Lipopolysaccharide Biosynthesis Research Articles

Effects of water-insoluble wheat bran-fraction powder on disease activity and caecal microbiota in dextran sodium sulphate-induced inflammatory bowel disease mouse model.

Water-soluble arabinoxylan exerts anti-colitic effect and exhibits ameliorative activity in an inflammatory bowel disease (IBD) mouse model. Water soluble fibre from wheat bran (WB) also exhibits anti-colitic effect. However, arabinoxylan is a primary compound of insoluble polysaccharide (hemicellulose) in WB. This study aimed to clarify the anti-IBD effects of the WB water-soluble (WBS) and water-insoluble (WBI) fractions. WB suspension was autoclaved and fractionated to WBS and WBI. C57BL/6 mice were divided into control (CT), dextran sodium sulphate (DSS), WBI, and WBS groups. They were fed as follows from day 1: CT, standard diet and distilled water; DSS and WBI, 3% (w/v) DSS in drinking water; WBI, 8% (w/w) WBI diet; and WBS, 50% (v/v) WBS and 3% (w/v) DSS in water. DSS group mice showed diarrhoea, body weight reduction, and blood in faeces by day 5 and colon tissue damage by day 6. These inflammatory indices were significantly inhibited by treatment with WBI. Amplicon sequencing of the 16S rDNA (V4) gene of the caecal contents of the CT, DSS, and WBI groups showed that the abundances of Escherichia, Allobaculum, and Bacteroidaceae increased and that of Faecalibaculum decreased in the DSS group. KEGG pathway prediction showed that amino acid metabolism and lipopolysaccharide biosynthesis decreased and increased, respectively, in the DSS group. However, WBI treatment tended to suppress these effects. WBI, rather than WBS, reduces inflammation and maintains the gut microbiota. However, further studies are warranted to elucidate the properties of the WBI active components and efficacy of WBI metabolites on gut microbiota, particularly on Faecalibaculum.

Role of R5 Pyocin in the Predominance of High-Risk Pseudomonas aeruginosa Isolates.

Infections with antimicrobial resistant pathogens, such as Pseudomonas aeruginosa, are a frequent occurrence in healthcare settings. Human P. aeruginosa infections are predominantly caused by a small number of sequence types (ST), such as ST235, ST111, and ST175. Although ST111 is recognized as one of the most prevalent high-risk P. aeruginosa clones worldwide and frequently exhibits multidrug-resistant or extensively drug-resistant phenotypes, the basis for this dominance remains unclear. In this study, we used a genome-wide transposon insertion library screen to discover that the competitive advantage of ST111 strains over certain non-ST111 strains is through production of R pyocins. We confirmed this finding by showing that competitive dominance was lost by ST111 mutants with R pyocin gene deletions. Further investigation showed that sensitivity to ST111 R pyocin (specifically R5 pyocin) is caused by deficiency in the O-antigen ligase waaL , which leaves lipopolysaccharide (LPS) bereft of O antigen, enabling pyocins to bind the LPS core. In contrast, sensitivity of waaL mutants to R1 or R2 pyocins depended on additional genomic changes. In addition, we found the PA14 mutants in lipopolysaccharide biosynthesis ( waaL , wbpL , wbpM ) that cause high susceptibility to R pyocins also exhibit poor swimming motility. Analysis of 5,135 typed P. aeruginosa strains revealed that several international, high-risk sequence types (including ST235, ST111, and ST175) are enriched for R5 pyocin production, indicating a correlation between these phenotypes and suggesting a novel approach for evaluating risk from emerging prevalent P. aeruginosa strains. Overall, our study sheds light on the mechanisms underlying the dominance of ST111 strains and highlighting the role of waaL in extending spectrum of R pyocin susceptibility.

Managing tobacco black shank disease using biochar: direct toxicity and indirect ecological mechanisms.

