Open Access Open Badges Research article

Insight into cross-talk between intra-amoebal pathogens

Gregory Gimenez1, Claire Bertelli2, Claire Moliner1, Catherine Robert1, Didier Raoult1, Pierre-Edouard Fournier1* and Gilbert Greub2*

Author Affiliations

1 Unité des rickettsies, Faculté de Médecine, Université de la Méditerranée, Marseille, France URMITE CNRS-IRD UMR 6236, Faculté de Médecine, 27 boulevard Jean Moulin, 13385 Marseille Cedex 05, France

2 Center for Research on Intracellular Bacteria, Institute of Microbiology, University of Lausanne and University Hospital, Bugnon 48, 1011 Lausanne, Switzerland

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BMC Genomics 2011, 12:542  doi:10.1186/1471-2164-12-542

Published: 2 November 2011



Amoebae are phagocytic protists where genetic exchanges might take place between amoeba-resistant bacteria. These amoebal pathogens are able to escape the phagocytic behaviour of their host. They belong to different bacterial phyla and often show a larger genome size than human-infecting pathogens. This characteristic is proposed to be the result of frequent gene exchanges with other bacteria that share a sympatric lifestyle and contrasts with the genome reduction observed among strict human pathogens.


We sequenced the genome of a new amoebal pathogen, Legionella drancourtii, and compared its gene content to that of a Chlamydia-related bacterium, Parachlamydia acanthamoebae. Phylogenetic reconstructions identified seven potential horizontal gene transfers (HGTs) between the two amoeba-resistant bacteria, including a complete operon of four genes that encodes an ABC-type transporter. These comparisons pinpointed potential cases of gene exchange between P. acanthamoebae and Legionella pneumophila, as well as gene exchanges between other members of the Legionellales and Chlamydiales orders. Moreover, nine cases represent possible HGTs between representatives from the Legionellales or Chlamydiales and members of the Rickettsiales order.


This study identifies numerous gene exchanges between intracellular Legionellales and Chlamydiales bacteria, which could preferentially occur within common inclusions in their amoebal hosts. Therefore it contributes to improve our knowledge on the intra-amoebal gene properties associated to their specific lifestyle.