Indigenous microbes inside the host intestine maintain a complex self-regulating community. The mechanisms by which gut microbes interact with intestinal pathogens remain largely unknown. Here we ...identify a commensal Escherichia coli strain whose expansion predisposes mice to infection by Vibrio cholerae, a human pathogen. We refer to this strain as 'atypical' E. coli (atEc) because of its inability to ferment lactose. The atEc strain is resistant to reactive oxygen species (ROS) and proliferates extensively in antibiotic-treated adult mice. V. cholerae infection is more severe in neonatal mice transplanted with atEc compared with those transplanted with a typical E. coli strain. Intestinal ROS levels are decreased in atEc-transplanted mice, favouring proliferation of ROS-sensitive V. cholerae. An atEc mutant defective in ROS degradation fails to facilitate V. cholerae infection when transplanted, suggesting that host infection susceptibility can be regulated by a single gene product of one particular commensal species.
IL-17 family cytokines are directly involved in host immune responses and the critical mediators for host defense against infection or inflammation. IL-17C is highly expressed in respiratory ...epithelium and is induced after acute bacterial lung infection. However, the definite function of IL-17C induced by
(PAO1 strain) is not fully understood, and our study was designed to demonstrate IL-17C-induced immune response against PAO1 infection in nasal epithelium. Passage-2 normal human nasal epithelial (NHNE) cells were infected with PAO1 and the relationship between IL-17C-related immune responses and the iron absorption of PAO1, depending on inoculation of recombinant human IL-17C (rhIL-17C), was assessed by measuring the siderophore activity of PAO1. Microarray data showed that IL-17C expression increased 34.7 times at 8 hours postinfection (hpi) in NHNE cells, and IL-17C mRNA levels increased until 48 hpi. The PAO1 colonies significantly increased from 8 hpi in NHNE cells, and siderophore activity of PAO1 was enhanced in the supernatants of PAO1-infected NHNE cells. Interestingly, PAO1 colonies were reduced in PAO1-infected NHNE cells treated with rhIL-17C, and supernatants from NHNE cells treated with rhIL-17C also exhibited decreased PAO1 colonies. We found that the siderophore activity of PAO1 was significantly reduced in the supernatants of NHNE cells treated with rhIL-17C where LCN2 expression was highly elevated. Our findings indicate that IL-17C mediates an antibacterial effect against PAO1 by inhibiting siderophore activity in nasal epithelium. We propose that IL-17C might be an efficient mediator to suppress PAO1 infection through disturbing iron absorption of PAO1 in nasal epithelium.
Pseudomonas aeruginosa establishes airway infections in Cystic Fibrosis patients. Here, we investigate the molecular interactions between P. aeruginosa and airway mucus secretions (AMS) derived from ...the primary cultures of normal human tracheal epithelial (NHTE) cells. PAO1, a prototype strain of P. aeruginosa, was capable of proliferating during incubation with AMS, while all other tested bacterial species perished. A PAO1 mutant lacking PA4834 gene became susceptible to AMS treatment. The ΔPA4834 mutant was grown in AMS supplemented with 100 μM ferric iron, suggesting that the PA4834 gene product is involved in iron metabolism. Consistently, intracellular iron content was decreased in the mutant, but not in PAO1 after the AMS treatment. Importantly, a PAO1 mutant unable to produce both pyoverdine and pyochelin remained viable, suggesting that these two major siderophore molecules are dispensable for maintaining viability during incubation with AMS. The ΔPA4834 mutant was regrown in AMS amended with 100 μM nicotianamine, a phytosiderophore whose production is predicted to be mediated by the PA4836 gene. Infectivity of the ΔPA4834 mutant was also significantly compromised in vivo. Together, our results identify a genetic element encoding a novel iron acquisition system that plays a previously undiscovered role in P. aeruginosa airway infection.
is capable of establishing airway infections. Human airway mucus contains a large amount of lysozyme, which hydrolyzes bacterial cell walls.
, however, is known to be resistant to lysozyme. Here, we ...performed a genetic screen using a mutant library of PAO1, a prototype
strain, and identified two mutants (Δ
and Δ
) that exhibited decrease in survival after lysozyme treatment. The
and
genes encode an outer membrane assembly protein and a fatty acid synthesis enzyme, respectively. These two mutants displayed retarded growth in the airway mucus secretion (AMS). In addition, these mutants exhibited reduced virulence and compromised survival fitness in two different
infection models. The mutants also showed susceptibility to several antibiotics. Especially, Δ
mutant was very sensitive to vancomycin, ampicillin, and ceftazidime that target cell wall synthesis. The Δ
displayed compromised membrane integrity. In conclusion, this study uncovered a common aspect of two different
mutants with pleiotropic phenotypes, and suggests that BamB and FabY could be novel potential drug targets for the treatment of
infection.