Black shank disease in tobacco, caused by Phytophthora nicotianae, can lead to yield losses of 30%-50% upon outbreak. Recently, biochar derived from agricultural waste has shown significant potential in controlling soil-borne diseases, though its mechanisms remain unclear. Over a 3-year observation period, we found that the incidence of black shank was significantly lower in plots amended with biochar compared with normal cultivation plots. To investigate the underlying mechanisms, we studied both the direct and indirect effects of biochar on black shank. Direct antifungal assays indicated that biochar reduced the total number of sporangia by 53.91%. Further pot experiments revealed a 62.34% reduction in the P. nicotianae population in the soil following biochar application. Additionally, biochar application led to notable changes in soil physicochemical properties and microbial community composition. Microbial species analysis showed that biochar promoted the aggregation of beneficial microbes such as Sphingomonas, Flavisolibacter, and Mucoromycota. Functional predictions using the PICRUSt 2 software revealed that biochar enhances bacterial functions related to antimicrobial substance synthesis (Tetracycline biosynthesis), detoxification metabolism (D-arginine and D-ornithine metabolism, arginine and proline metabolism), and lipid and fatty acid metabolism (Lipopolysaccharide biosynthesis, fatty acid biosynthesis), while fungal functions showed no significant changes. This suggests that rhizosphere bacteria play a more prominent role in the suppression of black shank by biochar, a finding supported by partial least squares path modeling analysis. Therefore, we hypothesize that biochar not only directly inhibits P. nicotianae growth but also regulates the composition of the rhizosphere microbial community, inducing the production of antimicrobial substances by rhizosphere bacteria, effectively preventing P. nicotianae invasion.IMPORTANCEBlack shank, a global soil-borne fungal disease in tobacco, currently lacks effective control methods. Notably, biochar derived from agricultural waste has shown significant potential in controlling soil-borne diseases. Over a 3-year observation period, we found that plots amended with biochar had a significantly lower incidence of black shank compared with normal cultivation plots. However, the mechanisms of disease suppression remained unclear. Through in vitro antifungal assays and pot experiments, we discovered that tobacco-derived biochar can directly inhibit the growth of the pathogen. Additionally, biochar regulates the composition of the rhizosphere microbial community, inducing rhizosphere bacteria to produce antimicrobial substances, effectively preventing pathogen invasion. This discovery reveals both the direct and indirect mechanisms by which biochar suppresses black shank in tobacco. It provides a scientific basis for developing green control technologies for black shank and offers theoretical support for the application of biochar in managing soil-borne diseases in tobacco cultivation areas.

Colanic acid and lipopolysaccharide in Pectobacterium carotovorum Pcc21 serve as receptors for the bacteriophage phiPccP-2

Bacteriophages (phages) are viruses that specifically bind to and infect target bacteria. The phage phiPccP-2, belonging to the Myoviridae family, efficiently controls Pectobacterium spp. In the present study, we aimed to elucidate the mechanism of recognition of P. carotovorum Pcc21 by phiPccP-2. The EZ-Tn5 transposon mutant library of Pcc21 was used to screen for phage-resistant mutants. Among 4,072 mutants screened, 12 harbored disruptions in genes associated with the biosynthesis of either colanic acid (CA) or lipopolysaccharide (LPS) showed resistance to phiPccP-2. Complementation of 4 representative phage-resistant mutants with the corresponding genes fully restored the binding ability and lytic activity of PhiPccP-2. The amounts of CA or LPS structure in these mutants were significantly altered compared with those in the wild-type strain. Adsorption competition assays between CA and LPS extracted from Pcc21 and the natural receptors in Pcc21 showed that unbound phages were significantly increased, indicating that both CA and LPS are associated with the adsorption of the phiPccP-2 to Pcc21. In contrast, the adsorption of phiPccP-2 to extracted CA or LPS did not inactivate the lytic activity of phiPccP-2, indicating that the adsorption to the extracted CA or LPS is not sufficient for DNA injection. Treatment with polymyxin B, which disrupts LPS, interfered with phiPccP-2 adsorption to Pcc21. Furthermore, phage-resistant mutants showed reduced virulence in the host plant, suggesting a trade-off between phage resistance and bacterial virulence. Overall, our results indicate that both CA and LPS serve as receptors for the binding of phiPccP-2 to P. carotovorum Pcc21.

