Jeri Barak

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Phone: 608-263-2097

790 Russell Labs
1630 Linden Dr
Madison, WI 53706

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  • BS 1993, San Jose State University, San Jose, CA; Major: Marine Biology, English, Minor: Chemistry
  • PhD 2000, University of California-Davis, Davis, CA; Department of Plant Pathology


Plant pathogens influence human pathogen growth on plants.

Unlike plant pathogens, S. enterica and E. coli grow poorly in the phyllosphere (on plant leaves), because unlike plant pathogens, they cannot liberate nutrients from plant cells. Nonetheless, many food-borne illness outbreaks have been caused by eating raw leaves and fruits. We found that if a plant pathogen (such as the tomato bacterial spot pathogen Xanthomonas perforans, Xanthomonas euvesicatoria, or Xanthomonas gardneri) is present on leaves, S. enterica grows to human infectious doses even under conditions where it cannot do so alone. This work suggests that plant disease in the field may be a risk factor for food-borne illness from consumption of raw produce. Future research will investigate how plant infection benefits Salmonella.

Soft rots of many fruits and vegetables, caused by Pectobacterium carotovorum, was singled out as a factor influencing human enteric pathogen contamination of raw produce. We discovered that under modified atmosphere packaging (such as bagged salads), the presence of S. enterica reduced Pectobacterium carotovorum populations and virulence by moderating local environmental pH elevation by Pectobacterium carotovorum. In contrast, E. coli O157:H7 failed to alter the leaf environment or suppress plant disease as S. enterica did. Whereas soft-rotted produce can alert consumers to the possibility of human pathogens, healthy-looking produce may entice consumption of contaminated vegetables. S. enterica inhibition of soft rot disease progress may conceal a rapidly growing human pathogen population. We plan to examine metabolic and nutritional differences between closely related plant-associated enteric human pathogens (S. enterica, E. coli) and plant pathogen (Pectobacterium carotovorum) to understand how enterics with different life styles avoid competition and what metabolic strategies lead to the success of symbiotic bacteria that inhabit multiple, discrete plant niches.

Phytophagous insects interact with Salmonella enterica in agricultural environments.

S. enterica phytophagous hemipterans interactions

We have found that phytophagous (plant eating) insects can become contaminated upon contact with S. enterica surface-contaminated plants. S. enterica can adhere to various structures of the exoskeleton and mouthparts of the insects, but can also be internalized. Internalized bacterial can be excreted in droplets of honeydew that are released onto leaves. S. enterica distribution on the leaf surface is altered by insect feeding, excretion and movement (dashed line) behavior. Both mechanical contaminated insects and insects with internalized S. enterica can increase the risk of dispersal of the pathogen within or among plants.

This project was highlighted in the Fall 2014 Issue of Grow.

Dissecting Salmonella enterica and E. coli plant colonization, one step at a time.

My research group investigates the biology of S. enterica and Shiga-toxin producing E. coli (STEC) in association with plants. Although enteric human pathogens are usually studied in the context of their animal hosts, a significant portion of their life cycle occurs on plants. We focus on S. enterica because it is most likely to be transmitted to humans on contaminated raw produce (not poultry, as many assume), and because the agricultural crops that transmit salmonellosis are more diverse than those that transmit STEC. We focus on the discovery of mechanisms that facilitate plant colonization, including attachment, growth, and persistence and interactions with other plant-associated organisms. To gain evolutionary insight, we compare and contrast our findings with other plant-associated enterics. S. enterica and STECs are both enteric plant symbionts, while Pectobacterium carotovorum subsp. carotovorum and Dickyea dadantii are enteric plant pathogens.

Courses Taught

Courses Taught by Dr. Jeri Barak

PP311 Global Food Security

PP 375,  Food Security Deep Dive, is the anchor course for the Global Food Security First-Year Interest Group and meets with PP 311. This learning community has a history of being dynamic and each year, a close knit group that often develops that lasts throughout their time at UW-Madison.

First Year Interest Group


GFS FIG students bring their passion for food security in a myriad of ways, even after their first semester at UW-Madison. In 2013, GFS FIG students brought the documentary, Give a Damn? to UW-Madison. A feature length documentary about three friends, two idealistic activists and one skeptic, attempting to live in poverty, on $1.25 a day, across 3 continents. The adventure takes a devastating turn when two of them survive a deadly plane crash in Africa, and all three must fight to finish what they started.



