Secretion Of Extracellular Polysaccharides Research Articles

Ser/Thr protein kinase Stk1 phosphorylates the key transcriptional regulator AlgR to modulate virulence and resistance in Pseudomonas aeruginosa

ABSTRACT Pseudomonas aeruginosa is one of the leading causes of nosocomial infections worldwide and has emerged as a serious public health threat, due in large part to its multiple virulence factors and remarkable resistance capabilities. Stk1, a eukaryotic-type Ser/Thr protein kinase, has been shown in our previous work to be involved in the regulation of several signalling pathways and biological processes. Here, we demonstrate that deletion of stk1 leads to alterations in several virulence- and resistance-related physiological functions, including reduced pyocyanin and pyoverdine production, attenuated twitching motility, and enhanced biofilm production, extracellular polysaccharide secretion, and antibiotic resistance. Moreover, we identified AlgR, an important transcriptional regulator, as a substrate for Stk1, with its phosphorylation at the Ser143 site catalysed by Stk1. Intriguingly, both the deletion of stk1 and the mutation of Ser143 of AlgR to Ala result in similar changes in the above-mentioned physiological functions. Furthermore, assays of algR expression in these strains suggest that changes in the phosphorylation state of AlgR, rather than its expression level, underlie changes in these physiological functions. These findings uncover Stk1-mediated phosphorylation of AlgR as an important mechanism for regulating virulence and resistance in P. aeruginosa.

Sustained and enhanced inhibitory effects of allelochemicals on Microcystis Aeruginosa during its recruitment stage

Microcystis aeruginosa is the main toxic strain in cyanobacterial blooms, and the recruitment stage in its temperature-dependent seasonal succession is considered as the key to its subsequent growth. In this study, a protocol with specific temperature settings was developed as the simulated recruitment stage in order to investigate and confirm the superior inhibitory effects of allelochemicals on M. aeruginosa at that stage of recruitment. One of the most common allelochemicals, gallic acid (GA) (10 mg/L, 20 mg/L) was employed to treat M. aeruginosa under initially low temperature condition (15 °C), then intermediate (20 °C) and last normal (26 °C), which corresponds to the critical temperatures for cyanobacterial recruitment and growth. Growth, metabolism, photosynthetic activity, extracellular polysaccharides (EPS) and microcystins (MCs) release were analyzed and discussed in this study, and a more sustained and better inhibitory effect over a 20-day period was achieved. Notably, GA (10 mg/L) markedly delayed the recruitment of M. aeruginosa from low temperature, with an inhibition efficiency of 85.71 %, and suppressing Fv/Fm and photosynthetic pigments production. It is also observed that M. aeruginosa at recruitment stage exhibited higher sensitivity and poorer resistance to allelochemical treatment, with variable responses suggesting that optimal dosages may alter. The antioxidant enzyme activities remained high under prolonged stress, and the secretion of EPS was stimulated, indicating that cyanobacteria were more inclined to form colonies. While the laboratory-based inhibitory mechanism appeared to increase the release of microcystins in individual cells, the actual concentration of microcystins in natural aquatic environments requires further investigation.

Ubiquitous nanocolloids suppress the conjugative transfer of plasmid-mediated antibiotic resistance in aqueous environment

Nanocolloids (Nc) are widespread in natural water environment, whereas the potential effects of Nc on dissemination of antibiotic resistance remain largely unknown. In this study, Nc collected from the Yellow River in Henan province was tested for its ability to influence the conjugative transfer of resistant plasmid in aqueous environment. The results revealed that the conjugative transfer of RP4 plasmid between Escherichia coli was down-regulated by 52%–91% upon exposure to 1–10 mg/L Nc and the reduction became constant when the dose became higher (20−200 mg/L). Despite the exposure of Nc activated the anti-oxidation and SOS response in bacteria through up-regulating genes involved in glutathione biosynthesis and DNA recombination, the inhibition on the synthesis and secretion of extracellular polysaccharide induced the prevention of cell-cell contact, leading to the reduction of plasmid transfer. This was evidenced by the decreased bacterial adhesion and lowered levels of genes and metabolites relevant to transmembrane transport and D-glucose phosphorylation, as clarified in phenotypic, transcriptomics and metabolomics analysis of E. coli. The significant down-regulation of glycolysis/gluconeogenesis and TCA cycle was associated with the shortage of ATP induced by Nc. The up-regulation of global regulatory genes (korA and trbA) and the reduction of plasmid genes (trfAp, trbBp, and traG) expression also contributed to the suppressed conjugation of RP4 plasmid. The obtained findings remind that the role of ubiquitous colloidal particles is nonnegligible when practically and comprehensively assessing the risk of antibiotic resistance in the environment.

