The immune system plays an important role in the body´s defense against bacterial infections. Here, we hypothesize that adding an artificial opsonin that binds to antigens on the surface of infecting bacteria as well as to endogenous IgG can increase the interaction between bacteria and immune cells. A chimeric protein was made by fusion of the Src homology domain 3b (SH3b) from the Staphylococcus phage K endolysin (LysK) and the IgG-binding C2 domain from Streptococcus Protein G. SH3b binds to the bacterial cell wall of staphylococci and the C2 domain to the Fab region of the IgG which in turn binds to the Fc receptors of the phagocytes, facilitating interaction between phagocytes and bacteria. Comparative experiments with and without the chimeric protein showed that it both increased the amount of Staphylococcus carnosus cells bound by a humanized monoclonal IgG1 with unrelated specificity and increased the interaction of phagocytes with bacteria. The results justify development of chimeric proteins with the ability to act as artificial opsonins since these possibly can become an addition to future treatments of infections caused by antibiotic resistant bacteria.

Bacteria forming biofilms on surgical implants is a problem that might be alleviated by the use of antibacterial coatings. In this article, recombinant spider silk was functionalized with the peptidoglycan degrading endolysin SAL-1 from the staphylococcal bacteriophage SAP-1 and the biofilm-matrix-degrading enzyme Dispersin B from Aggregatibacter actinomycetemcomitans using direct genetic fusion and/or covalent protein-protein fusion catalyzed by Sortase A. Spider silk assembly and enzyme immobilization was monitored using quartz crystal microbalance analysis. Enzyme activity was investigated both with a biochemical assay using cleavage of fluorescent substrate analogues and bacterial assays for biofilm degradation and turbidity reduction. Spider silk coatings functionalized with SAL-1 and Disperin B were found to exhibit bacteriolytic effect and inhibit biofilm formation, respectively. The strategy to immobilize antibacterial enzymes to spider silk presented herein show potential to be used as surface coatings of surgical implants and other medical equipment to avoid bacterial colonization.

The morphology, infection kinetics, genome sequence and phylogenetic characterization of the previously isolated bacteriophage vB_EcoD_SU57 are presented. The phage vB_EcoD_SU57 was isolated on Escherichia coli strain ECOR57 from the E. coli reference collection and was shown to produce four mm clear plaques with halos. Infection kinetics, as assessed by one-step growth analyses, suggest that vB_EcoD_SU57 is a virulent phage with an adsorption rate of 8.5 × 10^–10 mL × min^–1, a latency period of 14 min, and a burst size of 13 PFU per bacterium. Transmission electron microscopy confirmed vB_EcoD_SU57 to be a phage that used to be classified as a Siphoviridae phage. Bioinformatics analyses showed that the genome was 46,150 base pairs long, contained 29 genes with predicted protein functions, and 51 open reading frames encoding proteins with unknown function, many of which were gathered in clusters. A putative tRNA gene was also identified. Phylogenetic analyses showed that vB_EcoD_SU57 is a Braunvirinae phage of the newly formed Drexlerviridae family and closely related to T1-like E. coli phages vB_EcoS_ACG-M12 (Guelphvirus) and Rtp (Rtpvirus) as well as the unclassified phages vB_EcoS_CEB_EC3a and ECH1.

Endolysins are used by bacteriophages to break down the cell wall of the bacterial host towards the end of the infection cycle. Endolysins are interesting options for the creation of antibacterial substances and domains from endolysins can be combined with domains from other proteins to create antibacterial constructs. This article aims to find the tertiary structure and the enzymatically active site of the endolysin SU57e. This is done through the use of bioinformatics software, comparative analysis with other endolysins, and attempts at producing and purifying the protein for crystallization. SU57e is encoded by the phage vB_EcoD_SU57 (SU57) previously characterized by Koonjan et al. Bioinformatics analysis indicates that the structure is similar to that of endolysin R21 presented by Sun et al. SU57e also appears to have a signal-anchor-release-domain similar to that of R21.