of inorganic phosphate solubilization, and 4% of indole acetic acid production. Moreover, 17% of isolates could inhibit the growth of various phytopathogenic fungi. Statistical analyses of DGGE fingerprints (p < 0.05) showed that bacterial and fungal community structures in the rhizosphere were influenced by the seasons, supporting the results of the physicochemical analysis of the environment. Furthermore, as hypothesized, microbial communities differed statistically when comparing the MS and AFS. These findings provide important insights into the influence of climate and cultivation systems on soil microbial communities to guide the development of sustainable agricultural practices.

Mechanochemical C-H Arylation and Alkylation of Indoles Using 3 d Transition Metal and Zero-Valent Magnesium.

Although the 3 d transition-metal catalyzed C-H functionalization have been extensively employed to promote the formation of valuable carbon-carbon bonds, the persistent problems, including the use of sensitive Grignard reagents and the rigorous operations (solvent-drying, inert gas protection, metal pre-activation and RMgX addition rate control), still leave great room for further development of sustainable methodologies. Herein, we report a mechanochemical technology toward in-situ preparation of highly sensitive organomagnesium reagents, and thus building two general 3 d transition-metal catalytic platforms that enables regioselective arylation and alkylation of indoles with a wide variety of halides (including those containing post transformable functionalities and heteroaromatic rings). This mechanochemical strategy also brings unique reactivity and high step-economy in producing functionalized N-free indole products.

Fischer indolization of terpenes and steroids

AbstractHere we report a new synthetic approach to several intricate indoles and hydrazones starting with commercially available terpenes and steroids via Fischer indolization (FI) sequence under deep eutectic solvents (DES) conditions or by employing acetic acid reflux conditions. During the course of the reaction with pulegone 22 and pipertone 25 we observed Fischer indolization along with aromatization is occurring. In another instance, with thujone 32 we found cyclopropane ring is opening under thermal conditions leading to aromatized Fischer indole product. We also studied the FI sequence of some diketo derivatives to synthesize the corresponding bis indole derivatives, but instead we obtained mono hydrazone derivative which can be explained on the basis of steric reasons. In addition, we also modified other terpenes to study the FI sequence where we realized the formation of both hydrazone and indole derivatives. All the compounds synthesized here are well characterized by NMR and HRMS data.

A176 RESTORATION OF IMPAIRED MICROBIOTA-MEDIATED ARYL HYDROCARBON RECEPTOR SIGNALING IN PATIENTS WITH CELIAC DISEASE BY ORAL TRYPTOPHAN SUPPLEMENTATION: AN EXPLORATORY STUDY

Abstract Background Celiac disease (CeD) is an autoimmune condition driven by gluten in individuals expressing celiac-specific genes (HLA-DQ2 and/or DQ8). A strict gluten-free diet (GFD) is currently the only treatment. 30-40% of celiac patients exhibit persistent symptoms despite following a GFD ampersand:003E1 year and are considered non-responsive. Tryptophan is an essential amino acid metabolized by gut microbiota to produce indoles that activate aryl hydrocarbon receptor (AhR), contributing to intestinal barrier homeostasis. Our previous study showed CeD patients have altered tryptophan metabolism and limited AhR activation, only partially improving with a GFD. In healthy volunteers, oral tryptophan supplementation improved AhR activation in the small intestine, thus, indicating its feasibility as adjuvant to the GFD in non-responsive CeD. Aims The study aims were to: 1) determine whether tryptophan supplementation improves celiac specific symptoms in non-responders; and 2) if tryptophan supplementation modifies gut microbiota composition, intestinal indole production and AhR activity. Methods The study is a double-blind, randomized, placebo-controlled trial with the aim to recruit 50 adults from the McMaster University Celiac Clinic. At visit 1, consented participants are randomized 1:1 to L-tryptophan (3g/day) or placebo and receive intervention capsules to be taken for 3 weeks after Visit 2. At Visits 2 and 3, participants complete dietary and symptom questionnaires, provide blood, stool, and urine samples, and undergo endoscopy. The primary outcome, improvement in symptoms, is assessed using the Celiac Symptoms Index (CSI); general GI symptoms by Gastrointestinal Symptoms Rating Scale (GSRS); mood symptoms by Hospital Anxiety and Depression Scale (HADS); quality of life by Patient Assessment of Upper Gastrointestinal Disorders-Quality of Life questionnaire (PAGI-QoL). Results To- date we have recruited 10 participants. We will present blinded results from participants that have completed the study at the time of presentation based on responses to questionnaires pre, and post tryptophan/placebo intervention. At the time of analysis of this abstract, 5 participants had completed the study showing reduced CSI scores post intervention. The GSRS was also significantly reduced post intervention however, no change was observed in HADS and PAGI-QoL. Conclusions As all these results are currently blinded, we cannot attribute the symptom improvement to either tryptophan or the placebo effect. After unblinding the data, we will analyze the data to determine the extent of symptom reduction in relation to tryptophan metabolites (from urine, stool and duodenal aspirates) and AhR activation (from duodenal biopsy samples). Funding Agencies Weston Family Foundation

Citrobacter enshiensis sp. nov., isolated from seleniferous soil.