New insights into the antibiofilm activity and mechanism of Mannosylerythritol Lipid-A against Listeria monocytogenes EGD-e

Listeria monocytogenes is one of the leading causative agents of foodborne disease outbreaks worldwide. Herein, the antibiofilm effect and mechanism of Mannosylerythritol Lipid-A against L. monocytogenes EGD-e is reported for the first time. MEL-A effectively attenuated biofilm formation while reducing the viability and motility of bacteria within the biofilm in the early stage, and influenced bacterial adhesion by affecting the secretion of extracellular polysaccharides and eDNA. RT-qPCR revealed that MEL-A significantly suppressed the expression of genes involved in flagellar movement and virulence. Untargeted LC-MS metabolomics indicated that MEL-A affected the fluidity and permeability of cell membranes by significantly upregulating unsaturated fatty acids, lipids and glycoside metabolites, and affected protein biosynthesis, nucleotide metabolism and DNA synthesis and repair by significantly downregulating amino acid metabolism and nucleic acid metabolism. These pathways may constitute the key targets of biofilm formation inhibition by MEL-A. Furthermore, MEL-A showed good removal effects on mature biofilms under different temperatures, different materials and milk. Our data indicated that MEL-A could be used as a novel antibiofilm agent to improve food safety. Our study provides new insights into the possible inhibitory mechanism of MEL-A and the response of L. monocytogenes EGD-e to MEL-A.

Regulation and mechanism of organic selenium on quorum sensing, biofilm, and antioxidant effects of Lactobacillus paracasei.

Different organic compounds can have varying degrees of impact on the activity of Lactobacillus paracasei. The study focused on the impact and action mechanism of different organic selenium products on the bioactivity of two strains of L. paracasei. The growth, antioxidant activity, extracellular polysaccharide secretion, quorum sensing (QS), and biofilm formation of the strains before and after the addition of organic selenium crude products and three organic selenium standard were evaluated. The results showed that the addition of crude organic selenium promoted the various activities of the strain. l-selenocysteine had the strongest regulatory effect, with maximum GIM1.80 biofilm formation when it reached a critical concentration of 0.4 μg/mL; l-selenomethionine resulted in the highest activity of the signal molecule Auto inducer-2 of GDMCC1.155, when it reached a critical concentration of 0.4 μg/mL. The results of scanning electron microscopy demonstrated that the addition of organic selenium effectively improved the morphological structure of the two bacterial cells. Molecular docking revealed that the mechanism by which organic selenium regulates QS in Lactobacillus was achieved by binding two crucial receptor proteins (histidine protein kinase HKP and periplasmic binding protein LuxP) from specific sites. Furthermore, organic selenium products have a beneficial regulatory effect on the biological activity of L. paracasei. Overall, these findings provide a new alternative (organic selenium) for regulating the viability and beneficial activity of L. paracasei.

