The use of lysozyme modified with fluorescein for the detection of Gram-positive bacteria

Applying lysozyme, alkaline protease, and sodium hypochlorite to reduce bioclogging during managed aquifer recharge: A laboratory study

Alleviating bacterial-induced clogging is of great importance to improve the efficiency of managed aquifer recharge (MAR). Enzymes (lysozyme and alkaline protease) and sodium hypochlorite (NaClO) are common biological and chemical reagents for inhibiting bacterial growth and activity. To investigate the applicability of these reagents to reduce bioclogging, percolation experiments were performed to simulate a weak alkaline recharge water infiltration through laboratory-scale sand columns, with adding 10 mg/L lysozyme, alkaline protease, and NaClO, respectively. The results showed that, with the addition of lysozyme, alkaline protease, and NaClO, the average clogging rates (the reduced percentages of relative saturated hydraulic conductivity of the sand columns per hour during the percolation experiments) were 0.53%/h, 0.32%/h and 0.06%/h, respectively, which were much lower than that in the control group (0.99%/h). This implied that bioclogging could be alleviated to some extent following the treatments. For further analyzing the mechanisms of the regents on alleviating bioclogging, the bacterial cell amount and extracellular polymeric substances (EPS) concentration were also measured to study the effects of lysozyme, alkaline protease, and NaClO on bacterial growth and EPS secretion. Lysozyme and alkaline protease could disintegrate bacterial EPS by hydrolyzing polysaccharides and proteins, respectively, while they had little effect on the bacterial cell amount. The addition of NaClO significantly decreased the bacterial cell amount (P < 0.05) and thus greatly alleviated bioclogging. Although the lowest average clogging rate was achieved in the NaClO group, it can generate disinfection by-products that are potentially harmful to the environment and human health. Therefore, the biological-based method, i.e., enzyme treatment, could be a promising option for bioclogging control. Our results provide insights for understanding the mechanisms of lysozyme, alkaline protease, and NaClO to alleviate bioclogging, which is of great importance for addressing the clogging problem during MAR activities and achieving groundwater resources sustainable utilization.

Adsorption of conjugates of lysozyme and fluorescein isothiocyanate in hydrophobic interaction chromatography

Bioconjugates, such as antibody-drug conjugates or fluorescent-labeled proteins, are highly interesting for various applications in medicine and biology. In their production, not only the synthesis is challenging but also the downstream processing, for which hydrophobic interaction chromatography (HIC) is often used. However, in-depth studies of the adsorption of bioconjugates in HIC are still rare. Therefore, in the present work, three different conjugates of lysozyme and fluorescein isothiocyanate (FITC) were synthesized and isolated, and their adsorption on the hydrophobic resin Toyopearl PPG-600 M was systematically studied in batch experiments. The influence of sodium chloride and ammonium sulfate with ionic strengths up to 2000 mM on the adsorption isotherms was investigated at pH 7.0 and 25 °C, and the results were compared to those for pure lysozyme. The conjugation leads to an increase of the adsorption in all studied cases. All studied conjugates contain only a single FITC and differ only in the position of the conjugation on the lysozyme. Despite this, strong differences in the adsorption behavior were observed. Moreover, a mathematical model was developed, which enables the prediction of the adsorption isotherms in the studied systems for varying ionic strengths.

A novel c-type lysozyme from Litopenaeus vannamei exhibits potent antimicrobial activity

Lysozyme is relevant to the innate immune system as a vital protein for crustaceans. In the present study, we cloned and characterized a novel c-type lysozyme gene (LvLYZ) from the Pacific white shrimp (Litopenaeus vannamei). The obtained full-length cDNA of LvLYZ was 990 bp and contained an open reading frame of 693 bp. Its deduced amino acid sequence consisted of 230 amino acids (aa) with a 17 aa signal peptide at the N-terminal and 130 aa functional domains. The multiple sequence alignment (MSA) indicated that the typical active sites in LvLYZ were similarly conserved as c-type lysozymes from other species. The transcription of LvLYZ appeared in all detected tissues and had relatively higher expression levels in hemocytes, hepatopancreas, gill and intestine. The mRNA expression profiles of LvLYZ were up-regulated in hemocyte and hepatopancreas post the stimulation of Vibrio parahaemolyticus or white spot syndrome virus (WSSV), respectively. The recombinant protein of LvLYZ (rLvLYZ) exhibited antibacterial activities against various microbes, including Escherichia coli, Vibrio splendidus, Micrococcaus luteus, Vibrio parahaemolyticus and Staphylococcus aureus. These results indicated that LvLYZ could cope with bacteria in L. vannamei and may play a significant role in immune response against invading pathogens.

