Daâd A. Saffarini
Daâd A. Saffarini
Environmental and Molecular Microbiology

1979: B.S. Biology Department
University of Jordan

1988: Ph.D. Dept. Biological Sciences
University of Wisconsin-Milwaukee
1989-1992: Postdoctoral Research Fellow
Center for Great Lakes Studies
University of Wisconsin-Milwaukee

Office: Lapham N309
Phone: 414-229-2964
FAX: 414-229-3926
Email: daads@uwm.edu

Research Interests

We are interested in understanding the mechanisms of anaerobic respiration in the bacterium Shewanella oneidensis. This organism is a metal reducer that can use more than 14 different electron acceptors for respiration. These include oxygen, nitrate, fumarate, DMSO, and uranium (VI). Reduction of uranium is important environmentally because reduced uranium is insoluble and can be contained. The ability to reduce uranium makes S. oneidensis a useful tool for bioremediation. Other electron acceptors used by S. oneidensis include Fe(III) and Mn(IV) oxides. These are insoluble metals and their reduction plays an important role in the carbon and metal cycles in aquatic environments. Reduction of these metals occurs on the outer surface of the outer membrane. The ability to transfer electrons extracellularly to the metal reductase has been exploited for use in microbial fuel cells for electricity generation.

We are interested in understanding the mechanisms used by S. oneidensis to reduce different electron acceptors, especially metal oxides. We have identified several components of the metal reductase that include an outer membrane c cytochrome (MtrC) and a porin-like protein (MtrB). MtrC appears to play an important role in extracellular electron transfer to metal oxides and to anodes of microbial fuel cells. Analysis of the mechanisms that lead to electron transfer by MtrC, and identification of additional components involved, are being investigated.

In addition to understanding the mechanisms of anaerobic respiration, we are interested in determining the mechanisms that regulate this process. We have identified the cAMP receptor protein, CRP, as the major regulator of anaerobic respiration in S. oneidensis. Regulation of anaerobic respiration by this protein is unusual since in it lacks redox sensing domains, and in other bacteria this protein regulates carbon metabolism. We are currently investigating the mechanisms that lead to CRP activation under anaerobic conditions. We have identified two major adenylate cyclases that are involved in cAMP production under anaerobic conditions. One of these enzymes is membrane-bound, while the other is soluble. We are using molecular and biochemical techniques to investigate the mechanisms that lead to the expression and activation of the adenylate cyclases in S. oneidensis.

Selected Publications

Bouhenni, R., G. Vora, J. Biffinger, S. Shirodkar, K. Brockman, R. Ray, P. Wu, B. Johnson, E. Biddle, M. Marshall, L. Fizgerald, B. Little, J. Fredrickson, A. Beliaev, B. Ringeison, D. Saffarini. 2010. The role of Shewanella oneidesis outer surface structures in extracellular electron transfer. Electroanalysis: In press.

Reardon, C., A. Dohnalkova, P. Nachimuthu, D. Kennedy, D. Saffarini, B. Arey, L. Shi, Z. Wang, D. Moore, J. McLean, D. Moyles, M. Marshall, J. Zachara, J. Fredrickson, A. Beliaev. 2009. Role of outer-membrane cytrochromes MtrC and OmcA in the biomineralization of ferrihydrite by Shewanella oneidensis MR-1. Geobiology 8:56-58.

Charania, M., K.Brockman, Y. Zhang, g. Pinchuk, A. Belaiev, J. Fredrickson and D. Saffarini. 2009. Involvement of a class III adenylate cyclase in the regulation of anaerobic respiration in Shewanella oneidensis MR-1. J. Bacteriol. 191:4298-4306. http://jb.asm.org/cgi/reprint/191/13/4298

Fredrickson, J., M. Romine, A. Beliaev, J. Auchtung, M. Driscoll, T. Gardner, K. Nealson, A. Osterman, G. Pinchuk, J. Reed, D. Rodionov, J. Rodrigues, D. Saffarini, M. Serres, A. Spormann, I. Zhulin and J. Tiedje. 2008. Towards environmental systems biology of Shewanella. Nat. Rev. Microbiol. 6: 592-603. http://www.nature.com/nrmicro/journal/v6/n8/abs/nrmicro1947.html

McLean, J. S., G. Pinchuk, O. Geydebrekht, C. Bilskis, B. Zakrajsek, E. Hill, D. Saffarini, M. Romine, Y. Gorby, J. Fredrickson and A. Beliaev. 2008. Oxygen-dependent autoaggregation in Shewanella oneidensis MR-1. Environ. Microbiol. 10:1861-1876. http://www3.interscience.wiley.com/journal/120092113/abstract?CRETRY=1&SRETRY=0