Aged garlic oligosaccharides modulate host metabolism and gut microbiota to alleviate high-fat and high-cholesterol diet-induced atherosclerosis in ApoE−/− mice

Atherosclerosis (AS) is a cardiovascular disease caused by excessive accumulation of lipids in arterial walls. In this study, we developed an AS model in ApoE−/− mice using a high-fat, high-cholesterol diet and investigated the anti-AS mechanism of aged garlic oligosaccharides (AGOs) by focusing on the gut microbiota. Results revealed that AGOs exhibited significant anti-AS effects, reduced trimethylamine N-oxide levels from 349.9 to 189.2 ng/mL, and reduced aortic lipid deposition from 31.7 % to 9.5 %. AGOs significantly increased the levels of short-chain fatty acids in feces, in which acetic, propionic, and butyric acids were increased from 1.580, 0.364, and 0.469 mg/g to 2.233, 0.774, and 0.881 mg/g, respectively. An analysis of the gut microbiota indicated that AGOs restored alpha and beta diversity, decreased the Firmicutes/Bacteroidetes ratio, and promoted the dominance of the genus Akkermansia. A metagenomic analysis revealed that AGOs alleviated AS through the ABC transporter pathway and the lipopolysaccharide biosynthesis pathway.

Beneficial effects of Haematococcus pluvialis on growth and hepatopancreas health status in crayfish (Procambarus clarkii) via remodeling the gut microbial metabolic functions

Plant proteins fulfill roles in low-fishmeal diets for crustaceans, but their overuse could have negative effects. Haematococcus pluvialis has the potential to be used as a functional additive due to its high astaxanthin. As such, this study aimed to investigate the effects of dietary H. pluvialis supplementation on growth, hepatopancreas health, and gut metabolic functions in crayfish. 720 crayfish with average weight around 9.20 g were randomized into six treatments (HP0, HP0.3, HP0.6, HP0.9, HP1.2, and HP1.5) in three replications each, and fed six different dosages of H. pluvialis over sixty days. Crayfish exposed to H. pluvialis at concentrations of 0.3, 0.6, and 0.9 % showed significant increases in final average weight, weight gain rate, and specific growth rate (P < 0.05) compared to the HP0 group, together with the highest contents of muscle and shell astaxanthin in the HP0.9 group. Furthermore, increasing H. pluvialis supplementation exhibited the potential to repair hepatopancreas, as demonstrated by the decrease in hemolymph malondialdehyde (MDA) content and activities of alanine aminotransferase and aspartate aminotransferase, as well as the increase in the total protein content, superoxide dismutase, and glutathione peroxidase (GSH-Px) activities. Moreover, high H. pluvialis diets improved microbial dysbiosis by increasing specific microbes, the alpha diversity index, and shifting prominent phyla such as Proteobacteria and Firmicutes. Specifically, dietary H. pluvialis inclusion significantly decreased Vibrio (Proteobacteria) compared to the HP0 group (P < 0.05), but Tyzzerella (Firmicutes) showed the opposite regulatory pattern. A further statistical check revealed that 20 differential OTUs were shared by all H. pluvialis groups compared to the HP0 group, with OTU1439 and OTU2941 identified as the main growth-liver health contributors. Accordingly, high H. pluvialis diets contributed to more complex and stable microbial networks, and down-regulated alanine, aspartate, and glutamate metabolism, as well as lipopolysaccharide biosynthesis. Taken above, the optimal dietary H. pluvialis inclusion level was recommended to be 0.78–0.86 % according to the growth and astaxanthin contents. High H. pluvialis feeding reversed gut microbial dysfunction and improved hepatopancreas antioxidant capacity.

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.

Heterogeneity of Salmonella enterica lipopolysaccharide counteracts macrophage and antimicrobial peptide defenses.