Two Gram-stain-negative, facultative anaerobic, rod-shaped bacterial strains, S171T and S2-9, were isolated from seleniferous soil in China. Comprehensive phylogenetic analyses based on 16S rRNA genes, multilocus sequences and whole genome sequences indicated that the two strains belonged to the genus Citrobacter. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values of strains S171T and S2-9 with the closest relative Citrobacter koseri NCTC 10786T were 83.6-83.7% and 27.7-27.8 %, respectively, which were below the species cutoff values. The ANI and dDDH values between the two strains were 97.9% and 84.8 %, respectively. The biochemical characteristics revealed that selenite tolerance, H2S and indole production, arginine dihydrolase, ornithine decarboxylase, as well as acid production from carbon sources such as d-sorbitol and arbutin are distinctive features of the two strains. Based on these results, strain S171T and strain S2-9 represent a novel species of the genus Citrobacter, for which the name Citrobacter enshiensis sp. nov. is proposed, with strain S171T (=GDMCC 1.3637T=JCM 35851T) as the type strain. The genome size of strain S171T was 4.92 Mb with a G+C content of 52.6 mol%. The genome size of strain S2-9 was 4.89 Mb with a G+C content of 52.6 mol%.

A Rare Agent in Wound Infection: Leclercia adecarboxylata

As a rare infectious agent, Leclercia adecarboxylata is a gram-negative bacillus belonging to the Enterobacteriaceae family. It can be isolated from human blood, sterile body fluids, sputum, urine, fecal, and wound samples. In this case report, the isolation of L. adecarboxylata as a causative agent in the wound and tissue sample cultures of a soft tissue infection that developed after arthrodesis surgery on the right foot of a 47-year-old female patient who was followed up with Charcot foot treatment due to diabetes in our hospital is presented. The patient's general condition was good, his leukocyte count was 6000/ml, leukocyte distribution was 58% neutrophil predominance, erythrocyte sedimentation rate was 105 mm/hour, and C-reactive protein level was 90 mg/L. Wound and tissue samples from the area considered to be the focus of infection were sent to our laboratory for culture examination. In the samples inoculated into routine identification media and subjected to standard incubation and identification procedures, a growth consisting of pure colonies (monomicrobial) was detected on the culture media. The isolate was identified as L. adecarboxylata by colony morphology, microscopic examinations (gram-negative bacilli), other basic identification procedures, and mass spectrometry (MALDI-TOF MS). Since it is a rare infectious agent, additional biochemical tests were performed; glucose-sucrose-lactose utilization, motility, indole production, and esculin hydrolysis tests were found to be positive, while oxidase, ornithine decarboxylase, hydrogen-sulfide production, citrate utilization, and urease tests were found to be negative. Antibiotic susceptibility tests were performed with the VITEK 2® automated system (Biomérieux, France), and the results were evaluated according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) v13.0 criteria. The isolate, which has a generally sensitive antibiotic profile, was evaluated as the infectious agent and the patient was treated with intravenous ampicillin/sulbactam for five days. The patient, whose laboratory values tended to improve (leukocyte count 4400/ml, neutrophil rate 52.9%), was discharged with peroral amoxicillin/clavulanic acid treatment.

Indoles and the advances in their biotechnological production for industrial applications

AbstractIndole is a signalling molecule produced both by bacteria and plants. In this review its signalling role between microbes and in particular in the human gut is discussed. Besides the natural roles, indole also has value for flavour and fragrance applications, for example, in food industry or perfumery. Additionally, indole can be derivatized to several halogenated and oxygenated compounds that can be used as natural colourants or have promising bioactivity with therapeutic potential to treat human diseases. Indole is traditionally obtained from coal tar. Biocatalytic approaches have been developed to convert indole into halogenated and oxygenated derivatives. This review will discuss recent advances in production of indole from glucose or tryptophan by fermentation and the production of derived halogenated and oxygenated derivatives by microbial cell factories.

Antibiofilm activity of lawsone against polymicrobial enterohemorrhagic Escherichia coli O157:H7 and Candida albicans by suppression of curli production and hyphal growth

Most bacteria and fungi form biofilms that attach to living or abiotic surfaces. These biofilms diminish the efficacy of antimicrobial agents and contribute to chronic infections. Furthermore, multispecies biofilms composed of bacteria and fungi are often found at chronic infection sites. In this study, lawsone (2‑hydroxy-1,4-naphthoquinone) and its parent 1,4-naphthoquinone were studied for antimicrobial and antibiofilm activities against single-species and multispecies biofilms of enterohemorrhagic Escherichia coli O157:H7 (EHEC) and Candida albicans. Biofilm formation assays, biofilm eradication assays, antimicrobial assays, live cell imaging microscopy, confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), extracellular polymeric substances and indole production, cell surface hydrophilicity assay, cell motility, cell aggregation, hyphal growth, dual species biofilm formation, quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR), and toxicity assays on plant seed germination and nematode model were utilized to investigate how lawsone affect biofilm development. Sub-inhibitory concentrations of lawsone (35µg/ml) significantly inhibited single-and multispecies biofilm development. Lawsone reduced the production of curli and indole, and the swarming motility of EHEC, efficiently inhibited C. albicans cell aggregation and hyphal formation, and increased the cell surface hydrophilicity of C. albicans. Transcriptomic analysis showed that lawsone suppressed the expression of the curli-related genes csgA and csgB in EHEC, and the expression of several hypha- and biofilm-related genes (ALS3, ECE1, HWP1, and UME6) in C. albicans. In addition, lawsone up to 100µg/ml was nontoxic to the nematode Caenorhabditis elegans and to the seed growth of Brassica rapa and Triticum aestivum. These results show that lawsone inhibits dual biofilm development and suggest that it might be useful for controlling bacterial or fungal infections and multispecies biofilms.

