Laboratory experiments were carried out to determine the long-term effects of N-acyl-homoserine lactone (AHL)-based quorum sensing on the characteristics of ANAMMOX granules in high-loaded reactors. ...Results clearly showed that adding 30 mg L−1 N-octanoyl-DL-homoserinelactone (C8-HSL) at the initial stage (1–40 d) of the experiment had long-term positive effects on the settleability of granules and controlled the sludge floatation effectively. C8-HSL decreased the content of bound extracellular polymeric substances (B-EPS) and the ratio of protein to carbohydrate (PN/PS) by 17% and 48%, respectively and increased the relative hydrophobicity (RH) of the granules by 28%. The results of batch tests indicated that C8-HSL significantly reduced the content of loosely-bound EPS (LB-EPS) in the B-EPS, which was responsible for variations in granule settleability and stability. Thus, the settleability of the granules was improved significantly due to addition of C8-HSL, contributing to operational stability and the high TN removal efficiency of the reactor. On day 150, when the nitrogen loading rates of all reactors were 13.4 kg TN m−3 d−1, the nitrogen removal rate and nitrogen removal efficiency of the reactor with C8-HSL (R3) were up to 11.2 kg TN m−3 d−1 and 88%, respectively. N-hexanoyl-DL-homoserine lactone (C6-HSL) improved activity of the granules, while N-dodecanoyl-DL-homoserine lactone (C12-HSL) had no effect on the characteristics of the granules. The long-term effects of C8-HSL on the settleability of granules may be attributed to sustainable release of endogenous signals induced by exogenous signal.
•Additional C8-HSL improved ANAMMOX granules'settleability in high-loaded reactors.•Additional C6-HSL increased the activity of the ANAMMOX granules.•Additional C8-HSL or C6-HSL had long-term effects on the characteristics of granules.•Exogenous AHLs could induce the sustainable release of endogenous AHLs.•Opened a new window to control the flotation of the ANAMMOX granules.
Quorum sensing signal molecule is an important biomarker released by some microorganisms, which can regulate the adhesion and aggregation of marine microorganisms on the surface of engineering ...facilities. Thus, it is significant to exploit a convenient method that can effectively monitor the formation and development of marine biofouling. In this work, an advanced photoelectrochemical (PEC) aptamer biosensing platform was established and firstly applied for the rapid and ultrasensitive determination of N-(3-Oxodecanoyl)-l-homoserine lactone (3-O-C10-HL) released from marine fouling microorganism Ponticoccus sp. PD-2. The visible-light-driven Bi2WO6/Bi2S3 heterojunction derived from metal-organic frameworks (MOFs) CAU-17 and self-screened aptamer were employed as the photoactive materials and bioidentification elements, respectively. Appropriate amount of MoS2 quantum dots (QDs) conjugated with single-stranded DNA were introduced by hybridization to enhance the photocurrent response of the PEC biosensor. The self-screening aptamer can specifically recognize 3-O-C10-HL, accompanied by increasing the steric hindrance and forcing MoS2 QDs to leave the electrode surface, resulting in an obvious reduction of photocurrent and achieving a dual-inhibition signal amplification effect. Under the optimized conditions, the photocurrent response of PEC aptasensor was linear with 3-O-C10-HL concentration from 1 nM to 10 μM, and the detection limit was as low as 0.26 nM. The detection strategy also showed a high reproducibility, superior specificity and good stability. This work not only provides a simple, rapid and ultrasensitive PEC aptamer biosensing strategy for monitoring quorum sensing signal molecules in marine biofouling, but also broadens the application of MOFs-based heterojunctions in PEC sensors.
The visible-light-driven CAU-17-derived Bi2WO6/Bi2S3 heterojunctions were prepared as the photoactive materials to construct a novel PEC aptasensor, realizing the rapid, ultrasensitive and specifical recognition of quorum sensing signal molecule for monitoring marine biofouling. Display omitted
•Visible-light-driven CAU-17-derived Bi2WO6/Bi2S3 heterostructures were in-situ prepared as the photoactive materials.•MoS2 QDs were introduced to enhance the photocurrent response.•The specific aptamer was self-screened to recognize quorum sensing signal molecules.•The PEC aptasensor showed a high sensitivity to monitor quorum sensing signal molecules in marine biofouling.
