Professor Peter Young

University of York, UK,

We classify all organisms into species, but bacteriologists have always done it a little differently.  In the past two decades, we have acquired major new insights into bacterial genomes, diversity and evolution, and I believe it is time to rethink the species concept as applied to bacteria.  On the one hand, bacteria have species equivalent to the species of sexual eukaryotes, defined by recombination and barriers to recombination.  On the other hand, the dynamic nature of the bacterial accessory gene pool leads to high genetic and phenotypic diversity among members of the same species.   We can define species in a consistent and stable way, but the species name will not tell us all we need to know about a bacterium.  We also need a list of its most relevant accessory gene modules.  This has important implications for current attempts to describe the diversity of bacterial communities, as well as for our understanding of pathogens and their evolution.  I will illustrate these ideas with our own evidence from rhizobia, the symbiotic nitrogen-fixing bacteria.

Kumar N, Lad G, Giuntini E, Kaye ME, Udomwong P, Shamsani NJ, Young JPW, Bailly X (2015) Bacterial genospecies that are not ecologically coherent: population genomics of Rhizobium leguminosarum. Open Biology, 5: 140133. doi: 10.1098/rsob.140133

Remigi P, Zhu J, Young JPW, Masson-Boivin C (2016) Symbiosis within symbiosis: evolving nitrogen-fixing legume symbionts. Trends in Microbiology 24: 63-75 doi:10.1016/j.tim.2015.10.007

Host: Katharina Pawlowski