High cell-density fermentation, expression and purification of bacteriophage lysin TSPphg, a thermostable antimicrobial protein from extremophilic Thermus bacteriophage TSP4

A comparative guide to expression systems for phage lysin production

Phage lysins, bacteriophage-encoded enzymes tasked with degrading their host's cell wall, are increasingly investigated and engineered as novel antibacterials across diverse applications. Their rapid action, tuneable specificity, and low likelihood of resistance development make them particularly interesting. Despite numerous application-focused lysin studies, the art of their recombinant production remains relatively undiscussed. Here, we provide an overview of the available expression systems for phage lysin production and discuss key considerations guiding the choice of a suitable recombinant host. We systematically surveyed recent literature to evaluate the hosts used in the lysin field and cover various recombinant systems, including the well-known bacterial host Escherichia coli or yeast Saccharomyces cerevisiae, as well as plant, mammalian, and cell-free systems. Careful analysis of the limited studies expressing lysins in various hosts suggests a host-dependent effect on activity. Nonetheless, the multitude of available expression systems should be further leveraged to accommodate the growing interest in phage lysins and their expanding range of applications.

Enzymatic and antibacterial activity of the recombinant endolysin PVP-SE1gp146 expressed in Hansenula polymorpha

Antibiotic resistance, a major global concern, highlights the need for discovering alternative therapies. Recently, endolysins have garnered attention as antibacterial tools with a lower resistance development rate compared to conventional antibiotics, and their production in various expression hosts holds significance. Given its generally recognized as safe (GRAS) status and other advantages, Hansenula polymorpha offers a promising host for endolysin production. PVP-SE1gp146 originates from the Salmonella Enteritidis-specific phage PVP-SE1, which has been previously characterized. We inserted the PVP-SE1gp146 coding gene into the H. polymorpha expression vector pHIPX4. The resulting recombinant, pHIPX4-PVP-SE1gp146, was then introduced into H. polymorpha NCYC495 to facilitate the production of the endolysin PVP-SE1gp146. The expression level of the PVP-SE1gp146 protein was assessed, and it was determined to be approximately 43 mg/l of yeast culture medium. The enzymatic (muralytic) activity of this endolysin was also evaluated, corresponding to the version produced by the E. coli Bl21 strain. The endolysin exhibited admissible antibacterial activity against several gram-negative species, including P. aeruginosa, E. coli, and A. baumannii, while showing an almost negligible impact on K. pneumoniae. Endolysin production within GRAS-approved hosts holds potential for combating antibiotic-resistant bacteria. Challenges involve optimizing concentrations, targeting gram-negative species and improving attachment to bacterial cell walls. Addressing these issues requires dedicated research in endolysin engineering and a comprehensive evaluation of their production in diverse expression hosts.

Heterologous expression and purification of the phage lysin-like bacteriocin LysL from Lactococcus lactis LAC460

The wild-type Lactococcus lactis strain LAC460 produces two bacteriocin-like phage lysins, LysL and LysP. This study aimed to produce and secrete LysL in various heterologous hosts and an in vitro cell-free expression system for further functional studies. Initially, the lysL gene from L. lactis LAC460 was cloned into Lactococcus cremoris NZ9000 and L. lactis N8 strains, with and without the usp45 signal sequence (SSusp45), under a nisin-inducible promoter. Active LysL was primarily produced intracellularly in recombinant L. lactis N8, with some secretion into the supernatant. Recombinant L. cremoris NZ9000 lysed upon nisin induction, indicating successful lysL expression. However, fusion with Usp45 signal peptide (SPUsp45-LysL) weakened LysL activity, likely due to incomplete signal peptide cleavage during secretion. Active LysL was also produced in vitro, and analysed in SDS-PAGE, giving a 42-kDa band. However, the yield of LysL protein was still low when produced from recombinant lactococci or by in vitro expression system. Therefore, His-tagged LysL was produced in Escherichia coli BL21(DE3). Western blot confirmed the intracellular production of about 44-kDa His-tagged LysL in E. coli. His-tagged active LysL was then purified by Ni-NTA affinity chromatography yielding sufficient 4.34 mg of protein to be used in future functional studies.

