Steffen Porwollik
Biography
Steffen Porwollik, Ph.D., is an Associate Project Scientist in two University of California, Irvine departments, the Department of Microbiology and Molecular Genetics and the Department of Pharmaceutical Sciences. With over 28 years of experience in molecular biology, Dr. Porwollik specializes in high-throughput genome sequencing, mutagenesis, and protocol development with a primary focus on Salmonella enterica. His work includes the creation and maintenance of barcoded mutant libraries, template preparation and sequencing of complex mutant libraries after exposure to specific growth conditions, including plant surfaces, animal infections, and tumor environments, and primary analysis of Illumina sequencing data using custom R and Perl scripts. He is also involved in research exploring the effects of botanicals and nature therapy on human lifespan and health.
Dr. Porwollik has contributed to the genomic characterization of Salmonella and related bacteria throughout his career. He was a co-author on the complete genome sequence of Salmonella enterica serovar Typhimurium LT2 published in Nature in 2001, and on the complete genome sequence of Bacillus subtilis published in Nature in 1997. His research has encompassed evolutionary genomics, microarray-based typing, and the identification of genes required for bacterial survival under diverse conditions. He also served as sole editor of a compendium on the current state of molecular biology and genetic research in Salmonella for Caister Academic Press in 2011.
Dr. Porwollik received a Ph.D. in Molecular Biology from Massey University in New Zealand. Prior to his current position at UC Irvine, he held research positions at the Vaccine Research Institute of San Diego and the Sidney Kimmel Cancer Center in San Diego, where he coordinated array-based Salmonella research collaborations and managed genome core personnel. He has authored or co-authored over 120 peer-reviewed publications and has been key personnel on multiple NIH grants.
Return to topEducation
- Ph.D. in Molecular Biology, Massey University, 1999
- German Diploma (equivalent to MSc) in Biochemistry, Humboldt University, 1995
Areas of Expertise
- Bacterial Genomics and Evolution
- Herbal Supplement Quality Assessment
- High-Throughput Mutant Library Screening
- Transposon Insertion Sequencing Analysis
- Plant-Pathogen Colonization Mechanisms
- Oxidative Stress Response Pathways
- Nature Therapy Effects
Recent Publications
- Esteban-Cuesta I, Führer L, Porwollik S, Chu W, Fiddaman SR, Sah I, McClelland M, Guldimann C, “Genomic factors contributing to the resilience of Salmonella enterica on ready-to-eat muskmelon” (opens in new tab), Food Microbiology, vol. 134, 2026.
- Fuhrer L., Porwollik S., Chu W., Hohenester V., Sah I., McClelland M., Guldimann C., Esteban-Cuesta I., “A screen of Salmonella enterica mutants interacting with fresh onions and alfalfa sprouts” (opens in new tab), International Journal of Food Microbiology, vol. 453, 2026.
- Porwollik S., Jafari M., “The quality and safety of Rhodiola rosea supplements on the U.S. market: An analysis of biomarkers, heavy metals, and pesticide residues” (opens in new tab), Plos One, vol. 21, 2026.
- Margolis A., Liu L., Kim J.-S., Porwollik S., McClelland M., Vazquez-Torres A., “Amino acid decarboxylation preserves Salmonella fitness during phagocyte-derived oxidative stress” (opens in new tab), Mbio, vol. 17, 2026.
- Pickard JM, Porwollik S, Caballero-Flores G, Caruso R, Fukuda S, Soga T, Inohara N, McClelland M, Núñez G, “Dietary amino acids regulate Salmonella colonization via microbiota-dependent mechanisms in the mouse gut” (opens in new tab), Nature Communications, vol. 16, no. 1, pp. 4225, 2025.
- Allgood SC, Ewing CA, Chu W, Porwollik S, McClelland M, Detweiler CS, “Mutations in genes with a role in cell envelope biosynthesis render Gram-negative bacteria highly susceptible to the anti-infective small molecule D66” (opens in new tab), Microorganisms, vol. 13, no. 7, pp. 1521, 2025.
- Shahverdian A, Torabzadeh S, Watts D, Porwollik S, Padilla M, Lee J-S, Perez G, Jafari M, “Comparison of mineral levels in blood and hair samples of healthy adults: Evaluating the clinical utility of hair mineral analysis” (opens in new tab), Biological Trace Element Research, vol. 204, pp. 1915-1927, 2025.
- Jacob C, Student J, Bridges DF, Chu W, Porwollik S, McClelland M, Melotto M, “Intraspecies competition among Salmonella enterica isolates in the lettuce leaf apoplast” (opens in new tab), Frontiers in Plant Science, vol. 15, pp. 1302047, 2024.
- Porwollik S, Chu W, Desai PT, McClelland M, “A genome-wide collection of barcoded single-gene deletion mutants in Salmonella enterica serovar Typhimurium” (opens in new tab), PLoS One, vol. 19, no. 3, pp. e0298419, 2024.