Newly isolated lysozyme-producing strain Proteus mirabilis sp. SJ25 reduced the waste activated sludge: Performance and mechanism

To promote aerobic digestion of sludge, a lysozyme-producing strain was screened and identified as Proteus mirabilis sp. SJ25. The results of response surface methodology (RSM) showed that at the temperature of 30.8 °C, pH of 6.69, and the inoculum amount of 2.81%, the sludge reduced by 26.58%. Compared with the control group, the removal efficiency of suspended solids (SS) from sludge in the experimental group increased by 14.60%, the release of soluble chemical oxygen demand (SCOD) increased by 2.21 times, and the release of intracellular substances increased significantly. Actinobacteriota, Chloroflexi, Proteobacteria, Bacteroidota, and Firmicutes were the main phyla involved in the sludge reduction process. Strain SJ25 enhanced the degradation rate of sludge by releasing lysozyme lysis to lyse bacteria, enhancing the metabolism and membrane transport of carbohydrates and amino acids. This study provides a new perspective in the field of efficient degradation of waste sludge.

Lysozyme regulates the extracellular polymer of activated sludge and promotes the formation of electroactive biofilm

The formation of electroactive biofilm from activated sludge on electrode surface is a key step to construct a bio-electrochemical system, yet it is greatly limited by the poor affinity between the bacteria and the electrode interface. Herein, we report a new method to promote the formation of electroactive biofilm by regulating the extracellular polymeric substance (EPS) content in activated sludge with lysozyme. The investigation of the effect of lysozyme treatment on the content of extracellular polymers and the biofilm formation of electroactive bacteria suggests that lysozyme can improve the permeability of the positive bacterial cell membrane and thus increase the EPS content in the activated sludge. The characterizations of electrochemical activity, surface morphology and community structure of the anode biofilm indicate that increasing EPS content promotes the adhesion of the mixed bacteria in the activated sludge on the electrode and results in denser biofilms with better conductivities. The microbial fuel cell (MFC) inoculated with the sludge of high EPS content exhibits the power density up to 2.195 W/m², much higher than that inoculated with the untreated sludge (1.545 W/m²). The strategy of adjusting EPS content in activated sludge with a biological enzyme can effectively enhance the ability of the bacterial community to form biofilms and exhibits great application potentials in the construction of high efficiency bio-electrochemical systems.

Optimizing temperature for enhancing waste activated sludge decomposition in lysozyme and rhamnolipid pretreatment system

This study investigated the influence of temperature on the hydrolysis and decomposition of waste activated sludge (WAS) during the enhanced pretreatment system with lysozyme and rhamnolipid (Ly + RL). Results showed that temperature increasing from 15℃ to 55℃ could obviously enhance the release of soluble organic matters and WAS decomposition degree within the Ly + RL pretreatment system. Compared to the sum of sole Ly and sole RL pretreatment, Ly + RL combined pretreatment system at 45℃ presented best synergistic hydrolysis performance. The decomposition degree of bacteria and archaea reached 47.6% and 88.1%, respectively. Meanwhile, increasing temperature could recede the diversity of microbial community in the system. Gammaproteobacteria, with the relative abundance of 90.7%, occupied the absolute dominant position at 45℃. Furthermore, with the rise of temperature, more volatile fatty acids were harvested after anaerobic fermentation.