Promotion of rice seedlings growth and enhancement of cadmium immobilization under cadmium stress with two types of organic fertilizer

Cadmium (Cd)-contaminated soil poses a severe threat to crop production and human health, while also resulting in a waste of land resources. In this study, two types of organic fertilizer (ZCK: Low-content available iron; Z2: High-content available iron) were applied to Cd-contaminated soil for rice cultivation, and the effects of the fertilizer on rice growth and Cd passivation were investigated in conjunction with soil microbial analysis. Results showed that Z2 could alter the composition, structure, and diversity of microbial communities, as well as enhance the complexity and stability of the microbial network. Both 2% and 5% Z2 significantly increased the fresh weight and dry weight of rice plants while suppressing Cd absorption. The 2% Z2 exhibited the best Cd passivation effect. Gene predictions suggested that Z2 may promote plant growth by regulating microbial production of organic acids that dissolve phosphorus and potassium. Furthermore, it is suggested that Z2 may facilitate the absorption and immobilization of soil cadmium through the regulation of microbial cadmium efflux and uptake systems, as well as via the secretion of extracellular polysaccharides. In summary, Z2 can promote rice growth, suppress Cd absorption by rice, and passivate soil Cd by regulating soil microbial communities.

Phytofabricated bimetallic synthesis of silver-copper nanoparticles using Aerva lanata extract to evaluate their potential cytotoxic and antimicrobial activities

In this study, we demonstrate the green synthesis of bimetallic silver-copper nanoparticles (Ag–Cu NPs) using Aerva lanata plant extract. These NPs possess diverse biological properties, including in vitro antioxidant, antibiofilm, and cytotoxic activities. The synthesis involves the reduction of silver nitrate and copper oxide salts mediated by the plant extract, resulting in the formation of crystalline Ag–Cu NPs with a face-centered cubic structure. Characterization techniques confirm the presence of functional groups from the plant extract, acting as stabilizing and reducing agents. The synthesized NPs exhibit uniform-sized spherical morphology ranging from 7 to 12 nm. They demonstrate significant antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, inhibiting extracellular polysaccharide secretion in a dose-dependent manner. The Ag–Cu NPs also exhibit potent cytotoxic activity against cancerous HeLa cell lines, with an inhibitory concentration (IC50) of 17.63 µg mL−1. Additionally, they demonstrate strong antioxidant potential, including reducing capability and H2O2 radical scavenging activity, particularly at high concentrations (240 µg mL−1). Overall, these results emphasize the potential of A. lanata plant metabolite-driven NPs as effective agents against infectious diseases and cancer.

Evaluation of antibiotics and bioagents for the management of black rot disease of cabbage and their effect on extracellular polysaccharide secretion

Black rot disease caused by bacterium Xanthomonas campestris pv. campestris has been identified as major cause for low cabbage yields. The present study was conducted to evaluate the efficacy of various antibiotics and bioagents for controlling black rot disease and also their effect on extracellular polysaccharide secretion (EPS) of Xanthomonas campestris pv. campestris. Under in vitro conditions, bacterial proliferation and EPS production were examined on yeast peptone agar medium containing sucrose or trehalose with or without antibiotics. Number of Xanthomonas campestris pv. campestris on yeast peptone agar medium with Validamycin-A was less as compared to control. Extracellular polysaccharide secretion (EPS) was also inhibited on yeast peptone agar medium with antibiotic Validamycin-A. In vivo, disease intensity was recorded minimum in seed treatment + root dipping + foliar spray with Validamycin-A @ 500 µg/ml followed by seed treatment with Validamycin-A @ 500 µg/ml in comparison to control. Similarly, 45.61% higher cabbage yield was recorded in seed treatment + root dipping + foliar spray with Validamycin-A @ 500 as compared to untreated control. However, the antibiotic Validamycin-A which was found effective can be recommended to manage the disease. Bangladesh J. Bot. 52(4): 965-970, 2023 (December)

Study of the biofilm mechanism of C4-HSL and C6-HSL in the degradation of quinoline.

Quinoline is a hard-to-degrade organic compound widely found in coal chemical wastewater, that seriously affects the ecological environment and human health. A number of biochemical methods are already available for quinoline degradation, but the use of microbial community sensing for quinoline degradation has not been studied in depth. Therefore, this paper focuses on the enhanced mechanism of quorum-sensing signaling molecules in the biofilm formation process during quinoline degradation by functional strains of bacteria. In this paper, the effects of the signal molecules C4-HSL and C6-HSL on the adhesion ability, colony diameter, biofilm formation ability and biofilm morphology of functional strains of quinoline degrading bacteria (Ochrobactrum sp., LC-1) were investigated, and the results showed that both signal molecules promoted the biofilm formation process during the degradation of quinoline by exhibiting an efficient biofortification effect. Both signal molecules could enhance the colony diameter of strain LC-1, where C4-HSL could enhance the biomass of strain LC-1 and stimulate the secretion of extracellular polysaccharides; and C6-HSL could induce the enhancement of adhesion performance and the secretion of extracellular proteins from strain LC-1; both molecules together enhanced the biofilm formation process of strain LC-1. This study has practical application in the degradation of quinoline in coal chemical wastewater.

