IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Title Comparative analysis of genome sequences of Rhizobium galegae HAMBI 540 and
HAMBI 1141
Authors Janina Österman 1,3 , Lars Paulin 2 , Edward Alatalo 2 , J. Peter W. Young 3 , Kristina
Lindström 1
Poster Board Number 12
1 Department of Food and Environmental Sciences and
2 Institute of Biotechnology, University of Helsinki
3 Department of Biology, University of York
Rhizobium galegae (Lindström 1989) is taxonomically distinct and known for its strict host specificity both
regarding nodulation and nitrogen fixation. Our aim is to gain insight into molecular mechanisms behind the
specificity of nitrogen fixation. As a first step towards this goal we have performed whole genome sequencing of
R. galegae symbiovar orientalis strain HAMBI 540 (effective on Galega orientalis) and R. galegae symbiovar
officinalis strain HAMBI 1141 (effective on G. officinalis). The draft assembly indicates that both genomes are
about 6.4 Mb in size. Preliminary comparison of the genomes has been performed, with a more specific
comparison of the symbiotic gene regions of the two strains. Although the two genomes are of approximately the
same size, there are important genetic differences between the strains. The most obvious difference is that the
HAMBI 1141 genome harbours three replicons, while the corresponding number in HAMBI 540 is two.
Furthermore, HAMBI 1141 harbours conjugal transfer systems not present in HAMBI 540. The genes present in
the symbiotic regions are the same except for one gene, rpoN, the function of which will be further studied.
Annotation of the symbiotic region also led us to the identification of a candidate gene for acetylation of the
penultimate N-acetylglucosamine in the R. galegae Nod factor. Differences detected in the comparative analyses
will be discussed.
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2011