- Maurer JJ, Cheng Y, Pedroso A, Thompson KK, Akter S, Kwan T, Morota G, Kinstler S, Porwollik S, McClelland M, Escalante-Semerena JC, Lee MD, “Peeling back the many layers of competitive exclusion” (opens in new tab), Frontiers in Microbiology, vol. 15, pp. 1342887, 2024.
- Kurasz JE, Crawford MC, Porwollik S, Gregory O, Tadlock KR, Balding EC, Weinert EE, McClelland M, Karls AC, “Strain-specific Gifsy-1 prophage genes are determinants for expression of the RNA repair operon during the SOS response in Salmonella enterica serovar Typhimurium” (opens in new tab), Journal of Bacteriology, vol. 205, no. 1, pp. e0026222, 2023.
- Margolis A, Liu L, Porwollik S, Till JKA, Chu W, McClelland M, Vázquez-Torres A, “Arginine metabolism powers Salmonella resistance to oxidative stress” (opens in new tab), Infection and Immunity, vol. 91, no. 6, pp. e0012023, 2023.
- Esteves NC, Porwollik S, McClelland M, Scharf BE, “The multi-drug efflux system AcrABZ-TolC is essential for infection of Salmonella Typhimurium by the flagellum-dependent bacteriophage Chi” (opens in new tab), Journal of Virology, vol. 95, no. 11, pp. e00394-21, 2021.
- Edson JA, Chu W, Porwollik S, Tran K, Iribe N, McClelland M, Kwon YJ, “Eradication of intracellular Salmonella Typhimurium by polyplexes of acid-transforming chitosan and fragment DNA” (opens in new tab), Macromolecular Bioscience, vol. 21, no. 7, pp. e2000408, 2021.
Most Cited Publications
- F. Kunst, S. Porwollik, A. Danchin, “The complete genome sequence of the Gram-positive bacterium Bacillus subtilis” (opens in new tab), Nature, vol. 390, no. 6657, pp. 249-256, 1997.
- Navarre, W.W., Porwollik, S., Wang Y., McClelland, M., Rosen, H., Libby, S.J., Fang, F.C., “The H-NS Protein Selectively Silences Foreign DNA with Low GC Content in Salmonella Typhimurium” (opens in new tab), Science, vol. 313, no. 5784, pp. 236-8, 2006.
- Porwollik, S., Wong, R., McClelland, M., “Evolutionary genomics of Salmonella: Gene acquisitions revealed by microarray analysis” (opens in new tab), Proceedings of the National Academy of Sciences of the United States of America, vol. 99, no. 13, pp. 8956-61, 2002.
- Porwollik, S., Boyd, E.F., Choy, C., Cheng, P., Florea, L., Proctor, E., McClelland, M., “Characterization of Salmonella enterica subspecies I genovars by use of microarrays” (opens in new tab), Journal of Bacteriology, vol. 186, no. 17, pp. 5883-98, 2004.
- Suez J, Porwollik S, Dagan A, Schorr YI, Desai PT, Agmon V, McClelland M, Rahav G, Gal-Mor O, “Virulence Gene Profiling and Pathogenicity Characterization of Non-Typhoidal Salmonella Accounted for Invasive Disease in Humans” (opens in new tab), PloS One, vol. 8, no. 3, pp. e58449, 2013.
- Porwollik S, Santiviago CA, Cheng P, Long F, Desai P, Fredlund J, Srikumar S, Silva CA, Chu W, Chen X, Canals R, Reynolds MM, Bogomolnaya L, Shields C, Cui P, Guo J, Zheng Y, Endicott-Yazdani T, Yang HJ, Maple A, et al., “Defined single-gene and multi-gene deletion mutant collections in Salmonella enterica sv Typhimurium” (opens in new tab), PLoS One, vol. 9, no. 7, pp. e99820, 2014.
- Wang, Q., Suzuki, A., Mariconda, S., Porwollik, S., Harshey, R.M., “Sensing wetness: a new role for the bacterial flagellum” (opens in new tab), EMBO Journal, vol. 24, no. 11, pp. 2034-42, 2005.
- Faucher, S.P., Porwollik, S., Dozois, C.M., McClelland, M., Daigle, F., “Transcriptome of Salmonella enterica serovar Typhi within macrophages revealed through the selective capture of transcribed sequences” (opens in new tab), Proceedings of the National Academy of Sciences of the United States of America, vol. 103, no. 6, pp. 1906-11, 2006.
- Desai PT, Porwollik S, Long F, Cheng P, Wollam A, Clifton S, Weinstock G, McClelland M, “Evolutionary Genomics of Salmonella enterica subspecies” (opens in new tab), MBio, vol. 4, no. 2, pp. e00198-13, 2013.
- Yoon, H., Porwollik, S., McClelland, M., Heffron, F., “Coordinated regulation of virulence during systemic infection of Salmonella enterica serovar Typhimurium” (opens in new tab), PLoS Pathogens, vol. 5, no. 2, pp. e1000306, 2009.
Contact Information
Email: sporwoll@uci.edu
Phone: (949) 824-2583
Address: Med Surge I, Room 132
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Last updated on 6/25/2026.