metal efflux island of Legionella pneumophila is not required for survival in macrophages and amoebas

• Published in: FEMS microbiology letters 2009-12, Vol.301 (2), p.164-170
• Main Authors: Kim, Eun-Hae, Charpentier, Xavier, Torres-Urquidy, Oscar, McEvoy, Megan M, Rensing, Christopher
• Format: Article
• Language: English
• Subjects: Acanthamoeba castellanii - microbiology; Adenosine triphosphatase; Amoeba; Bacteriology; Biological and medical sciences; Cell Line; Clonal deletion; Cloning, Molecular; Copper; copper efflux; E coli; Efflux; Escherichia coli - drug effects; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; Gene deletion; Gene Expression; Genes; Genes, Bacterial; Genetic Complementation Test; Genomes; Genomic Islands; Heavy metals; Humans; Intracellular; intracellular survival; Legionella pneumophila; Legionella pneumophila - genetics; Legionella pneumophila - metabolism; Legionella pneumophila - pathogenicity; Legionnaires' disease bacterium; Macrophages; Macrophages - microbiology; Metal concentrations; metal resistance; metal tolerance; Metals - metabolism; Metals - toxicity; Microbial Sensitivity Tests; Microbial Viability; Microbiology; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Regulators; Sequence Deletion; Virulence
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1111/j.1574-6968.2009.01813.x

Legionella pneumophila is an intracellular pathogen causing pneumonia-like disease in humans. A 43-kb putative heavy metal efflux gene island was found on the L. pneumophila genome. Large Legionella deletion strains of the metal efflux genes were tested in human THP-1-derived macrophages and amoebal Acanthamoeba castellanii cells and were able to survive and replicate similar to the wild type, suggesting that they do not play a significant role within the intracellular environment. Examination of the sequence of this genomic island revealed that some genes were not accurately annotated and there were no known metal-responsive regulators encoded in this region. Therefore, functional roles of these metal resistance genes were tested by conducting metal resistance assays. Individual genes were cloned in an expression vector and expressed in an appropriate metal-sensitive Escherichia coli background with varying concentrations of the tested metal. Of the 11 efflux systems, a role was determined only for one. A Cu(I)-translocating PIB-type ATPase was shown to be encoded by lpg1024. This gene, termed copA, complemented a copper-sensitive (ΔcopA) E. coli strain in trans and was able to confer copper resistance.