Microbiota-dependent indole production stimulates the development of collagen-induced arthritis in mice.

Altered tryptophan catabolism has been identified in inflammatory diseases like rheumatoid arthritis (RA) and spondyloarthritis (SpA), but the causal mechanisms linking tryptophan metabolites to disease are unknown. Using the collagen-induced arthritis (CIA) model, we identified alterations in tryptophan metabolism, and specifically indole, that correlated with disease. We demonstrated that both bacteria and dietary tryptophan were required for disease and that indole supplementation was sufficient to induce disease in their absence. When mice with CIA on a low-tryptophan diet were supplemented with indole, we observed significant increases in serum IL-6, TNF, and IL-1β; splenic RORγt+CD4+ T cells and ex vivo collagen-stimulated IL-17 production; and a pattern of anti-collagen antibody isotype switching and glycosylation that corresponded with increased complement fixation. IL-23 neutralization reduced disease severity in indole-induced CIA. Finally, exposure of human colonic lymphocytes to indole increased the expression of genes involved in IL-17 signaling and plasma cell activation. Altogether, we propose a mechanism by which intestinal dysbiosis during inflammatory arthritis results in altered tryptophan catabolism, leading to indole stimulation of arthritis development. Blockade of indole generation may present a unique therapeutic pathway for RA and SpA.

Experimental and molecular insights on the separation of indole from wash oil by tetraethylammonium‐based ionic liquids

AbstractA method for separating indole (IND) from wash oil by tetraethylammonium‐based ionic liquid (IL) was proposed. The distribution coefficient and selectivity of 304 kinds of ILs to IND were predicted by using Conductor‐like Screening Model for the Segment Activity Coefficient model, and quaternary ammonium acetate ILs have excellent separation performance. The experimental conditions were validated, and the influence of these conditions was explored. The IL could be recycled with water, and its structure and performance remained unchanged after repeated use four times. The extraction efficiency for real wash oil provided by a company reached 91.6%. The structure–performance relationship was explored by using quantum chemistry and molecular dynamic simulation. A process combining liquid–liquid extraction and azeotropic distillation was established for the separation of IND mixtures, and an IND product with a purity of 99.9% was obtained. This work comprehensively analyzed the separation of IND from wash oil using ILs at an atomic‐molecular‐experimental‐process scale.

Multi-function screening of probiotics to improve oral health and evaluating their efficacy in a rat periodontitis model.

The oral cavity is the second most microbially rich region of the human body, and many studies have shown that there is a strong association between microorganisms and oral health. Some pathogenic bacteria produce biofilms and harmful metabolites in the mouth that may cause oral problems such as oral malodor, periodontitis, and dental caries. Altering the oral microbiota by using probiotics may alleviate oral health problems. Thus, using multi-function screening, we aimed to identify probiotics that can significantly improve oral health. The main parameters were the inhibition of pathogenic bacteria growth, inhibition of biofilm formation, reduction in the production of indole, H2S, and NH3 metabolites that cause halitosis, increase in the production of H2O2 to combat harmful bacteria, and co-aggregation with pathogens to prevent their adhesion and colonization in the oral cavity. Tolerance to cholic acid and choline was also assessed. Bifidobacterium animalis ZK-77, Lactobacillus salivarius ZK-88, and Streptococcus salivarius ZK-102 had antibacterial activity and inhibited biofilm production to prevent caries. They also improved the oral malodor parameter, H2S, NH3, and indole production. The selected probiotics (especially L. salivarius ZK-88) alleviated the inflammation in the oral cavity of rats with periodontitis. The analysis of the gingival crevicular fluid microbiome after probiotic intervention showed that B. animalis ZK-77 likely helped to restore the oral microbiota and maintain the oral microecology. Next, we determined the best prebiotics for each candidate probiotic in order to obtain a formulation with improved effects. We then verified that a probiotics/prebiotic combination (B. animalis ZK-77, L. salivarius ZK-88, and fructooligosaccharides) significantly improved halitosis and teeth color in cats. Using whole-genome sequencing and acute toxicity mouse experiments involving the two probiotics, we found that neither probiotic had virulence genes and they had no significant effects on the growth or development of mice, indicating their safety. Taking the results together, B. animalis ZK-77 and L. salivarius ZK-88 can improve oral health, as verified by in vivo and in vitro experiments. This study provides a reference for clinical research and also provides new evidence for the oral health benefits of probiotics.