Salmonella enterica is comprised of over 2,500 serovars, in which non-typhoidal serovars (NTS), Enteritidis (SE), and Typhimurium (STM) are the most clinically associated with human infections. Although NTS have similar genetic elements to cause disease, phenotypic variation including differences in lipopolysaccharide (LPS) composition may control immune evasion. Here, we demonstrate that macrophage host defenses and LL-37 antimicrobial efficacy against SE and STM are substantially altered by LPS heterogeneity. We found that SE evades macrophage killing by inhibiting phagocytosis while STM survives better intracellularly post-phagocytosis. SE-infected macrophages failed to activate the inflammasomes and subsequently produced less interleukin-1β (IL-1β), IL-18, and interferon λ. Inactivation of LPS biosynthesis genes altered LPS composition, and the SE LPS-altered mutants could no longer inhibit phagocytosis, inflammasome activation, and type II interferon signaling. In addition, SE and STM showed differential susceptibility to the antimicrobials LL-37 and colistin, and alteration of LPS structure substantially increased susceptibility to these molecules. Collectively, our findings highlight that modification of LPS composition by Salmonella increases resistance to host defenses and antibiotics.

Exploring fluorinated heptose phosphate analogues as inhibitors of HldA and HldE, key enzymes in the biosynthesis of lipopolysaccharide

The growing threat of bacterial resistance to antibiotics has led to the rise of anti-virulence strategies as a promising approach. These strategies aim to disarm bacterial pathogens and improve their clearance by the host immune system. Lipopolysaccharide, a key virulence factor in Gram-negative bacteria, has been identified as a potential target for anti-virulence agents. In this study, we focus on inhibiting HldA and HldE, bacterial enzymes from the heptose biosynthesis pathway, which plays a key role in lipopolysaccharide biosynthesis. We present the synthesis of two fluorinated non-hydrolysable heptose phosphate analogues. Additionally, the inhibitory activity of a family of eight heptose phosphate analogues against HldA and HldE was assessed. This evaluation revealed inhibitors with affinities in the low μM range, with the most potent compound showing inhibition constant values of 15.4 μM for HldA and 16.9 μM for HldE. The requirement for a phosphate group at the C-7 position was deemed essential for inhibitory activity, while the presence of a hydroxy anomeric group was found to be beneficial, a phenomenon rationalized through computational modeling. Additionally, the introduction of a single fluorine atom α to the phosphonate moiety conferred a slight advantage for inhibition. These findings suggest that mimicking the structure of d-glycero-β-d-manno-heptose 1,7-bisphosphate, the product of the phosphorylation step in heptose biosynthesis, could be a promising strategy to disrupt this biosynthetic pathway. In terms of the in vivo effects, these heptose phosphate analogues neither demonstrated significant LPS-disrupting effects nor exhibited growth inhibitory activity on their own. Additionally, they did not alter the susceptibility of bacteria to hydrophobic antibiotics. The highly charged nature of these molecules may hinder their ability to penetrate the bacterial cell wall. To overcome this limitation, alternative strategies such as incorporating protecting groups that facilitate their entry and can subsequently be cleaved within the bacterial cytoplasm could be explored.

Alteration of ascending colon mucosal microbiota in patients after cholecystectomy.

Cholecystectomy is a successful treatment option for gallstones, although the incidence of colorectal cancer (CRC) has notably increased in post-cholecystectomy (PC) patients. However, it remains uncertain whether the altered mucosal microbiota in the ascending colon is related. To investigate the potential correlation between gut microbiota and the surgical procedure of cholecystectomy. In total, 30 PC patients and 28 healthy controls underwent colonoscopies to collect mucosal biopsy samples. PC patients were divided based on their clinical features. Then, 16S-rRNA gene sequencing was used to analyze the amplicon, alpha diversity, beta diversity, and composition of the bacterial communities. Additionally, the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) database, sourced from the Kyoto Encyclopedia of Genes and Genomes, was used to predict the functional capabilities of the bacteria. PC patients were comparable with healthy controls. However, PC patients older than 60 years had a distinct composition compared to those under 60 years old. Bacteroidetes richness was considerably higher at the phylum level in PC patients. Bacteroides, Parabacteroides, and Bilophila were more abundant in the PC group than in the control group. Furthermore, PC patients exhibited greater enrichment in metabolic pathways, specifically those related to lipopolysaccharide biosynthesis and vancomycin group antibiotic production, than controls. This study indicated that the mucosal microbiota in PC patients was altered, perhaps offering new perspectives on the treatment possibilities for CRC and diarrhea following cholecystectomy.

