lifesciences
Innopsys

Genomic island excision in Bodetella petrii

Abstract:

Background

* Among the members of the genus Bordetella B. petrii is unique, since it is the only species isolated from the environment, while the pathogenic Bordetellae are obligately associated with host organisms. Another feature distinguishing B. petrii from the other sequenced Bordetellae is the presence of a large number of mobile genetic elements including several large genomic regions with typical characteristics of genomic islands collectively known as integrative and conjugative elements (ICEs). These elements mainly encode accessory metabolic factors enabling this bacterium to grow on a large repertoire of aromatic compounds.

Results

During in vitro culture of Bordetella petrii colony variants appear frequently. We show that this variability can be attributed to the presence of a large number of metastable mobile genetic elements on its chromosome. In fact, the genome sequence of B. petrii revealed the presence of at least seven large genomic islands mostly encoding accessory metabolic functions involved in the degradation of aromatic compounds and detoxification of heavy metals. Four of these islands (termed GI1 to GI3 and GI6) are highly related to ICEclc of Pseudomonas knackmussii sp. strain B13. Here we present first data about the molecular characterization of these islands. We defined the exact borders of each island and we show that during standard culture of the bacteria these islands get excised from the chromosome. For all but one of these islands (GI5) we could detect circular intermediates. For the clc-like elements GI1 to GI3 of B. petrii we provide evidence that tandem insertion of these islands which all encode highly related integrases and attachment sites may also lead to incorporation of genomic DNA which originally was not part of the island and to the formation of huge composite islands. By integration of a tetracycline resistance cassette into GI3 we found this island to be rather unstable and to be lost from the bacterial population within about 100 consecutive generations. Furthermore, we show that GI3 is self transmissible and by conjugation can be transferred to B. bronchiseptica thus proving it to be an active integrative and conjugative element

Credits:

Melanie Lechner1, Karin Schmitt1, Susanne Bauer1, David Hot2,5, Christine Hubans3, Erwan Levillain2,5, Camille Locht4,5, Yves Lemoine2,5 and Roy Gross1

  • a. Lehrstuhl für Mikrobiologie, Biozentrum, Universitât Würzburg, Am Hubland, D-97074 Würzburg, Germany
  • b. TAG – Transcriptomics and Applied Genomics UMR8161, Institut Pasteur de Lille, Lille, France
  • c. Genoscreen Company, Campus de l’Institut Pasteur de Lille, Lille, France
  • d. Mécanismes Moléculaires de la Pathogénie Bactérienne, INSERM U 629, Institut Pasteur de Lille, Lille, France
  • e. IFR 142, Molecular and Cellular Medecine, Institut Pasteur de Lille, Lille, France

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