Review Article | Published:

Engineering of obligate intracellular bacteria: progress, challenges and paradigms

Nature Reviews Microbiology volume 15, pages 544558 (2017) | Download Citation


It is estimated that approximately one billion people are at risk of infection with obligate intracellular bacteria, but little is known about the underlying mechanisms that govern their life cycles. The difficulty in studying Chlamydia spp., Coxiella spp., Rickettsia spp., Anaplasma spp., Ehrlichia spp. and Orientia spp. is, in part, due to their genetic intractability. Recently, genetic tools have been developed; however, optimizing the genomic manipulation of obligate intracellular bacteria remains challenging. In this Review, we describe the progress in, as well as the constraints that hinder, the systematic development of a genetic toolbox for obligate intracellular bacteria. We highlight how the use of genetically manipulated pathogens has facilitated a better understanding of microbial pathogenesis and immunity, and how the engineering of obligate intracellular bacteria could enable the discovery of novel signalling circuits in host–pathogen interactions.

Key points

  • Extracellular bacteria are free-living organisms, whereas facultative intracellular bacteria replicate either inside eukaryotic host cells or in an environmental niche.

  • Obligate intracellular bacteria, which include Chlamydia spp., Anaplasma spp., Ehrlichia spp., Rickettsia spp., Orientia spp. and Coxiella spp., replicate exclusively inside of eukaryotic host cells.

  • Genetic tools for the manipulation of obligate intracellular bacteria have historically been limited; however, there has been considerable recent progress in refining these methods. Such tools include transformation strategies, shuttle vectors, random and targeted mutagenesis through allelic exchange, and mobile group II introns.

  • Novel bacterial molecules that shed light on both microbial pathogenesis mechanisms and host cell biology have been characterized by applying genetic tools to study Chlamydia trachomatis serovar L2 and Rickettsia parkeri.

  • Vaccines against obligate intracellular bacterial infections are lacking. Refining genetic tools would enable the characterization of virulence factors and the development of vaccine candidates.

  • Key questions in bacterial pathogenesis and physiology are primed for investigation once all obligate intracellular bacteria can be genetically manipulated on a routine basis.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    Immunology taught by bacteria. J. Clin. Immunol. 30, 507–511 (2010).

  2. 2.

    , , & Deviant behavior: tick-borne pathogens and inflammasome signaling. Vet. Sci. 3, 27 (2016).

  3. 3.

    , & Expression of recombinant DNA introduced into Chlamydia trachomatis by electroporation. Can. J. Microbiol. 40, 583–591 (1994).

  4. 4.

    & Life on the outside: the rescue of Coxiella burnetii from its host cell. Annu. Rev. Microbiol. 65, 111–128 (2011). This review describes the development of an axenic medium for C. burnetii, which enabled the rapid development of genetic tools for this microorganism.

  5. 5.

    , , , & Advances in genetic manipulation of obligate intracellular bacterial pathogens. Front. Microbiol. 2, 97 (2011).

  6. 6.

    , , & Minimization of the Legionella pneumophila genome reveals chromosomal regions involved in host range expansion. Proc. Natl Acad. Sci. USA 108, 14733–14740 (2011).

  7. 7.

    Genetic manipulation of Coxiella burnetii. Adv. Exp. Med. Biol. 984, 249–271 (2012).

  8. 8.

    et al. Integrating chemical mutagenesis and whole-genome sequencing as a platform for forward and reverse genetic analysis of Chlamydia. Cell Host Microbe 17, 716–725 (2015). This article reports the generation of a large-scale chemical mutagenesis library for C. trachomatis serovar L2 and provides a systematic framework for screening mutants.

  9. 9.

    et al. The Chlamydia trachomatis inclusion membrane protein CpoS counteracts STING-mediated cellular surveillance and suicide programs. Cell Host Microbe 21, 113–121 (2017). This study describes a chlamydial effector that was discovered through chemical mutagenesis, verified through multiple genetic tools and shed light on the basic processes of eukaryotic host cell death.

