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Research Project: Identification of Tick Colonization Mechanisms and Vaccine Development for Anaplasmosis

Location: Animal Disease Research

Title: Engineering of obligate intracellular bacteria: progress, challenges and paradigms

item MCCLURE, ERIN - University Of Maryland
item OLIVA CHAVEZ, ADELA - University Of Maryland
item SHAW, DANA - University Of Maryland
item CARLYON, JASON - Virginia Commonwealth University
item GANTA, ROMAN - Kansas State University
item Noh, Susan
item WOOD, DAVID - University Of South Alabama
item BAVOIL, PATRIK - University Of Maryland
item BRAYTON, KELLY - Washington State University
item PEDRA, JOAO - University Of Maryland

Submitted to: Nature Reviews Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2017
Publication Date: 6/19/2017
Citation: McClure, E.E., Oliva Chavez, A.S., Shaw, D.K., Carlyon, J.A., Ganta, R.R., Noh, S.M., Wood, D.O., Bavoil, P.M., Brayton, K.A., Pedra, J.H. 2017. Engineering of obligate intracellular bacteria: progress, challenges and paradigms. Nature Reviews Microbiology.

Interpretive Summary: Approximately one billion people are at risk for infection by obligate intracellular bacteria and little is known about the underlying mechanisms that govern their lifecycle. The difficulty in studying Chlamydia, Rickettsia, Anaplasma, Ehrlichia and Orientia is in part due to their genetic intractability. Recently, genetic tools have been developed; however, fine-tuning the genomic manipulation of obligate intracellular bacteria remains challenging. In this Opinion, we describe the public health relevance and illustrate the progress as well as constraints that hinder the systematic development of a genetic toolbox for obligate intracellular bacteria. We also provide examples where the study of obligate intracellular bacteria has led to the discovery of novel scientific paradigms in the field of microbial pathogenesis and immunity. Microbial virulence and persistence of obligate intracellular bacteria have fascinated scientists for generations. We believe that regardless of their specialization, researchers will benefit from a current perspective on this topic.

Technical Abstract: Over twenty years have passed since the first report of genetic manipulation of an obligate intracellular bacterium. Through progress interspersed by bouts of stagnation, microbiologists and geneticists have developed approaches to genetically manipulate obligates. A brief overview of the current genetic toolbox available to the scientific community is provided in this review in order to inform the reader of the progress and challenges in the field, rather than provide a comprehensive technical review. Methods that have been successfully used to transform obligate intracellular bacteria include electroporation, chemical mutagenesis and polyamidoamine (PAMAM) dendrimers (from Greek “dendron” – tree and “meros” – branch) complexed with plasmids. Despite some successes, significant challenges hinder the development of sophisticated genetic tools similar to those available for facultatives and free-living bacteria. The refinement of genetic manipulation methods has proven to be exceedingly difficult for all obligate intracellular bacteria due to a biphasic lifecycle in which only some forms of the pathogen are infectious, the inability to persist outside of the host cells and a lack of functional redundancy within the genetic code of these pathogens.