Marshall, M., A. Plymale, D. Kennedy, L. Shi, Z. Wang, S. Reed, A. Dohnalkova, C. Simonson, C. Liu, D. Saffarini, M. Romine, J. Zachara, A. Beliaev and J. Fredrickson. 2008. Hydrogenase- and outer membrane c-type cytochrome- facilitated reduction of technetium(VII) by Shewanella oneidensis MR-1. Environ Microbiol. 10:125-136. http://www3.interscience.wiley.com/journal/119419893/abstract

Bretschger, O., A. Obraztsova, C. Sturm, I. Chang, Y. Gorby, S. Reed, C. Culley, C. Reardon, S. Barua, M. Romine, J. Zhou, A. Beliaev, R. Bouhenni, D. Saffarini, F. Mansfeld, B. Kim, J. Fredrickson, K. Nealson. 2007. Current Production and Metal Oxide Reduction by Shewanella oneidensis MR-1 Wild Type and Mutants. Appl Environ Microbiol. 73:7003-7012. http://aem.asm.org/cgi/reprint/73/21/7003

Marshall, M., A. Beliaev, A. Dohnalkova, D. Kennedy, L. Shi, Z. Wang, M. Boyanov, B. Lai, K. Kemner, J. McLean, S. Reed, D. Culley, V. Bailey, C. Simonson, D. Saffarini, M. Romine, J. Zachara and J. Fredrickson. 2006. c-Type cytochrome-dependent formation of U(IV) nanoparticles by Shewanella oneidensis. PloS Biology 4:1324-1333. http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.0040268

Bouhenni, R., A. Gehrke, and D. Saffarini. 2005. Identification of genes involved in cytochrome c biogenesis in Shewanella oneidensis using a modified mariner transposon. Appl. Environ. Microbiol. 71:4935-3937. http://aem.asm.org/cgi/reprint/71/8/4935

Saffarini, D. R. Schultz and A. Beliaev. 2003. Involvement of cyclic AMP (cAMP) and CAMP receptor protein in anaerobic respiration of Shewanella oneidensis. J. Bacteriol. 185:3668-3671. http://jb.asm.org/cgi/reprint/185/12/3668.pdf

Saffarini, D., S. Blumerman, and K. Mansoorabadi. 2002. Role of menaquinones in Fe(III) reduction by membrane fractions of Shewanella putrefaciens. J. Bacteriol. 184:846-848. http://jb.asm.org/cgi/reprint/184/3/846.pdf

Beliaev, A., Saffarini, D., McLaughlin, J. and Hunnicutt, D. 2001. MtrC, an outer membrane decaheme c cytochrome required for metal reduction in Shewanella putrefaciens MR-1. Molecular Microbiology. 39:722-730. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db= PubMed&dopt=Citation&list_uids=11169112

Venkateswaran, K., Moser, D.P., Dollhopf, M.E., Lies, D.P., Saffarini, D.A., MacGregor, B.J., Ringelberg, D.B., White, D.C., Nishijima, M., Sano, H., Burghardt, J. Stackebrandt, E. and Nealson, K.H. 1999. Polyphasic taxonomy of the genus Shewanella and description of Shewanella oneidensis sp. nov. Int. J. Syst. Bacteriol. 49: 705-724. http://www.ncbi.nlm.nih.gov:80/entrez/ query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10319494&dopt=Abstract

Beliaev, A. and D. Saffarini. 1998. Shewanella putrefaciens mtrB encodes an outer membrane protein required for Fe(III) and Mn(IV) reduction. J. Bacteriol. 181:6292-6297. http://jb.asm.org/cgi/reprint/180/23/6292.pdf

Lovley, D., J. Coates, D. Saffarini and D. Lonergan. 1997. Dissimilatory Iron Reduction. In:, G. Winkelmann and C. Carrano (Eds), Transition metals in microbial metabolism. pp 187-215.

Nealson, K.H., D. Moser and D. Saffarini. 1995. Anaerobic electron acceptor chemotaxis in Shewanella putrefaciens. Applied and Environmental Microbiology. 61:1551-1554. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC167410/

Saffarini, D., T. DiChristina, D. Bermudes and K. Nealson. 1994. Anaerobic respiration of Shewanella putrefaciens requires both chromosomal and plasmid-borne genes. FEMS Microbiol. Lett. 119:271-278.

Nealson, K. and D. Saffarini. 1994. Iron and manganese in anaerobic respiration: Environmental significance, physiology and regulation. Ann. Rev. Microbiol.48:311-343.

Nealson, K., D. Saffarini, D. Moser and M.J. Smith. 1994. A method for monitoring tactic responses of bacteria under anaerobic conditions. J. Microbiological Methods. 20:211-218.

Nealson, K., Saffarini, D., Lukiewicz, S. 1994. Bacterial mutant strains unable to reduce nitroxides. Current Topics in Biophysics 18:39-45.

Saffarini, D.A. and K.H. Nealson. 1993. Sequence and genetic characterization of etrA, an fnr analog that regulates anaerobic respiration in Shewanella putrefaciens MR-1. J. Bacteriol. 175:7938-7944.