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•Proliferation of filamentous bacteria was positively regulated by quorum sensing.•C6-HSL increased from 31.39 ± 3.52 to 125.29 ± 6.70 ng/g VSS during the bulking.•Expressions of ...hdtS, lasR, cciR genes significantly enhanced during the bulking.•Filamentous bulking was significantly inhibited by quorum sensing inhibitors.
The microcosmic mechanisms underlying filamentous bulking are still unclear. Quorum sensing (QS) is an important mechanism by which bacteria control self-reproduction and growth in response to changes in population density. The potential role of QS in filamentous bulking and the feasibility of using a Quorum quenching (QQ) strategy to inhibit filamentous bulking were investigated in this study. The results indicated that the rate of increase in the population density and the abundance of filamentous bacteria in the serious filamentous bulking stage (250 mL/g < SVI) was 1.46 and 2.76 times greater, respectively, than that of the limited filamentous bulking stage (150 mL/g < SVI < 250 mL/g). The proliferation of filamentous bacteria was clearly population density-dependent. The concentration of C6-HSL increased from 31.39 ± 3.52 ng/g VSS to 125.29 ± 6.70 ng/g VSS with an increase in the abundance of filamentous bacteria. Filamentous bulking could be promoted by exogenous N-acyl homoserines (AHLs), especially C6-HSL. The hdtS gene related to the synthesis of AHLs and the lasR and cciR genes related to receptors showed significantly increased expressions during filamentous bulking. SDHA, ND1, and CDK2 genes related to proliferation showed significantly increased expression during filamentous bulking. The QS-AHL system was triggered during filamentous bulking, which promoted the proliferation of filamentous bacteria. As expected, filamentous bulking was significantly inhibited by the addition of vanillin, a quorum sensing inhibitor. Therefore, QQ is a potential strategy for the prevention and control of filamentous bulking. This study provides new information regarding the microcosmic mechanisms of filamentous bulking.
Antibiotics are widely used drugs in the world and pose serious threats to ecosystems and human health. Although it has been reported that ammonia oxidizing bacteria (AOB) can cometabolize ...antibiotics, little has been reported on how AOB would respond to the exposure of antibiotics on extracellular and enzymatic levels, as well as the impact of antibiotics on the bioactivity of AOB. Therefore, in this study, a typical antibiotic, sulfadiazine (SDZ), was selected, and a series short-term batch tests using enriched AOB sludge were conducted to investigate the intracellular and extracellular responses of AOB along the cometabolic degradation process of SDZ. The results showed the cometabolic degradation of AOB made the main contribution to SDZ removal. When the enriched AOB sludge was exposed to SDZ, ammonium oxidation rate, ammonia monooxygenase activity, adenosine triphosphate concentration and dehydrogenases activity were negatively affected. The amoA gene abundance increased 1.5 folds within 24 h, which may enhance the uptake and utilization of substrates and maintain stable metabolic activity. In the tests with and without ammonium, the concentration of total EPS increased from 264.9 to 231.1 mg/gVSS to 607.7 and 538.2 mg/gVSS, respectively, under the exposure to SDZ, which was mainly contributed by the increase of proteins in tightly bound extracellular polymeric substances (EPS) and polysacharides in tightly bound EPS and soluble microbial products. The proportion of tryptophan-like protein and humic acid-like organics in EPS also increased. Moreover, SDZ stress stimulated the secretion of three quorum sensing signal molecules, C4-HSL (from 140.3 to 164.9 ng/L), 3OC6-HSL (from 17.8 to 42.4 ng/L) and C8-HSL (from 35.8 to 95.9 ng/L) in the enriched AOB sludge. Among them, C8-HSL may be a key signal molecule that promoted the secretion of EPS. The findings of this study could shed more light on the cometabolic degradation of antibiotics by AOB.
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•Sulfadiazine (SDZ) removal by AOB was mainly through cometabolic degradation.•SDZ negatively affected ammonia monooxygenase activity, adenosine triphosphate concentration, and dehydrogenases activity.•The proportion of tyrosine-like protein and humic acid-like organics in EPS increased.•Addition of SDZ stimulated the secretion of C4-HSL, 3OC6-HSL and C8-HSL.•C8-HSL may be a key signal molecule that promoted the secretion of PS and PN in the cometabolic process of AOB.
