Address:

Dana Science Center Room 317
Biology Department
Skidmore College
Saratoga Springs, NY 12866

Telephone: (518) 580-5076

Fax: (518) 580-5071

E-mail: sfranke@skidmore.edu

Education:

B.S., Biology, Martin-Luther-University Halle, Germany (1996)
M.S., Microbiology, Martin-Luther-University Halle, Germany (1999)
Ph.D., Microbiology/Molecular Biology, Martin-Luther-University Halle, Germany (2002)
Postdoctoral Associate, Martin-Luther-University Halle, Germany (2002-2003)
Postdoctoral Associate, University of Arizona (2003-2006)

Courses Taught:

Microbial Genetics
General Microbiology
Microbes in Society
Bacterial Pathogens

Research Interests:

Several transition metals are essential for life as trace elements. These metal ions are found as cofactor in enzymes and are necessary for their proper function, e.g. nickel in hydrogenases, zinc in polymerases, iron and copper in redox enzymes. For other transition metals, like silver, no biological function is known. However, if the concentration of these metals exceeds a certain level, all of them, independent from wether they essential or not, are toxic. For this, organisms have to regulate their internal metal concentration tightly.

My research concentrates on different aspects of microbial metal homoeostasis: i) Mechanism of copper and silver resistance in Escherichia coli and ii) Influence of zinc on pathogenicity of Salmonella typhimurium .

i) Mechanism of copper and silver resistance in E. coli
Whereas copper is essential for enzymes carrying out redox reactions, no biological function is known for silver. However, bacterial resistance against both metals (metal inons) is mediated by the same system. In the enterobacterium Escherichia coli no system is known for specific uptake of copper ions. Excess copper (Cu+ in the cytoplasm) is exported into the periplasm, where it is oxidized to the less toxic Cu2+ (aerob) or transported into the surrounding medium (anaerob). The same transport system is also able to export low silver concentrations. Similar transporters have been identified, which seem to be specific for silver detoxification. I am interested in the interaction of the various components, which play a role in copper/silver resistance and in understanding the mechanism of metal ion transport in bacteria.

Why is this important?

a)  transport from the periplasm into the surrounding medium is accomplished by a transport complex homologue to transporters involved in antibiotic resistance

b)  Silver ions are used as biocide in a time in which more and more antibiotic resistant pathogenic bacteria are emerging. Understanding silver resistance and how it spreads is essential to be able to “keep up” with the amazing ability of bacteria to adapt to their environment.

ii) Influence of zinc on pathogenicity of Salmonella typhimurium
Transition metals are not only essential for life itself but are also found to be involved in pathogenicity. I am interested in how zinc is used in pathogenicity of S. typhimurium . In a first approach, deletion of zinc uptake mechanisms resulted in a lower infection and survival rate of S. typhimurium in macrophages. However, more important is which zinc dependent enzymes are involved in infection and progeny and how to use this knowledge to reduce Salmonella related sickness as well as to what extent this knowledge is transferable to other pathogens.

Recent Publications:

Rensing, C., and S. Franke.   11 January 2007, posting date. Chapter 5.4.4.1, Copper Homeostasis in Escherichia coli and Other Enterobacteriaceae . In A. Böck , R. Curtiss III, J. B. Kaper, F. C. Neidhardt, T. Nyström, K. E. Rudd, and C. L. Squires (ed.), EcoSal ­Escherichia coli and Salmonella: cellular and molecular biology . http://www.ecosal.org. ASM Press, Washington , D.C.

Franke, S. and C. Rensing. 2007. Acidophiles: mechanisms to tolerate metal and acid toxicity. In Physiology and Biochemistry of Extremophiles. Gerday, C., and N. Glansdorff , editors. ASM Press, Washington , D.C. 271-278. (publication date: April 2007)

Qin, J., B.P. Rosen, Y. Zhang, G. Wang, S. Franke and C. Rensing (2006) Properties and function of ArsM: a bacterial arsenite S-adenosylmethionine methyltransferase. PNAS 103:2075-2080.

Loftin * , I.R., S. Franke * , S.A. Roberts, A. Weichsel, A. Heroux, W.R. Montfort, C. Rensing and M.M. McEvoy (2005) A novel copper-binding fold for the periplasmic copper resistance protein CusF. Biochemistry 44:10533-10540. (* these authors contributed equally)

Hasman, H., S. Franke and C. Rensing (2005) Resistance to metals used in agricultural production. pp 99-114. In: (Aarestrup, F.M., and H.C. Wegener, eds.) Antimicrobial Resistance in Bacteria of Animal Origin. ASM Press, Washington , D.C.

Haney, C.J., G. Grass, S. Franke and C. Rensing (2005) New developments in the understanding of the cation diffusion facilitator family. J Ind Microbiol Biotechnol 32:215-226.

Grass, G., S. Franke, N. Taudte, D.H. Nies, L.M. Kucharski, M.E. Maguire and C. Rensing (2005) The metal permease ZupT from Escherichia coli is a transporter with a broad substrate spectrum. J Bacteriol 187:1604-11.

Anton, A., A. Weltrowski, C.J. Haney, S. Franke, G. Grass, C. Rensing and D.H. Nies (2004) Characteristics of zinc transport by two bacterial cation diffusion facilitators from Ralstonia metallidurans CH34 and Escherichia coli . J Bacteriol 186:7499-507.

Grosse, C., A. Anton, T. Hoffmann, S. Franke, G. Schleuder and D.H. Nies (2004) Identification of a regulatory pathway that controls the heavy-metal resistance system Czc via promoter czcNp in Ralstonia metallidurans . Arch Microbiol. 182:109-18.

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