Institute for Integrative Genome Biology


joel sachsJoel Sachs

Associate Professor

Mailing Address:

Spieth Hall /3314
University of California
Riverside, CA 92521

Phone: (951) 827-6357
Fax: (951) 827-4286
Email: joels@ucr.edu

Lab Website


PhD 2004 University of Texas
MS 1998 University of North Dakota
BA 1993 University of Iowa

College/Division Affiliation:

College of Natural and Agricultural Sciences

Areas Of Expertise:

Evolution of Symbiotic Bacteria; Evolutionary Genetics; Experimental Evolution; Evolution of Cooperation & Conflict; Host-microbial Coevolution

Awards / Honors:

2012-2017  NSF CAREER Award (DEB/IOS)
2008-2011  NSF Award- Division of Environmental Biology
2006-2007  NIH National Research Service Award
2004  Bess Heflin Fellowship
2003  Carl Gottfried Hartman Fellowship
2003  NSF Doctoral Dissertation Improvement Award

Research Summary:

Symbiotic bacteria are a key yet poorly understood facet of our natural world. Yet humans and our food sources often depend on bacterial cooperation for health and fitness. Current research is beginning to unravel the molecular and selective basis of bacterial cooperation. In the process we are discovering that beneficial infections are often evolutionarily unstable and more dynamic than expected. In the Sachs Lab we investigate the forces that shape bacterial cooperation with hosts as well as the origins and evolution of harmful strains. Our current focus is on rhizobial bacteria that live in soils throughout the world and nodulate the roots of many legume hosts. Projects in the Sachs Lab often utilize a wide range of techniques to answer basic questions. These include field collections of wild bacteria, experimental infections and experimental evolution, sequencing and phylogenetic analysis. Below are two broad research themes that we are currently investigating:

The evolutionary origins of uncooperative symbionts
Rhizobia are bacteria that fix nitrogen in legume roots in exchange for photosynthates from their hosts. However, non-beneficial rhizobia are widespread, including non-fixing strains that appear to be cheaters and non-nodulating strains that fail to infect hosts. Recent research has shown that legumes can punish some uncooperative rhizobia and substantially reduce their fitness, but these sanctions must not be universally effective. Important questions about uncooperative rhizobia remain unresolved. (i) Is it adaptive for rhizobia to be uncooperative with hosts? (ii) Do uncooperative rhizobia evolve from cooperative ancestors? (iii) What are the mechanisms of rhizobial exploitation? We are using experimental approaches as well as phylogenetic analyses to address these key gaps in our knowledge.

Microecology of symbiotic bacteria
Symbiotic bacteria often encounter hosts from environmental sources and can exhibit multiple life histories including host-inhabiting and environmental stages. Research on host-associated bacteria -- including pathogens and beneficial symbionts -- has primarily focused on infection of hosts. In the mean time, key questions about the ecology and evolution of free-living stages has remained unanswered. For instance, is host association ubiquitous within bacterial lineages, or do host-infecting genotypes represent subsets of environmental populations? Assuming that host infection and free-living existence exert different selective pressures, do diverged bacterial lineages result? Another set of questions addresses the degree to which bacteria associate with specific host partners. Do bacterial genotypes invariably associate with specific host lineages, and is such specificity based on control by one or both partners? Alternatively, is specificity a byproduct of ecological co-occurrence among bacteria and hosts? We have been using a combination of phylogenetic and population genetic approaches to tackle these questions.

Related Press Releases:

Selected Publications:

List of publications from PubMed and Personal Website 

Lab Personnel:

Hollowell, Amanda C. 
Ph.D. Student —   
Regus , John U.
Ph.D. Student — 
Gano, Kelsey
Ph.D. Student —
O'Neill, Matt
Ph.D. Student —
Bantay, Roxanne M.
Research Assistant —
Gleason, Nathan
Research Assistant — 

More Information

General Campus Information

University of California, Riverside
900 University Ave.
Riverside, CA 92521
Tel: (951) 827-1012

Career OpportunitiesUCR Libraries
Campus StatusDirections to UCR

Genomics Information

Institute of Integrative Genome Biology
2150 Batchelor Hall

Tel: (951) 827-7177
E-mail: Aurelia Espinoza, Managing Director