Endocannabinoids Inhibit the Induction of Virulence in Enteric Pathogens.

Endocannabinoids are host-derived lipid hormones that fundamentally impact gastrointestinal (GI) biology. The use of cannabis and other exocannabinoids as anecdotal treatments for various GI disorders inspired the search for mechanisms by which these compounds mediate their effects, which led to the discovery of the mammalian endocannabinoid system. Dysregulated endocannabinoid signaling was linked to inflammation and the gut microbiota. However, the effects of endocannabinoids on host susceptibility to infection has not been explored. Here, we show that mice with elevated levels of the endocannabinoid 2-arachidonoyl glycerol (2-AG) are protected from enteric infection by Enterobacteriaceae pathogens. 2-AG directly modulates pathogen function by inhibiting virulence programs essential for successful infection. Furthermore, 2-AG antagonizes the bacterial receptor QseC, a histidine kinase encoded within the core Enterobacteriaceae genome that promotes the activation of pathogen-associated type three secretion systems. Taken together, our findings establish that endocannabinoids are directly sensed by bacteria and can modulate bacterial function.

Epinephrine and norepinephrine regulate the expression of virulence factors in Gallibacterium anatis.

Gallibacterium anatis is a member of the Pasteurellaceae family and is an opportunistic pathogen that causes gallibacteriosis in chickens. Stress plays a relevant role in promoting the development of pathogenicity in G. anatis. Epinephrine (E) and norepinephrine (NE) are relevant to stress; however, their effects on G. anatis have not been elucidated. In this work, we evaluated the effects of E and NE on the growth, biofilm formation, expression of adhesins, and proteases of two G. anatis strains, namely, the hemolytic 12656-12 and the nonhemolytic F149T biovars. E (10 µM/mL) and NE (30 and 50 µM/mL) increased the growth of G. anatis 12656-12 by 20% and 25%, respectively. E did not affect the growth of F149T, whereas 40 µM/mL NE decreased bacterial growth by 25%. E and NE at a dose of 30-50 µM/mL upregulated five fibrinogen adhesins in the 12565-12 strain, whereas no effect was observed in the F149T strain. NE increased proteolytic activity in both strains, whereas E diminished proteolytic activity in the 12656-12 strain. E and NE reduced biofilm formation (30%) and increased Congo red binding (15%) in both strains. QseBC is the E and NE two-component detection system most common in bacteria. The qseC gene, which is the E and NE receptor in bacteria, was identified in the genomic DNA of the 12565-12 and F149TG. anatis strains via PCR amplification. Our results suggest that QseC can detect host changes in E and NE concentrations and that catecholamines can modulate the expression of several virulence factors in G. anatis.

Evaluation of immunoregulation and immunoprotective efficacy of Glaesserella parasuis histidine kinase QseC.

QseC is a membrane sensor kinase that enables bacteria to perceive autoinducers -3, adrenaline, and norepinephrine to initiate downstream gene transcription. In this study, we found that the QseC protein of Glaesserella parasuis can serve as an effective antigen to activate the host's immune response. Therefore, we investigated the immunogenicity and host protective effect of this protein. ELISA and indirect immunofluorescence results showed that QseC protein can induce high titer levels of humoral immunity in mice and regularly generate specific serum antibodies. We used MTS reagents to detect lymphocyte proliferation levels and found that QseC protein can cause splenic lymphocyte proliferation with memory and specificity. Further immunological analysis of the spleen cell supernatant revealed significant upregulation of levels of IL-1ß, IL-4 and IFN-γ in the QseC + adjuvant group. In the mouse challenge experiment, it was found that QseC + adjuvant can provide effective protection. The results of this study demonstrate that QseC protein provides effective protection in a mouse model and has the potential to serve as a candidate antigen for a novel subunit vaccine for further research.

A genetic screen to identify factors affected by undecaprenyl phosphate recycling uncovers novel connections to morphogenesis in Escherichia coli.