Biochemical responses of freshwater microalgae Chlorella sorokiniana to combined exposure of Zn(Ⅱ) and estrone with simultaneous pollutants removal

With the development of livestock industry, contaminants such as divalent zinc ions (Zn (Ⅱ)) and estrone are often simultaneously detected in livestock wastewater. Nevertheless, the combined toxicity of these two pollutants on microalgae is still unclear. Moreover, microalgae have the potential for biosorption and bioaccumulation of heavy metals and organic compounds. Thus, this study investigated the joint effects of Zn (Ⅱ) and estrone on microalgae Chlorella sorokiniana, in terms of growth, photosynthetic activity and biomolecules, as well as pollutants removal by algae. Interestingly, a low Zn (Ⅱ) concentration promoted C. sorokiniana growth and photosynthetic activity, while the high concentration experienced inhibition. As the increase of estrone concentration, chlorophyll a content increased continuously to resist the environmental stress. Concurrently, the secretion of extracellular polysaccharides and proteins by algae increased with exposure to Zn (Ⅱ) and estrone, reducing toxicity of pollutants to microalgae. Reactive oxygen species and superoxide dismutase activity increased as the increase of pollutant concentration after 96 h cultivation, but high pollutant concentrations resulted in damage of cells, as proved by increased MDA content. Additionally, C. sorokiniana displayed remarkable removal efficiency for Zn (Ⅱ) and estrone, reaching up to 86.14% and 84.96% respectively. The study provides insights into the biochemical responses of microalgae to pollutants and highlights the potential of microalgae in pollutants removal.

Short Pathways to Highly Active Antimicrobial: Structurally Diverse Polyamines Derivatives from Amino-Aldehyde Condensation Strategy.

Chemical fungicides are the mainstay of plant disease control in agricultural production, but there are a very limited number of drugs that can effectively control plant diseases. Two series of secondary amine derivatives were synthesized using the diamine skeleton combined with saturated aromatic and aliphatic aldehydes, and their antibacterial and antifungal activities against plant pathogens were determined. In addition, the antimicrobial mechanism of the highly active compound A26 was preliminarily examined against Xanthomonas oryzae (Xoo). Compound A26 exhibited the highest antibacterial potency among all the target compounds, with MIC values of 3.12, 3.12, and 12.5 μg/mL against Xoo, Xanthomonas axonopodis pv. Citri (Xac) and Pseudomonas sollamacearum (Ps), respectively. In addition, compound A26 had powerful curative and protective effects against Xoo at 200 μg/mL, and was better than the control agent Xinjunan. Preliminary mechanistic studies showed that compound A26 reduced the bacterial pathogenicity by targeting cell membranes and inhibiting the secretion of extracellular polysaccharides (EPS). Meanwhile, the toxicity of compound A26 to Human Embryonic Kidney 293 cells and Human Liver-7702 was similar to that of Xinjunan, and it had the moderate toxicity according to the World Health Organization classification standard of oral exogenous toxicity with the LD50 of 245.47 mg/kg. Secondary amines have efficient and broad-spectrum antibacterial activity against plant pathogenic bacteria and are expected to be a new class of candidate compounds for antibacterial drugs. This article is protected by copyright. All rights reserved.