Association between Gut Microbiota Profiles, Dietary Intake, and Inflammatory Markers in Overweight and Obese Women.

Being overweight and obesity are significant global public health challenges due to their association with adipose tissue dysfunction, pro-inflammatory marker production, and alterations in gut microbiota composition. To explore the relationship between gut microbiota, dietary factors, and inflammatory markers in overweight or obese women, we conducted a cross-sectional study involving a healthy group (n = 20) and an overweight or obese group (n = 75). We collected data, including clinical, anthropometric, and dietary assessments, and carried out a blood biochemical analysis, the measurement of inflammatory biomarkers (hs-CRP, IL-6, and TNF-α), and the 16S rRNA gene sequencing of fecal samples. The gut microbiota analysis revealed notable differences in alpha and beta diversity between the two groups. Moreover, the abundance of gut microbiota in the overweight or obese group correlated positively with adiposity markers, blood pressure, lipid profiles, and inflammatory markers. These findings highlight significant changes in gut microbiota associated with obesity, potentially implicating pathways such as lipopolysaccharide biosynthesis. Understanding the role of the gut microbiome in obesity could reveal specific avenues for intervention.

Associations between gut microbiota and incident fractures in the FINRISK cohort

The gut microbiota (GM) can regulate bone mass, but its association with incident fractures is unknown. We used Cox regression models to determine whether the GM composition is associated with incident fractures in the large FINRISK 2002 cohort (n = 7043, 1092 incident fracture cases, median follow-up time 18 years) with information on GM composition and functionality from shotgun metagenome sequencing. Higher alpha diversity was associated with decreased fracture risk (hazard ratio [HR] 0.92 per standard deviation increase in Shannon index, 95% confidence interval 0.87–0.96). For beta diversity, the first principal component was associated with fracture risk (Aitchison distance, HR 0.90, 0.85–0.96). In predefined phyla analyses, we observed that the relative abundance of Proteobacteria was associated with increased fracture risk (HR 1.14, 1.07–1.20), while the relative abundance of Tenericutes was associated with decreased fracture risk (HR 0.90, 0.85–0.96). Explorative sub-analyses within the Proteobacteria phylum showed that higher relative abundance of Gammaproteobacteria was associated with increased fracture risk. Functionality analyses showed that pathways related to amino acid metabolism and lipopolysaccharide biosynthesis associated with fracture risk. The relative abundance of Proteobacteria correlated with pathways for amino acid metabolism, while the relative abundance of Tenericutes correlated with pathways for butyrate synthesis. In conclusion, the overall GM composition was associated with incident fractures. The relative abundance of Proteobacteria, especially Gammaproteobacteria, was associated with increased fracture risk, while the relative abundance of Tenericutes was associated with decreased fracture risk. Functionality analyses demonstrated that pathways known to regulate bone health may underlie these associations.

The intrinsic macrolide resistome of Escherichia coli.

Intrinsic resistance to macrolides in Gram-negative bacteria is primarily attributed to the low permeability of the outer membrane, though the underlying genetic and molecular mechanisms remain to be fully elucidated. Here, we used transposon directed insertion-site sequencing (TraDIS) to identify chromosomal non-essential genes involved in Escherichia coli intrinsic resistance to a macrolide antibiotic, tilmicosin. We constructed two highly saturated transposon mutant libraries of >290,000 and >390,000 unique Tn5 insertions in a clinical enterotoxigenic strain (ETEC5621) and in a laboratory strain (K-12 MG1655), respectively. TraDIS analysis identified genes required for growth of ETEC5621 and MG1655 under 1/8 MIC (n = 15 and 16, respectively) and 1/4 MIC (n = 38 and 32, respectively) of tilmicosin. For both strains, 23 genes related to lipopolysaccharide biosynthesis, outer membrane assembly, the Tol-Pal system, efflux pump, and peptidoglycan metabolism were enriched in the presence of the antibiotic. Individual deletion of genes (n = 10) in the wild-type strains led to a 64- to 2-fold reduction in MICs of tilmicosin, erythromycin, and azithromycin, validating the results of the TraDIS analysis. Notably, deletion of surA or waaG, which impairs the outer membrane, led to the most significant decreases in MICs of all three macrolides in ETEC5621. Our findings contribute to a genome-wide understanding of intrinsic macrolide resistance in E. coli, shedding new light on the potential role of the peptidoglycan layer. They also provide an in vitro proof of concept that E. coli can be sensitized to macrolides by targeting proteins maintaining the outer membrane such as SurA and WaaG.