Understanding microbial interactions in the methanogenesis system through quorum sensing (QS) is very important for system optimization. Known QS genes were collected and classified into seven groups ...based on the signal molecules, which were used for constructing a hierarchical quorum sensing database (QSDB). QSDB containing 39,981 QS genes of seven QS groups was constructed and QS genes were analyzed with QSDB. Methanogen genomes were aligned with QSDB and acyl-homoserine lactones (AHLs) system was predicted as the most probable QS system. This database was further applied to analyze QS in methanogens from two upflow anaerobic sludge blanket-anaerobic filter hybrid reactors with conductive filter (CFB) and nonconductive filter (SEP), and a control without filter (CON). The maximum COD degradation rates in CFB (722.2 ± 10.1 mg/L·h) was elevated by 42.9% compared to CON (505.4 ± 5.98 mg/L·h). Metagenomic sequencing revealed Methanosaeta, Methanobacterium, and Methanosarcina were dominant, and the abundances was 4.3 times higher in the sludge of CFB compared to CON. The overall abundance of QS genes was CFB > SEP > CON, and AHLs were the most abundant group of QS genes. The filI/filR system, a luxI/luxR homolog, was firstly detected in methanogens, showing a high abundance in the CFB (0.085%) compared to in the CON (0.058%). The concentration of AHL molecules in CFB biofilms (0.04%) was about four times that in the CON (0.01%). Syntrophobacter and Smithella were the two major syntrophic bacteria of methanogens, and their abundances were positively correlated with methanogens. In addition, Syntrophobacter and Smithella harbored QS RpfB (component of the diffusible signal factor system) and PDE (component of cyclic di-GMP system). This study provides useful guidance for deeply understanding of QS in anaerobic digestion systems.
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•Methane yield was enhanced in the bioreactor with conductive filter.•A comprehensive and public microbial quorum sensing database was constructed.•Acyl-homoserine lactone system is the most probable quorum sensing in methanogens.•The abundant AHLs and AHL-based QS genes coupled with a high methane production•Syntrophobacter and Smithella may use RpfB and PDE to communicate with methanogens.
Mitochondrial autophagy plays an important role in maintaining the complexity of mitochondrial functions and removing damaged mitochondria, of which the PINK1-Parkin signal pathway is one of the most ...classical pathways. Thus, a comprehensive and in-depth interpretation of the PINK1-Parkin signal pathway might deepen our understanding on the impacts of mitochondrial autophagy. Alzheimer's disease (AD) is a classical example of neurodegenerative disease. Research on the pathogenesis and treatments of AD has been a focus of scientific research because of its complexity and the limitations of current drug therapies. It was reported that the pathogenesis of AD might be related to mitochondrial autophagy due to excessive deposition of Aβ protein and aggravation of the phosphorylation of Tau protein. Two key proteins in the PINK1-Parkin signaling pathway, PINK1 and Parkin, have important roles in the folding and accumulation of Aβ protein and the phosphorylation of Tau protein. In addition, the intermediate signal molecules in the PINK1-Parkin signal pathway also have certain effects on AD. In this paper, we first described the role of PINK1-Parkin signal pathway on mitochondrial autophagy, then discussed and analyzed the effect of the PINK1-Parkin signal pathway in AD and other metabolic diseases. Our aim was to provide a theoretical direction to further elucidate the pathogenesis of AD and highlight the key molecules related to AD that could be important targets used for AD drug development.