Undecaprenyl phosphate (Und-P) is an essential lipid carrier that ferries cell wall intermediates across the cytoplasmic membrane in bacteria. Und-P is generated by dephosphorylating undecaprenyl pyrophosphate (Und-PP). In Escherichia coli, BacA, PgpB, YbjG, and LpxT dephosphorylate Und-PP and are conditionally essential. To identify vulnerabilities that arise when Und-P metabolism is defective, we developed a genetic screen for synthetic interactions which, in combination with ΔybjG ΔlpxT ΔbacA, are lethal or reduce fitness. The screen uncovered novel connections to cell division, DNA replication/repair, signal transduction, and glutathione metabolism. Further analysis revealed several new morphogenes; loss of one of these, qseC, caused cells to enlarge and lyse. QseC is the sensor kinase component of the QseBC two-component system. Loss of QseC causes overactivation of the QseB response regulator by PmrB cross-phosphorylation. Here, we show that deleting qseB completely reverses the shape defect of ΔqseC cells, as does overexpressing rprA (a small RNA). Surprisingly, deleting pmrB only partially suppressed qseC-related shape defects. Thus, QseB is activated by multiple factors in QseC's absence and prior functions ascribed to QseBC may originate from cell wall defects. Altogether, our findings provide a framework for identifying new determinants of cell integrity that could be targeted in future therapies.

Human microbiota modulation via QseC sensor kinase mediated in the Escherichia coli O104:H4 outbreak strain infection in microbiome model.

BACKGROUND: The intestinal microbiota plays a crucial role in human health, adjusting its composition and the microbial metabolites protects the gut against invading microorganisms. Enteroaggregative E. coli (EAEC) is an important diarrheagenic pathogen, which may cause acute or persistent diarrhea (≥14 days). The outbreak strain has the potent Shiga toxin, forms a dense biofilm and communicate via QseBC two-component system regulating the expression of many important virulence factors. RESULTS: Herein, we investigated the QseC histidine sensor kinase role in the microbiota shift during O104:H4 C227-11 infection in the colonic model SHIME® (Simulator of the Human Intestinal Microbial Ecosystem) and in vivo mice model. The microbiota imbalance caused by C227-11 infection affected ỿ-Proteobacteria and Lactobacillus spp. predominance, with direct alteration in intestinal metabolites driven by microbiota change, such as Short-chain fatty acids (SCFA). However, in the absence of QseC sensor kinase, the microbiota recovery was delayed on day 3 p.i., with change in the intestinal production of SCFA, like an increase in acetate production. The higher predominance of Lactobacillus spp. in the microbiota and significant augmented qseC gene expression levels were also observed during C227-11 mice infection upon intestinal depletion. Novel insights during pathogenic bacteria infection with the intestinal microbiota were observed. The QseC kinase sensor seems to have a role in the microbiota shift during the infectious process by Shiga toxin-producing EAEC C227-11. CONCLUSIONS: The QseC role in C227-11 infection helps to unravel the intestine microbiota modulation and its metabolites during SHIME® and in vivo models, besides they contribute to elucidate bacterial intestinal pathogenesis and the microbiota relationships.

In Silico and in Vitro Study of Trace Amines (TA) and Dopamine (DOP) Interaction with Human Alpha 1-Adrenergic Receptor and the Bacterial Adrenergic Receptor QseC.

BACKGROUND/AIMS: Trace amines (TA) are small organic compounds that have neuromodulator activity due to their interaction with some neuron-related receptors, such as trace amine associated receptors (TAARs), α2-adrenergic receptor (α2-AR) and ß-adrenergic receptor (ß-AR). However, there is little information on whether TA and dopamine (DOP) can interact with other adrenergic receptors (ARs) such as the mammalian α1-AR and the bacterial counterpart QseC, which is involved in quorum sensing of some Gram-negative pathogens. The aim of this study was to investigate the interaction of TA and DOP with α1-AR and QseC. METHODS: We performed an in silico study using 3D structure from SWISS MODEL and analyzed the protein interaction via molecular docking using PyMol, PoseView and PyRX 8.0. For the in vitro study, we investigated the QseC kinase activity by measuring the remaining ATP in a reaction containing QseC-enriched membrane incubated together with purified QseB and EPI, TA, DOP, or PTL respectively. We also measured the intracellular Ca++ levels, which represents the α1-AR activation, in LNCAP (pancreatic cell line) cells treated with EPI, TA, DOP and PTL respectively using a fluorescence-based assay. The LNCAP cell proliferation was measured using an MTT-based assay. RESULTS: Our in silico analysis revealed that TAs and DOP have high binding affinity to the human α1-AR and the bacterial adrenergic receptor (QseC), comparable to epinephrine (EPI). Both are membrane-bound kinases. Experimental studies with pancreatic cell line (LNCAP) showed that the TAs and DOP act as α1-AR antagonist by counteracting the effect of EPI. In the presence of EPI, TA and DOP trigger an increase of the intracellular Ca++ levels in the LNCAP cells leading to an inhibition of cell proliferation. Although in silico data suggest an interaction of TA and DOP with QseC, they do not inhibit the kinase activity of QseC, a histidine kinase receptor involved in quorum sensing which is also sensitive to EPI. CONCLUSION: Our study showed that the TAs and DOP act as α1-AR antagonist but no effect was observed for QseC.

