Characterization of a holin (HolNU3-1) in methicillin-resistant Staphylococcus aureus host

Bacteriophage-encoded protein utilization in bacterial ghost production: a mini-review

Bacterial ghosts (BGs) are described as bacterial cell envelopes that retain their structure but lack cytoplasmic contents. The study of BGs spans multiple disciplinary domains, and the development of BG production techniques to obtain ample and stable BG samples holds significant implications for probing the biological characteristics of BGs, devising novel disease treatment strategies, and leveraging their industrial applications. Numerous products encoded within bacteriophage (phage) genomes possess the capability to lyse bacteria, thereby inducing BG formation primarily via disruption of bacterial cell wall integrity. This review comprehensively surveys the utilization of phage-encoded proteins in BG production techniques, encompassing methodologies such as phage E protein-mediated lysis, perforin protein-induced lysis, and strategies combining E protein with holin-endolysin systems. Additionally, discussions and summaries are provided on the current applications, challenges, and modification strategies associated with different techniques. Through a focused exploration of BG production techniques, with an emphasis on precise manipulation of BG formation using phage-encoded protein technologies, this study aims to furnish robust tools and methodologies for delving into the mechanisms underlying BG formation, as well as for the development of novel therapeutic strategies and applications based on BGs.

The Use of Bacteriophages in Biotechnology and Recent Insights into Proteomics

Phages have certain features, such as their ability to form protein-protein interactions, that make them good candidates for use in a variety of beneficial applications, such as in human or animal health, industry, food science, food safety, and agriculture. It is essential to identify and characterize the proteins produced by particular phages in order to use these viruses in a variety of functional processes, such as bacterial detection, as vehicles for drug delivery, in vaccine development, and to combat multidrug resistant bacterial infections. Furthermore, phages can also play a major role in the design of a variety of cheap and stable sensors as well as in diagnostic assays that can either specifically identify specific compounds or detect bacteria. This article reviews recently developed phage-based techniques, such as the use of recombinant tempered phages, phage display and phage amplification-based detection. It also encompasses the application of phages as capture elements, biosensors and bioreceptors, with a special emphasis on novel bacteriophage-based mass spectrometry (MS) applications.

Bacteriophages and phage-derived proteins--application approaches

Currently, the bacterial resistance, especially to most commonly used antibiotics has proved to be a severe therapeutic problem. Nosocomial and community-acquired infections are usually caused by multidrug resistant strains. Therefore, we are forced to develop an alternative or supportive treatment for successful cure of life-threatening infections. The idea of using natural bacterial pathogens such as bacteriophages is already well known. Many papers have been published proving the high antibacterial efficacy of lytic phages tested in animal models as well as in the clinic. Researchers have also investigated the application of non-lytic phages and temperate phages, with promising results. Moreover, the development of molecular biology and novel generation methods of sequencing has opened up new possibilities in the design of engineered phages and recombinant phage-derived proteins. Encouraging performances were noted especially for phage enzymes involved in the first step of viral infection responsible for bacterial envelope degradation, named depolymerases. There are at least five major groups of such enzymes – peptidoglycan hydrolases, endosialidases, endorhamnosidases, alginate lyases and hyaluronate lyases – that have application potential. There is also much interest in proteins encoded by lysis cassette genes (holins, endolysins, spanins) responsible for progeny release during the phage lytic cycle. In this review, we discuss several issues of phage and phage-derived protein application approaches in therapy, diagnostics and biotechnology in general.

Characterization of DLP12 Prophage Membrane Associated Protein: HolinGFP

Lysis cassette genes from phages determine the final lytic event of the host cells. The lysis cassette genes are conserved in phages and prophages. The membrane associated holin from DLP12 prophage, available as a GFP fusion construct, was shown to be overexpressed, using confocal microscopy analysis, in bacterial cells. The protein expression caused cell death in E. coli AG1 strain suggesting the protein was functional. The His-tag HolinGFP protein was purified using cobalt affinity column and was eluted in the presence of different non-ionic detergents DDM (n-dodecyl-ß-d-maltoside), LDAO (Lauryldimethylamine-oxide), OG (n-octyl β-d-glucopyranoside) and C12E9 (dodecyl nonaoxyethylene ether). HolinGFP existed predominantly as a dimer in LDAO in Superdex S200 gel filtration chromatography. Circular dichroism and fluorescence spectroscopy of the fluorescent HolinGFP in all four detergents (C12E9, DDM, LDAO, and OG) confirmed the folded state. Both dithiobis succinimidyl propionate and gluteraldehyde crosslinking revealed the existence of higher order oligomers and dimers. HolinGFP has been functionally and biophysically characterised and is being explored for crystallographic structure determination.

Characterization and determination of holin protein of Streptococcus suis bacteriophage SMP in heterologous host

BACKGROUND

Holins are a group of phage-encoded membrane proteins that control access of phage-encoded endolysins to the peptidoglycan, and thereby trigger the lysis process at a precise time point as the 'lysis clock'. SMP is an isolated and characterized Streptococcus suis lytic phage. The aims of this study were to determine the holin gene, HolSMP, in the genome of SMP, and characterized the function of holin, HolSMP, in phage infection.

RESULTS

HolSMP was predicted to encode a small membrane protein with three hydrophobic transmembrane helices. During SMP infections, HolSMP was transcribed as a late gene and HolSMP accumulated harmlessly in the cell membrane before host cell lysis. Expression of HolSMP in Escherichia coli induced an increase in cytoplasmic membrane permeability, an inhibition of host cell growth and significant cell lysis in the presence of LySMP, the endolysin of phage SMP. HolSMP was prematurely triggered by the addition of energy poison to the medium. HolSMP complemented the defective λ S allele in a non-suppressing Escherichia coli strain to produce phage plaques.

CONCLUSIONS

Our results suggest that HolSMP is the holin protein of phage SMP and a two-step lysis system exists in SMP.

Evidence for two putative holin-like peptides encoding genes of Bacillus pumilus strain WAPB4

An open reading frame encoding a 71-amino acid BhlA bacteriocin-related holin-like peptide was present upstream of 86-amino acid holin-like peptide, xhlB, encoding gene in the genome of Bacillus pumilus strain WAPB4. Analysis of BhlA using TMHMM server suggested one putative transmembrane domain at the N-terminal part and a number of highly charged amino acid residues at the C-terminal part. XhlB of B. pumilus strain WAPB4 composed of two putative transmembrane domains separated by a β-turn, and numerous charged residues in the C-terminus. The dual start motifs were found in both BhlA and XhlB. Structural analysis of their sequence revealed features characteristic for holin. To analyze the effect of BhlA on bacteria cell, its ORF was cloned and expressed in Escherichia coli BL21(DE3). Expression of holin-like peptide, BhlA, was found to be toxic to the host cell. The site of action of BhlA is on the cell membrane and caused bacterial death by cell membrane disruption as clearly demonstrated by transmission electron microscopy or TEM.