Significance of Legionella pneumophila phospholipases for modification of lipids within the phagosomal membrane

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Legionellae are the causative agent of Legionnaires’ disease, a potentially severe pneumonia. Phospholipases may contribute to bacterial virulence, for example via modification of eukaryotic membranes. At least 15 phospholipases A which in part also show lysophospholipase A and/or glycerolphospholipid:cholesterol acyltransferase activity have been described for L. pneumophila. Most of those activities are delivered into the host cell via type IVB (Dot/Icm) secretion, type II (Lsp) secretion, or by means of outer membrane vesicles and they might consequently be present in the Legionella-containing phagosome. It has been described that dramatic changes occur at the phagosomal membrane which is transformed into an endoplasmic reticulum-like compartment within minutes after Legionella infection. However, the lipid composition of the Legionella phagosome and whether phospholipases contribute to the lipid rearrangements is currently not known and will be investigated by the following objectives: 1.) Determination of eukaryotic target lipids of selected L. pneumophila phospholipases, 2.) Isolation of Legionella-containing phagosomes from wild type, secretion, and phospholipase mutant infections and examination of the phagosomal lipidome, 3.) Localization of specific phospholipases within an infected host cell.