  10. 10.

    et al. Rickettsia Sca4 reduces vinculin-mediated intercellular tension to promote spread. Cell 167, 670–683.e10 (2016). This article reports the mechanism of intercellular spread for R. parkeri and the first published case of complementation of a rickettsial mutant with a shuttle vector.

  11. 11.

    et al. Development of a transformation system for Chlamydia trachomatis: restoration of glycogen biosynthesis by acquisition of a plasmid shuttle vector. PLoS Pathog. 7, e1002258 (2011). This protocol establishes a robust transformation method for C. trachomatis serovar L2 that is currently used extensively by the field.

  12. 12.

    , , & Transformation of Rickettsia prowazekii to rifampin resistance. J. Bacteriol. 180, 2118–2124 (1998).

  13. 13.

    et al. Transformation of Anaplasma phagocytophilum. BMC Biotechnol. 6, 42 (2006). This study describes the generation of a Himar1 transposon mutagenesis library for A. phagocytophilum.

  14. 14.

    , , & Overcoming barriers to the transformation of the genus Ehrlichia. Ann. NY Acad. Sci. 1063, 403–410 (2005).

  15. 15.

    et al. Targeted and random mutagenesis of Ehrlichia chaffeensis for the identification of genes required for in vivo infection. PLoS Pathog. 9, e1003171 (2013).

  16. 16.

    , , , & Dendrimer-enabled modulation of gene expression in Chlamydia trachomatis. Mol. Pharm. 9, 413–421 (2012).

  17. 17.

    et al. Dendrimer-enabled DNA delivery and transformation of Chlamydia pneumoniae. Nanomedicine 9, 996–1008 (2013).

  18. 18.

    et al. Dendrimer-enabled transformation of Anaplasma phagocytophilum. Microbes Infect. 17, 817–822 (2015).

  19. 19.

    , , & Plasmid diversity in Chlamydia. Microbiology 143, 1847–1854 (1997).

  20. 20.

    et al. Co-evolution of genomes and plasmids within Chlamydia trachomatis and the emergence in Sweden of a new variant strain. BMC Genomics 10, 239 (2009).

  21. 21.

    & C. trachomatis cloning vector and the generation of C. trachomatis strains expressing fluorescent proteins under the control of a C. trachomatis promoter. PLoS ONE 8, e57090 (2013).

  22. 22.

    & Expression and targeting of secreted proteins from Chlamydia trachomatis. J. Bacteriol. 196, 1325–1334 (2014).

  23. 23.

    , , & Conditional gene expression in Chlamydia trachomatis using the Tet system. PLoS ONE 8, e76743 (2013).

  24. 24.

    & Emancipating Chlamydia: advances in the genetic manipulation of a recalcitrant intracellular pathogen. Microbiol. Mol. Biol. Rev. 80, 411–427 (2016).

  25. 25.

    & Molecular genetic analysis of Chlamydia species. Annu. Rev. Microbiol. 70, 179–198 (2016).

  26. 26.

    & Application of β-lactamase reporter fusions as an indicator of effector protein secretion during infections with the obligate intracellular pathogen Chlamydia trachomatis. PLoS ONE 10, e0135295 (2015).

  27. 27.

    , & Gene deletion by fluorescence-reported allelic exchange mutagenesis in Chlamydia trachomatis. mBio 7, e01817-15 (2016).

  28. 28.

    & Transformation and isolation of allelic exchange mutants of Chlamydia psittaci using recombinant DNA introduced by electroporation. Proc. Natl Acad. Sci. USA 106, 292–297 (2009).

  29. 29.

    et al. Development of shuttle vectors for transformation of diverse Rickettsia species. PLoS ONE 6, e29511 (2011). This article reports the generation of shuttle vectors that can be used to ectopically express proteins in diverse Rickettsia spp.

  30. 30.

    et al. Establishment of a replicating plasmid in Rickettsia prowazekii. PLoS ONE 7, e34715 (2012).