Molecular and proteomic response of Pseudomonas fluorescens biofilm cultured on lettuce (Lactuca sativa L.) after ultrasound treatment at different intensity levels

Ultrasonic treatment is widely used for surface cleaning of vegetables in the processing of agricultural products. In the present study, the molecular and proteomic response of Pseudomonas fluorescens biofilm cultured on lettuce was investigated after ultrasound treatment at different intensity levels. The results show that the biofilm was efficiently removed after ultrasound treatment with intensity higher than 21.06 W/cm2. However, at an intensity of less than 18.42 W/cm2, P. fluorescens was stimulated by ultrasound leading to promoted bacterial growth, extracellular protease activity, extracellular polysaccharide secretion (EPS), and synthesis of acyl-homoserine lactones (AHLs) as quorum-sensing signaling molecules. The expression of biofilm-related genes, stress response, and dual quorum sensing system was upregulated during post-treatment ultrasound. Proteomic analysis showed that ultrasound activated proteins in the flagellar system, which led to changes in bacterial tendency; meanwhile, a large number of proteins in the dual-component system began to be regulated. ABC transporters accelerated the membrane transport of substances inside and outside the cell membrane and equalized the permeability conditions of the cell membrane. In addition, the expression of proteins related to DNA repair was upregulated, suggesting that bacteria repair damaged DNA after ultrasound exposure.

Promotion effects and mechanisms of molybdenum disulfide on the propagation of antibiotic resistance genes in soil

The rapid development of nanotechnology has aroused considerable attentions toward understanding the effects of engineered nanomaterials (ENMs) on the propagation of antibiotic resistance. Molybdenum disulfide (MoS2) is an extensively used ENM and poses potential risks associated with environmental exposure; nevertheless, the role of MoS2 toward antibiotic resistance genes (ARGs) transfer remains largely unknown. Herein, it was discovered that MoS2 nanosheets accelerated the horizontal transfer of RP4 plasmid across Escherichia coli in a dose-dependent manner (0.5–10 mg/L), with the maximum transfer frequency 2.07-fold higher than that of the control. Integration of physiological, transcriptomics, and metabolomics analyses demonstrated that SOS response in bacteria was activated by MoS2 due to the elevation of oxidative damage, accompanied by cell membrane permeabilization. MoS2 promoted bacterial adhesion and intercellular contact via stimulating the secretion of extracellular polysaccharides. The ATP levels were maximally increased by 305.7 % upon exposure to MoS2, and the expression of plasmid transfer genes was up-regulated, contributing to the accelerated plasmid conjugation and increased ARG abundance in soil. Our findings highlight the roles of emerging ENMs (e.g., MoS2) in ARGs dissemination, which is significant for the safe applications and risk management of ENMs under the development scenarios of nanotechnology.

Antibacterial Activity and Antibacterial Mechanism of Lemon Verbena Essential Oil

The destructive effect and mode of action of lemon verbena essential oil on cells were investigated, taking the isolated Pseudosciaena D4 as the research object. The extracellular absorbance of the Pseudosciaena D4 increased at OD260 and OD280 after being treated with lemon verbena essential oil, which destroyed the integrity of Pseudosciaena D4 cells, showing a significant effect on preventing biomembrane formation and destroying the formed biomembrane. With an increased concentration of lemon verbena essential oil, extracellular polysaccharide showed a significant decrease in content and a significant increase in inhibition rate, indicating that the secretion of extracellular polysaccharide by Pseudosciaena D4 cells could be inhibited by lemon verbena essential oil during the process of biomembrane formation. Cell introcession and shrinkage appeared after the treatment with essential oil, and a transparent cavity was formed by the out-flowed cell content. Lemon verbena essential oil destroyed the cell wall, resulting in an enhanced permeability of the cell membrane and leakage of the contents, thereby causing cell death.

