Raul Barletta

Raul Barletta, professor, UNL School of Veterinary Medicine and Biomedical Sciences

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Faculty Profile


Dr. Raul G. Barletta is a microbiologist with over 30 years of experience as an independent researcher with pathogenic microorganisms. His areas of interest are in diseases that are of chronic nature and difficult to diagnose: Tuberculosis (TB), Bovine Tuberculosis and Johne's disease (JD). There are no effective vaccines against these devastating diseases caused by mycobacterial pathogens. In addition, antibiotic resistance, especially in TB, has made it difficult to prevent and treat these conditions. Dr. Barletta hopes his research will lead to vaccines, new drugs and research tools to provide more accurate and faster tests to identify these pathogens. His approaches are based on the understanding of mycobacterial physiology by the use of molecular genetics and redox biology. He also works on the development of novel diagnosis that could be adapted to all mycobacterial diseases, whether they infect humans or animals.


  • Post-Doctoral work in Microbial Genetics, Albert Einstein College of Medicine, New York, 1991
  • Ph.D. in Microbiology, University of Alabama, Birmingham, 1987
  • M.S. in Biochemistry, Universidad Nacional de La Plata (Argentina), 1976
  • B.S. in Chemistry, Universidad Nacional de La Plata (Argentina), 1976

Professional Responsibilities and Activities

  • Internal collaborations:

    1. University of Nebraska-Lincoln (UNL) School of Veterinary Medicine and Biomedical Sciences in pathogenic mycobacterial diagnosis and histopathology (Drs. David Steffen and Christina Topliff), BCG trained immunity (Dr. Jay Reddy), TB-HIV interactions (Dr. Shi-Hua Xiang) and protein purification (Dr. Asit Pattnaik).

    2. UNL School of Biological Sciences in TB-HIV interactions and drug delivery models (Drs. Qingsheng Li and Subhra Mandal).

    3. UNL Department of Chemistry in Nuclear Magnetic Resonance metabolomics (Dr. Robert Powers) and chemical synthesis (Drs. Patrick H. Dussault and James M. Takacs).

    4. University of Nebraska Medical Center on developing gallium derivatives to treat mycobacterial diseases (Drs. Bradley Britigan and Prabagaran Narayanasamy).
  • External collaborations:

    1. National Animal Disease Center (Ames, Iowa) to develop live-attenuated vaccines that can differentiate vaccinated from infected animals (DIVA) against JD (Drs. John P. Bannantine and Judith R. Stabel).

    2. University of Georgia (Athens, Georgia) to develop novel animal models to study transmission and pathogenesis of mycobacterial diseases (Drs. Frederick D. Quinn and Tuhina Gupta).

    3. Universidad Nacional Autónoma de México (Mexico City, Mexico) to diagnose Bovine Tuberculosis and JD (José Ángel Gutiérrez Pabello).

    4. Michigan State University (East Lansing, Michigan) to determine the role of iron metabolism in JD (Dr. Srinand Sreevatsan).
  • Editorial boards:

    Frontiers in Veterinary Science (Review Editor; 2015 - present)

    Frontiers in Cellular and Infection Microbiology (Review Editor 2016 - present)

    Infection and Immunity (2016 - 2024)


View complete list of published work

Bannantine, J.P., D.K. Zinniel and R.G. Barletta. 2019. Transposon mutagenesis in Mycobacterium avium subspecies paratuberculosis. Methods Mol Biol 2016:117-125. doi: 10.1007/978-1-4939-9570-7_11.

Rathnaiah, G., D.K. Zinniel, J.P. Bannantine, J.R. Stabel, Y.T. Gröhn, M.T. Collins, and R.G. Barletta*. 2017. Pathogenesis, Molecular Genetics and Genomics of Mycobacterium avium subsp. paratuberculosis, the Etiologic Agent of Johne’s Disease. Frontiers in Veterinary Science, 4 (Article 187):1-13. doi: 10.3389/fvets.2017.00187.

Halouska, S., R.J. Fenton, D.K. Zinniel, D.D. Marshall, R.G. Barletta*, R. Powers. 2014. Metabolomics analysis identifies D-Alanine-D-alanine ligase as the primary lethal target of D-cycloserine in mycobacteria. Journal of Proteome Research 13:1065-1076. doi: 10.1021/pr4010579.

