N-dodecanoyl-l-homoserine lactone (C12-HSL) is a signaling molecule that mediates bacterial quorum sensing, regulating bacterial population behaviors. This study investigated the effects of C12-HSL on the isolation and cultivation of gut microbiota, with the goal of enriching the diversity and number of cultivable bacterial strains from the mouse gut microbiota. Using a culture medium supplemented with C12-HSL, we isolated and cultivated bacterial strains from mouse intestinal contents, obtaining a total of 235 isolates. Preliminary identification based on the 16S rRNA gene revealed 54 bacterial species, including 4 potential new species, 4 potential new genera and 1 potential new family. Compared with the previously established mouse gut microbial biobank (mGMB), this study newly identified 42 bacterial species, enhancing the diversity of the strain library. Statistical analysis showed that the proportion of Gram-negative bacteria, particularly those belonging to Proteobacteria, isolated by this method was significantly higher than that obtained by conventional isolation and cultivation methods without the addition of C12-HSL. Subsequent cultivation experiments with one of the newly discovered bacterial species indicated that exogenous C12-HSL at 20-200 μmol/L significantly promoted the growth of this species, while higher concentrations of C12-HSL significantly reduced the cell density of this bacterium. This work confirms that quorum sensing molecules, such as C12-HSL, can enhance the growth, isolation, and cultivation of Gram-negative bacteria in the gut within a specific concentration range. Although the mechanism by which C12-HSL promotes the growth of gut bacterial strains requires further investigation, the findings of this study provide new insights into the targeted isolation, cultivation, and regulation of gut microbiota using bacterial quorum sensing signal molecules.
Animals ; Mice ; Acyl-Butyrolactones/pharmacology* ; Gastrointestinal Microbiome/drug effects* ; Quorum Sensing ; Gram-Negative Bacteria/classification* ; Intestines/microbiology* ; RNA, Ribosomal, 16S/genetics* ; Culture Media

Shewanella oneidensis MR-1, a Gram-negative bacterium with a significant role in the adsorption and reduction of uranium in wastewater and a quorum-sensing effect, can be used to remove uranium from wastewater. Exogenous signaling molecules (acyl-homoserine lactones, AHLs) can be added to induce the quorum sensing behavior for rapid biofilm formation, thereby improving the removal efficiency of this bacterium for uranium. Extracellular polymeric substances (EPS), as the significant components of biofilm, play a key role in biofilm formation. To investigate the quorum sensing behavior induced by AHLs, we systematically investigated the effects of AHLs on the EPS secretion and biofilm properties of S. oneidensis MR-1 by regulating parameters such as AHL species, concentration, addition time point, and contact time. The results showed that the addition of 10 μmol/L N-butyryl-l-homoserine lactone (C4-HSL) after 6 h of culture and continued incubation to reach the time point of 72 h significantly promoted the secretion of EPSs, in which the content of extracellular proteins and extracellular polysaccharides was increased by 15.2% and 28.2%, respectively, compared with that of the control group. The biofilm electrodes induced by signaling molecules showed superior properties, which were evidenced by an increase of exceeding 20 μm in biofilm thickness, an increase of 33.9% in the proportion of living cells, enhanced electroactivity, and an increase of 10.7% in the uranium removal rate. The biofilm electrode was confirmed to immobilize uranium in wastewater mainly by electrosorption, physicochemical adsorption, and electro-reduction through characterization means such as X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). This study provides a new technical idea for the efficient recovery of uranium in wastewater and enriches the theoretical system of quorum sensing regulation of electroactive biofilms.
Biofilms/drug effects* ; Acyl-Butyrolactones/pharmacology* ; Quorum Sensing/drug effects* ; Uranium/metabolism* ; Shewanella/metabolism* ; Adsorption ; Uranium Compounds/metabolism* ; Wastewater/chemistry* ; Biodegradation, Environmental ; Extracellular Polymeric Substance Matrix/metabolism*

Quorum sensing(QS) is one of the research hotspots in the fields of microbiology and medicine in recent years. Quorum sensing is a cell communication regulatory system, which is used by bacterial flora to pass on information of population density by sensing specific signaling molecules to the environment. The QS system of bacteria can impact biological functions, such as bacterial growth, proliferation, biofilm formation, virulence factor production, antibiotic synthesis, and ultimately adapt the bacteria to environmental changes. At present, more and more active ingredients can regulate quorum sensing have been found in traditional Chinese medicines(TCM). TCM and their active ingredients can promote the growth of beneficial bacteria, inhibit the proliferation of pathogenic bacteria and finally achieve the purpose of treating diseases. It embodies multi-pathway and multi-target characteristics of traditional Chinese medicine. This article first introduces molecular types and regulation mechanisms of quorum sensing signals between bacteria. On this basis, the human health-related bacterial quorum sensing is summarized, and the regulatory effect of TCM on bacterial quorum sensing system is discussed. Finally, it is noted that the material basis and mechanisms of TCM in improving human health through bacterial quorum sensing system are still unclear. Future research hotspots will focus on quorum sensing active substances, quorum sensing key nodes and relevant targets. In a word, this article provides reference for the treatment of relevant diseases.
Bacteria/drug effects* ; Humans ; Medicine, Chinese Traditional ; Quorum Sensing

OBJECTIVETo investigate the effect of andrographolide (AG) on quroum sensing (QS) and relevant virulence genes of Candida albicans.