  31. 31.

    et al. GFPuv-expressing recombinant Rickettsia typhi: a useful tool for the study of pathogenesis and CD8+ T cell immunology in Rickettsia typhi infection. Infect. Immun. (2017).

  32. 32.

    & Mechanisms of plasmid segregation: have multicopy plasmids been overlooked? Plasmid 75, 27–36 (2014).

  33. 33.

    , & Electrotransformation and clonal isolation of Rickettsia species. Curr. Protoc. Microbiol. 39, 3A.6.1–3A.6.20 (2015).

  34. 34.

    et al. Nonselective persistence of a Rickettsia conorii extrachromosomal plasmid during mammalian infection. Infect. Immun. 84, 790–797 (2016).

  35. 35.

    , , , & Motility characteristics are altered for Rickettsia bellii transformed to overexpress a heterologous rickA gene. Appl. Environ. Microbiol. 80, 1170–1176 (2014).

  36. 36.

    et al. Large-scale identification and translocation of type IV secretion substrates by Coxiella burnetii. Proc. Natl Acad. Sci. USA 107, 21755–21760 (2010).

  37. 37.

    et al. The Coxiella burnetii cryptic plasmid is enriched in genes encoding type IV secretion system substrates. J. Bacteriol. 193, 1493–1503 (2011).

  38. 38.

    , & Coxiella burnetii: turning hostility into a home. Cell. Microbiol. 17, 621–631 (2015).

  39. 39.

    , & A purified mariner transposase is sufficient to mediate transposition in vitro. EMBO J. 15, 5470–5479 (1996).

  40. 40.

    et al. Characterization of a Coxiella burnetii ftsZ mutant generated by Himar1 transposon mutagenesis. J. Bacteriol. 191, 1369–1381 (2009).

  41. 41.

    , , , & Rickettsia actin-based motility occurs in distinct phases mediated by different actin nucleators. Curr. Biol. 24, 98–103 (2014).

  42. 42.

    , , & Mariner-based transposon mutagenesis of Rickettsia prowazekii. Appl. Environ. Microbiol. 73, 6644–6649 (2007).

  43. 43.

    et al. Knockout of an outer membrane protein operon of Anaplasma marginale by transposon mutagenesis. BMC Genomics 15, 278 (2014).

  44. 44.

    et al. Transformation of Anaplasma marginale. Vet. Parasitol. 167, 167–174 (2010).

  45. 45.

    In vitro and in vivo properties of chemically induced temperature-sensitive mutants of Chlamydia psittaci var. ovis: screening in a murine model. Infect. Immun. 42, 525–530 (1983).

  46. 46.

    et al. Generation of targeted Chlamydia trachomatis null mutants. Proc. Natl Acad. Sci. USA 108, 7189–7193 (2011).

  47. 47.

    et al. Interrogating genes that mediate Chlamydia trachomatis survival in cell culture using conditional mutants and recombination. J. Bacteriol. 198, 2131–2139 (2016).

  48. 48.

    & Virulence determinants in the obligate intracellular pathogen Chlamydia trachomatis revealed by forward genetic approaches. Proc. Natl Acad. Sci. USA 109, 1263–1268 (2012). This study details the chemical mutagenesis procedure for Chlamydia trachomatis serovar L2 and describes the linkage analysis conducted to link mutation and phenotype.

  49. 49.

    et al. Directed mutagenesis of the Rickettsia prowazekii pld gene encoding phospholipase D. Infect. Immun. 77, 3244–3248 (2009).

  50. 50.

    , & Transformation of Coxiella burnetii to ampicillin resistance. J. Bacteriol. 178, 2701–2708 (1996).

  51. 51.

    & Group II introns: mobile ribozymes that invade DNA. Cold Spring Harb. Perspect. Biol. 3, a003616 (2011).

  52. 52.

    & Site-specific, insertional inactivation of incA in Chlamydia trachomatis using a group II intron. PLoS ONE 8, e83989 (2013).

  53. 53.

