coli O157.H7 Bacteriophage Endolysin: A Potential Building Block for Chimeric Enzybiotics

Bacteriophage endolysins are potential alternatives to conventional antibiotics for treating multidrug-resistant gram-negative bacterial infections. However, their structure-function relationships are poorly understood, hindering their optimization and application. In this study, we focused on the individual functionality of the C-terminal muramidase domain of Gp127, a modular endolysin from E. coli O157:H7 bacteriophage PhaxI. This domain is responsible for the enzymatic activity, whereas the N-terminal domain binds to the bacterial cell wall. Through protein modeling, docking experiments, and molecular dynamics simulations, we investigated the activity, stability, and interactions of the isolated C-terminal domain with its ligand. We also assessed its expression, solubility, toxicity, and lytic activity using the experimental data. Our results revealed that the C-terminal domain exhibits high activity and toxicity when tested individually, and its expression is regulated in different hosts to prevent self-destruction. Furthermore, we validated the muralytic activity of the purified refolded protein by zymography and standardized assays. These findings challenge the need for the N-terminal binding domain to arrange the active site and adjust the gap between crucial residues for peptidoglycan cleavage. Our study shed light on the three-dimensional structure and functionality of muramidase endolysins, thereby enriching the existing knowledge pool and laying a foundation for accurate in silico modeling and the informed design of next-generation enzybiotic treatments.

Regulation of Lysozyme Activity by Human Hormones

Background

Lysozyme is a part of human and animal noncellular immunity. The regulation of its activity by hormones is poorly studied. The aim of this study was to test the in vitro activity of lysozyme in the presence of catecholamines, natriuretic hormones, and estradiol (E2).

Methods

Hormones were incubated with lysozyme, and the activity of lysozome was further determined using a test culture of Micrococcus luteus in the early exponential growth stage. The activity of lysozyme was assessed based on the rate of change in the OD of the test culture. Molecular docking was performed using SwissDock server http://www.swissdock.ch/docking), and molecular structures were further analyzed and visualized in the UCSF Chimera 1.15rc software.

Results

According to the results, epinephrine and norepinephrine increased lysozyme activity up to 180% compared to the hormone-free enzyme. Changing the pH of the medium from 6.3 to 5.5, increased the lysozyme activity in the presence of E2 up to 150-200 %. The results also showed that exposure to hormones could modify lysozyme ctivity, and this effect depends on the temperature and pH value. The molecular docking revealed a decrease in the activation energy of the active site of enzyme during the interaction of catecholamines with the amino acid residues, asp52 and glu35 of the active site.

Conclusion

Our findings demonstrate an additional mechanism for the involvement of lysozyme in humoral regulation of nonspecific immunity with respect to human pathogenic microflora and bacterial skin commensals by direct modulation of its activity using human hormones.

A muramidase from Acremonium alcalophilum hydrolyse peptidoglycan found in the gastrointestinal tract of broiler chickens

This study evaluates peptidoglycan hydrolysis by a microbial muramidase from the fungus Acremonium alcalophilum in vitro and in the gastrointestinal tract of broiler chickens. Peptidoglycan used for in vitro studies was derived from 5 gram-positive chicken gut isolate type strains. In vitro peptidoglycan hydrolysis was studied by three approaches: (a) helium ion microscopy to identify visual phenotypes of hydrolysis, (b) reducing end assay to quantify solubilization of peptidoglycan fragments, and (c) mass spectroscopy to estimate relative abundances of soluble substrates and reaction products. Visual effects of peptidoglycan hydrolysis could be observed by helium ion microscopy and the increase in abundance of soluble peptidoglycan due to hydrolysis was quantified by a reducing end assay. Mass spectroscopy confirmed the release of hydrolysis products and identified muropeptides from the five different peptidoglycan sources. Peptidoglycan hydrolysis in chicken crop, jejunum, and caecum samples was measured by quantifying the total and soluble muramic acid content. A significant increase in the proportion of the soluble muramic acid was observed in all three segments upon inclusion of the microbial muramidase in the diet.