Rathnaiah, G., Lamont, E.A., Harris, N. Beth, Fenton, R.J., Zinniel, D.K., Liu, X., Sotos, J., Feng, Z., Livneh-Kol, A., Shpigel, N.Y., Czuprynski, C.J., Sreevatsan, S., Barletta*, R.G. 2014. Generation and screening of a comprehensive Mycobacterium avium subsp. paratuberculosis transposon mutant bank. Front Cell Infect Microbiol 4 (Article 144):1-17. doi: 10.3389/fcimb.2014.00144.

Feng, Z., and R.G. Barletta*. 2003. Roles of Mycobacterium smegmatis D-alanine-Dalanine ligase and D-alanine racemase in the mechanisms of action and resistance to the peptidoglycan inhibitor D-cycloserine. Antimicrob Agents Chemother 47:283-91. doi: 10.1128/aac.47.1.283-291.2003.

Chacon, O., Z. Feng, N.B. Harris, N.E. Cáceres, L.G. Adams and R.G. Barletta*. 2002. Mycobacterium smegmatis D-alanine racemase mutants are not dependent on D-alanine for growth. Antimicrob Agents Chemotherapy 46:47-54. doi: 10.1128/aac.46.2.47-54.2002.

Zinniel, D.K,, P. Lambretch, N.B. Harris, Z. Feng, D. Kuczmarski, P. Higley, C.A. Ishimaru, A. Arunakumari, R.G. Barletta* and A.K. Vidaver. 2002. Isolation and characterization of endophytic colonizing bacteria from agronomic crops and prairie plants. Applied and Environmental Microbiology 68:2198-2208. doi: 10.1128/aem.68.5.2198-2208.2002.

Harris N.B., Z. Feng, X. Liu, S.L.G. Cirillo, J.D. Cirillo and R.G. Barletta*. 1999. Development of a transposon mutagenesis system for Mycobacterium avium subsp. paratuberculosis. FEMS Microbiology Letters 175:21-6. doi: 10.1111/j.1574-6968.1999.tb13597.x.

Cáceres, N.E., N.B. Harris, J.F. Wellehan, Z. Feng, V. Kapur and R.G. Barletta*. 1997. Overexpression of the D-alanine racemase gene confers resistance to D-cycloserine in Mycobacterium smegmatis. J Bacteriol 179: 5046-55. doi: 10.1128/jb.179.16.5046-5055.1997.

Jacobs Jr., W.R., R.G. Barletta, R. Udani, J. Chan, G. Kalkut, G. Sosne, T. Kieser, G.J. Sarkis, G.F. Hatfull, and B.R. Bloom. 1993. Rapid assessment of drug susceptibilities of Mycobacterium tuberculosis by means of luciferase reporter phages. Science 260:819-22. doi: 10.1126/science.8484123.


  • Development and testing of Mycobacterium avium subsp. paratuberculosis DIVA vaccines in ruminants. R.G. Barletta, J. Bannantine and J. Stabel. United States Department of Agriculture-NIFA; $500,000; 07/01/20 - 06/30/23.
  • Mycobacterial diseases of animals (NE1201 and NE1701): development and testing of a safe and effective one-health DIVA vaccine against bovine tuberculosis and Johne’s disease. R.G. Barletta, D. Steffen and C. Topliff. $330,553; 10/01/17 - 09/30/22.
  • Trained immunity in the prevention of viral myocarditis and pancreatitis. J.R. Reddy, D. Steffen, J. Seravalli and R.G. Barletta. National Institutes of Health; $217,570; 09/01/2021 - 08/31/23.


  • Amphiphilic Cyclobutenes and Cyclobutanes. W. Sittiwong, P. Dussault, R.G. Barletta and R. Powers. U.S. Patent No. 10,538,475. Granted January 21, 2020.
  • Methods for the identification of Virulence Determinants. R.G. Barletta, N.B. Harris. U.S. Patent No. 7,740,867, Granted June 22, 2010.
  • D-alanine Racemase Mutants of Mycobacteria and Uses Therefore. R.G. Barletta, O. Chacon. U.S. Patent No. 6,929,799 B2, Granted August 16, 2005.