Bioremediation of a saline-alkali soil polluted with Zn using ryegrass associated with Fusariumincarnatum

Biotechnological strategies have become effective in the remediation of polluted soils as they are cost-effective and do not present a risk of secondary pollution. However, using a single bioremediation technique (microorganism or plant) is not suitable for achieving a high remediation rate of polluted saline-alkali soils with heavy metals. Therefore, the present study aims to assess the effects and mechanisms of combined ryegrass and Fusarium incarnatum on the zinc (Zn)-polluted saline-alkali soil over 45 days. According to the obtained results, the combined Fusarium incarnatum-ryegrass showed the highest remediation rate of 49.35% after 45 days, resulting in a significantly lower soil Zn concentration than that observed in the control group. In addition, the inoculation of Fusarium incarnatum showed a positive effect on the soil EPS secretion. The soil protein contents ranged from 0.035 to 0.055 mg/kg, while the soil polysaccharide contents increased from 0.25 to 0.61 mg/g. The soil microbial flora and ryegrass showed resistance to saline and alkaline stresses through the secretion of extracellular polysaccharides. The three-dimensional fluorescence spectrum (3D-EEM) confirmed that EPS in the soil was mainly a fulvic acid-like substance. The fluorescein diacetate (FDA) hydrolase activity in the saline-alkali soil was first increased due to the effect of Fusarium incarnatum and then decreased to a minimum value of 96 μg/(g·h). In addition, the Fusarium incarnatum inoculation improved the diversity and richness of soil fungi. Although the Fusarium incarnatum inoculation had a slight effect on the germination of ryegrass, it increased the biomass and enrichment coefficient. The results revealed a translocation factor (TF) value of 0.316 at 45 days after ryegrass sowing, showing significant enrichment of the soil Zn heavy metal zinc in the ryegrass roots.

Molecular mechanism of increasing extracellular polysaccharide production of Paenibacillus mucilaginosus K02 by adding mineral powders

Bacterial polysaccharides are widely applied in a range of products and increasing bacterial polysaccharide production is important commercially. In this study, attapulgite, serpentine, talc, biotite, and hydroxylapatite were used to stimulate extracellular polysaccharide (EPS) production by Paenibacillus mucilaginosus K02. The viscosity, polysaccharides, and proteins in culture medium in shaking flasks were quantified after addition of different minerals to the culture medium, and the molecular mechanism of serpentine on stimulating bacterial EPS synthesis was further revealed by proteomic and metabolomic analysis. The results showed that the viscosity, EPS, and protein contents in the culture were significantly increased by the introduction of minerals. The underlying mechanism for increased EPS production was due to a series of protective strategies of the bacterium against the damage arising from collision and friction caused by mineral powders. That is, bacteria protect and maintain their normal life by synthesis and secretion of excessive EPS, enhancement of oxidation resistance and secretion of various organic acids under these mineral treatments. The results not only show the importance of polysaccharide production for bacteria survival under adverse conditions, but also provide a new way of increasing bacterial production of more EPSs.

Screening and Characterization of Two Extracellular Polysaccharide-Producing Bacteria from the Biocrust of the Mu Us Desert.

The extracellular polysaccharide (EPS) matrix embedding microbial cells and soil particles plays an important role in the development of biological soil crusts (BSCs), which is widely recognized as beneficial to soil fertility in dryland worldwide. This study examined the EPS-producing bacterial strains YL24-1 and YL24-3 isolated from sandy soil in the Mu Us Desert in Yulin, Shaanxi province, China. The strains YL24-1 and YL24-3 were able to efficiently produce EPS; the levels of EPS were determined to be 257.22 μg/mL and 83.41 μg/mL in cultures grown for 72 h and were identified as Sinorhizobium meliloti and Pedobacter sp., respectively. When the strain YL24-3 was compared to Pedobacter yulinensis YL28-9T using 16S rRNA gene sequencing, the resemblance was 98.6% and the strain was classified as Pedobacter sp. using physiological and biochemical analysis. Furthermore, strain YL24-3 was also identified as a subspecies of Pedobacter yulinensis YL28-9T on the basis of DNA–DNA hybridization and polar lipid analysis compared with YL28-9T. On the basis of the EPS-related genes of relevant strains in the GenBank, several EPS-related genes were cloned and sequenced in the strain YL24-1, including those potentially involved in EPS synthesis, assembly, transport, and secretion. Given the differences of the strains in EPS production, it is possible that the differences in gene sequences result in variations in the enzyme/protein activities for EPS biosynthesis, assembly, transport, and secretion. The results provide preliminary evidence of various contributions of bacterial strains to the formation of EPS matrix in the Mu Us Desert.