Dietary muramidase degrades bacterial peptidoglycan to NOD-activating muramyl dipeptides and reduces duodenal inflammation in broiler chickens

Muramidases constitute a superfamily of enzymes that hydrolyse peptidoglycan (PGN) from bacterial cell walls. Recently, a fungal muramidase derived from Acremonium alcalophilum has been shown to increase broiler performance when added as a feed additive. However, the underlying mechanisms of action are not yet identified. Here, we investigated the hypothesis that this muramidase can cleave PGN to muramyl dipeptide (MDP), activating nucleotide-binding oligomerisation domain-containing protein 2 (NOD2) receptors in eukaryotic cells, potentially inducing anti-inflammatory host responses. Using Micrococcus luteus as a test bacterium, it was shown that muramidase from A. alcalophilum did not display antimicrobial activity, while it could cleave fluorescently labelled PGN. It was shown that the muramidase could degrade PGN down to its minimal bioactive structure MDP by using UPLC-MS/MS. Using HEK-Blue™-hNOD2 reporter cells, it was shown that the muramidase-treated PGN degradation mixture could activate NOD2. Muramidase supplementation to broiler feed increased the duodenal goblet cell and intraepithelial lymphocyte abundance while reducing duodenal wall CD3+ T lymphocyte levels. Muramidase supplementation to broiler feed only had moderate effects on the duodenal, ileal and caecal microbiome. It was shown that the newly discovered muramidase hydrolysed PGN, resulting in MDP that activates NOD2, potentially steering the host response for improved intestinal health.

Analysis of Gram-negative Bacteria Peptidoglycan by Ultra-performance Liquid Chromatography

Bacteria are surrounded by a protective peptidoglycan cell wall. Provided that this structure and the enzymes involved are the preferred target for our most successful antibiotics, determining its structural and chemical complexity is of the highest interest. Traditionally, high-performance liquid chromatography (HPLC) analyses have been performed, but these methods are very time consuming in terms of sample preparation and chromatographic separation. Here we describe an optimized method for preparation of Gram-negative bacteria peptidoglycan and its subsequent analysis by ultra-performance liquid chromatography (UPLC). The use of UPLC in peptidoglycan analyses provides a dramatic reduction of the sample volume and hands-on time required and, furthermore, permits in-line mass spectrometry (MS) of the UPLC resolved muropeptides, thus facilitating their identification. This method improves our capability to perform high throughput analysis to better understand the cell-wall biology.

Dietary microbial muramidase improves feed efficiency, energy and nutrient availability and welfare of broilers fed commercial type diets containing exogenous enzymes

1. The aim of this study was to evaluate the effect of graded levels of the microbially derived feed lysozyme, muramidase (MUR) on feed intake (FI), weight gain (WG), feed conversion ratio (FCR), European Performance Index (EPI), dietary N-corrected apparent metabolisable energy (AMEn), footpad dermatitis score (FPD) and other welfare variables, when fed to broilers from 0 to 42d age. 2. A four-phase dietary programme and four experimental pelleted diets were used; a control diet (following breeder recommendations without MUR supplementation), and three diets based on the control diet supplemented with 25,000, 35,000 and 45,000 LSU (F)/kg of MUR, respectively. In addition, all experimental diets contained exogenous xylanase, phytase and a coccidiostat. Each diet was fed to birds in 24 pens (20 male Ross 308 chicks in each pen) following randomisation. Dietary AMEn was determined at 21 d of age, and FPD was evaluated at the end of the study. Data were analysed by ANOVA, using orthogonal polynomials for assessing linear and quadratic responses to MUR activity. 3. The inclusion of MUR did not change FI (P > 0.05), but increased WG in a linear manner (P < 0.05) and reduced FCR in a quadratic manner, with optimum WG and FCR observed in birds fed approximately 35 000 LSU (F)/kg. In accordance with the improvement in FCR, 35 000 LSU (F)/kg MUR supplementation produced the highest EPI (P < 0.05). FPD score was linearly decreased with increased addition of MUR (P < 0.05). Dietary AMEn responded in a quadratic fashion to the MUR inclusion, as the highest values were obtained with the highest inclusion rate (P < 0.05). 4. In conclusion, the results showed that inclusion of MUR improved feed efficiency and the foot health of birds.

Safety and efficacy evaluation of a novel dietary muramidase for swine

The safety of a novel microbial muramidase (Muramidase 007) as a feed additive for swine was evaluated in a target animal safety study (Experiment 1). Forty weanling pigs were allotted to 4 dietary treatments: T1 control group, and 3 groups receiving Muramidase 007 in increasing doses: T2 65,000 (1X), T3 325,000 (5X) and T4 650,000 (10X) LSU(F)/kg feed. The efficacy of Muramidase 007 on growth performance was evaluated in a feeding experiment (Experiment 2). A total of 288 piglets were allotted to two groups: T1 control group and T2 receiving Muramidase 007 at 50,000 (LSU(F)/kg feed. In Experiment 1, no growth depression of pigs was observed. No adverse effects of Muramidase 007 were observed for any of the hematology and serum chemistry parameters measured or on pig health status. Post-mortem evaluation showed no adverse effects due to Muramidase 007 supplementation in the gross pathology or in the histological examination. In Experiment 2, Muramidase 007 significantly increased overall (d 0-42) average daily gain (ADG) and tended to improve overall average daily feed intake (ADFI) and day 42 body weight of nursery pigs and had no effect on feed conversion ratio (FCR). Overall, results of these studies show that there were no adverse effects of Muramidase 007 compared to the control group.

