Autolysin-mediated peptidoglycan hydrolysis is required for the surface display of Staphylococcus aureus cell wall-anchored proteins.

Peptidoglycan hydrolases, or autolysins, play a critical role in cell wall remodeling and degradation, facilitating bacterial growth, cell division, and cell separation. In Staphylococcus aureus, the so-called "major" autolysin, Atl, has long been associated with host adhesion; however, the molecular basis underlying this phenomenon remains understudied. To investigate, we used the type V glycopeptide antibiotic complestatin, which binds to peptidoglycan and blocks the activity of autolysins, as a chemical probe of autolysin function. We also generated a chromosomally encoded, catalytically inactive variant of the Atl enzyme. Autolysin-mediated peptidoglycan hydrolysis, in particular Atl-mediated daughter cell separation, was shown to be critical for maintaining optimal surface levels of S. aureus cell wall-anchored proteins, including the fibronectin-binding proteins (FnBPs) and protein A (Spa). As such, disrupting autolysin function reduced the affinity of S. aureus for host cell ligands, and negatively impacted early stages of bacterial colonization in a systemic model of S. aureus infection. Phenotypic studies revealed that Spa was sequestered at the septum of complestatin-treated cells, highlighting that autolysins are required to liberate Spa during cell division. In summary, we reveal the hydrolytic activities of autolysins are associated with the surface display of S. aureus cell wall-anchored proteins. We demonstrate that by blocking autolysin function, type V glycopeptide antibiotics are promising antivirulence agents for the development of strategies to control S. aureus infections.

The gut virome in health and disease: new insights and associations.

PURPOSE OF REVIEW: Recent years have seen great strides made in the field of viral metagenomics. Many studies have reported alterations in the virome in different disease states. The vast majority of the human intestinal virome consists of bacteriophages, viruses that infect bacteria. The dynamic relationship between gut bacterial populations and bacteriophages is influenced by environmental factors that also impact host health and disease. In this review, we focus on studies highlighting the dynamics of the gut virome and fluctuations associated with disease states. RECENT FINDINGS: Novel correlations have been identified between the human gut virome and diseases such as obesity, necrotizing enterocolitis and severe acute respiratory syndrome coronavirus 2 infection. Further associations between the virome and cognition, diet and geography highlight the complexity of factors that can influence the dynamic relationship between gut bacteria, bacteriophages and health. SUMMARY: Here, we highlight some novel associations between the virome and health that will be the foundation for future studies in this field. The future development of microbiome-based interventions, identification of biomarkers, and novel therapeutics will require a thorough understanding of the gut virome and its dynamics.

Does over a century of aerobic phage work provide a solid framework for the study of phages in the gut?

Bacterial viruses (bacteriophages, phages) of the gut have increasingly become a focus in microbiome studies, with an understanding that they are likely key players in health and disease. However, characterization of the virome remains largely based on bioinformatic approaches, with the impact of these viromes inferred based on a century of knowledge from aerobic phage work. Studying the phages infecting anaerobes is difficult, as they are often technically demanding to isolate and propagate. In this review, we primarily discuss the phages infecting three well-studied anaerobes in the gut: Bifidobacterium, Clostridia and Bacteroides, with a particular focus on the challenges in isolating and characterizing these phages. We contrast the lessons learned from these to other anaerobic work on phages infecting facultative anaerobes of the gut: Enterococcus and Lactobacillus. Phages from the gut do appear to adhere to the lessons learned from aerobic work, but the additional challenges of working on them has required ingenious new approaches to enable their study. This, in turn, has uncovered remarkable biology likely underpinning phage-host relationships in many stable environments.