IroT/mavN , a new iron‐regulated gene involved in L egionella pneumophila virulence against amoebae and macrophages

Abstract

Summary L egionella pneumophila is a pathogenic bacterium commonly found in water. Eventually, it could be transmitted to humans via inhalation of contaminated aerosols. Iron is known as a key requirement for the growth of L . pneumophila in the environment and within its hosts. Many studies were performed to understand iron utilization by L . pneumophila but no global approaches were conducted. In this study, transcriptomic analyses were performed, comparing gene expression in L . pneumophila in standard versus iron restricted conditions. Among the regulated genes, a newly described one, lpp_2867 , was highly induced in iron‐restricted conditions. Mutants lacking this gene in L . pneumophila were not affected in siderophore synthesis or utilization. On the contrary, they were defective for growth on iron‐depleted solid media and for ferrous iron uptake. A sequence analysis predicts that L pp_2867 is a membrane protein, suggesting that it is involved in ferrous iron transport. We thus named it IroT , for iron transporter. Infection assays showed that the mutants are highly impaired in intracellular growth within their environmental host A canthamoeba castellanii and human macrophages. Taken together, our results show that IroT is involved, directly or indirectly, in ferrous iron transport and is a key virulence factor for L . pneumophila .

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