[Antiseptic effect of compound lysostaphin disinfectant and its preventive effect on infection of artificial dermis after graft on full-thickness skin defect wound in rats]

Objective: To study the antiseptic effect of compound lysostaphin disinfectant and its preventive effect on infection of artificial dermis after graft on full-thickness skin defect wound in rats. Methods: (1) Each one standard strain of Klebsiella pneumoniae, Acinetobacter baumannii, and Staphylococcus aureus were selected. Each 20 clinical strains of Klebsiella pneumoniae, Acinetobacter baumannii, and Staphylococcus aureus were collected from those isolated from wound exudates of burn patients hospitalized in our wards from January 2014 to December 2016 according to the random number table. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of compound lysostaphin disinfectant to above-mentioned strains were detected. The experiment was repeated 3 times. Compared with the corresponding standard strain, the clinical strain with higher MIC and/or MBC was considered as having decreased sensitivity to the disinfectant. The percentage of strains of each of the three kinds of bacteria with decreased sensitivity was calculated. (2) Artificial dermis pieces were soaked in compound lysostaphin disinfectant for 5 min, 1 h, 2 h, and 4 h, respectively, with 21 pieces at each time point. After standing for 0 (immediately), 12, 24, 36, 48, 60, 72 h (with 3 pieces at each time point), respectively, the diameters of their inhibition zones to standard strains of Klebsiella pneumoniae, Acinetobacter baumannii, and Staphylococcus aureus were measured. The experiment was repeated 3 times. The shortest soaking time corresponding to the longest standing time, after which the disinfectant-soaked artificial dermis could form an effective inhibition zone (with diameter more than 7 mm), was the sufficient soaking time of the disinfectant to the artificial dermis. (3) Forty Sprague-Dawley rats were divided into post injury day (PID) 3, 7, 14, and 21 sampling groups according to the random number table, with 10 rats in each group. A full-thickness skin defect wound with a diameter of 20 mm was made on both sides of the spine on the back of each rat. Immediately after injury, the artificial dermis without any treatment was grafted on the wound on left side of the spine (hereinafter referred to as control wound), while the sufficiently soaked artificial dermis with compound lysostaphin disinfectant was grafted on the wound on right side of the spine (hereinafter referred to as disinfectant wound). On PID 3, 7, 14, and 21, the gross condition of wounds of all the surviving rats was observed, and the new infection rates of control wounds and disinfectant wounds were calculated. Then, the rats in the sampling group with corresponding time were killed, and the full-thickness wound tissue containing artificial dermis was collected for quantitative analysis of bacteria. Bacteria content of the uninfected control wounds and that of the uninfected disinfectant wounds were compared. Data were processed with chi-square test and Wilcoxon rank sum test. Results: (1) The MIC of compound lysostaphin disinfectant to standard strains of Staphylococcus aureus, Klebsiella pneumoniae, and Acinetobacter baumannii were 1/32, 1/32, and 1/512 of the original concentration of the disinfectant, respectively, and the MBC were 1/32, 1/16, and 1/512 of the original concentration of the disinfectant, respectively. The percentages of clinical strains of Klebsiella pneumoniae, Acinetobacter baumannii and Staphylococcus aureus with decreased sensitivity to compound lysostaphin disinfectant were 15% (3/20), 20% (4/20), and 10% (2/20), respectively. (2) After being soaked in compound lysostaphin disinfectant for 2 and 4 h, the longest standing time, after which the artificial dermis could form an effective inhibition zone against Klebsiella pneumoniae, Acinetobacter baumannii, and Staphylococcus aureus, were 24, 36, and 48 h respectively, longer than 12, 24, and 24 h of soaking for 5 min and 24, 24, and 36 h of soaking for 1 h. The sufficient soaking time of compound lysostaphin disinfectant to artificial dermis was 2 h. (3) On PID 3, no infection symptom was observed in all the wounds, and so both the new infection rate of control wounds and that of disinfectant wounds were 0. The artificial dermis was transparent but not well connected with the wound. On PID 7, the new infection rate of control wounds was 20.00% (6/30), which was obviously higher than 3.33% (1/30) of disinfectant wounds, χ(2)=4.043, P<0.05. On the infected wound, a large amount of purulent exudates were observed, and the artificial dermis was not connected with the wound and degraded partially. On the uninfected wound, artificial dermis was transparent and had a partial connection with the wound. On PID 14 and 21, no new infected wound was observed, and so both the new infection rate of control wounds and that of disinfectant wounds were 0. There was no obvious improvement on the infected wounds. The collagen layers of artificial dermis in the uninfected wound established a good connection with the wound and were separating from the silica gel layer gradually. Infection occurred in 2, 3, 1 control wound (s) in PID 7, 14, and 21 sampling groups, respectively, and in 1 disinfectant wound in PID 14 sampling group. The bacteria content of the infected wounds tissue was 0.79×10(6) to 7.22×10(9) colony-forming unit (CFU)/g. The bacteria content of uninfected control wounds tissue in PID 3, 7, and 14 sampling groups were (3.43±1.88)×10(2,) (2.37±0.43)×10(3,) and (8.40±1.03)×10(3) CFU/g, respectively, which were significantly higher than (0.33±0.12)×10(2,) (0.43±0.17)×10(3,) (2.16±0.52)×10(3) CFU/g of uninfected disinfectant wounds tissue (Z=-3.780, -3.554, -3.334, P<0.05). The bacteria content of uninfected control wounds tissue and that of uninfected disinfectant wounds tissue in PID 21 sampling group were similar (Z=-0.490, P>0.05). Conclusions: Compound lysostaphin disinfectant has quite strong antibacterial ability against Klebsiella pneumoniae, Acinetobacter baumannii, and Staphylococcus aureus. Clinical strains of the three kinds of bacteria were highly sensitive to compound lysostaphin disinfectant. Saturation of absorption of compound lysostaphin disinfectant achieves in artificial dermis after 2 hours' soaking. After 24, 36, and 48 hours' standing, the soaked artificial dermis still has the antibacterial effect on Klebsiella pneumoniae, Acinetobacter baumannii, and Staphylococcus aureus, respectively. The infection rate and the bacteria content of full-thickness skin defect wound in rats are all decreased when grafted with soaked artificial dermis.

