It's All In The Enterobacteriaceae Family For University of Bern's Dr. Kuhnert
Editor's Note: This is another report on the presentations that were made in Dublin earlier this year at the 1st International Meeting on Cronobacter (Enterobacter Sakazakii). Below we hear from Professor Peter Kuhnert of the Institute of Veterinary Bacteriology, University of Bern, Switzerland.
Biography: Peter Kuhnert is working at the University of Bern, Switzerland as an associate professor in bacteriology. He completed a PhD in molecular biology studying gene regulation of the porcine TNF-locus.
As a postdoc at the Weizmann Institute of Science in Israel he focused on the regulation of the human TNF-receptor genes and its role in the immune response. After his return 1994 he switched topics and is since then working at the Institute of Veterinary Bacteriology where he focuses on bacterial virulence, phylogeny and taxonomy. His work includes pathotyping of E. coli, genotyping of foodborne pathogens with an emphasis on Campylobacter, pathogenesis and virulence mechanisms of Pasteurellaceae as well as work on Mycoplasma hyopneumoniae.
Summary - Multilocus sequence analysis (MLSA) of Cronobacter and related taxa Genetic similarity as determined by DNA-DNA hybridization is still considered the ‘gold standard’ method to determine relatedness between bacterial species. Nevertheless, it is very time consuming and cumbersome to perform and requires cross-hybridization between representatives of a species and related taxa. Moreover, variation between experiments, techniques and laboratories make exchange and comparison of data difficult. Whole genome sequence comparisons could be an alternative to DNA-DNA hybridization however, data handling and the
open question as to what genes should be used for defining genome similarity cannot be neglected. Therefore, for taxonomic purposes investigating as many isolates of a species as possible in order to respect the biodiversity of taxa, a few representative genes indicative for genetic similarity between isolates is the optimal way to go. Recently, we showed that the three genes recN, rpoA, and thdF can be used to estimate whole genome similarity of representatives of the family Pasteurellaceae [Kuhnert & Korczak (2006) Int.J.Syst.Evol.Microbiol 152: 2537-2548]
In the presented work multilocus sequence analysis (MLSA) based on recN, rpoA and thdF genes was done on more than 30 species of the family Enterobacteriaceae with a focus on Cronobacter and the related genus Enterobacter. The sequences provided valuable data for phylogenetic, taxonomic and diagnostic purposes. Phylogenetic analysis showed that the genus Cronobacter forms a homogenous cluster related to recently described species of Enterobacter, but distant to
other species of this genus. Combining sequence information on all three genes is highly representative for the species’ percentage of GC-content used as taxonomic marker. Sequence similarity of the three genes and even of recN alone can also be used to extrapolate genetic similarities between species of Enterobacteriaceae, being an alternative to DNA-DNA hybridization. Finally, the rpoA gene sequence, which is the easiest one to determine, provides a powerful diagnostic tool to identify and differentiate pathogens of this family. The comparative analysis gives important
insights into the phylogeny and genetic relatedness of the family Enterobacteriaceae and will serve as a basis for further studies and clarifications on the taxonomy of this large and heterogeneous family.
Powerpoint: Find it here.