    , & Targeted knockout of the Rickettsia rickettsii OmpA surface antigen does not diminish virulence in a mammalian model system. mBio 6, e00323-15 (2015). This article uses targeted mutagenesis to show that a classical virulence factor in R. rickettsii is not important for virulence.

  54. 54.

    , , , & Fluorescence activated cell sorting of Rickettsia prowazekii-infected host cells based on bacterial burden and early detection of fluorescent rickettsial transformants. PLoS ONE 11, e0152365 (2016).

  55. 55.

    , & Green fluorescent protein as a marker in Rickettsia typhi transformation. Infect. Immun. 67, 3308–3311 (1999).

  56. 56.

    , , , & Clonal isolation of Chlamydia-infected cells using flow cytometry. J. Microbiol. Methods 68, 201–208 (2007).

  57. 57.

    et al. Isolation of single Chlamydia-infected cells using laser microdissection. J. Microbiol. Methods 109, 123–128 (2015).

  58. 58.

    , & Chlamydia cell biology and pathogenesis. Nat. Rev. Microbiol. 14, 385–400 (2016).

  59. 59.

    , & Evolution and conservation of predicted inclusion membrane proteins in chlamydiae. Comp. Funct. Genomics 2012, 362104 (2012).

  60. 60.

    & ARF family G proteins and their regulators: roles in membrane transport, development and disease. Nat. Rev. Mol. Cell Biol. 12, 362–375 (2011).

  61. 61.

    et al. The capping domain in RalF regulates effector functions. PLoS Pathog. 8, e1003012 (2012).

  62. 62.

    et al. Which way in? The RalF Arf-GEF orchestrates Rickettsia host cell invasion. PLoS Pathog. 11, e1005115 (2015).

  63. 63.

    & Legionella phagosomes intercept vesicular traffic from endoplasmic reticulum exit sites. Nat. Cell Biol. 4, 945–954 (2002).

  64. 64.

    , & AMP-activated kinase (AMPK) promotes innate immunity and antiviral defense through modulation of stimulator of interferon genes (STING) signaling. J. Biol. Chem. 292, 292–304 (2017).

  65. 65.

    et al. Membrane perturbation-associated Ca2+ signaling and incoming genome sensing are required for the host response to low-level enveloped virus particle entry. J. Virol. 90, 3018–3027 (2015).

  66. 66.

    , , & Recent molecular insights into rickettsial pathogenesis and immunity. Future Microbiol. 8, 1265–1288 (2013).

  67. 67.

    et al. Secretome of obligate intracellular Rickettsia. FEMS Microbiol. Rev. 39, 47–80 (2015).

  68. 68.

    , , , & The rickettsia surface cell antigen 4 applies mimicry to bind to and activate vinculin. J. Biol. Chem. 286, 35096–35103 (2011).

  69. 69.

    Anaplasma phagocytophilum and Ehrlichia chaffeensis: subversive manipulators of host cells. Nat. Rev. Microbiol. 8, 328–339 (2010).

  70. 70.

    et al. Anaplasma phagocytophilum dihydrolipoamide dehydrogenase 1 affects host-derived immunopathology during microbial colonization. Infect. Immun. 80, 3194–3205 (2012).

  71. 71.

    & Bacterial virulence in the moonlight: multitasking bacterial moonlighting proteins are virulence determinants in infectious disease. Infect. Immun. 79, 3476–3491 (2011).

  72. 72.

    The biological basis of severe outcomes in Anaplasma phagocytophilum infection. FEMS Immunol. Med. Microbiol. 64, 13–20 (2012).

  73. 73.

    , , & Mutations in Ehrlichia chaffeensis causing polar effects in gene expression and differential host specificities. PLoS ONE 10, e0132657 (2015).

  74. 74.

    et al. Attenuated mutants of Ehrlichia chaffeensis induce protection against wild-type infection challenge in the reservoir host and in an incidental host. Infect. Immun. 83, 2827–2835 (2015).

  75. 75.

