Comparative proteome profiling of bovine and human Staphylococcus epidermidis strains for screening specifically expressed virulence and adaptation proteins

Skin-to-blood pH shift triggers metabolome and proteome global remodelling in Staphylococcus epidermidis

Staphylococcus epidermidis is one of the most common bacteria of the human skin microbiota. Despite its role as a commensal, S. epidermidis has emerged as an opportunistic pathogen, associated with 80% of medical devices related infections. Moreover, these bacteria are extremely difficult to treat due to their ability to form biofilms and accumulate resistance to almost all classes of antimicrobials. Thus new preventive and therapeutic strategies are urgently needed. However, the molecular mechanisms associated with S. epidermidis colonisation and disease are still poorly understood. A deeper understanding of the metabolic and cellular processes associated with response to environmental factors characteristic of SE ecological niches in health and disease might provide new clues on colonisation and disease processes. Here we studied the impact of pH conditions, mimicking the skin pH (5.5) and blood pH (7.4), in a S. epidermidis commensal strain by means of next-generation proteomics and 1H NMR-based metabolomics. Moreover, we evaluated the metabolic changes occurring during a sudden pH change, simulating the skin barrier break produced by a catheter. We found that exposure of S. epidermidis to skin pH induced oxidative phosphorylation and biosynthesis of peptidoglycan, lipoteichoic acids and betaine. In contrast, at blood pH, the bacterial assimilation of monosaccharides and its oxidation by glycolysis and fermentation was promoted. Additionally, several proteins related to virulence and immune evasion, namely extracellular proteases and membrane iron transporters were more abundant at blood pH. In the situation of an abrupt skin-to-blood pH shift we observed the decrease in the osmolyte betaine and changes in the levels of several metabolites and proteins involved in cellular redoxl homeostasis. Our results suggest that at the skin pH S. epidermidis cells are metabolically more active and adhesion is promoted, while at blood pH, metabolism is tuned down and cells have a more virulent profile. pH increase during commensal-to-pathogen conversion appears to be a critical environmental signal to the remodelling of the S. epidermidis metabolism toward a more pathogenic state. Targeting S. epidermidis proteins induced by pH 7.4 and promoting the acidification of the medical device surface or surrounding environment might be new strategies to treat and prevent S. epidermidis infections.

Applied Proteomics in 'One Health'

‘One Health’ summarises the idea that human health and animal health are interdependent and bound to the health of ecosystems. The purpose of proteomics methodologies and studies is to determine proteins present in samples of interest and to quantify changes in protein expression during pathological conditions. The objectives of this paper are to review the application of proteomics technologies within the One Health concept and to appraise their role in the elucidation of diseases and situations relevant to One Health. The paper develops in three sections. Proteomics Applications in Zoonotic Infections part discusses proteomics applications in zoonotic infections and explores the use of proteomics for studying pathogenetic pathways, transmission dynamics, diagnostic biomarkers and novel vaccines in prion, viral, bacterial, protozoan and metazoan zoonotic infections. Proteomics Applications in Antibiotic Resistance part discusses proteomics applications in mechanisms of resistance development and discovery of novel treatments for antibiotic resistance. Proteomics Applications in Food Safety part discusses the detection of allergens, exposure of adulteration, identification of pathogens and toxins, study of product traits and characterisation of proteins in food safety. Sensitive analysis of proteins, including low-abundant ones in complex biological samples, will be achieved in the future, thus enabling implementation of targeted proteomics in clinical settings, shedding light on biomarker research and promoting the One Health concept.

The Diverse Functional Roles of Elongation Factor Tu (EF-Tu) in Microbial Pathogenesis

Elongation factor thermal unstable Tu (EF-Tu) is a G protein that catalyzes the binding of aminoacyl-tRNA to the A-site of the ribosome inside living cells. Structural and biochemical studies have described the complex interactions needed to effect canonical function. However, EF-Tu has evolved the capacity to execute diverse functions on the extracellular surface of both eukaryote and prokaryote cells. EF-Tu can traffic to, and is retained on, cell surfaces where can interact with membrane receptors and with extracellular matrix on the surface of plant and animal cells. Our structural studies indicate that short linear motifs (SLiMs) in surface exposed, non-conserved regions of the molecule may play a key role in the moonlighting functions ascribed to this ancient, highly abundant protein. Here we explore the diverse moonlighting functions relating to pathogenesis of EF-Tu in bacteria and examine putative SLiMs on surface-exposed regions of the molecule.

Comparative exoproteome profiling of an invasive and a commensal Staphylococcus haemolyticus isolate

Staphylococcus haemolyticus is a skin commensal emerging as an opportunistic pathogen. Nosocomial isolates of S. haemolyticus are the most antibiotic resistant members of the coagulase negative staphylococci (CoNS), but information about other S. haemolyticus virulence factors is scarce. Bacterial membrane vesicles (MVs) are one mediator of virulence by enabling secretion and long distance delivery of bacterial effector molecules while protecting the cargo from proteolytic degradation from the environment. We wanted to determine if the MV protein cargo of S. haemolyticus is strain specific and enriched in certain MV associated proteins compared to the totalsecretome. The present study shows that both clinical and commensal S. haemolyticus isolates produce membrane vesicles. The MV cargo of both strains was enriched in proteins involved in adhesion and acquisition of iron. The MV cargo of the clinical strain was further enriched in antimicrobial resistance proteins. Data are available via ProteomeXchange with identifier PXD010389. BIOLOGICAL SIGNIFICANCE: Clinical isolates of Staphylococcus haemolyticus are usually multidrug resistant, their main virulence factor is formation of biofilms, both factors leading to infections that are difficult to treat. We show that both clinical and commensal S. haemolyticus isolates produce membrane vesicles. Identification of staphylococcal membrane vesicles can potentially be used in novel approaches to combat staphylococcal infections, such as development of vaccines.

Induced surface proteins of Staphylococcus [corrected] epidermidis adhering to titanium implant substrata

OBJECTIVE

Staphylococcus epidermidis, as a primary colonizer, is strongly associated with infections of (dental) implants (i.e., peri-implantitis), but little is known about the surface proteome of this bacterium. For the identification of bacterial adhesins, this study investigated the surface proteome of S. epidermidis adhering directly to titanium implant substrata.

MATERIALS AND METHODS

S. epidermidis strain ATTC 35984 was cultured either planktonically or on titanium implant specimens. The surface proteomes were isolated by mutanolysin digestion, and proteins were separated by 2D gel electrophoreses to reveal highly expressed proteins only. Protein spots were visualized by silver staining and proteins were identified by mass spectrometry.

RESULTS

Surface proteome analyses of S. epidermidis on titanium identified six expressed proteins. Three proteins were highly expressed on the titanium implants including accumulation-associated protein Q8CQD9. These specific proteins could be potential pathogenicity factors of bacteria in peri-implant biofilms.

CONCLUSION

For the first time, our study identified S. epidermidis surface proteins, which are expressed after adhesion to titanium implant materials.

CLINICAL RELEVANCE

Our study reveals possible candidates for a newly protein-based vaccine against peri-implantitis.