Antimicrobial Capacity of Casein Phosphopeptide/Amorphous Calcium Phosphate and Enzymes in Glass Ionomer Cement in Dentin Carious Lesions

OBJECTIVE

To evaluate the ability of casein phosphopeptide/amorphous calcium phosphate (CPP/ACP) and lysozyme, lactoferrin, and lactoperoxidase (LLL) added to glass ionomer cement (GIC) to inhibit the growth of S. mutans in a caries model.

MATERIAL AND METHODS

Eighty permanent third molars were selected. The dentin of these teeth was exposed and flattened. Except for the coronal dentin, the specimens were waterproofed, autoclaved, and submitted to cariogenic challenge with standard strain of S. mutans. The carious lesions were sealed as follows: group 1 (n=20): GIC without additives; group 2 (n=20): GIC + CPP/ACP; group 3 (n=20): GIC + LLL; group 4 (n=20): GIC + CPP/ACP + LLL. S. mutans counts were performed before the caries were sealed (n=5), after 24 hours (n=5), at 1 month (n=5), and at 6 months (n=5). The results were analyzed using descriptive statistical analysis and the Kruskal-Wallis test (Student-Newman-Keuls test).

RESULTS

GIC + LLL caused a significant reduction of S. mutans 1 month after sealing (p<0.01); however, there was a significant growth of S. mutans 6 months after sealing. GIC, GIC + CPP/ACP, and GIC + CPP/ACP + LLL showed similar behavior with significant reduction of S. mutans after 24 hours (p<0.05) and increase after 1 and 6 months.

CONCLUSION

The addition of LLL to GIC increases the antimicrobial action of GIC on S. mutans. This leads to control of bacterial biofilm for 1 month, thus stopping the progression of carious lesions.

