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Joseph J. Gillespie, PhD

Academic Title:

Assistant Professor

Primary Appointment:

Microbiology and Immunology


HSFII, 431

Phone (Primary):


Phone (Secondary):




Education and Training

Widener University, BS, Biology, 1998

University of Delaware, MS, Entomology/Applied Ecology, 2001

Texas A&M University, PhD, Entomology, 2005

Virginia Bioinformatics Institute (Virginia Tech), Post-Doctoral Fellow, 2006-2008

Virginia Bioinformatics Institute (Virginia Tech), Senior Research Associate, 2009-2013


Dr. Gillespie is an evolutionary biologist with broad interests in organismal and molecular evolution.  The major focus of his current research is deciphering the mechanisms by which obligate intracellular species of Rickettsiales (Alphaproteobacteria) invade, survive and replicate within eukaryotic cells.

In research funded by the National Institutes of Health, Dr. Gillespie utilizes phylogenetics, comparative genomics and bioinformatics to guide experimental studies on various pathogenic species of Rickettsia and their associated arthropod vectors.  His early research resulted in the reclassification of Rickettsia species and the identification of many lineage-specific pathogenicity factors.  Through years of intense scrutinization of dozens of diverse rickettsial genomes, Dr. Gillespie and colleagues have described a large, dynamic mobilome for Rickettsia species, resulting in the identification of integrative conjugative elements as the vehicles for seeding Rickettsia genomes with many of the factors underlying obligate intracellular biology and pathogenesis.  Via an iterative process of genome sequencing, phylogenomics, bioinformatics, and classical molecular biology and microbiology, Dr. Gillespie continues to lead and assist research projects on the characterization of rickettsial gene and protein function.

A particular focal area of Dr. Gillespie’s research is the Rickettsia secretome, which includes the secretion systems and their cognate substrates, many of which directly engage arthropod and vertebrate molecules throughout the rickettsial infection process.  Dr. Gillespie led a study that identified across all genera of Rickettsiales the composition of an enigmatic type IV secretion system (T4SS), termed rvh (Rickettsiales vir homolog).  Several collaborative efforts have begun elucidating the odd architecture of the rvh T4SS, as well as the protein substrates it translocates into host cells during infection.  Dr. Gillespie is currently a co-Principal Investigator on a National Institutes of Health award to decipher the structure and function of the rvh T4SS.

Research/Clinical Keywords

Evolutionary Biology, Rickettsiology, Rickettsia, Microbiology, Molecular Biology, Genetics, Bioinformatics, Phylogenetics, Phylogenomics, Metabolomics, Structural Biology, Type IV Secretion Systems, Secretome, Pathogenesis, Genome Sequencing, Arthropods, Ticks, Fleas, Body Lice, Epidemic Typhus, Murine Typhus, Rocky Mountain Spotted Fever, Transitional Group rickettsiae

Highlighted Publications

Gillespie, J.J., Beier, M.S., Rahman, M.S., Ammerman, N.C., Purkayastha, A., Shallom, J.M., Sobral, B.S., Azad, A.F.  (2007)  Plasmids and rickettsial evolution: insight from Rickettsia felis. PLoS ONE 2: e266.

Gillespie, J.J., Joardar, V., Williams, K.P., Driscoll, T., Hostetler, J.B., Nordberg, E.K., Shukla, M., Walenz, B., Hill, C.A., Nene, V.M., Azad, A.F., Sobral, B.W. & Caler, E.  (2012)  A Rickettsia genome overrun by mobile genetic elements provides insight into the acquisition of genes characteristic of an obligate intracellular lifestyleJournal of Bacteriology 194: 376-394.

Gillespie, J.J., Kaur, S.J., Rahman, M.S., Rennoll-Bankert, K., Sears, K.T., Beier-Sexton, M. & Azad, A.F.  (2015)  Secretome of obligate intracellular RickettsiaFEMS Microbiology Reviews 39: 47-80.

Rennoll-Bankert, K., Rahman, M.S., Gillespie, J.J., Guillotte, M.L., Kaur, S.J., Lehman, S.S., Beier-Sexton, M., Azad, A.F.  (2015)  Which Way In? The RalF Arf-GEF Orchestrates Rickettsia Host Cell InvasionPLoS Pathogens 11: e1005115.

Gillespie, J.J., Phan IQ, Scheib H, Subramanian, S., Edwards, T.E., Lehman, S.S., Piitulainen, H., Rahman, M.S., Rennoll-Bankert, K., Staker, B.L., Taira, S., Stacy, R., Myler, P.J., Azad, A.F., & Pulliainen, A.T.  (2015)  Structural Insight into How Bacteria Prevent Interference between Multiple Divergent Type IV Secretion SystemsMBio 6: e01867-15.

Gillespie, J.J., Phan, I.Q., Driscoll, T., Guillotte, M.L., Lehman, S.S., Rennoll-Bankert, K.E., Subramanian, S., Beier-Sexton, M., Myler, P.J., Rahman, M.S., Azad, A.F.  (2016)  The Rickettsia type IV secretion system: unrealized complexity mired by gene family expansionPathogens and Disease 74: ftw058 [Editor’s Choice].

Driscoll, T.P., Verhoevea, V.I., Guillotte, M.L., Lehman, S.S., Rennoll, S.A., Beier, M.S., Rahman, M.S., Azad, A.F., Gillespie, J.J.  (2017)  Wholly Rickettsia! Reconstructed Metabolic Profile of the Quintessential Bacterial Parasite of Eukaryotic CellsMBio 8: e00859-17.


Additional Publication Citations

Dr. Gillespie's publications and related information can be found on the following web sites:


Google Scholar




Grants and Contracts

R21 AI126108
Gillespie (PI), Rahman (PI)
5/23/16 - 4/30/18
Characterizing gene family expansion in an atypical bacterial secretion system