Novel Micro-Nano Optoelectronic Biosensor for Label-Free Real-Time Biofilm Monitoring

According to the World Health Organization forecasts, AntiMicrobial Resistance (AMR) is expected to become one of the leading causes of death worldwide in the following decades. The rising danger of AMR is caused by the overuse of antibiotics, which are becoming ineffective against many pathogens, particularly in the presence of bacterial biofilms. In this context, non-destructive label-free techniques for the real-time study of the biofilm generation and maturation, together with the analysis of the efficiency of antibiotics, are in high demand. Here, we propose the design of a novel optoelectronic device based on a dual array of interdigitated micro- and nanoelectrodes in parallel, aiming at monitoring the bacterial biofilm evolution by using optical and electrical measurements. The optical response given by the nanostructure, based on the Guided Mode Resonance effect with a Q-factor of about 400 and normalized resonance amplitude of about 0.8, allows high spatial resolution for the analysis of the interaction between planktonic bacteria distributed in small colonies and their role in the biofilm generation, calculating a resonance wavelength shift variation of 0.9 nm in the presence of bacteria on the surface, while the electrical response with both micro- and nanoelectrodes is necessary for the study of the metabolic state of the bacteria to reveal the efficacy of antibiotics for the destruction of the biofilm, measuring a current change of 330 nA when a 15 µm thick biofilm is destroyed with respect to the absence of biofilm.

The response of yeast vacuolar proteins: A novel rapid tool for Salmonella sp. screening

Human health is recently affected by several factors in which food contamination is one of the most dangerous elements that damage directly on our bodies. In this study, we provided a novel approach for the rapid detection of Salmonella sp. at the molecular level using the response of Saccharomyces cerevisiae's vacuoles. First, an augmentation of vacuoles intensity was observed by confocal microscopy after treating Salmonella strains with yeast cells. Second, the vacuolar enzymes were isolated and then analyzed by two-dimensional electrophoresis for the screening of specific biomarkers. After that, various recombinant yeasts containing exclusive biomarkers were constructed by fusing these biomarkers with several fluorescent proteins. Finally, the recombinant strains showed the ability to detect Salmonella strains specifically by appropriate fluorescent signals from 20 CFU/mL after 15 Min of exposure.

Hydrolysis and decomposition of waste activated sludge with combined lysozyme and rhamnolipid treatment: Effect of pH

Effect of pH on waste activated sludge (WAS) hydrolysis and decomposition treating with lysozyme and rhamnolipid combined (Ly + RL) was investigated in this study. Results showed that Ly + RL system could significantly improve the release of soluble organic matters at the optimal RL dosage of 0.3 g/gSS and lysozyme dosage of 0.15 g/gSS. Alkali conditions showed better effect than that of acid on the release of soluble organics, improvement of WAS biodegradability and reduction of big floc size within Ly + RL treatment system and the optimal pH was 10. And 9591.6 mg/L soluble chemical oxygen demand (SCOD), 1612.0 mg/L protein and 1211.6 mg/L polysaccharide were released at pH10 after 12 h co-digestion. 83.7% bacteria and 92.2% archaea were decomposed at pH10. Class Gammaproteobacteria (82.4%) was the predominant bacteria after treated by Ly + RL system, and the treated WAS was beneficial for the subsequent organics bio-degradation and volatile fatty acids accumulation.

Enhancement of excess sludge hydrolysis and decomposition by combined lysozyme and rhamnolipid pretreatment

Feasibility of combined lysozyme and rhamolipid (RL) pretreatment on the enhancement of excess sludge (ES) hydrolysis and decomposition was assessed in this study. Results showed lysozyme and RL combined treatment could significantly promote ES hydrolysis and decomposition, an additional 1196.9 mg/L soluble chemical oxygen demand (SCOD), 792.5 mg/L protein and 133.5 mg/L polysaccharide were released compared with the sum of sole RL and sole lysozyme treatment at the optimal RL dosage of 0.3 g/gSS and lysozyme dosage of 0.15 g/gSS after 8 h co-digestion. 45.3% bacteria and 84.5% archaea decomposition degree were gained under the combined treatment at the optimal RL dosage. Class Gammaproteobacteria and genus Methanothrix were the predominant bacteria and archaea with the relative abundance of 72.4% and 60.8%, respectively. After the combined pretreatment, ES was beneficial for volatile fatty acids accumulation and acetic acid dependent methane generating inferred from the results of microbial community composition.

