Rapid metabolic profiling of developing Pseudomonas aeruginosa biofilms by high-resolution mass spectrometry fingerprinting

Biofilms are single- or multi-species communities of bacteria that are enclosed in an extracellular matrix. These cells generally exhibit phenotypes that are significantly different from those of planktonic cells, yet detailed elucidation of the causality and the exact nature of this metabolic shift remains challenging. Considering the strong correlation of biofilms with pathogenicity and disease in the clinic, as well as the veritable economic impact of biofilms in other areas, a methodology for in-vivo monitoring of biofilm development is necessary. Here, we present high-resolution mass spectrometry fingerprinting as a rapid, sensitive, and generic technique for online, non-invasive monitoring of developing biofilms. The opportunistic pathogen Pseudomonas aeruginosa is used as a model system, and it is demonstrated that strain- and time-dependent changes in biofilm extracellular metabolites are easily detected.     

Psoriasis pathogenesis – Pso p27 constitutes a compact structure forming large aggregates

Psoriasis is a chronic inflammatory skin disease. The absence of microbial organisms as potential causal agents has given rise to the hypothesis that the inflammation is due to an autoimmune reaction. The defined inflamed areas of the skin lesions argue for an immunological disease with a local production of a causal antigen. Pso p27 is a protein generated in mast cells in psoriatic plaques, but not in uninvolved skin. We recently demonstrated that the Pso p27 is generated by cleavage of SerpinB3 (SCCA1) in the presence of mast cell associated chymase.In this communication we demonstrate by X-ray crystallographic analysis that the cleavage products associate into a complex similar to SCCA1, but with the reactive centre loop inserted into a 5-stranded central β-sheet.Native gel electrophoresis show that these Pso p27 complexes form large aggregates which may be of significance with respect to an immunogenic role of Pso p27.