title: Identification of a lineage specific zinc responsive genomic island in Mycobacterium avium ssp. paratuberculosis.
abstract: BACKGROUND
  Maintenance of metal homeostasis is crucial in bacterial pathogenicity as metal starvation is the most important mechanism in the nutritional immunity strategy of host cells. Thus, pathogenic bacteria have evolved sensitive metal scavenging systems to overcome this particular host defence mechanism. The ruminant pathogen Mycobacterium avium ssp. paratuberculosis (MAP) displays a unique gut tropism and causes a chronic progressive intestinal inflammation. MAP possesses eight conserved lineage specific large sequence polymorphisms (LSP), which distinguish MAP from its ancestral M. avium ssp. hominissuis or other M. avium subspecies. LSP14 and LSP15 harbour many genes proposed to be involved in metal homeostasis and have been suggested to substitute for a MAP specific, impaired mycobactin synthesis.
  
  
  RESULTS
  In the present study, we found that a LSP14 located putative IrtAB-like iron transporter encoded by mptABC was induced by zinc but not by iron starvation. Heterologous reporter gene assays with the lacZ gene under control of the mptABC promoter in M. smegmatis (MSMEG) and in a MSMEG∆furB deletion mutant revealed a zinc dependent, metalloregulator FurB mediated expression of mptABC via a conserved mycobacterial FurB recognition site. Deep sequencing of RNA from MAP cultures treated with the zinc chelator TPEN revealed that 70 genes responded to zinc limitation. Remarkably, 45 of these genes were located on a large genomic island of approximately 90 kb which harboured LSP14 and LSP15. Thirty-five of these genes were predicted to be controlled by FurB, due to the presence of putative binding sites. This clustering of zinc responsive genes was exclusively found in MAP and not in other mycobacteria.
  
  
  CONCLUSIONS
  Our data revealed a particular genomic signature for MAP given by a unique zinc specific locus, thereby suggesting an exceptional relevance of zinc for the metabolism of MAP. MAP seems to be well adapted to maintain zinc homeostasis which might contribute to the peculiarity of MAP pathogenicity.
authors.forename: Elke
authors.initials: E
authors.lastname: Eckelt
authors.forename: Michael
authors.initials: M
authors.lastname: Jarek
authors.forename: Cornelia
authors.initials: C
authors.lastname: Frömke
authors.forename: Jochen
authors.initials: J
authors.lastname: Meens
authors.affiliation: Institute for Microbiology, Department of Infectious Diseases, University of Veterinary Medicine Hannover, Bischofsholer Damm 15, 30173 Hannover, Germany. ralph.goethe@tiho-hannover.de.
authors.forename: Ralph
authors.initials: R
authors.lastname: Goethe
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D016000:Cluster Analysis; D005798:Genes, Bacterial; D056426:Genetic Loci; D044404:Genomic Islands; D059014:High-Throughput Nucleotide Sequencing; D008969:Molecular Sequence Data; D016927:Mycobacterium avium subsp. paratuberculosis / Q000235:genetics*; D009876:Operon / Q000235:genetics; D016415:Sequence Alignment; D017423:Sequence Analysis, RNA; D015032:Zinc / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D015032:Zinc