A novel bacteriocin against multiple foodborne pathogens from Lacticaseibacillus rhamnosus isolated from juice ferments: ATF perfusion-based preparation of viable cells, characterization, antibacterial and antibiofilm activity

Foodborne pathogens and their biofilms pose a risk to human health through food chain. However, the bacteriocin resources combating this threat are still limited. Here, Lacticaseibacillus rhamnosus, one of the most used probiotics in food industry, was prepared on a large scale using alternating tangential flow (ATF) perfusion-based technology. Compared to the conventional fed-batch approach, ATF perfusion remarkably increased the viable cells of L. rhamnosus CLK 101 to 11.93 ± 0.14 log CFU/mL. Based on obtained viable cells, we purified and characterized a novel bacteriocin CLK_01 with a broad spectrum of activity against both Gram-positive and Gram-negative foodborne pathogens. LC-MS/MS analysis revealed that CLK_01 has a molecular mass of 701.49 Da and a hydrophobic amino acid composition of I-K-K-V-T-I. As a novel bacteriocin, CLK_01 showed high thermal stability and acid-base tolerance over 25-121 °C and pH 2-10. It significantly reduced cell viability of bacterial pathogens (p < 0.001), and strongly inhibited their biofilm formation. Scanning electron microscopy demonstrated deformation of pathogenic cells caused by CLK_01, leading to cytoplasmic content leakage and bacterial death. Summarily, we employed ATF perfusion to obtain viable L. rhamnosus, and presented that bacteriocin CLK_01 could serve as a promising biopreservative for controlling foodborne pathogenic bacteria and their biofilms.

Bacteriophage Lytic Enzyme P9ly as an Alternative Antibacterial Agent Against Antibiotic-Resistant Shigella dysenteriae and Staphylococcus aureus

Developing new strategies to replace or supplement antibiotics to combat bacterial infection is a pressing task in the field of microbiological research. In this study, we report a lytic enzyme named P9ly deriving from the bacteriophage PSD9 that could infect multidrug-resistant Shigella. This enzyme was identified through whole-genome sequencing of PSD9. The results show that P9ly contains a conserved T4-like_lys domain and belongs to the phage lysozyme family. Recombinant P9ly obtained from protein purification presented biological activity and could digest bacterial cell walls (CW), resulting in the destruction of cell structure and leakage of intracellular components. Furthermore, P9ly exhibited bacteriolytic and bactericidal activity on different strains, especially multidrug-resistant Gram-negative Shigella dysenteriae and Gram-positive Staphylococcus aureus. Additionally, combined use of P9ly with ceftriaxone sodium (CRO) could decrease necessary dose of the antibiotic used and improve the antibacterial effect. In summary, under the current backdrop of extensive antibiotic usage and the continuous emergence of bacterial resistance, this study provides an insight into developing bacteriophage-based antibacterial agents against both Gram-negative and Gram-positive pathogens.

Role of ClpB From Corynebacterium crenatum in Thermal Stress and Arginine Fermentation

ClpB, an ATP-dependent molecular chaperone, is involved in metabolic pathways and plays important roles in microorganisms under stress conditions. Metabolic pathways and stress resistance are important characteristics of industrially -relevant bacteria during fermentation. Nevertheless, ClpB-related observations have been rarely reported in industrially -relevant microorganisms. Herein, we found a homolog of ClpB from Corynebacterium crenatum. The amino acid sequence of ClpB was analyzed, and the recombinant ClpB protein was purified and characterized. The full function of ClpB requires DnaK as chaperone protein. For this reason, dnaK/clpB deletion mutants and the complemented strains were constructed to investigate the role of ClpB. The results showed that DnaK/ClpB is not essential for the survival of C. crenatum MT under pH and alcohol stresses. The ClpB-deficient or DnaK-deficient C. crenatum mutants showed weakened growth during thermal stress. In addition, the results demonstrated that deletion of the clpB gene affected glucose consumption and L-arginine, L-glutamate, and lactate production during fermentation.