METHODGas-chromatography-mass spectrometry (GC-MS) was applied to detect the changes in the content of farnesol and tyrosol in C. albicans intervened by AG. The real-time quantitative PCR (qRT-PCR) was adopted to inspect the expressions of relevant virulence genes such as CHK1, PBS2 and HOG1 regulated by QS.

RESULTAt 2 h after the growth of C. albican, the farnesol and tyrosol secretions reduced, without notable change after intervention with AG. The secretions were highest at 12 h and decreased at 24 h. After the intervention with different concentrations of AG, the farnesol content reduces, whereas tyrosol increased, indicating a dose-dependence, particularly with 1 000 mg x L(-1) AG. qRT-PCR revealed that 1 000 mg x L(-1) AG could down-regulate CHK1 by 2.375, 3.330 and 4.043 times and PBS2 by 2.010, 4.210 and 4.760 times, with no significant change in HOG1.

CONCLUSIONAG could inhibit the farnesol secretion, promote the tyrosol secretion and down-regulate QS-related virulence genes CHK1 and PBS2 expressions.

Candida albicans ; drug effects ; genetics ; physiology ; Diterpenes ; pharmacology ; Farnesol ; analysis ; metabolism ; Gas Chromatography-Mass Spectrometry ; Genes, Fungal ; Phenylethyl Alcohol ; analogs & derivatives ; analysis ; metabolism ; Quorum Sensing ; drug effects ; Real-Time Polymerase Chain Reaction ; Virulence ; genetics

The discovery of quorum sensing (QS) system and its critical role in bacterial virulence have revealed a new way to attack pathogenic bacterium. The pathogenecity of QS deletion mutants decreases significantly. Targeting bacterial QS system is a promising therapeutic approach to control infections and anti-microbial resistance. To obtain natural QS inhibitors from marine organisms, marine fungi (69 strains) were isolated from marine mollusca, and their extracts were screened using improved QSIS2 (Quorum Sensing Inhibitor Selector 2) assay and Chromobacterium violaceum CV026. To improve the efficiency of QSIS2 screening, 2,3,5-triphenyltetrazolium chloride (TTC) staining method was used. Extract from strain QY013 was found to have QS inhibitory activity. Further experiment indicated that pyocyanin in Pseudomonas aeruginosa PAOI and violacein in C. violaceum CV026 were reduced by QY013 extract, without affecting bacterial growth. Morphological and 18S rDNA sequence analysis revealed that strain QY013 was most closely related to Penicillium species. The above results suggest that active constituents from QY013 may be used as novel antimicrobial agents against bacterial infection.
Animals ; Anti-Infective Agents ; isolation & purification ; metabolism ; pharmacology ; Bacterial Physiological Phenomena ; Fungi ; isolation & purification ; physiology ; Marine Biology ; Mollusca ; microbiology ; Penicillium ; isolation & purification ; metabolism ; Pseudomonas aeruginosa ; drug effects ; metabolism ; pathogenicity ; Quorum Sensing ; drug effects ; Virulence ; drug effects

In recent years, antibiotic resistance of bacteria has become a global health crisis. Especially, the new class of "superbug" was found in South Asia, which is resistant to almost known antibiotics and causes worldwide alarm. Through the underlying mechanisms of bacterial pathogenecity, the expression of many pathogen virulence factors is regulated by the process of quorum sensing. Screening efficient quorum sensing inhibitors is an especially compelling approach to the future treatment of bacterial infections and antibiotic resistance. This article focuses on bacterial quorum sensing system, quorum sensing screening model for in vitro and evaluation of animal models in vivo, recent research of quorum sensing inhibitors and so on.
Animals ; Anti-Bacterial Agents ; pharmacology ; therapeutic use ; Bacterial Infections ; drug therapy ; Disease Models, Animal ; Drug Resistance, Bacterial ; Drugs, Chinese Herbal ; pharmacology ; Humans ; Pseudomonas aeruginosa ; drug effects ; pathogenicity ; physiology ; Quorum Sensing ; drug effects ; physiology ; Virulence ; drug effects ; Virulence Factors ; metabolism

Bacterial biofilms can be viewed as a specific type of persistent bacterial infection. After initial invasion, microbes can attach to living and non-living surfaces, such as prosthetics and indwelling medical devices, and form a biofilm composed of extracellular polysaccharides, proteins, and other components. In hosts, biofilm formation may trigger drug resistance and inflammation, resulting in persistent infections. The clinical aspects of biofilm formation and leading strategies for biofilm inhibitors will be discussed in this mini-review.
Adhesins, Bacterial ; drug effects ; physiology ; Aminoacyltransferases ; antagonists & inhibitors ; genetics ; Animals ; Antimicrobial Cationic Peptides ; genetics ; pharmacology ; Bacterial Infections ; microbiology ; surgery ; Bacterial Proteins ; antagonists & inhibitors ; genetics ; Biofilms ; drug effects ; growth & development ; Chronic Disease ; Cysteine Endopeptidases ; genetics ; Cysteine Proteinase Inhibitors ; pharmacology ; Humans ; Inflammation ; microbiology ; Quorum Sensing ; drug effects ; physiology ; Wound Infection ; microbiology ; surgery