Cheer Banner

Food insecurity is a local issue too, including UW-Madison. Food assistance is available in several forms on campus: Food Recovery Network, Slow Food UW featuring 2014 GFS FIG student volunteer, Harvest Handouts, and The Open Seat.

In 2019, the Student Organic Farm UW Organic Collaborative was born, thanks to the hard work of GFS FIG student, Sofia Weinstein, the word is spreading. 2021-2022 Sofia took charge of the collaborative’s media presence and merged her skills developed as a double major, Plant Pathology and Agriculture & Applied Economics, to demonstrate the feasibility of a food truck as a buyer for the Student Organic Farm which will contribute to UW-Madison’s sustainability and local food system. Thus, the UW Electric Food Truck will launch April, 2022.

A GFS FIG student (2016) was motivated to secure a Wisconsin Idea Fellowship from UW–Madison’s Morgridge Center for Public Service to fund her Patio Tomato Project with the objective to bring container gardening to food insecure folks in Madison, focusing on kids.

Child and Tomato



Victoria L. Harrod, Russell Groves, Ellie Guillemette, Jeri Barak. 2022. Give and Take: Salmonella enterica alters Macrosteles auadrilineatus feeding behaviors resulting in altered S. enterica populations and distribution on leaves. Sci Rep 12, 8544 Link.

Kimberly N. Cowles, Anna K. Block, Jeri D. Barak. 2022. Xanthomonas hortorum pv. gardneri TAL effector AvrHah1 is necessary and sufficient for increased persistence of Salmonella enterica on tomato leaves. Sci Rep 12, 7313. Link

Harrod, V.L., Groves, R.L., Maurice, M.A., and Barak J.D. 2021. Frankliniella occidentalis facilitate Salmonella enterica survival in the phyllosphere. PLoS ONE 16(2): e0247325. Link.

Nicola Holden, László Kredics, Jeri Barak. 2020. Editorial for the thematic issue, “Human Pathogens in the Environment.” FEMS Microbiology Letters Link

Cowles, K.N, Groves, R.L., and Barak, J.D. 2018. Leafhopper-induced activation of the jasmonic acid response benefits Salmonella enterica in a flagellum-dependent manner. Front. Microbiol. doi: 10.3389/fmicb.2018.01987 Link

Grace Kwan, Brett Plagenz, Kimberly Cowles, Tippapha Pisithkul, Daniel Amador-Noguez, and Jeri D. Barak. 2018. Few Differences in metabolic network use found between Salmonella enterica colonization of plants and typhoidal mice. Front. Microbiol. doi: 10.3389/fmicb.2018.00695 Link

Jeri D. Barak, Taca Vancheva, Pierre Lefeuvre, Jeffrey B. Jones, Sujan Timilsina, Gerald V. Minisavage, Gary E. Vallad, and Ralf Koebnik. 2016. Whole-genome sequences of Xanthomonas euvesicatoria strains clarify taxonomy and reveal a stepwise erosion of type 3 effectors. Front. Plant  Sci. doi: 10.3389/fpls.2016.01805 Link

Cowles KN, Willis DK, Engel TN, Jones JB, and Barak J.D. 2016. Diguanylate cyclases, AdrA and STM1987, regulate Salmonella enterica exopolysaccharide production during plant colonization in an environment-dependent manner. Appl Environ Microbiol. 82(4): 1237-1248. Link

Potnis, N., Colee, J., Jones, J.B., and Barak, J.D. 2015. Plant pathogen induced watersoaking promotes Salmonella enterica growth on tomato leaves. Appl. Environ. Microbiol. 81(23): 8126-34. Link

Dundore-Arias, J.P., Groves, R.L. and Barak, J.D. 2015. Influence of prgH on the persistence of ingested Salmonella enterica in the leafhopper Macrosteles quadrilineatus. Appl. Environ. Microbiol. 81 (18): 6345-6354. Link

Schwartz AR, Potnis N, Timilsina S, Wilson M, Patané J, Martins J Jr., Minsavage GV, Dahlbeck D, Akhunova A, Almeida N, Vallad GE, Barak JD, White FF, Miller SA, Ritchie D, Goss E, Bart RS, Setubal JC, Jones JB and Staskawicz BJ 2015. Phylogenomics of Xanthomonas field strains infecting pepper and tomato reveals diversity in effector repertoires and identifies determinants of host specificity. Front. Microbiol6:535. Link

