The bacteriolytic activity of native and covalently immobilized lysozyme against Gram-positive and Gram-negative bacteria is differentially affected by charged amino acids and glycine

Strategies for enhancing the antibacterial efficacy of lysozyme and the resulting outcome

Lysozyme is a biological macromolecule with potent bactericidal activity, providing a foundation for its use as a natural preservative. It was extensively applicated in the food and pharmaceutical industries, where its active properties are harnessed effectively and sustainably. However, the effect of natural lysozyme on individual gram-positive bacteria and most gram-negative bacteria is not ideal. At present, some antibacterial profiles of extended lysozyme have been developed. With the recent advancements in biotechnology, there has been a notable increase in the potential of methods and techniques for modifying protein enzymes. This paper mainly introduces the basic structural properties of natural hen egg white lysozyme, its bactericidal properties, and mode of action, and focuses on the comparison of different methods and strategies for lysozyme modification at present, including differential isomerization of lysozyme, surface hydrophobicity modification, chemical modification and combination, and influence on lysozyme properties. These findings emphasize that the key to augmenting lysozyme's efficacy lies in manipulating charge, ion characteristics, and modifying active amino acid groups to optimize interactions with bacterial cell walls and membranes, facilitating bacterial autolysis. By applying these principles, it can lay a solid foundation for developing more effective and versatile protein-based lysozyme antibacterial agents.

Expression of BSN314 lysozyme genes in Escherichia coli BL21: a study to demonstrate microbicidal and disintegarting potential of the cloned lysozyme

This study is an extension of our previous studies in which the lysozyme was isolated and purified from Bacillus subtilis BSN314 (Naveed et al., 2022; Naveed et al., 2023). In this study, the lysozyme genes were cloned into the E. coli BL21. For the expression of lysozyme in E. coli BL21, two target genes, Lyz-1 and Lyz-2, were ligated into the modified vector pET28a to generate pET28a-Lyz1 and pET28a-Lyz2, respectively. To increase the production rate of the enzyme, 0.5-mM concentration of IPTG was added to the culture media and incubated at 37 °C and 220 rpm for 24 h. Lyz1 was identified as N-acetylmuramoyl-L-alanine amidase and Lyz2 as D-alanyl-D-alanine carboxypeptidase. They were purified by multi-step methodology (ammonium sulfate, precipitation, dialysis, and ultrafiltration), and antimicrobial activity was determined. For Lyz1, the lowest MIC/MBC (0.25 μg/mL; with highest ZOI = 22 mm) were recorded against Micrococcus luteus, whereas the highest MIC/MBC with lowest ZOI were measured against Salmonella typhimurium (2.50 μg /mL; with ZOI = 10 mm). As compared with Aspergillus oryzae (MIC/MFC; 3.00 μg/mL), a higher concentration of lysozyme was required to control the growth of Saccharomyces cerevisiae (MIC/MFC; 50 μg/mL). Atomic force microscopy (AFM) was used to analyze the disintegrating effect of Lyz1 on the cells of selected Gram-positive bacteria, Gram-negative bacteria, and yeast. The AFM results showed that, as compared to Gram-negative bacteria, a lower concentration of lysozyme (Lyz1) was required to disintegrate the cell of Gram-positive bacteria.

Fluorescence-Polarization-Based Assaying of Lysozyme with Chitooligosaccharide Tracers

Lysozyme is a well-known enzyme found in many biological fluids which plays an important role in the antibacterial protection of humans and animals. Lysozyme assays are used for the diagnosis of a number of diseases and utilized in immunohistochemistry, genetic and cellular engineering studies. The assaying methods are divided into two categories measuring either the concentration of lysozyme as a protein or its activity as an enzyme. While the first category of methods traditionally uses an enzyme-linked immunosorbent assay (ELISA), the methods for the determination of the enzymatic activity of lysozyme use either live bacteria, which is rather inconvenient, or natural peptidoglycans of high heterogeneity and variability, which leads to the low reproducibility of the assay results. In this work, we propose the use of a chemically synthesized substrate of a strictly defined structure to measure in a single experiment both the concentration of lysozyme as a protein and its enzymatic activity by means of the fluorescence polarization (FP) method. Chito-oligosaccharides of different chain lengths were fluorescently labeled and tested leading to the selection of the pentasaccharide as the optimal size tracer and the further optimization of the assay conditions for the accurate (detection limit 0.3 μM) and rapid (<30 min) determination of human lysozyme. The proposed protocol was applied to assay human lysozyme in tear samples and resulted in good correlation with the reference assay. The use of synthetic fluorescently labeled tracer, in contrast to natural peptidoglycan, in FP analysis allows for the development of a reproducible method for the determination of lysozyme activity.

