Wisniewski-Dyé, F. et al., 2011. PLoS Genetics

Azospirillum Genomes Reveal Transition of Bacteria from Aquatic to Terrestrial Environments

Florence Wisniewski-Dyé, Kirill Borizak, Gurusahai Khalsa-Moyers, Gladys Alexandre, Leonid O. Sukharnikov, Kristin Wuichet, Gregory B. Hurst, W. Hayes McDonald, Jon S. Robertson, Valérie Barbe, Alexandra Calteau, Zoé Rouy, Sophie Mangenot, Claire Prignet-Combaret, Philippe Normand,Michaël Boyer, Patricia Siguier, Yves Dessaux, Claudine Elmerich, Guy Condemine, Ganisan Kirshnen, Ivan Kennedy, Andrew H. Paterson, Victor González, Patrick Mavingui, and Igor B. Zhulin
2011 December 22, PLoS Genetics 7(12): e1002430
Download Publication: Wisniewski-Dye 2011-PMI.pdf


Fossil records indicate that life appeared in marine environments ~3.5 billion years ago (Gyr) and transitioned to terrestrial ecosystems nearly 2.5 Gyr. Sequence analysis suggests that “hydrobacteria” and “terrabacteria” might have diverged as early as 3 Gyr. Bacteria of the genus Azospirillum are associated with roots of terrestrial plants; however, virtually all their close relatives are aquatic. We obtained genome sequences of two Azospirillum species and analyzed their gene origins. While most Azospirillum house-keeping genes have orthologs in its close aquatic relatives, this lineage has obtained nearly half of its genome from terrestrial organisms. The majority of genes encoding functions critical for association with plants are among horizontally transferred genes. Our results show that transition of some aquatic bacteria to terrestrial habitats occurred much later than the suggested initial divergence of hydro- and terrabacterial clades. The birth of the genus Azospirillum approximately coincided with the emergence of vascular plants on land.


Figure 1 Habitats of Azospirillum and its closest aquabacterial relatives
Figure 1: Habitats of Azospirillum and its closest aquabacterial relatives.

A maximum-likelihood tree built from 16S rRNA sequences from members of Rhodospirillaceae. Acetobacter acetii, a member of the same order Rhodospirillales, but a different family, Acetobacteriaceae, is shown as an outgroup. Aquatic inhabitants are not highlighted; terrestrial are highlighted in brown and plant-associated Azospirillum is highlighted in green. See Table S1 for details

Figure 2 Whole-genome alignments for Azospirillum and related multi-replicon rhizobial species
Figure 2: Whole-genome alignments for Azospirillum and related multi-replicon rhizobial species.
Relative distances between genomes (calculated from a concatenated ribosomal protein tree): A. lipoferum 4B to Azospirillum sp.510 – 0.01; Rhizobium etli to Rhizobium leguminosarum – 0.02; A. lipoferum 4B to A. brasilense Sp245 – 0.10; Rhizobium etli to S. meliloti – 0.11.
Figure 3 Scheme for detecting ancestral and horizontally transferred genes

Figure 3: Scheme for detecting ancestral and horizontally transferred genes.


Wisniewski-Dyé F, Borziak K, Khalsa-Moyers G, Alexandre G, Sukharnikov LO, et al. (2011) Azospirillum Genomes Reveal Transition of Bacteria from Aquatic to Terrestrial Environments. PLoS Genet 7(12): e1002430. doi:10.1371/journal.pgen.1002430

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