Potnis, N., Timilsina, S., Strayer, A., Shantharaj, D., Barak, J.D., Paret, M.L., Vallad, G.E., and Jones, J.B. 2015. Bacterial spot of tomato and pepper: diverse Xanthomonas species with a wide variety of virulence factors posing a worldwide challenge. Mol. Plant Pathol. Link

Kwan, G., Pisithkul, T., Amador-Noguez, D., and Barak, J.D. 2015. De novo amino acid biosynthesis contributes to Salmonella enterica growth in alfalfa seedling exudates.  Appl. Environ. Microbiol. 81(3): 861-73  Link

Soto-Arias, J.P., Groves, R.L., and Barak, J.D. 2014. Transmission and retention of Salmonella enterica by phytophagous hemipteran insects.  Appl. Environ. Microbiol. 80(17): 5447-5456. Link

Potnis, N., Soto-Arias, J.P., Cowles, K., van Bruggen, A.H.C., Jones, J.B., and Barak, J.D. 2014. Xanthomonas perforans colonization influences Salmonella enterica in the tomato phyllosphere. Appl. Environ. Microbiol80(10): 3173-3180. Link

Pollard, S., Barak, J.D., Royer, R., Grabau, E., Reiter, M., Gu, G., and Rideout, S. 2014. Potential interactions between Salmonella enterica and Ralstonia solanacearum in tomato plants. J. Food Prot 77(2): 320-324. Link

Soto-Arias, J.P., Groves, R.L., and Barak, J.D. 2013. Benefits of piercing and sucking, enhanced persistence of Salmonella enterica on plants due to phyophagous hemipterans. PLoSONE 8(10): e79404. Link

Kwan, G., Charkowski, A.O., and Barak, J.D. 2013. Salmonella enterica moderates Pectobacterium carotovorum populations and virulence on lettuce. mBio. 4:e00557-12. Link

Jeri D. Barak and Brenda Schroeder. 2012. Interrelationships of Food Safety and Plant Pathology: The Life Cycle of Human Pathogens. Ann Rev Phytopathol 50: 241-266. Link

Hao, L., H. Andrews-Polymenis, M. McClelland, D. K. Willis, J. D. Barak. 2012. Salmonella enterica requires siderophore biosynthesis to colonize plants. Appl. Environ. Microbiol. 13:4561-4570. Link

Barak, J. D. 2012. The biggest food safety threat from the tiniest of crops. Cereal Foods World. 57(3): 123-124. Link

Courtney E. Jahn, Dija A. Selimi, Jeri D. Barak, and Amy O. Charkowski. 2011. The Dickeya dadantii biofilm matrix consists of cellulose nanofibers and is an emergent property dependent upon the type III secretion system and the cellulose synthesis operon. Microbiol. 157: 2733-2744. Link

Jeri D. Barak, Kramer, L., and Hao, L. 2011. Plant cultivar alters Salmonella enterica colonization of tomato and Type 1 trichomes are preferential colonization sites. Appl. Environ. Microbiol. 77(2): 498-504. Link

Jeri D. Barak, L. Gorski, Anita S. Liang, and Kohn-Eun Narm. 2009. Previously uncharacterized Salmonella enterica genes required for swarming play a role in plant colonization. Microbiol. 155: 3701-3709. Link

Teplitski, M., Barak, J., and Schneider, K. R. 2009. Human enteric pathogens in produce: un-answered ecological questions with direct implications for food safety. Curr. Opin. Biotech. 20(2): 166-71. Link

Csordas, A.T., M.J. Delwiche and J.D. Barak. 2008. Nucleic acid sensor and fluid handling for detection of bacterial pathogens. Sensors and Actuators B: Chemical. 134: 1-8. Link

Csordas, A.T., M.J. Delwiche and J.D. Barak. 2008. Automatic detection of Salmonella enterica in sprout irrigation water using a nucleic acid sensor. Sensors and Actuators B: Chemical. 134: 9-17. Link

Barak, J.D., A. S. Liang and K. Narm. 2008. Differential attachment and subsequent contamination of agricultural crops by Salmonella enterica. Appl. Environ. Microbiol. 74(17): 5568-5570. Link