QseC inhibition as an antivirulence approach for colitis-associated bacteria.

Hosts and their microbes have established a sophisticated communication system over many millennia. Within mammalian hosts, this dynamic cross-talk is essential for maintaining intestinal homeostasis. In a genetically susceptible host, dysbiosis of the gut microbiome and dysregulated immune responses are central to the development of inflammatory bowel disease (IBD). Previous surveys of stool from the T-bet-/-Rag2-/- IBD mouse model revealed microbial features that discriminate between health and disease states. Enterobacteriaceae expansion and increased gene abundances for benzoate degradation, two-component systems, and bacterial motility proteins pointed to the potential involvement of a catecholamine-mediated bacterial signaling axis in colitis pathogenesis. Enterobacteriaceae sense and respond to microbiota-generated signals and host-derived catecholamines through the two-component quorum-sensing Escherichia coli regulators B and C (QseBC) system. On signal detection, QseC activates a cascade to induce virulence gene expression. Although a single pathogen has not been identified as a causative agent in IBD, adherent-invasive Escherichia coli (AIEC) have been implicated. Flagellar expression is necessary for the IBD-associated AIEC strain LF82 to establish colonization. Thus, we hypothesized that qseC inactivation could reduce LF82's virulence, and found that an absence of qseC leads to down-regulated flagellar expression and motility in vitro and reduced colonization in vivo. We extend these findings on the potential of QseC-based IBD therapeutics to three preclinical IBD models, wherein we observe that QseC blockade can effectively modulate colitogenic microbiotas to reduce intestinal inflammation. Collectively, our data support a role for QseC-mediated bacterial signaling in IBD pathogenesis and indicate that QseC inhibition may be a useful microbiota-targeted approach for disease management.

QseC Signaling in the Outbreak O104:H4 Escherichia coli Strain Combines Multiple Factors during Infection.

Enteroaggregative Escherichia coli (EAEC) from the O104:H4 specific serotype caused a large outbreak of bloody diarrhea with some complicated cases of hemolytic-uremic syndrome (HUS) in Europe in 2011. The outbreak strain consisted in an EAEC capable to produce the Shiga toxin (Stx) subtype 2a, a characteristic from enterohemorrhagic E. coli QseBC two-component system detects AI-3/Epi/NE and mediates the chemical signaling between pathogen and mammalian host. This system coordinates a cascade of virulence genes expression in important human enteropathogens. The blocking of QseC of EAEC C227-11 (Stx+) strain by N-phenyl-4-{[(phenylamino) thioxomethyl]amino}-benzenesulfonamide (also known as LED209) in vivo demonstrated a lower efficiency of colonization. The periplasmic protein VisP, which is related to survival mechanisms in a colitis model of infection, bacterial membrane maintenance, and stress resistance, here presented high levels of expression during the initial infection within the host. Under acid stress conditions, visP expression levels were differentiated in an Stx-dependent way. Together, these results emphasize the important role of VisP and the histidine kinase sensor QseC in the C227-11 (Stx+) outbreak strain for the establishment of the infectious niche process in the C57BL/6 mouse model and of LED209 as a promising antivirulence drug strategy against these enteric pathogens.IMPORTANCE EAEC is a remarkable etiologic agent of acute and persistent diarrhea worldwide. The isolates harbor specific subsets of virulence genes and their pathogenesis needs to be better understood. Chemical signaling via histidine kinase sensor QseC has been shown as a potential target to elucidate the orchestration of the regulatory cascade of virulence factors.

