Open Access Research article

Genome sequence and phenotypic analysis of a first German Francisella sp. isolate (W12-1067) not belonging to the species Francisella tularensis

Kerstin Rydzewski1, Tino Schulz1, Elzbieta Brzuszkiewicz2, Gudrun Holland3, Christian Lück4, Jens Fleischer5, Roland Grunow6 and Klaus Heuner1*

Author Affiliations

1 Cellular Interactions of Bacterial Pathogens, Centre for Biological Threats and Special Pathogens, Division 2 (ZBS 2), Robert Koch Institute, Nordufer 20, Berlin 13353, Germany

2 Department of Genomics and Applied Microbiology & Göttinger Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August-University of Göttingen, Grisebachstr. 8, Göttingen 37077, Germany

3 Centre for Biological Threats and Special Pathogens, Division 4 (ZBS 4), Advanced Light and Electron Microscopy, Robert Koch Institute, Nordufer 20, Berlin 13353, Germany

4 Institute of Medical Microbiology and Hygiene, Consultant Laboratory for Legionella, TU Dresden, Fiedlerstr. 42, Dresden 01307, Germany

5 Landesgesundheitsamt Baden-Württemberg, Nordbahnhof 135, Stuttgart 70191, Germany

6 Centre for Biological Threats and Special Pathogens, Division 2 (ZBS 2), Highly Pathogenic Microorganisms, Robert Koch Institute, Nordufer 20, Berlin 13353, Germany

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BMC Microbiology 2014, 14:169  doi:10.1186/1471-2180-14-169

Published: 25 June 2014

Abstract

Background

Francisella isolates from patients suffering from tularemia in Germany are generally strains of the species F. tularensis subsp. holarctica. To our knowledge, no other Francisella species are known for Germany. Recently, a new Francisella species could be isolated from a water reservoir of a cooling tower in Germany.

Results

We identified a Francisella sp. (isolate W12-1067) whose 16S rDNA is 99% identical to the respective nucleotide sequence of the recently published strain F. guangzhouensis. The overall sequence identity of the fopA, gyrA, rpoA, groEL, sdhA and dnaK genes is only 89%, indicating that strain W12-1067 is not identical to F. guangzhouensis. W12-1067 was isolated from a water reservoir of a cooling tower of a hospital in Germany. The growth optimum of the isolate is approximately 30°C, it can grow in the presence of 4–5% NaCl (halotolerant) and is able to grow without additional cysteine within the medium. The strain was able to replicate within a mouse-derived macrophage-like cell line. The whole genome of the strain was sequenced (~1.7 mbp, 32.2% G + C content) and the draft genome was annotated. Various virulence genes common to the genus Francisella are present, but the Francisella pathogenicity island (FPI) is missing. However, another putative type-VI secretion system is present within the genome of strain W12-1067.

Conclusions

Isolate W12-1067 is closely related to the recently described F. guangzhouensis species and it replicates within eukaryotic host cells. Since W12-1067 exhibits a putative new type-VI secretion system and F. tularensis subsp. holarctica was found not to be the sole species in Germany, the new isolate is an interesting species to be analyzed in more detail. Further research is needed to investigate the epidemiology, ecology and pathogenicity of Francisella species present in Germany.

Keywords:
Francisella isolate; W12-1067; Cooling tower; Genome sequence; Pathogenicity island FPI; Environmental; Legionella; Germany