Research description

JD caused by Mycobacterium avium subsp. paratuberculosis (MAP) is one of the most significant problems in animal health, especially for the dairy industry. Moreover, the potential linkage with Crohn’s disease makes MAP a concern as a zoonotic and/or food-borne pathogen. We developed a novel approach to comprehensively identify MAP essential genes, and mine its genome for virulence determinants encoded by non-essential genes involved in intracellular (macrophage) survival or required for infection of calves. Mariner transposon mutagenesis coupled with new generation sequencing technologies for high-resolution phenotypic profiling (Tn-seq) and Transposon Site Hybridization (TraSH) will be applied to analyze fully random mutant banks representing genomic regions that are likely significantly underrepresented from current collections. We hypothesize that these approaches will result in mining of the MAP genome for virulence determinant discovery, independently of their constitutive or regulated expression. We are currently applying these studies to develop MAP live-attenuated vaccines with DIVA capabilities. The overall impact is the embodiment of a JD vaccine with DIVA capabilities. Achievement of this goal would be of significant importance in ameliorating the negative impact of JD on national and international trade.

Re-emergence of TB is caused by multiple drug-resistant strains and the need to develop new drug therapies and other control strategies. In this aspect, my research on anti-TB drug development and biodefense focuses on D-alanine racemase and D-alanine ligase, the presumed lethal target of D-cycloserine, an analog of D-alanine. This enzyme forms the critical dipeptide D-alanyl-D-alanine, an essential building block of peptidoglycan. Institutional grants allowed my laboratory to develop a "proof of concept" in the model system Mycobacterium smegmatis while a National Institutes of Health grant permitted us to further pursue the development of D-alanine ligase as a target for rational drug design. My laboratory analyzed the crystal structure of this drug target by completing collaborations with Dr. James Sacchettini (Department of Biochemistry and Biophysics, Texas A&M University). These research studies resulted in various publications and the granting of a US patent.

Ongoing research:

  1. DIVA grant objectives. (1) Generate attenuated unmarked in-frame deletion mutants with DIVA capabilities. New unmarked deletion mutants in MAP_1152 and MAP_1156 from MAP wild type strain K-10 will be generated. We have demonstrated that the original marked DMAP52 and DMAP56, already available in our laboratories, are attenuated in bovine macrophages. These mutants will be complemented and tested for invasion and intracellular survival in bovine macrophages. (2) Test novel antigens for DIVA capabilities. Recombinant capture antigens MAP_1152 and MAP_1156 have been shown to differentiate between seropositive and seronegative samples. Herein, we will expand the humoral immunity test to a greater number of samples from JD natural and experimentally infected animals, and develop tests of cellular immunity. (3) Assess the immunogenicity and pathogenicity of unmarked mutants and their complemented strains in calves.
  2. Expand drug target search to additional essential steps in peptidoglycan biosynthesis and D-alanine metabolism such as L-alanine dehydrogenase.
  3. Determine the essential roles of D-alanine ligase and D-alanine racemase in the physiology of Mycobacterium tuberculosis (MTB). Search for novel inhibitors of the MTB D-alanine ligase that could serve as novel anti-tuberculosis drugs.

Teaching and training program:

My teaching commitments involve pathogenic microbiology courses: I am the main instructor of Basic (VBMS424/824) and Advanced (VBMS951) Infectious Diseases, and contribute to lectures in Pathogenic Microbiology (VBMS441/841) and VMED686. These courses are an essential component to instruct both undergraduate, graduate and professional veterinary students interested in the molecular basis of infectious diseases. The Advanced course is also geared to provide elements of proposal writing to advanced graduate students. Regarding training, 3 senior personnel, 4 post-doctoral fellows, and 15 graduate students (5 PhD and 10 MS) trained under my supervision. Finally, I work with undergraduate students in the UNL UCARE program, Honors Thesis and Independent Research.


211 VBS
1880 N 42nd St
East Campus Loop and Fair Street
Lincoln, NE 68583-0905


88% Research, 10% Teaching, 2% Service

Research Areas

  • Bacteriology

Professional Society Memberships

  • American Society for Microbiology
  • Conference of Research Workers in Animal Diseases
  • National Institute of Antimicrobial Resistance Research and Education
  • Regional Research Group on Mycobacterial Diseases of Animals