Cloning and Characterization of the Gene Encoding the Major Cell-Associated Phospholipase A of Legionella pneumophila, plaB, Exhibiting Hemolytic Activity

AUTOR(ES)

Flieger, Antje

FONTE

American Society for Microbiology

RESUMO

Legionella pneumophila, the causative agent of Legionnaires' disease, is an intracellular pathogen of amoebae, macrophages, and epithelial cells. The pathology of Legionella infections involves alveolar cell destruction, and several proteins of L. pneumophila are known to contribute to this ability. By screening a genomic library of L. pneumophila, we found an additional L. pneumophila gene, plaB, which coded for a hemolytic activity and contained a lipase consensus motif in its deduced protein sequence. Moreover, Escherichia coli harboring the L. pneumophila plaB gene showed increased activity in releasing fatty acids predominantly from diacylphospho- and lysophospholipids, demonstrating that it encodes a phospholipase A. It has been reported that culture supernatants and cell lysates of L. pneumophila possess phospholipase A activity; however, only the major secreted lysophospholipase A PlaA has been investigated on the molecular level. We therefore generated isogenic L. pneumophila plaB mutants and tested those for hemolysis, lipolytic activities, and intracellular survival in amoebae and macrophages. Compared to wild-type L. pneumophila, the plaB mutant showed reduced hemolysis of human red blood cells and almost completely lost its cell-associated lipolytic activity. We conclude that L. pneumophila plaB is the gene encoding the major cell-associated phospholipase A, possibly contributing to bacterial cytotoxicity due to its hemolytic activity. On the other hand, in view of the fact that the plaB mutant multiplied like the wild type both in U937 macrophages and in Acanthamoeba castellanii amoebae, plaB is not essential for intracellular survival of the pathogen.

Documentos Relacionados

• Phospholipase PlaB of Legionella pneumophila Represents a Novel Lipase Family: PROTEIN RESIDUES ESSENTIAL FOR LIPOLYTIC ACTIVITY, SUBSTRATE SPECIFICITY, AND HEMOLYSIS*
• Effect of quinolones and other antimicrobial agents on cell-associated Legionella pneumophila.
• Cell-associated collagenolytic activity by group B streptococci.
• Characterization of a Legionella pneumophila extracellular protease exhibiting hemolytic and cytotoxic activities.
• Molecular characterization of pldA, the structural gene for a phospholipase A from Campylobacter coli, and its contribution to cell-associated hemolysis.