Genetic and Mechanistic Analyses of the Periplasmic Domain of the Enterohemorrhagic Escherichia coli QseC Histidine Sensor Kinase.

The histidine sensor kinase (HK) QseC senses autoinducer 3 (AI-3) and the adrenergic hormones epinephrine and norepinephrine. Upon sensing these signals, QseC acts through three response regulators (RRs) to regulate the expression of virulence genes in enterohemorrhagic Escherichia coli (EHEC). The QseB, QseF, and KdpE RRs that are phosphorylated by QseC constitute a tripartite signaling cascade having different and overlapping targets, including flagella and motility, the type three secretion system encoded by the locus of enterocyte effacement (LEE), and Shiga toxin. We modeled the tertiary structure of QseC's periplasmic sensing domain and aligned the sequences from 12 different species to identify the most conserved amino acids. We selected eight amino acids conserved in all of these QseC homologues. The corresponding QseC site-directed mutants were expressed and still able to autophosphorylate; however, four mutants demonstrated an increased basal level of phosphorylation. These mutants have differential flagellar, motility, LEE, and Shiga toxin expression phenotypes. We selected four mutants for more in-depth analyses and found that they differed in their ability to phosphorylate QseB, KdpE, and QseF. This suggests that these mutations in the periplasmic sensing domain affected the region downstream of the QseC signaling cascade and therefore can influence which pathway QseC regulates.IMPORTANCE In the foodborne pathogen EHEC, QseC senses AI-3, epinephrine, and norepinephrine, increases its autophosphorylation, and then transfers its phosphate to three RRs: QseB, QseF, and KdpE. QseB controls expression of flagella and motility, KdpE controls expression of the LEE region, and QseF controls the expression of Shiga toxin. This tripartite signaling pathway must be tightly controlled, given that flagella and the type three secretion system (T3SS) are energetically expensive appendages and Shiga toxin expression leads to bacterial cell lysis. Our data suggest that mutations in the periplasmic sensing loop of QseC differentially affect the expression of the three arms of this signaling cascade. This suggests that these point mutations may change QseC's phosphotransfer preferences for its RRs.

The Histidine Residue of QseC Is Required for Canonical Signaling between QseB and PmrB in Uropathogenic Escherichia coli.

Two-component systems are prototypically comprised of a histidine kinase (sensor) and a response regulator (responder). The sensor kinases autophosphorylate at a conserved histidine residue, acting as a phosphodonor for subsequent phosphotransfer to and activation of a cognate response regulator. In rare cases, the histidine residue is also essential for response regulator dephosphorylation via a reverse-phosphotransfer reaction. In this work, we present an example of a kinase that relies on reverse phosphotransfer to catalyze the dephosphorylation of its cognate partner. The QseC sensor kinase is conserved across several Gram-negative pathogens; its interaction with its cognate partner QseB is critical for maintaining pathogenic potential. Here, we demonstrate that QseC-mediated dephosphorylation of QseB occurs via reverse phosphotransfer. In previous studies, we demonstrated that, in uropathogenic Escherichia coli, exposure to high concentrations of ferric iron (Fe3+) stimulates the PmrB sensor kinase. This stimulation, in turn, activates the cognate partner, PmrA, and noncognate QseB to enhance tolerance to polymyxin B. We demonstrate that in the absence of signal, kinase-inactive QseC variants, in which the H246 residue was changed to alanine (A) aspartate (D) or leucine (L), rescued a ΔqseC deletion mutant, suggesting that QseC can control QseB activation via a mechanism that is independent of reverse phosphotransfer. However, in the presence of Fe3+, the same QseC variants were unable to mediate a wild-type stimulus response, indicating that QseC-mediated dephosphorylation is required for maintaining proper QseB-PmrB-PmrA interactions.IMPORTANCE Two-component signaling networks constitute one of the predominant methods by which bacteria sense and respond to their changing environments. Two-component systems allow bacteria to thrive and survive in a number of different environments, including within a human host. Uropathogenic Escherichia coli, the causative agent of urinary tract infections, rely on two interacting two-component systems, QseBC and PmrAB, to induce intrinsic resistance to the colistin antibiotic polymyxin B, which is a last line of defense drug. The presence of one sensor kinase, QseC, is required to regulate the interaction between the other sensor kinase, PmrB and the response regulators from both systems, QseB and PmrA, effectively creating a "four-component" system required for virulence. Understanding the important role of the sensor kinase QseC will provide insight into additional ways to therapeutically target uropathogens that harbor these signaling systems.