Our recent study presented that human nasal commensal Staphylococcus epidermidis could potentiate antiviral immunity in the nasal mucosa through interferon-related innate responses. Here, we found ...that human nasal commensal S. epidermidis promoted protease-protease inhibitor balance in favor of the host and prevented influenza A virus (IAV) replication in the nasal mucosa and lungs. A relatively higher induction of Serpine1 exhibited in S. epidermidis-inoculated nasal epithelium and S. epidermidis-induced Serpine1 significantly decreased the expression of serine proteases. Furthermore, the transcription of urokinase plasminogen activator (uPA) and Serpine1 was biologically relevant in S. epidermidis-inoculated nasal epithelium, and the induction of uPA might be related to the sequential increase of Serpine1 in human nasal epithelium. Our findings reveal that human nasal commensal S. epidermidis manipulates the cellular environment lacking serine proteases in the nasal epithelium through Serpine1 induction and disturbs IAV spread to the lungs at the level of the nasal mucosa.
Pseudomonas aeruginosa, a Gram-negative bacterium of clinical significance, produces elastase as a predominant exoprotease. Here, we screened a library of chemical compounds currently used for human ...medication and identified diethylene triamine penta-acetic acid (DTPA, pentetic acid) as an agent that suppresses the production of elastase. Elastase activity found in the prototype P. aeruginosa strain PAO1 was significantly decreased when grown with a concentration as low as 20 μM DTPA. Supplementation with Zn(2+) or Mn(2+) ions restored the suppressive effect of DTPA, suggesting that the DTPA-mediated decrease in elastase activity is associated with ion-chelating activity. In DTPA-treated PAO1 cells, transcription of the elastase-encoding lasB gene and levels of the Pseudomonas quinolone signal (PQS), a molecule that mediates P. aeruginosa quorum sensing (QS), were significantly downregulated, reflecting the potential involvement of the PQS QS system in DTPA-mediated elastase suppression. Biofilm formation was also decreased by DTPA treatment. When A549 alveolar type II-like adenocarcinoma cells were infected with PAO1 cells in the presence of DTPA, A549 cell viability was substantially increased. Furthermore, the intranasal delivery of DTPA to PAO1-infected mice alleviated the pathogenic effects of PAO1 cells in the animals. Together, our results revealed a novel function for a known molecule that may help treat P. aeruginosa airway infection.
Accumulating evidence indicates that microbial communities in the human body crucially affect health through the production of chemical messengers. However, the relationship between human microbiota ...and cancer has been underexplored. As a result of a biochemical investigation of the commensal oral microbe, Corynebacterium durum, we identified the non-enzymatic transformation of tryptamine into an anticancer compound, durumamide A (1). The structure of 1 was determined using LC-MS and NMR data analysis as bis(indolyl)glyoxylamide, which was confirmed using one-pot synthesis and X-ray crystallographic analysis, suggesting that 1 is an oxidative dimer of tryptamine. Compound 1 displayed cytotoxic activity against various cancer cell lines with IC50 values ranging from 25 to 35 μM. A drug affinity responsive target stability assay revealed that survivin is the direct target protein responsible for the anticancer effect of 1, which subsequently induces apoptosis-inducing factor (AIF)-mediated apoptosis. Inspired by the chemical structure and bioactivity of 1, a new derivative, durumamide B (2), was synthesized using another indole-based neurotransmitter, serotonin. The anticancer properties of 2 were similar to those of 1; however, it was less active. These findings reinforce the notion of human microbiota-host interplay by showing that 1 is naturally produced from the human microbial metabolite, tryptamine, which protects the host against cancer.
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Obesity is a major public health problem related to various chronic health conditions.
species has been reported in obese individuals; however, its role is unknown. We compared the abundance and ...composition of
species by analyzing feces from 64 healthy control subjects and 88 obese subjects. We isolated one
strain from the feces of a subject with obesity and further analyzed its genetic and molecular features. We found that an increased abundance and higher prevalence of Lactobacillus sakei distinguished the fecal microbiota of the obese group from that of healthy subjects and that it was related to the increased levels of reactive oxygen species (ROS) induced by higher fat intake. The
ob4.1 strain, isolated from the feces of a subject with obesity, showed high catalase activity, which was regulated by oxidative stress at the gene transcription level.