Bacteria survive in nature by forming biofilms on surfaces and probably most, if not all, bacteria (and fungi) are capable of forming biofilms. A biofilm is a structured consortium of bacteria embedded in a self-produced polymer matrix consisting of polysaccharide, protein and extracellular DNA. Bacterial biofilms are resistant to antibiotics, disinfectant chemicals and to phagocytosis and other components of the innate and adaptive inflammatory defense system of the body. It is known, for example, that persistence of staphylococcal infections related to foreign bodies is due to biofilm formation. Likewise, chronic Pseudomonas aeruginosa lung infections in cystic fibrosis patients are caused by biofilm growing mucoid strains. Gradients of nutrients and oxygen exist from the top to the bottom of biofilms and the bacterial cells located in nutrient poor areas have decreased metabolic activity and increased doubling times. These more or less dormant cells are therefore responsible for some of the tolerance to antibiotics. Biofilm growth is associated with an increased level of mutations. Bacteria in biofilms communicate by means of molecules, which activates certain genes responsible for production of virulence factors and, to some extent, biofilm structure. This phenomenon is called quorum sensing and depends upon the concentration of the quorum sensing molecules in a certain niche, which depends on the number of the bacteria. Biofilms can be prevented by antibiotic prophylaxis or early aggressive antibiotic therapy and they can be treated by chronic suppressive antibiotic therapy. Promising strategies may include the use of compounds which can dissolve the biofilm matrix and quorum sensing inhibitors, which increases biofilm susceptibility to antibiotics and phagocytosis.
Animals ; Antibiotic Prophylaxis ; Biofilms ; drug effects ; growth & development ; Chronic Disease ; Cystic Fibrosis ; microbiology ; Drug Resistance, Microbial ; physiology ; Foreign Bodies ; microbiology ; Humans ; Microbial Consortia ; drug effects ; genetics ; immunology ; Phagocytosis ; Pseudomonas Infections ; microbiology ; Pseudomonas aeruginosa ; drug effects ; genetics ; physiology ; Quorum Sensing ; drug effects ; genetics

OBJECTIVETo investigate the relationship among oxygen concentration, quorum sensing system, type secretion system, and biofilm production of Pseudomonas aeruginosa.

METHODSA total of 23 clinical strains of Pseudomonas aeruginosa were cultured at different levels of environmental oxygen for three days. Then biofilm mass and alginate were quantified. The expression levels of LasI and RhlI were detected by real time polymerase chain reaction (PCR). The secretion of exoenzyme S was examined by Western blot.

RESULTSBoth the biofilm mass (R=0.455, P=0.000) and alginate (R=0.367, P=0.000) were positively correlated with oxygen concentration. Real time PCR showed that the expression levels of LasI and RhlI were not significantly correlated with oxygen concentration (R=0.025, P=0.794; R=-0.044, P=0.653), the production of biofilm (R=0.001, P=0.990; R=0.011, P=0.909), or alginate(R=0.029, P=0.770; R=0.193, P=0.064). Western blot showed that the optimal oxygen concentration range for exoenzyme S secretion of Pseudomonas aeruginosa ranged 10% to 30%.

CONCLUSIONSHyperoxia can promote the production of biofilm and alginate by Pseudomonas aeruginosa. Las/Rhl system may not participate in biofilm production at the early stage due to the low bacteria amount. The increased production of biofilm may inhibit the expression of Type Secretion system and thus inhibit bacterial virulence.

Alginates ; metabolism ; Biofilms ; drug effects ; Oxygen ; metabolism ; Pseudomonas aeruginosa ; metabolism ; physiology ; Quorum Sensing ; drug effects ; physiology

Quorum sensing is an important gene regulatory mechanism in Pseudomonas aeruginosa and controls the expression of numerous virulence factors. We designed and constructed a screening system for quorum-sensing inhibitors. We developed the system by using the lasI and rhlA promoters fused with promoterless sacB as reporters. Using this system we screened a number of Chinese herb extracts, and identified three herb extracts containing inhibitors to the quorum-sensing system and to its regulated genes. The screening system developed was highly efficient and sensitive. It could serve as a useful tool to identify herb compounds that block infections but unlikely render antibiotic resistance in pathogens.
Acanthaceae ; chemistry ; Anti-Bacterial Agents ; pharmacology ; Drug Evaluation, Preclinical ; methods ; Drugs, Chinese Herbal ; pharmacology ; Genes, Reporter ; Promoter Regions, Genetic ; Pseudomonas aeruginosa ; drug effects ; genetics ; Quorum Sensing ; drug effects ; Valerianaceae ; chemistry