Altered gut microbiota and systemic immunity in Chinese patients with schizophrenia comorbid with metabolic syndrome

BackgroundMetabolic syndrome (MetS) is highly prevalent in individuals with schizophrenia (SZ), leading to negative consequences like premature mortality. Gut dysbiosis, which refers to an imbalance of the microbiota, and chronic inflammation are associated with both SZ and MetS. However, the relationship between gut dysbiosis, host immunological dysfunction, and SZ comorbid with MetS (SZ-MetS) remains unclear. This study aims to explore alterations in gut microbiota and their correlation with immune dysfunction in SZ-MetS, offering new insights into its pathogenesis.Methods and resultsWe enrolled 114 Chinese patients with SZ-MetS and 111 age-matched healthy controls from Zhejiang, China, to investigate fecal microbiota using Illumina MiSeq sequencing targeting 16 S rRNA gene V3-V4 hypervariable regions. Host immune responses were assessed using the Bio-Plex Pro Human Cytokine 27-Plex Assay to examine cytokine profiles. In SZ-MetS, we observed decreased bacterial α-diversity and significant differences in β-diversity. LEfSe analysis identified enriched acetate-producing genera (Megamonas and Lactobacillus), and decreased butyrate-producing bacteria (Subdoligranulum, and Faecalibacterium) in SZ-MetS. These altered genera correlated with body mass index, the severity of symptoms (as measured by the Scale for Assessment of Positive Symptoms and Scale for Assessment of Negative Symptoms), and triglyceride levels. Altered bacterial metabolic pathways related to lipopolysaccharide biosynthesis, lipid metabolism, and various amino acid metabolism were also found. Additionally, SZ-MetS exhibited immunological dysfunction with increased pro-inflammatory cytokines, which correlated with the differential genera.ConclusionThese findings suggested that gut microbiota dysbiosis and immune dysfunction play a vital role in SZ-MetS development, highlighting potential therapeutic approaches targeting the gut microbiota. While these therapies show promise, further mechanistic studies are needed to fully understand their efficacy and safety before clinical implementation.

Synergy between Group 2 capsules and lipopolysaccharide underpins serum resistance in extra-intestinal pathogenic Escherichia coli.

Escherichia coli (E. coli) is a major cause of urinary tract infections, bacteraemia, and sepsis. CFT073 is a prototypic, urosepsis isolate of sequence type (ST) 73. This laboratory, among others, has shown that strain CFT073 is resistant to serum, with capsule and other extracellular polysaccharides imparting resistance. The interplay of such polysaccharides remains under-explored. This study has shown that CFT073 mutants deficient in lipopolysaccharide (LPS) O-antigen and capsule display exquisite serum sensitivity. Additionally, O-antigen and LPS outer core mutants displayed significantly decreased surface K2 capsule, coupled with increased unbound K2 capsule being detected in the supernatant. The R1 core and O6 antigen are involved in the tethering of K2 capsule to the CFT073 cell surface, highlighting the importance of the R1 core in serum resistance. The dependence of capsule on LPS was shown to be post-transcriptional and related to changes in cell surface hydrophobicity. Furthermore, immunofluorescence microscopy suggested that the surface pattern of capsule is altered in such LPS core mutants, which display a punctate capsule pattern. Finally, targeting LPS biosynthesis using sub-inhibitory concentrations of a WaaG inhibitor resulted in increased serum sensitivity and decreased capsule in CFT073. Interestingly, the dependency of capsule on LPS has been observed previously in other Enterobacteria, indicating that the synergy between these polysaccharides is not just strain, serotype or species-specific but may be conserved across several pathogenic Gram-negative species. Therefore, using WaaG inhibitor derivatives to target LPS is a promising therapeutic strategy to reduce morbidity and mortality by reducing or eliminating surface capsule.