Design, Screening, and Characterization of Engineered Phage Endolysins with Extracellular Antibacterial Activity against Gram-Negative Bacteria

Phage-encoded endolysins are emerging antibacterial agents based on their ability to efficiently degrade peptidoglycan on Gram-positive bacteria, but the envelope characteristics of Gram-negative bacteria limit their application. Engineering modifications of endolysins can improve the optimization of their penetrative and antibacterial properties. This study constructed a screening platform to screen for engineered Artificial-Bp7e (Art-Bp7e) endolysins with extracellular antibacterial activity against Escherichia coli. An oligonucleotide of 20 repeated NNK codons was inserted upstream of the endolysin gene Bp7e to construct a chimeric endolysin library in the pColdTF vector. The chimeric Art-Bp7e proteins were expressed by transforming the plasmid library into E. coli BL21 and released by chloroform fumigation, and the protein activities were evaluated by the spotting method and the colony-counting method to screen for promising proteins. Sequence analysis showed that all screened proteins with extracellular activities had a chimeric peptide with a positive charge and an α-helical structure. Also, a representative protein, Art-Bp7e6, was further characterized. It exhibited broad antibacterial activity against E. coli (7/21), Salmonella enterica serovar Enteritidis (4/10), Pseudomonas aeruginosa (3/10), and even Staphylococcus aureus (1/10). In the transmembrane process, the chimeric peptide of Art-Bp7e6 depolarized the host cell envelope, increased the permeability of the cell, and facilitated the movement of Art-Bp7e6 across the envelope to hydrolyze the peptidoglycan. In conclusion, the screening platform successfully screened for chimeric endolysins with extracellular antibacterial activities against Gram-negative bacteria, which provides methodological support for the further screening of engineered endolysins with high extracellular activities against Gram-negative bacteria. Also, the established platform showed broad application prospects and can be used to screen various proteins. IMPORTANCE The presence of the envelope in Gram-negative bacteria limits the use of phage endolysins, and engineering endolysins is an efficient way to optimize their penetrative and antibacterial properties. We built a platform for endolysin engineering and screening. A random peptide was fused with the phage endolysin Bp7e to construct a chimeric endolysin library, and engineered Artificial-Bp7e (Art-Bp7e) endolysins with extracellular activity against Gram-negative bacteria were successfully screened from the library. The purposeful Art-Bp7e had a chimeric peptide with an abundant positive charge and an α-helical structure, which led Bp7e to acquire the ability for the extracellular lysis of Gram-negative bacteria and showed a broad lysis spectrum. The platform provides a huge library capacity without the limitations of reported proteins or peptides. It can be utilized for the further screening of optimal endolysins against Gram-negative bacteria as well as for the screening of additional proteins with specific modifications.

In-silico identification of lysine residue for lysozyme immobilization on dialdehyde cellulose

In the realm of enzymes, the Enzyme Immobilization technique can be extremely beneficial. More research into computational approaches could lead to a better understanding as well as lead us in the direction of a more environmentally friendly and greener path. In this study, molecular modelling techniques were used to collect information regarding the immobilization of Lysozyme (EC 3.2.1.17) on Dialdehyde Cellulose (CDA). Lysine, being the most nucleophilic, is most likely to interact with dialdehyde cellulose. Enzyme substrate interactions have been studied with and without the refinement of modified lysozyme molecules. A total of six CDA-modified lysine residues were selected for the study. The docking process for all modified lysozymes was carried out using four distinct docking programs: Autodock Vina, GOLD, Swissdock, and iGemdock. The binding affinity (-7.8 & -8.0 kcal mol^-1 in case of non-refinement and -4.7 & -5.0 kcal mol^-1 in case of refinement), calculated from Autodock vina, as well as the interaction similarity of Lys¹¹⁶ immobilized lysozyme with its substrate, were found to be 75 % (W/o simulation) & 66.7 % (With simulation) identical with the reference case (unmodified lysozyme) if Lys¹¹⁶ is bound to Dialdehyde Cellulose. The approach described here is utilized to identify amino acid residues that are used in the immobilization of lysozyme.

The Adsorption of Lysozyme on Living Escherichia Coli Bacterial Cells in the Presence of Charged Amino Acids and Glycine

The effect of glycine, glutamate, aspartate, lysine, histidine, and arginine on the adsorption of lysozyme on living Escherichia coli bacterial cells under conditions close to those for the functioning of the enzyme in saliva was studied. It was shown that the addition of the listed amino acids at concentrations of 1.5 mM for glycine and 5 mM for charged amino acids reduced the desorption constant of lysozyme by 1.4–2.0 times, while the rate of cell lysis (lysozyme activity) increased by 1.4–1.9 times. The maximum amount of lysozyme that can bind to bacteria (adsorption capacity) did not change. An increase in the efficiency of cell lysis in the presence of glycine and charged amino acids can be explained by an increase in the productive adsorption of the enzyme on the surface of bacterial cells.