Design and Synthesis of Novel c-di-GMP G-Quadruplex Inducers as Bacterial Biofilm Inhibitors

The formation of biofilms by clinical pathogens typically leads to chronic and recurring antibiotic-resistant infections. High cellular levels of cyclic diguanylate (c-di-GMP), a ubiquitous secondary messenger of bacteria, have been proven to be associated with a sessile biofilm lifestyle of pathogens. A promising antibiofilm strategy involving the induction of c-di-GMP to form dysfunctional G-quadruplexes, thereby blocking the c-di-GMP-mediated biofilm regulatory pathway, was proposed in this study. In this new strategy, a series of novel c-di-GMP G-quadruplex inducers were designed and synthesized for development of therapeutic biofilm inhibitors. Compound 5h exhibited favorable c-di-GMP G-quadruplex-inducing activity and 62.18 ± 6.76% biofilm inhibitory activity at 1.25 μM without any DNA intercalation effect. Moreover, the favorable performance of 5h in interfering with c-di-GMP-related biological functions, including bacterial motility and bacterial extracellular polysaccharide secretion, combined with the reporter strain and transcriptome analysis results confirmed the c-di-GMP signaling-related action mechanism of 5h.

Responses of electroactive biofilms to chronic chlorine exposure: Insights from the composition and spatial structure of extracellular polymeric substances

Extensive amounts of chlorine disinfectants have been applied to wastewater system since the outbreak of coronavirus disease 2019 (COVID-19), which inevitably affects the pollutant degradation via interfering with electron transfer mediated by electroactive bacteria. Herein, the response of electroactive biofilm (EAB) to chronic chlorine exposure was investigated. Results showed the EAB formed without exposure (EAB-0) exhibited a 53% and 123% higher current output than that formed with 0.1 mg L−1 (EAB-0.1) and 0.5 mg L−1 (EAB-0.5) chlorine, respectively. The chronic chlorine exposure of EAB boosted the contents of extracellular polymeric substances (EPS) in EAB-0.1 and EAB-0.5 by over secretion of extracellular polysaccharides. The EAB-0.1 and EAB-0.5 also presented lower electron exchange capacities (EECs) of EPS, coincided with reduced relative abundance of Geobacter from 61% in EAB-0 to 52% in EAB-0.5. This study provided new insights into the application of engineered EAB for wastewater treatment in a disinfection environment.

Evaluation of Anti-Biofilm Capability of Cordycepin Against Candida albicans.

IntroductionThe opportunistic pathogen Candida albicans can form biofilms, resulting in drug resistance with great risk to medical treatment.MethodologyWe investigated the ability of C. albicans to form biofilms on different materials, as well as the inhibitory and eradicating effects of cordycepin on biofilm. The action mechanism of cordycepin against biofilm was studied by crystal violet staining, XTT [2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] reduction method, phenol-sulfuric acid method, cellular superficial hydrophobicity (CSH) assay, and confocal laser scanning microscope observation. We also evaluated the acute toxicity of cordycepin in vivo.ResultsThe results showed facile formation of biofilms by C. albicans on polypropylene. The 50% minimum inhibitory concentration (MIC50) of cordycepin was 0.062 mg/mL. A concentration of 0.125 mg/mL significantly decreased biofilm formation, metabolic activity, secretion of extracellular polysaccharides, and relative CSH. Cordycepin could inhibit biofilm formation at low concentration without affecting fungal growth. In addition, cordycepin effectively eradicated 59.14% of mature biofilms of C. albicans at a concentration of 0.5 mg/mL. For acute toxicity, the LD50 (50% of lethal dose) of cordycepin was determined as higher than 500 mg/kg for mice.ConclusionThe results of this study show that cordycepin significantly inhibited and eradicated biofilms by decreasing metabolic activity, the ratio of living cells, the hydrophobicity, and damaging the extracellular polysaccharides of biofilm. These findings should facilitate more effective application of cordycepin and suggest a new direction for the treatment of fungal infections.