Faculty

Figure 1

Figure 2

Figure 3

Figure 4

Anne O. Summers
Professor of Microbiology
Ph.D. (1973) Washington University

Address: Department of Microbiology
263A Biological Sciences Building
Athens, GA 30602-2605
Phone: (706) 542-2669
E-mail: summers@uga.edu
COS CV: http://myprofile.cos.com/summersa70
PubMed: summers ao

Research Interests:
Though some metals are essential for life others, such as mercury (Hg), are toxic. Bacteria have evolved a detoxification system, the Hg resistance (mer) operon, often found on bacterial plasmids which also carry antibiotic resistance genes. We study the mechanism of Hg resistance and the co-evolution of metal and antibiotic resistance plasmids in the commensal microbiota of humans and animals. Collaborating with enzymologist Sue Miller at UCSF, we are determining the role of a small metallochaperone domain in the key Hg-detoxification enzyme, MerA (mercuric reductase). We are also dissecting the mechanism of MerB (organomercurial lyase) and determining its 3D structure with UGA crystallographer, Cory Momany. The Hg-binding domain of the metalloregulator, MerR, which controls expression of the mer operon (merTPCABD) lies in a novel anti-parallel coiled-coil structure. MerR also captures RNA polymerase (RNAP) in a unique, pre-initiation complex at the mer promoter. We have identified the sub-domains of MerR involved in interactions with RNAP and are now determining the mechanistic basis of MerR's metal affinity and specificity. Hg resistant bacteria are unusually abundant in the commensal intestinal and oral microbiota. They are also typically multiple antibiotic resistant since Hg and antibiotic resistance genes are genetically linked on conjugative plasmids. Using microarrays we have found Hg exposure significantly alters the composition of the commensal ecosystem. In related work, we've also found an unexpected reservoir of multi-resistant integrons in the commercial poultry production ecosystem. What we learn will provide tools for ameliorating metal pollution and intoxication and will enable a longer usable lifetime for new and existing antibiotics.