Inactivation of Staphylococcal Phenol Soluble Modulins by Serum Lipoprotein Particles

Staphylococcus aureus virulence has been associated with the production of phenol soluble modulins (PSM). PSM are known to activate, attract and lyse neutrophils. However, the functional characterizations were generally performed in the absence of human serum. Here, we demonstrate that human serum can inhibit all the previously-described activities of PSM. We observed that serum can fully block both the cell lysis and FPR2 activation of neutrophils. We show a direct interaction between PSM and serum lipoproteins in human serum and whole blood. Subsequent analysis using purified high, low, and very low density lipoproteins (HDL, LDL, and VLDL) revealed that they indeed neutralize PSM. The lipoprotein HDL showed highest binding and antagonizing capacity for PSM. Furthermore, we show potential intracellular production of PSM by S. aureus upon phagocytosis by neutrophils, which opens a new area for exploration of the intracellular lytic capacity of PSM. Collectively, our data show that in a serum environment the function of PSM as important extracellular toxins should be reconsidered

Functional Amyloids Composed of Phenol Soluble Modulins Stabilize Staphylococcus aureus Biofilms

Staphylococcus aureus is an opportunistic pathogen that colonizes the skin and mucosal surfaces of mammals. Persistent staphylococcal infections often involve surface-associated communities called biofilms. Here we report the discovery of a novel extracellular fibril structure that promotes S. aureus biofilm integrity. Biochemical and genetic analysis has revealed that these fibers have amyloid-like properties and consist of small peptides called phenol soluble modulins (PSMs). Mutants unable to produce PSMs were susceptible to biofilm disassembly by matrix degrading enzymes and mechanical stress. Previous work has associated PSMs with biofilm disassembly, and we present data showing that soluble PSM peptides disperse biofilms while polymerized peptides do not. This work suggests the PSMs' aggregation into amyloid fibers modulates their biological activity and role in biofilms

Große plastische Verformung von Stahlplatten bei impulsartiger Blastbelastung

Die Untersuchung homogener, quadratischer Stahlplatten wurde auf rechteckige Platten mit Versteifungen erweitert. Konstruktive Maßnahmen, welche bei statischer Belastung die Tragfähigkeit einer Stahlkonstruktion wesentlich erhöhen, erweisen sich bei impulsartiger Belastung als wenig hilfreich. Grundsätzliche experimentelle Untersuchungen werden an fest eingespannten Stahlblechen mit aufgeschweißten Trägern durch Ansprengungen mit Explosivstoffladungen von 16 Gramm bis zu 1 kg durchgeführt. Die Spitzenüberdrücke liegen bei 100 bar, die Belastungsdauern bei 0,1 ms und die Zeitdauern bis zum Stillstand nach der Verformung bei 1 ms. Das Cranz'sche Modellgesetz gilt für diese Anordungen, womit eine Übertragung der Ergebnisse auf Prototypdimensionen möglich wird. Berechnungen mit einem Finite Element Rechenverfahren liefern gute Übereinstimmungen bezüglich der endgültigen Verformung und ermöglichen einen detaillierten, quantitativen Einblick in den dynamischen Ablauf

Empirical analysis of blast wave propagation in tunnels and rooms.

The objective of this report is to present a system of approximation formulae which may be used to calculate pressure-time histories inside underground tunnel and chamber system in case of conventional weapon detonation at the entrance. It is necessary to know a blastwave propagates through tunnels and rooms inside a structure in order to define the loading on blast closures or ventilation systems of an underground shelter