Association of breast milk-derived arachidonic acid-induced infant gut dysbiosis with the onset of atopic dermatitis

ObjectiveThe specific breast milk-derived metabolites that mediate host–microbiota interactions and contribute to the onset of atopic dermatitis (AD) remain unknown and require further investigation.DesignWe enrolled 250 mother–infant pairs and collected...

The transcriptional regulator Fur modulates the expression of uge, a gene essential for the core lipopolysaccharide biosynthesis in Klebsiella pneumoniae

BackgroundKlebsiella pneumoniae is a Gram-negative pathogen that has become a threat to public health worldwide due to the emergence of hypervirulent and multidrug-resistant strains. Cell-surface components, such as polysaccharide capsules, fimbriae, and lipopolysaccharides (LPS), are among the major virulence factors for K. pneumoniae. One of the genes involved in LPS biosynthesis is the uge gene, which encodes the uridine diphosphate galacturonate 4-epimerase enzyme. Although essential for the LPS formation in K. pneumoniae, little is known about the mechanisms that regulate the expression of uge. Ferric uptake regulator (Fur) is an iron-responsive transcription factor that modulates the expression of capsular and fimbrial genes, but its role in LPS expression has not yet been identified. This work aimed to investigate the role of the Fur regulator in the expression of the K. pneumoniae uge gene and to determine whether the production of LPS by K. pneumoniae is modulated by the iron levels available to the bacterium.ResultsUsing bioinformatic analyses, a Fur-binding site was identified on the promoter region of the uge gene; this binding site was validated experimentally through Fur Titration Assay (FURTA) and DNA Electrophoretic Mobility Shift Assay (EMSA) techniques. RT-qPCR analyses were used to evaluate the expression of uge according to the iron levels available to the bacterium. The iron-rich condition led to a down-regulation of uge, while the iron-restricted condition resulted in up-regulation. In addition, LPS was extracted and quantified on K. pneumoniae cells subjected to iron-replete and iron-limited conditions. The iron-limited condition increased the amount of LPS produced by K. pneumoniae. Finally, the expression levels of uge and the amount of the LPS were evaluated on a K. pneumoniae strain mutant for the fur gene. Compared to the wild-type, the strain with the fur gene knocked out presented a lower LPS amount and an unchanged expression of uge, regardless of the iron levels.ConclusionsHere, we show that iron deprivation led the K. pneumoniae cells to produce higher amount of LPS and that the Fur regulator modulates the expression of uge, a gene essential for LPS biosynthesis. Thus, our results indicate that iron availability modulates the LPS biosynthesis in K. pneumoniae through a Fur-dependent mechanism.

Low salinity stress increases the risk of Vibrio parahaemolyticus infection and gut microbiota dysbiosis in Pacific white shrimp

BackgroundExtreme precipitation events often cause sudden drops in salinity, leading to disease outbreaks in shrimp aquaculture. Evidence suggests that environmental stress increases animal host susceptibility to pathogens. However, the mechanisms of how low salinity stress induces disease susceptibility remain poorly understood.MethodsWe investigated the acute response of shrimp gut microbiota exposed to pathogens under low salinity stress. For comparison, shrimp were exposed to Vibrio infection under two salinity conditions: optimal salinity (Control group) and low salinity stress (Stress group). High throughput 16S rRNA sequencing and real-time PCR were employed to characterize the shrimp gut microbiota and quantify the severity level of Vibrio infection.ResultsThe results showed that low salinity stress increased Vibrio infection levels, reduced gut microbiota species richness, and perturbed microbial functions in the shrimp gut, leading to significant changes in lipopolysaccharide biosynthesis that promoted the growth of pathogens. Gut microbiota of the bacterial genera Candidatus Bacilliplasma, Cellvibrio, and Photobacterium were identified as biomarkers of the Stress group. The functions of the gut microbiota in the Stress group were primarily associated with cellular processes and the metabolism of lipid-related compounds.ConclusionsOur findings reveal how environmental stress, particularly low salinity, increases shrimp susceptibility to Vibrio infection by affecting the gut microbiota. This highlights the importance of avoiding low salinity stress and promoting gut microbiota resilience to maintain the health of shrimp.

