Beta toxin catalyzes formation of nucleoprotein matrix in staphylococcal biofilms

Abstract

Biofilms are surface-associated communities of microbes encompassed by an extracellular matrix. It is estimated that 80% of all bacterial infections involve biofilm formation, but the structure and regulation of biofilms are incompletely understood. Extracellular DNA (eDNA) is a major structural component in many biofilms of the pathogenic bacterium Staphylococcus aureus, but its role is enigmatic. Here, we demonstrate that beta toxin, a neutral sphingomyelinase and a virulence factor of S. aureus, forms covalent cross-links to itself in the presence of DNA (we refer to this as biofilm ligase activity, independent of sphingomyelinase activity) producing an insoluble nucleoprotein matrix in vitro. Furthermore, we show that beta toxin strongly stimulates biofilm formation in vivo as demonstrated by a role in causation of infectious endocarditis in a rabbit model. Together, these results suggest that beta toxin cross-linking in the presence of eDNA assists in forming the skeletal framework upon which staphylococcal biofilms are established.Staphyloccus aureus | virulence | exotoxins

Endocarditis Pathogen Promotes Vegetation Formation by Inducing Intravascular Neutrophil Extracellular Traps Through Activated Platelets

“…It is well known that bacterial extracellular DNA contributes to formation of bacterial biofilms. 33,34 Only NETs and their component, histones, but not bacterial DNA, could trigger subsequent platelet aggregation and coagulation activation ( Figure VII in the online-only Data Supplement). 24,25 In addition to histones, NETs could trap platelets through the von Willebrand factor and activate .…”

Phospholipases during membrane dynamics in malaria parasites

“…SMases C were also shown to play an important role in bacterial virulence, e.g. for Bacillus cereus (Oda et al, 2014(Oda et al, , 2012, Staphylococcus aureus (Hayashida et al, 2009;Huseby et al, 2010;Katayama et al, 2013) or Listeria ivanovii (Gonzalez-Zorn et al, 1999). The SMase C inhibitor SMY-540 exhibits a strong inhibitory effect against B. cereus and significantly reduces lethality of B. cereusinfected mice (Oda et al, 2014).…”

Bacterial Sphingomyelinases and Phospholipases as Virulence Factors

“…It also inhibits interleukin-8 (IL-8) expression by endothelial cells, which decreases neutrophil transendothelial migration (44). Furthermore, beta-toxin is cytotoxic to polymorphonuclear leukocytes, monocytes, and proliferating T lymphocytes (24,28), contributes to the phagosomal escape of S. aureus (42), and induces biofilm formation (45). The hemolytic and lymphotoxic activities of betatoxin are linked to its SMase C activity (24), but its capacity to induce biofilm formation is catalysis independent (45).…”

“…The hemolytic and lymphotoxic activities of betatoxin are linked to its SMase C activity (24), but its capacity to induce biofilm formation is catalysis independent (45). S. aureus mutant strains lacking hlb have reduced virulence in pneumonia and murine ear skin infection models (43,46), and a mutant strain expressing a biofilm formation-deficient beta-toxin had a diminished pathogenicity in an endocarditis model in rabbits (45). Purified beta-toxin is cytotoxic for bovine mammary epithelial cells, and non-beta-toxin-producing strains have reduced virulence in a mouse model of intramammary infection (47).…”

“…Furthermore, beta-toxin is cytotoxic to polymorphonuclear leukocytes, monocytes, and proliferating T lymphocytes (24,28), contributes to the phagosomal escape of S. aureus (42), and induces biofilm formation (45). The hemolytic and lymphotoxic activities of betatoxin are linked to its SMase C activity (24), but its capacity to induce biofilm formation is catalysis independent (45). S. aureus mutant strains lacking hlb have reduced virulence in pneumonia and murine ear skin infection models (43,46), and a mutant strain expressing a biofilm formation-deficient beta-toxin had a diminished pathogenicity in an endocarditis model in rabbits (45).…”