    , , & A mutation inactivating the methyltransferase gene in avirulent Madrid E strain of Rickettsia prowazekii reverted to wild type in the virulent revertant strain Evir. Vaccine 24, 2317–2323 (2006).

  76. 76.

    , , , & Expression of the Rickettsia prowazekii pld or tlyC gene in Salmonella enterica serovar Typhimurium mediates phagosomal escape. Infect. Immun. 73, 6668–6673 (2005).

  77. 77.

    & rOmpA is a critical protein for the adhesion of Rickettsia rickettsii to host cells. Microb. Pathog. 24, 289–298 (1998).

  78. 78.

    , , , & Identification of a chlamydial protease-like activity factor responsible for the degradation of host transcription factors. J. Exp. Med. 193, 935–942 (2001).

  79. 79.

    , , , & CPAF: a chlamydial protease in search of an authentic substrate. PLoS Pathog. 8, e1002842 (2012). This study shows that several substrates of a chlamydial protease are artefacts of sample processing.

  80. 80.

    et al. Reassessing the role of the secreted protease CPAF in Chlamydia trachomatis infection through genetic approaches. Pathog. Dis. 71, 336–351 (2014). This article shows that several substrates of a chlamydial protease are artefactual through the use of a CPAF-processing-defective C. trachomatis serovar L2 strain.

  81. 81.

    et al. Chlamydial protease-like activity factor and type III secreted effectors cooperate in inhibition of p65 nuclear translocation. mBio 7, e01427-16 (2016).

  82. 82.

    et al. The Chlamydia-secreted protease CPAF promotes chlamydial survival in the mouse lower genital tract. Infect. Immun. 84, 2697–2702 (2016).

  83. 83.

    & Analysis of CPAF mutants: new functions, new questions (the ins and outs of a chlamydial protease). Pathog. Dis. 71, 287–291 (2014).

  84. 84.

    et al. Comparative genomics of emerging human ehrlichiosis agents. PLoS Genet. 2, e21 (2006).

  85. 85.

    et al. The Orientia tsutsugamushi genome reveals massive proliferation of conjugative type IV secretion system and host-cell interaction genes. Proc. Natl Acad. Sci. USA 104, 7981–7986 (2007).

  86. 86.

    et al. The Rickettsia type IV secretion system: unrealized complexity mired by gene family expansion. Pathog. Dis. 74, ftw058 (2016).

  87. 87.

    & Anaplasma phagocytophilum and Ehrlichia chaffeensis type IV secretion and Ank proteins. Curr. Opin. Microbiol. 13, 59–66 (2010).

  88. 88.

    & Ankyrin domains across the tree of life. PeerJ 2, e264 (2014).

  89. 89.

    et al. Hacker within! Ehrlichia chaffeensis effector driven phagocyte reprogramming strategy. Front. Cell. Infect. Microbiol. 6, 58 (2016).

  90. 90.

    , & Bacterial iron homeostasis. FEMS Microbiol. Rev. 27, 215–237 (2003).

  91. 91.

    et al. Complete genome sequencing of Anaplasma marginale reveals that the surface is skewed to two superfamilies of outer membrane proteins. Proc. Natl Acad. Sci. USA 102, 844–849 (2005).

  92. 92.

    et al. The influence of the synergistic anion on iron chelation by ferric binding protein, a bacterial transferrin. Proc. Natl Acad. Sci. USA 100, 3659–3664 (2003).

  93. 93.

    , , & fbpABC gene cluster in Neisseria meningitidis is transcribed as an operon. Infect. Immun. 68, 7166–7171 (2000).

  94. 94.

    , , & An immunoreactive 38-kilodalton protein of Ehrlichia canis shares structural homology and iron-binding capacity with the ferric ion-binding protein family. Infect. Immun. 73, 62–69 (2005).

  95. 95.

    & Subversion of host cell signaling by Orientia tsutsugamushi. Microbes Infect. 13, 638–648 (2011).

  96. 96.

    , , & Two systems for targeted gene deletion in Coxiella burnetii. Appl. Environ. Microbiol. 78, 4580–4589 (2012).

