I use molecular genetics to investigate evolutionary questions.

My research focuses on Bradyrhizobium japonicum, a bacterial symbiont of the wild legume Lotus strigosus. The genome of Bradyrhizobium japonicum contains a genomic island that includes the genes necessary for the symbiotic lifestyle with a host legume. The capacity for this island to be horizontally transferred, and selection on the part of the host plant, may lead to different evolutionary histories and population structures for these two regions of the genome. Utilizing a number of collections from sites across California I am investigating the population structure and evolutionary forces on these two genomic regions.


I am also using strains of Bradyrhizobium japonicum to investigate questions about the evolution of antibiotic resistance in natural populations. Antibiotic resistance has been widely studied in hospitals and agricultural settings. However, less is known about the variation in resistance and the evolution of resistance in wild populations of bacteria. Previous studies have shown Bradyrhizobium japonicum vary in antibiotic resistance. Many of these  past studies focused on single populations in agricultural settings. I am assessing variation in antibiotic resistance in wild Bradyrhizobium japonicum collected from multiple sites from across California.

Amanda C. Hollowell -- Ph. D. Candidate

 Peer reviewed publications:

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


  • 2  The legume-rhizobium symbiosis  Sachs, J. L. Gano, K. A., Hollowell, A. C., Regus, J. U. 2013 Oxford Bibliographies in Ecology [PDF]
  • 3   The origins of cooperative bacterial communities  Sachs, J. L.,  and Hollowell, A. C. 2012. mBIO e00099-12 [PDF]

  • 4  Evolutionary instability of symbiotic function in Bradyrhizobium  Sachs, J. L., Russell, J. E. and Hollowell, A. C. 2011. PLoS One 6:11:e26370 [PDF]