Zymographic Techniques for the Analysis of Bacterial Cell Wall in Bacillus

Zymography of cell wall hydrolases is a simple technique to specifically detect cell wall or peptidoglycan hydrolytic activity. The zymographic method can be used for assessing the hydrolytic activities of purified target proteins, cell surface proteins, and proteins secreted to culture. Here, methods of cell wall and peptidoglycan purification, extraction of cell surface proteins containing cell wall hydrolases, and zymographic analysis are described. The purified or extracted proteins are separated by electrophoresis using an SDS gel containing cell wall or peptidoglycan material and then the proteins are renatured in the gel. The renatured cell wall hydrolases in the gel hydrolyze the material around the proteins. The cell wall or peptidoglycan in the gel is stained by methylene blue and the hydrolyzed material cannot be stained, resulting in the detection of cell wall hydrolytic activities of the enzymes on the gel.

Vaginal Protection by H2O2-Producing Lactobacilli

Background:

Peroxide-producing lactobacilli provide protection from infection for the female reproductive tract. However, in vitro studies demonstrated that H₂O₂-produced by Lactobacillus is not the cause of inhibition of pathogens. It is not exactly known how H₂O₂-producing lactobacilli are involved in the protection of the vaginal environment.

Objectives:

This study aimed to evaluate the importance of the interaction between H₂O₂-producing lactobacilli and their host for the resistance of the vaginal biotope.

Materials and Methods:

In this study, we used vaginal lactobacilli (11 H₂O₂-roducing strains and 11 non-H₂O₂-producing strains). The influence of epithelial cells on the growth and antibacterial activity of lactobacilli were evaluated. The effects of lactobacilli on the antibacterial activity of the epithelial cells, muramidase and lactoferrin were also determined.

Results:

Vaginal epithelial cells stimulated the growth and antibacterial activity of H₂O₂-producing lactobacilli in a greater extent than that of the non-H₂O₂-producing lactobacilli. Mainly, the H₂O₂-producing lactobacilli were capable of increasing the activity of the host antimicrobial peptides (muramidase and lactoferrin) as well as the antibacterial activity of the epithelial cells.

Conclusions:

The involvement of the peroxide-producing lactobacilli in the protection of vagina was due to their ability to effectively interact with the host. This is expressed on one side to stimulate the growth and antagonistic activity of lactobacilli and on the other side to increase the antibacterial activity of the host defense factors (muramidase, lactoferrin and metabolites of epithelial cells).

The essential protein for bacterial flagella formation FlgJ functions as a β-N-acetylglucosaminidase

The flagellum is a major virulence factor of motile pathogenic bacteria. This structure requires more than 50 proteins for its biogenesis and function, one of which is FlgJ. Homologs of FlgJ produced by the β- and γ-proteobacteria, such as Salmonella enterica, Vibrio spp., and both Sphingomonas sp. and Pseudomonas spp. are bifunctional, possessing an N-terminal domain responsible for proper rod assembly and a C-terminal domain possessing peptidoglycan lytic activity. Despite the amount of research conducted on FlgJ from these and other bacteria over the past 15 years, no biochemical analysis had been conducted on any FlgJ and consequently confusion exists as to whether the enzyme is a peptidoglycan hydrolase or a lytic transglycosylase. In this study, we present the development of a novel assay for glycoside lytic enzymes and its use to provide the first enzymatic characterization of the lytic domain of FlgJ from S. enterica as the model enzyme. Surprisingly, FlgJ functions as neither a muramidase nor a lytic transglycosylases but rather as a β-N-acetylglucosaminidase. As such, FlgJ represents the first autolysin with this activity to be characterized from a Gram-negative bacterium. At its optimal pH of 4.0, the Michaelis-Menten parameters of K(m) and k(cat) for FlgJ from S. enterica were determined to be 0.64 ± 0.18 mg ml(-1) and 0.13 ± 0.016 s(-1), respectively, using purified PG as substrate. Its catalytic residues were identified as Glu(184) and Glu(223).

Serum Lysozyme (Muramidase) Levels in Intra-Abdominal Abscesses: An Experimental Study

The role of serum lysozyme in the presence of intra-abdominal sepsis was studied to act as an adjunct to various other modalities used for diagnosing intra-abdominal abscesses. Lysozyme (muramidase) is a bacteriolytic enzyme located within phagocytic cells including leukocytes. We measured serum concentrations of lysozyme by a standard turbidimetric method on three groups of murine models. One group underwent caecal ligation and puncture (CLP), the second group underwent a sham operation, and the third group was used as controls. In mice with intra-abdominal abscesses secondary to caecal ligation and perforation (n = 30), the serum lysozyme levels were increased compared to the sham-operated mice (n = 30) and controls (n = 30) (p = <0.001). In this study, serum lysozyme levels have a high sensitivity and specificity related to the presence of an intra-abdominal abscess in mice. Clinical studies are required to demonstrate its role in humans.