الفهرس 
Characterization of the type II secretion system T2SS in Acinetobacter baumannii and its potential role in virulence
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Abstract
Acinetobacter baumannii is by far one of the most remarkable emerging microbes in the post-antibiotic era. Secreted proteins represent intriguing targets for new drug development. Currently, very little is known about these proteins, and their secretion mechanisms in A. baumannii. Despite the fact that medically relevant species of Acinetobacter possess a type II secretion system (T2SS), only recently, its role has gained attention. In silico analysis showed the unique arrangement of the T2SS genetic determinants. When compared to other T2SS orthologs, individual components of the T2SS apparatus are closest to those of Pseudomonas aeruginosa. A mutant of Acinetobacter baumannii strain ATCC 17978 lacking the secretin component of the T2SS (gspD), together with a trans-complemented mutant, were tested in a series of in vitro and in vivo assays to determine the role of T2SS in pathogenicity. The xgspD mutant displayed decreased lipolytic activity, associated with attenuated colonization ability in a murine pneumonia model. These phenotypes are linked to LipAN, a novel plasmid-encoded phospholipase, identified through mass spectroscopy as a T2SS substrate. Proteomics on the T2-dependent secretome of ATCC 17978 strain, and the multi-drug resistant, hyper-virulent AB5075 revealed its potential dedication to the secretion of a number of lipolytic enzymes, among others which could contribute to its virulence. This study highlights the role of T2SS as an active contributor to the virulence of A. baumannii potentially through secretion of a newly identified phospholipase