Evolutionary Timeline and Genomic Plasticity Underlying the Lifestyle Diversity in Rhizobiales

• DOI: 10.1128/msystems.00438-20
• Publication Date: 2020-07-13T13:55:31Z
• Authors: Sishuo Wang; Andrew Meade; Hon-Ming Lam; Haiwei Luo
• Keywords: Time line

Members of the order Rhizobiales include those capable nitrogen fixation in nodules as well pathogens animals and plants. This lifestyle diversity has important implications for agricultural medical research. Leveraging large-scale genomic data, we infer that originated a free-living ancestor ∼1,500 million years ago (Mya) later emergence host-associated lifestyles broadly coincided with rise their eukaryotic hosts. In particular, first nodulating lineage arose from either Azorhizobium or Bradyrhizobium 150 to 80 Mya, time range general concurrent legumes. The rates transitions are highly variable; nodule association is more likely be lost than gained, whereas animal represents an evolutionary dead end. We searched statistical correlations between gene presence identified genes contributing transition adaptation same divergent lineages. Among potentially promoting successful major nodulation lineages, nod nif clusters fixation, respectively, were repeatedly acquired during each transition; fix, dct, phb involved energy conservation under micro-oxic conditions present nonnodulating ancestors; secretion systems lineage-specific patterns. Our study data suggest increased eukaryote drives diversification bacteria highlight both preexisting traits facilitating origin host association.IMPORTANCE Bacteria form diverse interactions represented by Rhizobiales, clade Alphaproteobacteria strategically large To investigate evolution, compiled comprehensive set genomes information over 1,000 genomes. show origins lineages emergences plants/animals, suggesting bacterium-host driving force evolution further found that, addition gains, recurrent losses specific may have played underrecognized roles providing clues genetic engineering microbial inoculants prevention potential plant/animal pathogens.