Jeri D. Barak and Anita S. Liang. 2008. Role of soil, crop debris, and a plant pathogen in Salmonella enterica contamination of tomato plants. PLoS ONE 3(2): e1657. Link

Lermo, A., E. Zacco, J. Barak, M. Delwiche, S. Campoy, J. Barbe, S. Alegret and M.I. Pividor. 2008. Towards q-PCR of pathogenic bacteria with improved electrochemical double-tagged genosensing detection. Biosensors Bioelectronics. 23(12):1805-1811. Link

Mohle-Boetani, J., J. Farrar, P. Bradley, J. Barak, M. Miller, R. Mandrel, P. Mead, W. Keen, K. Cummings, S. Abbott and S. Benson Werner. 2008. Salmonella infections associated with mung bean sprouts: epidemiology and environmental investigations. Epidemiol. Inf. doi: 10.1017/S0950268808000411. Link

Barak, J.D., C.E. Jahn, D.L. Gibson and A.O. Charkowski. 2007. The role of cellulose, lipopolysaccharide O-polysaccharide, and O-antigen capsule in the colonization of plants by Salmonella enterica. Mol. Plant-Microbe Interact. 20:1083-1091. *Faculty of 1,000 recommended. Link

Barak, J., L. Gorski, P. Naraghi-Arani and A.O. Charkowski. 2005. Salmonella enterica virulence genes are required for bacterial attachment to plant tissue. Appl. Environ. Microbiol. 71:5685-5691. Link

Yap, M.-N, C.-H. Yang, J.D. Barak, C.E. Jahn and A.O. Charkowski. 2005. The Erwinia chrysanthemi type III secretion system is required for multicellular behavior. J. Bacteriol. 187:639-648. Link

Barak, J.D., K. Sananikone and M.J. Delwiche. 2005. Comparison of primers for detection of pathogenic E. coli using real-time PCR. Lett. Appl. Microbiol. 41:112-118. Link

Yap, M. N., Barak, J. D., and Charkowski, A. O. 2004. Genomic diversity of Erwinia carotovora subsp. carotovora and its correlation with virulence. Appl. Environ. Microbiol. 70: 3013-3023. Link

Csordas, A. T., Barak, J. D., and Delwiche, M. J. 2004. Comparison of primers for the detection of Salmonella enterica serovars using real-time PCR. Lett. Appl. Microbiol. 39: 187-193. Link

Barak, J. D., Chue, B., and Mills, D. 2003. Recovery of surface bacteria from and surface sanitization of cantaloupes. J. Food Prot. 66: 1805-1810. Link

Barak, J. D. and Gilbertson, R. L. 2003. Genetic diversity of Xanthomonas campestris pv. vitians, the causal agent of bacterial leafspot of lettuce. Phytopathology 93: 596-603. Link

Barak, J. D., Whitehand, L. C., and Charkowski, A. O. 2002. Differences in attachment of Salmonella enterica serovars and Escherichia coli O157:H7 to alfalfa sprouts. Appl. Environ. Microbiol. 68: 4758-4763. Link

Charkowski, A. O., Barak, J. D., Sarreal, C. Z., and Mandrell, R. E. 2002. Growth and colonization of Salmonella enterica and Escherichia coli O157:H7 on alfalfa sprouts and the effects of sprouting temperature, inoculum dose, and frequency of irrigation on bacterial levels. Appl. Environ. Microbiol. 68: 3114-3120. Link

Barak, J. D., Koike, S. T, and Gilbertson, R. L. 2002. Long-distance movement of Xanthomonas campestris pv. vitians in the stems of lettuce plants. Plant Pathology 51: 506-512. Link

Barak, J. D., Koike, S. T, and Gilbertson, R. L. 2001. Role of crop debris and weeds in the epidemiology of bacterial leaf spot of lettuce, caused by Xanthomonas campestris pv. vitians, in California. Plant Disease 85: 169-178. Link

Koike, S. T. *, Barak, J. D. *, Henderson, D. M., and Gilbertson, R. L. 1999. Bacterial blight of leek: a new disease in California caused by Pseudomonas syringae. Plant Disease 83: 165-170. *co-first authors. Link

Tomasky, G; Barak, J; Valiela, I; Behr, P; Soucy, L; Foreman, K. 1999. Nutrient limitation of phytoplankton growth in Waquoit Bay, Massachusetts, USA: a nutrient enrichment study. Aquat. Ecol. 33(2):147-155. Link