Modulating the biosynthesis and TLR4-interaction of lipopolysaccharide as an approach to counter gut dysbiosis and Parkinson's disease: Role of phyto-compounds

The prevalence of the world's second leading neurodegenerative disorder Parkinson's disease (PD) is well known while its pathogenesis is still a topical issue to explore. Clinical and experimental reports suggest the prevalence of disturbed gut microflora in PD subjects, with an abundance of especially Gram-negative bacteria. The endotoxin lipopolysaccharide (LPS) released from the outer cell layer of these bacteria interacts with the toll-like receptor 4 (TLR4) present on the macrophages and it stimulates the downstream inflammatory cascade in both the gut and brain. Recent research also suggests a positive correlation between LPS, alpha-synuclein, and TLR4 levels, which indicates the contribution of a parallel LPS-alpha-synuclein-TLR4 axis in stimulating inflammation and neurodegeneration in the gut and brain, establishing a body-first type of PD. However, owing to the novelty of this paradigm, further investigation is mandatory. Modulating LPS biosynthesis and LPS-TLR4 interaction can ameliorate gut dysbiosis and PD. Several synthetic LpxC (UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase; LPS-synthesizing enzyme) inhibitors and TLR4 antagonists are reported to show beneficial effects including neuroprotection in PD models, however, are not devoid of side effects. Plant-derived compounds have been long documented for their benefits as nutraceuticals and thus to search for effective, safer, and multitarget therapeutics, the present study focused on summarizing the evidence reporting the potential of phyto-compounds as LpxC inhibitors and TLR4 antagonists. Studies demonstrating the dual potential of phyto-compounds as the modulators of LpxC and TLR4 have not yet been reported. Also, very few preliminary studies have reported LpxC inhibition by phyto-compounds. Nevertheless, remarkable neuroprotection along with TLR4 antagonism has been shown by curcumin and juglanin in PD models. The present review thus provides a wide look at the research progressed to date in discovering phyto-compounds that can serve as LpxC inhibitors and TLR4 antagonists. The study further recommends the need for expanding the search for potential candidates that can render dual protection by inhibiting both the biosynthesis and TLR4 interaction of LPS. Such multitarget therapeutic intervention is believed to bring fruitful yields in countering gut dysbiosis, neuroinflammation, and dopaminergic neuron damage in PD patients through a single treatment paradigm.

Distinct Plasma Metabolomic and Gut Microbiome Profiles after Gestational Diabetes Mellitus Diet Treatment: Implications for Personalized Dietary Interventions.

Gestational diabetes mellitus (GDM) triggers alterations in the maternal microbiome. Alongside metabolic shifts, microbial products may impact clinical factors and influence pregnancy outcomes. We investigated maternal microbiome-metabolomic changes, including over 600 metabolites from a subset of the "Choosing Healthy Options in Carbohydrate Energy" (CHOICE) study. Women diagnosed with GDM were randomized to a diet higher in complex carbohydrates (CHOICE, n = 18, 60% complex carbohydrate/25% fat/15% protein) or a conventional GDM diet (CONV, n = 16, 40% carbohydrate/45% fat/15% protein). All meals were provided. Diets were eucaloric, and fiber content was similar. CHOICE was associated with increases in trimethylamine N-oxide, indoxyl sulfate, and several triglycerides, while CONV was associated with hippuric acid, betaine, and indole propionic acid, suggestive of a healthier metabolome. Conversely, the microbiome of CHOICE participants was enriched with carbohydrate metabolizing genes and beneficial taxa such as Bifidobacterium adolescentis, while CONV was associated with inflammatory pathways including antimicrobial resistance and lipopolysaccharide biosynthesis. We also identified latent metabolic groups not associated with diet: a metabolome associated with less of a decrease in fasting glucose, and another associated with relatively higher fasting triglycerides. Our results suggest that GDM diets produce specific microbial and metabolic responses during pregnancy, while host factors also play a role in triglycerides and glucose metabolism.