Adhesive polypeptides of Staphylococcus aureus identified using a novel secretion library technique in Escherichia coli

Structures, functions, and regulatory networks of universal stress proteins in clinically relevant pathogenic Bacteria

Universal stress proteins are a class of proteins widely present in bacteria, archaea, plants, and invertebrates, playing essential roles in bacterial adaptation to various environmental stresses. The functions of bacterial universal stress proteins are versatile, including resistance to oxidative stress, maintenance of cell wall integrity, DNA damage repair, regulation of cell division and growth, among others. When facing stresses such as temperature changes, pH shifts, fluctuations in oxygen concentration, and exposure to toxins, these proteins can bind to specific DNA sequences and rapidly adjust bacterial metabolic pathways and gene expression patterns to adapt to the new environment. In summary, bacterial universal stress proteins play a crucial role in bacterial adaptability and survival. A comprehensive understanding of bacterial stress response mechanisms and the development of new antibacterial strategies are of great significance. This review summarizes the research progress on the structure, function, and regulatory factors of universal stress proteins in clinically relevant bacteria, aiming to facilitate deeper investigations by clinicians and researchers into universal stress proteins.

Parasite Survival and Disease Persistence in Cystic Fibrosis, Schistosomiasis and Pathogenic Bacterial Diseases: A Role for Universal Stress Proteins?

Universal stress proteins (USPs) were originally discovered in Escherichia coli over two decades ago and since then their presence has been detected in various organisms that include plants, archaea, metazoans, and bacteria. As their name suggests, they function in a series of various cellular responses in both abiotic and biotic stressful conditions such as oxidative stress, exposure to DNA damaging agents, nutrient starvation, high temperature and acidic stress, among others. Although a highly conserved group of proteins, the molecular and biochemical aspects of their functions are largely evasive. This is concerning, as it was observed that USPs act as essential contributors to the survival/persistence of various infectious pathogens. Their ubiquitous nature in various organisms, as well as their augmentation during conditions of stress, is a clear indication of their direct or indirect importance in providing resilience against such conditions. This paper seeks to clarify what has already been reported in the literature on the proposed mechanism of action of USPs in pathogenic organisms.

Penicillin binding protein 3 of Staphylococcus aureus NCTC 8325-4 binds and activates human plasminogen

Background

Staphylococcus aureus is a versatile pathogen expressing a number of virulence-associated adhesive molecules. In a previous study, we generated in a secretion-competent Escherichia coli strain a library of random FLAG-tag positive (FTP) polypeptides of S. aureus. To identify adhesive proteins and gain additional knowledge on putative virulence factors of S. aureus, we here screened the FTP library against human serum proteins.

Findings

Staphylococcus aureus NCTC 8325-4, origin of the FTP library, adhered to immobilized plasminogen in vitro. In an enzyme-linked immunoassay a C-terminal part of penicillin binding protein 3 (PBP3), included in the FTP library, bound to immobilized plasminogen. We expressed and purified full-length PBP3 and its C-terminal fragments as recombinant proteins. In a time-resolved fluorometry—based assay the PBP3 polypeptides bound to immobilized plasminogen. The polypeptides enhanced formation of plasmin from plasminogen as analyzed by cleavage of a chromogenic plasmin substrate.

Conclusions

The present findings, although preliminary, demonstrate reliably that S. aureus NCTC 8325-4 adheres to immobilized plasminogen in vitro and that the adhesion may be mediated by a C-terminal fragment of the PBP3 protein. The full length PBP3 and the penicillin binding C-terminal domain of PBP3 expressed as recombinant proteins bound plasminogen and activated plasminogen to plasmin. These phenomena were inhibited by the lysine analogue ε-aminocaproic acid suggesting that the binding is mediated by lysine residues. A detailed molecular description of surface molecules enhancing the virulence of S. aureus will aid in understanding of its pathogenicity and help in design of antibacterial drugs in the future.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-016-2190-4) contains supplementary material, which is available to authorized users.

Analysis of the Staphylococcus aureus abscess proteome identifies antimicrobial host proteins and bacterial stress responses at the host-pathogen interface

Abscesses are a hallmark of invasive staphylococcal infections and the site of a dynamic struggle between pathogen and host. However, the precise host and bacterial factors that contribute to abscess formation and maintenance have not been completely described. In this work, we define the Staphylococcus aureus abscess proteome from both wild-type and neutropenic mice to elucidate the host response to staphylococcal infection and uncover novel S. aureus virulence factors. Among the proteins identified, the mouse protein histone H4 was enriched in the abscesses of wild-type compared with neutropenic animals. Histone H4 inhibits staphylococcal growth in vitro demonstrating a role for this protein in the innate immune response to staphylococcal infection. These analyses also identified staphylococcal proteins within the abscess, including known virulence factors and proteins with previously unrecognized roles in pathogenesis. Within the latter group was the universal stress protein Usp2, which was enriched in kidney lesions from neutropenic mice and required for the S. aureus response to stringent stress. Taken together, these data describe the S. aureus abscess proteome and lay the foundation for the identification of contributors to innate immunity and bacterial pathogenesis.