A potent and selective antimicrobial poly(amidoamine) dendrimer conjugate with LED209 targeting QseC receptor to inhibit the virulence genes of gram negative bacteria.

The pandemic of multidrug-resistant Gram negative bacteria (GNB) is a worldwide healthcare concern, and very few antibiotics are being explored to match the clinical challenge. Recently, amino-terminated poly(amidoamine) (PAMAM) dendrimers have shown potential to function as broad antimicrobial agents. However, PAMAM displays a generation dependent cytotoxicity to mammalian cells and low selectivity on bacterial cells, which limits PAMAM to be developed as an antibacterial agent for systemic administration. We conjugated G3 PAMAM with LED209, a specific inhibitor of quorum sensor QseC of GNB, to generate a multifunctional agent PAMAM-LED209. Intriguingly, PAMAM-LED209 showed higher selectivity on GNB and lower cytotoxicity to mammalian cells, yet remained strong antibacterial activity. PAMAM-LED209 also inhibited virulence gene expression of GNB, and did not induce antibiotic-resistance. The present work firstly demonstrated that PAMAM-LED209 conjugate had a highly selective anti-GNB activity and low cytotoxicity, which offered a feasible strategy for combating multidrug-resistant GNB infections. FROM THE CLINICAL EDITOR: This research team demonstrated that a novel PAMAM-LED209 conjugate had highly selective activity against Gram-negative bacteria, coupled with low cytotoxicity, offering a potential strategy for combating multidrug-resistant infections.

The Norepinephrine-QseC Axis Aggravates F. nucleatum-associated Colitis Through Interkingdom Signaling.

AIMS: Inflammatory bowel disease (IBD) is associated with F. nucleatum, and chronic stress can increase the risk of aggravation. However, whether norepinephrine (NE) can enhance the pathogenicity of F. nucleatum to aggravate dextran sulfate sodium salt (DSS)-induced colitis is unclear. METHODS: Transcriptome sequencing was used to identify differentially expressed genes in bacteria treated with NE. Affinity testing and molecular docking were applied to calculate and predict the binding of NE and Quorum sensing  regulators C (QseC). The pathogenicity of Fusobacterium nucleatum treated with NE and QseC inhibitors was examined in vitro and further verified using the IBD mouse model induced by DSS. RESULTS: Norepinephrine could bind to QseC directly to upregulate the quorum sensing pathway of F. nucleatum and enhance its virulence gene expression (FadA, FomA, Fap2) and invasiveness in vitro. Meanwhile, it promoted the invasion of F. nucleatum into the intestine and increased the expression of host inflammatory cytokines (IL-6, IL-1ß) to aggravate colonic inflammation in IBD mice. The QseC inhibitor LED209 inhibited the effect of NE on F. nucleatum and partially restored short-chain fatty acid (SCFA)-producing bacteria (Prevotellaceae, Lactobacillaceae) to attenuate colonic inflammation in IBD mice. CONCLUSIONS: Generally, the NE-QseC axis enhanced the pathogenicity of F. nucleatum through interkingdom signaling to aggravate colonic inflammation in IBD mice. We see that QseC may be a potential target for microbiota management of IBD under chronic pressure.

Norepinephrine could bind to QseC directly to enhance the pathogenicity of F. nucleatum to aggravate colonic inflammation. The QseC inhibitor inhibited the effect of NE on F. nucleatum and partially restored short-chain fatty acid­producing bacteria to attenuate colonic inflammation.

Histidine Kinase QseC in Glaesserella parasuis Enhances the Secretion of Proinflammatory Cytokines by Macrophages via the p38 and NF-κB Signaling Pathways.