Elicitation is a possible aid to overcome various difficulties associated with the large‐scale production of most commercially important bioactive secondary metabolites from wild and cultivated ...plants, undifferentiated or differentiated cultures. Secondary metabolite accumulation in vitro or their efflux in culture medium has been elicited in the undifferentiated or differentiated tissue cultures of several plant species by the application of a low concentration of biotic and abiotic elicitors in the last three decades. Hairy root cultures are preferred for the application of elicitation due to their genetic and biosynthetic stability, high growth rate in growth regulator‐free media, and production consistence in response to elicitor treatment. Elicitors act as signal, recognized by elicitor‐specific receptors on the plant cell membrane and stimulate defense responses during elicitation resulting in increased synthesis and accumulation of secondary metabolites. Optimization of various parameters, such as elicitor type, concentration, duration of exposure, and treatment schedule is essential for the effectiveness of the elicitation strategies. Combined application of different elicitors, integration of precursor feeding, or replenishment of medium or in situ product recovery from the roots/liquid medium with the elicitor treatment have showed improved accumulation of secondary metabolites due to their synergistic effect. This is a comprehensive review about the progress in the elicitation approach to hairy root cultures from 2010 to 2019 and the information provided is valuable and will be of interest for scientists working in this area of plant biotechnology.
Quorum sensing signal molecules can be used to regulate the formation of biofilm, but it has not been reported that outer membrane vesicles (OMVs) can package and mediate signal molecules to regulate ...biofilm. We isolated and purified OMVs packaged with Pseudomonas quinolone signal (PQS) released by Pseudomonas aeruginosa and studied the effects of OMV-mediated PQS on the formation and structure of biofilms. OMV-mediated PQS promoted the growth of biofilm, and the cells in the biofilm were stretched, deformed and “bridged” with the surrounding cells. Raman spectrometry showed that the structure and components of the extracellular polymeric substances of P. aeruginosa changed; moreover extracellular proteins rather than polysaccharides played the dominant role in the formation of P. aeruginosa biofilms when regulated by OMV-mediated PQS. In the combination biofilm formed by P. aeruginosa and Staphylococcus aureus, the mediation of OMVs enhanced the inhibitory effect of PQS to the growth of S. aureus, resulting a decrease in EPS produced by the two bacteria. OMV-mediated PQS led to changes in the biodiversity, richness and structure of the microbial community in biofilms formed by active sludge. This work reveals the mechanism of OMVs mediated signal molecules regulating biofilm, which lays a new theoretical and practical foundation for guiding the operation of low-level of biofouling MBRs.
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•OMV-mediated PQS can regulate the formation and structure of biofilms.•OMV-mediated PQS changed the structure and components of EPS.•OMV-mediated PQS promoted the inhibitory effects of PQS in interspecific species.•OMV-mediated PQS changed the microbial community in mixed biofilms.
Recently, plant secondary metabolites are considered as important sources of pharmaceuticals, food additives, flavours, cosmetics, and other industrial products. The accumulation of secondary ...metabolites in plant cell and organ cultures often occurs when cultures are subjected to varied kinds of stresses including elicitors or signal molecules. Application of exogenous jasmonic acid (JA) and methyl jasmonate (MJ) is responsible for the induction of reactive oxygen species (ROS) and subsequent defence mechanisms in cultured cells and organs. It is also responsible for the induction of signal transduction, the expression of many defence genes followed by the accumulation of secondary metabolites. In this review, the application of exogenous MJ elicitation strategies on the induction of defence mechanism and secondary metabolite accumulation in cell and organ cultures is introduced and discussed. The information presented here is useful for efficient large-scale production of plant secondary metabolites by the plant cell and organ cultures.
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•BHT induced astaxanthin and lipid production in H. pluvialis under abiotic stress.•BHT alleviated the oxidative damage caused by abiotic stress.•BHT upregulated the signal molecular ...level of nitric oxide.•A useful strategy for lipid and astaxanthin synthesis was proposed.
The aim of this study was to investigate the effects of butylated hydroxytoluene (BHT) on the production of astaxanthin and lipids in Haematococcus pluvialis LUGU under high-light and nitrogen-deficiency conditions. Astaxanthin and lipid contents were increased by 71.13% and 10.71%, respectively, in algal cells treated with 2 mg L−1 BHT. The maximal contents of astaxanthin and lipids were 3.17% and 46%, respectively. The levels of reactive oxygen species (ROS) in the presence of BHT were lower than in the control, and this effect involved strong activation of several antioxidases. Additionally, BHT application upregulated endogenous nitric oxide (NO) production. These results showed that this approach is useful for stimulating production of astaxanthin and lipids in H. pluvialis and that exogenous BHT induces astaxanthin and lipid production, which is responsible for the signalling molecule responses against abiotic stress conditions in H. pluvialis.
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