ob4.1 maintained colon epithelial cell adhesion ability under ROS stimulation, and treatment with saturated fatty acid increased colon epithelial ROS levels in a dose-dependent manner; however,
ob4.1 did not change the level of fat-induced colon epithelial ROS. Exposing mice to a high-fat diet revealed that high-fat-diet-induced colon ROS was associated with the increased colonization of
ob4.1 through catalase activity. Four-week supplementation with this strain in mice fed a high-fat diet did not change their body weights or ROS levels. A high-fat diet induces changes in the colon environment by increasing ROS levels, which provides a colonization benefit to an
strain with high catalase activity.
provides many health benefits; its various species are widely used as probiotics. However, an increased abundance of
has been reported in obesity, and the role of
strains in obesity remains unknown. We found a high abundance of the Lactobacillus sakei species in a group of obese subjects and examined its relationship with a high-fat diet and reactive oxygen species (ROS) in the feces. To find the underlying mechanism, we analyzed and characterized an
strain isolated from a severely obese individual. We found that higher gut oxidative stress could link high-fat-diet-induced obesity and
This translational research identifies the roles of the host gut environment in the colonization and survival of
.
Abstract
Alginate-overproducing mucoid Pseudomonas aeruginosa, responsible for chronic airway infections in cystic fibrosis (CF) patients, is resistant to antibiotic treatments and host immune ...clearance. In this study, we performed a phenotype microarray screen and identified sulfate ion as a molecule that can suppress alginate production. When a mucoid P. aeruginosa strain CM21 and additional mucoid isolates were grown with 5% sodium sulfate, significantly decreased levels of alginate were produced. Suppression of alginate production was also induced by other sulfate salts. Expression of a reporter gene fused to the algD promoter was considerably decreased when grown with sulfate. Furthermore, bacterial cell shape was abnormally altered in CM21, but not in PAO1, a prototype nonmucoid strain, suggesting that sulfate-stimulated cell shape change is associated with transcriptional suppression of the alginate operon. Finally, a CM21 lpxC mutant defective in lipid A biosynthesis continued to produce alginate and maintained the correct cell shape when grown with sulfate. These results suggest a potential involvement of lipoploysaccharide biosynthesis in the sulfate-induced reversion to nonmucoid phenotype. This study proposes a novel strategy that can be potentially applied to treat persistent infection by recalcitrant mucoid P. aeruginosa.
Alginate-overproducing mucoid Pseudomonas aeruginosa are resistant to many stress conditions; here we show that alginate production is suppressed by sulfate, suggesting that sulfate compounds could be used to down-regulate the virulence of mucoid P. aeruginosa.
Alginate-overproducing mucoid Pseudomonas aeruginosa are resistant to many stress conditions; here we show that alginate production is suppressed by sulfate, suggesting that sulfate compounds could be used to down-regulate the virulence of mucoid P. aeruginosa.
Vibrio cholerae is a Gram-negative bacterium that causes cholera. Although the pathogenesis caused by this deadly pathogen takes place in the intestine, commonly thought to be anaerobic, ...anaerobiosis-induced virulence regulations are not fully elucidated. Anerobic growth of the V. cholerae strain, N16961, was promoted when trimethylamine N-oxide (TMAO) was used as an alternative electron acceptor. Strikingly, cholera toxin (CT) production was markedly induced during anaerobic TMAO respiration. N16961 mutants unable to metabolize TMAO were incapable of producing CT, suggesting a mechanistic link between anaerobic TMAO respiration and CT production. TMAO reductase is transported to the periplasm via the twin arginine transport (TAT) system. A similar defect in both anaerobic TMAO respiration and CT production was also observed in a N16961 TAT mutant. In contrast, the abilities to grow on TMAO and to produce CT were not affected in a mutant of the general secretion pathway. This suggests that V. cholerae may utilize the TAT system to secrete CT during TMAO respiration. During anaerobic growth with TMAO, N16961 cells exhibit green fluorescence when stained with 2′,7′-dichlorofluorescein diacetate, a specific dye for reactive oxygen species (ROS). Furthermore, CT production was decreased in the presence of an ROS scavenger suggesting a positive role of ROS in regulating CT production. When TMAO was co-administered to infant mice infected with N16961, the mice exhibited more severe pathogenic symptoms. Together, our results reveal a novel anaerobic growth condition that stimulates V. cholerae to produce its major virulence factor.
Background: The human intestine, in which Vibrio cholerae exerts its virulence, is an anaerobic environment.
Results: When grown anaerobically with trimethylamine N-oxide (TMAO), V. cholerae exhibited enhanced growth and cholera toxin (CT) production was remarkably induced.
Conclusion: Anaerobic TMAO respiration may serve as a signal to increase V. cholerae virulence.
Significance: A novel growth condition that induces CT production is uncovered.
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