  97. 97.

    , , , & Molecular pathogenesis of the obligate intracellular bacterium Coxiella burnetii. Nat. Rev. Microbiol. 11, 561–573 (2013).

  98. 98.

    & Approaches to vaccines against Orientia tsutsugamushi. Front. Cell. Infect. Microbiol. 2, 170 (2013).

  99. 99.

    et al. Human and pathogen factors associated with Chlamydia trachomatis-related infertility in women. Clin. Microbiol. Rev. 28, 969–985 (2015).

  100. 100.

    , & Trachoma: protective and pathogenic ocular immune responses to Chlamydia trachomatis. PLoS Negl. Trop. Dis. 7, e2020 (2013).

  101. 101.

    , , & Ehrlichioses in humans: epidemiology, clinical presentation, diagnosis, and treatment. Clin. Infect. Dis. 45, S45–S51 (2007).

  102. 102.

    , & Anaplasma phagocytophilum — a widespread multi-host pathogen with highly adaptive strategies. Front. Cell. Infect. Microbiol. 3, 31 (2013).

  103. 103.

    , , & Genotyping, evolution and epidemiological findings of Rickettsia species. Infect. Genet. Evol. 25, 122–137 (2014).

  104. 104.

    et al. Endemic scrub typhus in South America. N. Engl. J. Med. 375, 954–961 (2016).

  105. 105.

    et al. Global estimates of the prevalence and incidence of four curable sexually transmitted Infections in 2012 based on systematic review and global reporting. PLoS ONE 10, e0143304 (2015).

  106. 106.

    , , , & Trachoma. Lancet 384, 2142–2152 (2014).

  107. 107.

    , , & Diagnosis, treatment, and prevention of Lyme disease, human granulocytic anaplasmosis, and babesiosis: a review. JAMA 315, 1767–1777 (2016).

  108. 108.

    , , , & Increasing incidence of Ehrlichia chaffeensis and Anaplasma phagocytophilum in the United States, 2000–2007. Am. J. Trop. Med. Hyg. 85, 124–131 (2011).

  109. 109.

    , , , & The past and present threat of rickettsial diseases to military medicine and international public health. Clin. Infect. Dis. 34, S145–S169 (2002).

  110. 110.

    Worldwide detection and identification of new and old rickettsiae and rickettsial diseases. FEMS Immunol. Med. Microbiol. 64, 107–110 (2012).

  111. 111.

    et al. The whole-genome sequencing of the obligate intracellular bacterium Orientia tsutsugamushi revealed massive gene amplification during reductive genome evolution. DNA Res. 15, 185–199 (2008).

Download references


The authors apologize to those colleagues whose work could not be cited owing to the broad scope of the Review and space limitations. Work in the authors' laboratories was supported by the US National Institutes of Health (Institutional Training Grant T32AI007540 to E.E.M.; R01 AI072683, R56 AI123346 and R21 AI122014 to J.A.C.; R01 AI100759 to R.H.V.; U19 AI084044 to P.M.B.; R01 AI070908 to R.R.G.; R01 AI020384 and R21 AI103272 to D.O.W.; R01 AI042792 to U.G.M. and K.A.B.; R01 AI072606 and R21 AI111086 to J.J.M.; R01 AI106859 and R21 AI115449 to J.W.M.; and R01 AI093653 and R01AI116523 to J.H.F.P.), the US Department of Agriculture (USDA-ARS 2090-32000-038-00D to S.M.N.), the Center of Excellence for Vector-Borne Diseases at Kansas State University (to R.R.G.) and the University of Maryland School of Medicine (to J.H.F.P.). The content of this Review is solely the responsibility of the authors and does not necessarily represent the official views of the US National Institute of Allergy and Infectious Diseases or the US National Institutes of Health.

Author information

Author notes

    • Ulrike G. Munderloh
    •  & Joao H. F. Pedra

    These authors contributed equally to this work.


  1. Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.