The qseC gene is a two-component system that encodes a histidine protein kinase and is highly conserved among different Glaesserella parasuis strains. In this study, we used qRT-PCR and enzyme-linked immunosorbent assay to confirm that Toll-like receptor 4 (TLR4) plays a role in the expression of proinflammatory cytokines interleukin (IL)-1ß and IL-6 by stimulating RAW 264.7 macrophages with QseC. Furthermore, we revealed that blocking the p38 and NF-κB pathways that regulate signaling can significantly reduce the production of proinflammatory cytokines induced by QseC. In summary, our data suggest that QseC is a novel proinflammatory mediator that induces TLR4-dependent proinflammatory activity in RAW 264.7 macrophages through the p38 and NF-κB pathways.

QseC sensor kinase modulates the human microbiota during enterohemorrhagic Escherichia coli O157:H7 infection in the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®).

Enterohemorrhagic Escherichia coli (EHEC) is an important gastrointestinal pathogen known for its ability to cause hemorrhagic colitis and induce hemolytic-uremic syndrome. The inner membrane QseC histidine kinase sensor has shown to be an important regulator of the locus of enterocyte effacement (LEE) island, where important EHEC key virulence genes are located. However, the QseC role during EHEC infection in human microbiota remains unknown. Herein, using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®), we investigated whether the QseC sensor has a role in human microbiota modulation by EHEC in a dynamic model. Our data demonstrated that the QseC sensor modulates human microbiota during EHEC infection, and its absence leads to an increase in Lactobacillaceae and Bifidobacterium genus predominance, although non-effect on Bacteroides genus by EHEC strains was observed. In co-culture, the Lactobacillus acidophilus has affected EHEC growth and impaired the EHEC growth under space-niche competition, although no growth difference was observed in the QseC sensor presence. Also, differences in EHEC growth were not detected in competition with Bacteroides thetaiotaomicron and EHEC strains did not affect B. thetaiotaomicron growth either. When investigating the mechanisms behind the SHIME results, we found that hcp-2 expression for the type 6 secretion system, known to be involved in bacterial competition, is under QseC sensor regulation beneath different environmental signals, such as glucose and butyrate. Our findings broaden the knowledge about the QseC sensor in modulating the human microbiota and its importance for EHEC pathogenesis.

QseB/QseC: a two-component system globally regulating bacterial behaviors.

QseB/QseC is a two-component system that is involved in the regulation of multiple bacterial behaviors by regulating quorum sensing, bacterial pathogenicity, and antibiotic resistance. Thus, QseB/QseC could provide a target for new antibiotic development. Recently, QseB/QseC has been found to confer survival advantages to environmental bacteria under stress conditions. The molecular mechanistic understanding of QseB/QseC has become an active area of research and revealed some emerging themes, including a deeper understanding of QseB/QseC regulation in different pathogens and environmental bacteria, the functional difference of QseB/QseC among species, and the possibility of analyzing QseB/QseC evolution. Here, we discuss the progression of QseB/QseC studies and describe several unresolved issues and future directions. Resolving these issues is among the challenges of future QseB/QseC studies.

Characterisation of the E. coli and Salmonella qseC and qseE mutants reveals a metabolic rather than adrenergic receptor role.

Catecholamine stress hormones (norepinephrine, epinephrine, and dopamine) are signals that have been shown to be used as environmental cues, which affect the growth and virulence of normal microbiota as well as pathogenic bacteria. It has been reported that Escherichia coli and Salmonella use the two-component system proteins QseC and QseE to recognise catecholamines and so act as bacterial adrenergic receptors. In this study, we mutated the E. coli O157:H7 and Salmonella enterica serovar Typhimurium genes encoding QseC and QseE and found that this did not block stress hormone responsiveness in either species. Motility, biofilm formation, and analysis of virulence of the mutants using two infection models were similar to the wild-type strains. The main differences in phenotypes of the qseC and qseE mutants were responses to changes in temperature and growth in different media particularly with respect to salt, carbon, and nitrogen salt sources. In this physiological respect, it was also found that the phenotypes of the qseC and qseE mutants differed between E. coli and Salmonella. These findings collectively suggest that QseC and QseE are not essential for E. coli and Salmonella to respond to stress hormones and that the proteins may be playing a role in regulating metabolism.