Molecular characterization, expression and antimicrobial activities of a c-type lysozyme from the mud crab, Scylla paramamosain

Lysozyme is an important immune protein involved in the first line of defense for crustaceans. In the present study, a c-type lysozyme gene (SpLyzC) was cloned and characterized from the mud crab, Scylla paramamosain. The full-length cDNA was 849 bp with an open reading frame of 669 bp, and encoded a polypeptide of 223 amino acids with a calculated molecular mass of 23.7 kDa and an isoelectric point of 8.90. SpLyzC shared conserved active sites with c-type lysozymes from other species, detected in all tested tissues and had higher expression levels in hepatopancreas and gill tissues. The expression of SpLyzC was up-regulated in hepatopancreas and gill after infection with Vibrio parahaemolyticus and Staphylococcus aureus. The density of bacteria in the hemolymph and the mortality of crabs increased following infection with V. parahaemolyticus after SpLyzC expression was silenced by injecting double-strand RNA of SpLyzC. The recombinant protein of the S. paramamosain c-type lysozyme (rSpLyzC) exhibited antibacterial activities against Micrococcus lysodeikticus, S. aureus, Vibrio harveyi and V. parahaemolyticus. These results indicate that SpLyzC could help eliminate bacteria in S. paramamosain and may play an important role in resistance to bacterial infection.

Monitoring of individual bacteria using electro-photonic traps

Antimicrobial resistance (AMR) describes the ability of bacteria to become immune to antimicrobial treatments. Current testing for AMR is based on culturing methods that are very slow because they assess the average response of billions of bacteria. In principle, if tests were available that could assess the response of individual bacteria, they could be much faster. Here, we propose an electro-photonic approach for the analysis and the monitoring of susceptibility at the single-bacterium level. Our method employs optical tweezers based on photonic crystal cavities for the trapping of individual bacteria. While the bacteria are trapped, antibiotics can be added to the medium and the corresponding changes in the optical properties and motility of the bacteria be monitored via changes of the resonance wavelength and transmission. Furthermore, the proposed assay is able to monitor the impedance of the medium surrounding the bacterium, which allows us to record changes in metabolic rate in response to the antibiotic challenge. For example, our simulations predict a variation in measurable electrical current of up to 40% between dead and live bacteria. The proposed platform is the first, to our knowledge, that allows the parallel study of both the optical and the electrical response of individual bacteria to antibiotic challenge. Our platform opens up new lines of enquiry for monitoring the response of bacteria and it could lead the way towards the dissemination of a new generation of antibiogram study, which is relevant for the development of a point-of-care AMR diagnostics.

Investigation of tetrazine reactivity towards C-nucleophiles: pyrazolone-based modification of biomolecules

Chemoselective, biocompatible ligation reactions are the key components for efficient and modular access to biomolecular scaffolds. Tetrazine ligation leads to the formation of a mixture of isomers, which makes reaction monitoring, purification and characterization of conjugates difficult. We report herein a modified tetrazine ligation strategy based on the use of a pyrazolone coupling partner, which provides a single molecule conjugate.

Baicalin promotes the bacteriostatic activity of lysozyme on S. aureus in mammary glands and neutrophilic granulocytes in mice

Staphylococcus aureus causes mastitis as a result of community-acquired or nosocomial infections. Lysozyme (LYSO) is an enzyme that is upregulated in many organisms during the innate immune response against infection by bacterial pathogens. Baicalin is a bioactive flavonoid that can bind to enzymes, often to potentiate their effect. Here we tested the effects of baicalin on the activity of LYSO using the S. aureus mastitis mouse model and neutrophilic granulocyte model of S. aureus infection. In our experiments, S. aureus counts decreased with increasing baicalin concentration. Furthermore, qPCR and western blot analyses showed that LYSO expression was unaffected by baicalin, while fluorescence quenching and UV fluorescence spectral analyses showed that baicalin binds to LYSO. To test whether this binding increased LYSO activity, we assessed LYSO-induced bacteriostasis in the presence of baicalin. Our results showed that LYSO-induced S. aureus bacteriostasis increased with increasing concentrations of baicalin, and that baicalin binding to LYSO synergistically increased the antibacterial activity of LYSO. These results demonstrate that baicalin enhances LYSO-induced bacteriostasis during the innate immune response to S. aureus. They suggest baicalin is a potentially useful therapeutic agent for the treatment of bacterial infections.

Role of manganese-based surfactant towards solubilization and photophysical properties of fluorescein

Interactions between fluorescein dye and manganese-based, water-soluble surfactant for modulating photophysical properties of such photosensitizer in a metal-containing microheterogeneous environment and for evaluating their role in solubilization have been explored.