My research focuses on mutually beneficial interactions between bacteria and multi-cellular eukaryotes. Legume-rhizobia symbiosis is my current study system where I examine how host legumes control the spread of ineffective (less beneficial) rhizobia. Since rhizobia fix nitrogen for the host and legumes can also acquire N from the soil, I experiment with how variation in exogenous can alter the cost and benefits of symbiosis for the host and symbiont. Elevated soil nitrogen can potentially lead to situations where symbiosis with rhizobia provides little or no benefit to the host or is even costly. In cases of elevated soil nitrogen, hosts can relax control over symbionts when control is costly leading to the spread of ineffective rhizobia. Alterations in the costs and benefits of symbiosis are particularly important agriculture where chemical nitrogen fertilizer is prevalent in legume crops. But environmental nitrogen variation is increasingly important in the context of anthropogenic nitrogen deposition. Such deposition has the potential to drive the abandonment of legume-rhizobium symbiosis. Understanding how legume-rhizobium symbiosis is potentially affected by exogenous nitrogen variation has important implications for agronomic and natural systems.


John Regus - Ph.D. 



Peer-reviewed publications

  • 6 -  Regus, J. U., Gano, K. A., Hollowell, A. C., Sachs, J. L. 2014 Efficiency of partner choice and sanctions in Lotus is not altered by nitrogen fertilization Proceedings of the Royal Society of London. 281, 20132587.


  • 5 -  Pietrasiak, N, Regus, J. U., Johansen, J. R., Lam, D., Sachs, J. L.., Santiago, L. S., 2013. Biological soil crust communities differ in key ecological functions. Soil Biology and Biochemistry 65: 168-171.
  • 4 - Sachs, J.L., Gano, K.A., Regus, J.U., Hollowell, A. C. 2013 The legume-rhizobium symbiosis: an integrative evolutionary perspective. Oxford Bibliographies.
  • 3 - Regus, J. U., Reznick, D. N., Webb, S. A. 2013 Comparative life histories of fishes in the genus Phallichthys (Pisces: Poeciliidae). Journal of Fish Biology. 83: 144-155.
  • 2 - Sachs, J.L., Skophammer, R.G., and Regus, J. U. 2011. Evolutionary transitions in bacterial symbiosis. Proceedings of the National Academy of Sciences USA. Vol. 108(28).
  • 1 - Pires, M., Bassar, R. D., McBride, K., Regus, J. U., Garland, T., Reznick, D. N. 2011. Why do placentas evolve? An evaluation of the life history facilitation hypothesis in the northern clade of the fish genus Poeciliopsis (Poeciliidae:Cyprinodontiformes) Functional Ecology. Vol 25(4).