Gut colonization by Proteobacteria alters host metabolism and modulates cocaine neurobehavioral responses.

Gut-microbiota membership is associated with diverse neuropsychological outcomes, including substance use disorders (SUDs). Here, we use mice colonized with Citrobacter rodentium or the human γ-Proteobacteria commensal Escherichia coli HS as a model to examine the mechanistic interactions between gut microbes and host responses to cocaine. We find that cocaine exposure increases intestinal norepinephrine levels that are sensed through the bacterial adrenergic receptor QseC to promote intestinal colonization of γ-Proteobacteria. Colonized mice show enhanced host cocaine-induced behaviors. The neuroactive metabolite glycine, a bacterial nitrogen source, is depleted in the gut and cerebrospinal fluid of colonized mice. Systemic glycine repletion reversed, and γ-Proteobacteria mutated for glycine uptake did not alter the host response to cocaine. γ-Proteobacteria modulated glycine levels are linked to cocaine-induced transcriptional plasticity in the nucleus accumbens through glutamatergic transmission. The mechanism outline here could potentially be exploited to modulate reward-related brain circuits that contribute to SUDs.

Detection and genomic characterization of mcr-9 in Enterobacter hormaechei recovered from a pediatric patient in Lebanon.

BACKGROUND: The emergence and spread of mobilized colistin resistance (mcr) genes are a global health concern. OBJECTIVES: In this study, we report the detection and genomic characterization of mcr-9 in a colistin-susceptible Enterobacter hormaechei (EH23) recovered from a pediatric patient in Lebanon. RESULTS: EH23 was susceptible to colistin with a minimal inhibitory concentration (MIC) of 0.25 mg/L. Studying the mcr-9 genetic environment revealed that it was chromosomal and was bracketed by IS903 and IS26. QseCB, a two-component regulatory system, mediating the inducible expression of mcr-9 gene was not detected within the mcr-9 cassette but elsewhere on the genome. EH23 was 99.96% similar based on average nucleotide identity (ANI) to another mcr-negative E. hormaechei OIPH-N069 isolate recovered from Japan. wgSNP-based phylogenetic analysis divided all mcr-9 positive E. hormaechei isolates into five clades (I to V), with isolates from the same ST being clustered together. CONCLUSION: The silent spread of mcr-9, particularly in the globally successful ST-78 Enterobacter lineage, is worrisome and requires close monitoring in humans and animals.

Endocannabinoids Attenuate the Virulence of Certain Enteropathogenic Bacteria.

The mammalian endocannabinoid system modulates gastrointestinal physiology and immunity via lipid hormones (endocannabinoids). Ellermann et al. have recently revealed the effect of the endocannabinoid, 2-arachidonoyl glycerol (2-AG) on intestinal infection. They show that 2-AG directly modulates bacterial function by antagonizing the provirulence receptor QseC, thereby protecting mice against enteric infection. The endocannabinoid system has already been identified as a promising target in the treatment of inflammatory bowel diseases, but these new findings raise questions about the possible benefits of using cannabinoids to treat intestinal bacterial infections.

The Escherichia coli QseB/QseC signaling is required for correct timing of replication initiation and cell motility.

The Escherichia coli QseB/QseC signaling regulates expressions of more than 50 genes encoding flagellar proteins and proteins associated with virulence. Here we found that absence of the QseB/QseC signaling led to an early initiation of chromosomal replication and higher concentration of DnaA which is initiator for replication. The upstream region of dnaA promoter contains three potential QseB binding sites and absence of these binding sites increased transcription of the dnaA gene in wild-type cells but not in the cells lacking the qseB/qseC genes, showing that the QseB/QseC signaling regulates dnaA expression through the QseB binding sites. Also increased cell motility but neither cell size nor growth rate in ΔqseBC and ΔqseB cells was observed and these effects were reversed by ectopic expression of QseBC. Further, it was found that QseB interacted with the DnaK chaperone and FtsZ cell division protein in vivo, and absence of DnaK or partial inactivation of FtsZ decreased cell motility. Thus, we conclude that the QseB/QseC signaling modulates timing of replication initiation by regulating expression of DnaA, coordinates cell motility with cell division through interacting with the DnaK and FtsZ protein.