The evolution and origins of uncooperative rhizobia

University Of California-Riverside, Riverside CA

Investigators

Abstract

Infection by symbiotic bacteria is critical to plant and animal health. However, these beneficial infections are predicted to be evolutionarily unstable. Bacteria that help hosts can potentially evolve into parasites that exploit hosts. Alternatively, they might shift into novel life histories and abandon host interaction entirely. Both evolutionary pathways can be harmful to hosts, as uncooperative bacteria spread and take over beneficial populations. Here, the symbiotic bacteria (rhizobia) found on legume roots will be used to examine instability of beneficial bacterial infections. Field surveys, inoculation assays, experimental evolution studies and molecular analyses will (i) assess the frequency with which uncooperative rhizobia emerge in wild symbiont populations, (ii) investigate the reproductive success of uncooperative strains, and (iii) test hypotheses about the evolutionary forces that can shape uncooperative rhizobial strategies. Symbiotic bacteria are a key yet poorly understood facet of life. Humans and our food sources often depend upon bacterial cooperation for health, and research is needed to investigate the origins of harmful strains. This research will provide clues about how and why host-beneficial bacteria shift into harmful modes. It will provide training opportunities to students, and results will be incorporated into classroom activities.