Nonpolar hydrophobic amino acids tune the enzymatic activity of lysozyme

We have used five different hydrophobic L-amino acids (Gly, Ala, Val, Leu, Ile) as molecular crowders to investigate their role on the enzymatic activity of lysozyme towards Micrococcus lysodeikticus (M. lys.)cell as substrate. We found that except Ile, all other amino acids show a bell like profile of catalytic efficiency (k_cat/K_m) with their increasing concentration whereas for Ile, the value is gradually increasing. The trend of activation energy (E_a) is also well correlated with the catalytic efficiency of lysozyme. At low concentration of amino acids, soft interaction predominates whereas at higher concentration range, excluded volume, viscosity, hydrophobicity combinedly decrease the activity of lysozyme.

Applications of Lysozyme, an Innate Immune Defense Factor, as an Alternative Antibiotic

Lysozyme is a ~14 kDa protein present in many mucosal secretions (tears, saliva, and mucus) and tissues of animals and plants, and plays an important role in the innate immunity, providing protection against bacteria, viruses, and fungi. Three main different types of lysozymes are known: the c-type (chicken or conventional type), the g-type (goose type), and the i-type (invertebrate type). It has long been the subject of several applications due to its antimicrobial properties. The problem of antibiotic resistance has stimulated the search for new molecules or new applications of known compounds. The use of lysozyme as an alternative antibiotic is the subject of this review, which covers the results published over the past two decades. This review is focused on the applications of lysozyme in medicine, (the treatment of infectious diseases, wound healing, and anti-biofilm), veterinary, feed, food preservation, and crop protection. It is available from a wide range of sources, in addition to the well-known chicken egg white, and its synergism with other compounds, endowed with antimicrobial activity, are also summarized. An overview of the modified lysozyme applications is provided in the form of tables.

Targeting Pathogenic Biofilms: Newly Developed Superhydrophobic Coating Favors a Host-Compatible Microbial Profile on the Titanium Surface

Polymicrobial infections are one of the most common reasons for inflammation of surrounding tissues and failure of implanted biomaterials. Because microorganism adhesion is the first step for biofilm formation, physical-chemical modifications of biomaterials have been proposed to reduce the initial microbial attachment. Thus, the use of superhydrophobic coatings has emerged because of their anti-biofilm properties. However, these coatings on the titanium (Ti) surface have been developed mainly by dual-step surface modification techniques and have not been tested using polymicrobial biofilms. Therefore, we developed a one-step superhydrophobic coating on the Ti surface by using a low-pressure plasma technology to create a biocompatible coating that reduces polymicrobial biofilm adhesion and formation. The superhydrophobic coating on Ti was created by the glow discharge plasma using Ar, O_2, and hexamethyldisiloxane gases, and after full physical, chemical, and biological characterizations, we evaluated its properties regarding oral biofilm inhibition. The newly developed coating presented an increased surface roughness and, consequently, superhydrophobicity (contact angle over 150°) and enhanced corrosion resistance (p < 0.05) of the Ti surface. Furthermore, proteomic analysis showed a unique pattern of protein adsorption on the superhydrophobic coating without drastically changing the biologic processes mediated by proteins. Additionally, superhydrophobic treatment did not present a cytotoxic effect on fibroblasts or reduction of proliferation; however, it significantly reduced (≈8-fold change) polymicrobial adhesion (bacterial and fungal) and biofilm formation in vitro. Interestingly, superhydrophobic coating shifted the microbiological profile of biofilms formed in situ in the oral cavity, reducing by up to ≈7 fold pathogens associated with the peri-implant disease. Thus, this new superhydrophobic coating developed by a one-step glow discharge plasma technique is a promising biocompatible strategy to drastically reduce microbial adhesion and biofilm formation on Ti-based biomedical implants.

Covalently immobilized chemically modified lysozyme as a sorbent for bacterial endotoxins (lipopolysaccharides)

Chemical modification of lysozyme was carried out using benzaldehyde and anisaldehyde. It was shown that chemical modification affects only 1-2 amino groups of the protein molecule which does not prevent further covalent immobilization of lysozyme using the remaining free amino groups. The bacteriolytic activity of lysozyme is preserved after chemical modification and after subsequent covalent immobilization. As a result of chemical modification immobilized lysozyme more effectively adsorbs bacterial lipopolysaccharides (endotoxins). Adsorption of immunoglobulin G does not increase after modification. The sorbents obtained in this work can be used for the future development of new medical material for the extracorporeal treatment of sepsis. The proposed scheme for the modification and immobilization of lysozyme can be used with various aldehydes for the preparation of sorbents with different properties.