    • Erin E. McClure
    • , Adela S. Oliva Chávez
    • , Dana K. Shaw
    •  & Joao H. F. Pedra
  2. Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298, USA.

    • Jason A. Carlyon
  3. Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas 66506, USA.

    • Roman R. Ganta
  4. Animal Disease Research Unit, Agricultural Research Service, U.S. Department of Agriculture and the Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington 99164, USA.

    • Susan M. Noh
  5. Department of Microbiology and Immunology, University of South Alabama College of Medicine, Mobile, Alabama 36688, USA.

    • David O. Wood
  6. Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, Maryland 21201, USA.

    • Patrik M. Bavoil
  7. Department of Veterinary Microbiology and Pathology and the Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, 99164, USA.

    • Kelly A. Brayton
  8. Vector Borne Disease Laboratories, Department of Pathobiological Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana 70803, USA.

    • Juan J. Martinez
  9. Department of Pathology, University of Texas Medical Branch, Galveston, Texas 77555, USA.

    • Jere W. McBride
  10. Department for Molecular Genetics and Microbiology, Duke University, Durham, North Carolina 27710, USA.

    • Raphael H. Valdivia
  11. Department of Entomology, University of Minnesota, St. Paul, Minnesota 55108, USA.

    • Ulrike G. Munderloh


  1. Search for Erin E. McClure in:

  2. Search for Adela S. Oliva Chávez in:

  3. Search for Dana K. Shaw in:

  4. Search for Jason A. Carlyon in:

  5. Search for Roman R. Ganta in:

  6. Search for Susan M. Noh in:

  7. Search for David O. Wood in:

  8. Search for Patrik M. Bavoil in:

  9. Search for Kelly A. Brayton in:

  10. Search for Juan J. Martinez in:

  11. Search for Jere W. McBride in:

  12. Search for Raphael H. Valdivia in:

  13. Search for Ulrike G. Munderloh in:

  14. Search for Joao H. F. Pedra in:

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Joao H. F. Pedra.

Supplementary information

PDF files

  1. 1.

    Supplementary information S1 (figure)

    Disease pathogenesis and immune response against selected obligates.



A technique that induces bacteria to take up exogenous DNA molecules, usually through chemical or electrical methods.

Polyamidoamine dendrimers

(PAMAM dendrimers). Highly branched polymers that can be used to deliver small molecules or DNA to cells.

Allelic exchange

A common method that is used to knock in, knock out or otherwise mutagenize a DNA segment that relies on homologous recombination between the wild-type gene and an exogenous DNA construct.

Fluorescence-reported allelic exchange mutagenesis

(FRAEM). A method for allelic exchange in Chlamydia trachomatis serovar L2 that can be monitored byobserving fluorescent chlamydial inclusions.

Dot/Icm type IV secretion system

A set of bacterial proteins that inject effector molecules into the eukaryotic host cytosol to remodel the intracellular niche.

Mariner transposon

An abundant class II transposable element first discovered in Drosophila spp. that integrates into a wide range of genomes.

Ethyl methanesulfonate mutagenesis

(EMS mutagenesis). A technique in which a DNA-alkylating agent (EMS) is applied to a population of cells to create a library of strains that contain random mutations.

Mobile group II introns

Mobile bacterial ribozymes that self-splice, reverse transcribe the spliced RNA into DNA, and then integrate the DNA into the bacterial chromosome.


A type of inflammatory cell death that occurs spontaneously after damage to a cell.


A mode of non-inflammatory programmed cell death.

Stimulator of interferon genes

(STING). An endoplasmic reticulum-associated cytosolic intracellular pattern recognition molecule that senses cyclic dinucleotides and induces the production of type I interferons.


A mammalian cytoskeletal protein that anchors the cell membrane to the actin cytoskeleton.

Granulocytic anaplasmosis

A mild-to-severe tick-borne infectious disease caused by Anaplasma phagocytophilum, which infects neutrophils and myeloid cells, that is characterized by fever, thrombocytopenia, leukopenia and liver damage.

About this article

Publication history



Further reading