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Updated: May 22, 2026
An Electroporation Method to Transform Rickettsia spp. with a Fluorescent Protein-Expressing Shuttle Vector in Tick Cell Lines
Published on: October 11, 2022
Establishment of a replicating plasmid in Rickettsia prowazekii
David O Wood1, Andria Hines, Aimee M Tucker
1Department of Microbiology and Immunology, Laboratory of Molecular Biology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America. dowood@jaguar1.usouthal.edu
Abstract:
Rickettsia prowazekii, the causative agent of epidemic typhus, grows only within the cytosol of eukaryotic host cells. This obligate intracellular lifestyle has restricted the genetic analysis of this pathogen and critical tools, such as replicating plasmid vectors, have not been developed for this species. Although replicating plasmids have not been reported in R. prowazekii, the existence of well-characterized plasmids in several less pathogenic rickettsial species provides an opportunity to expand the genetic systems available for the study of this human pathogen. Competent R. prowazekii were transformed with pRAM18dRGA, a 10.3 kb vector derived from pRAM18 of R. amblyommii. A plasmid-containing population of R. prowazekii was obtained following growth under antibiotic selection, and the rickettsial plasmid was maintained extrachromosomally throughout multiple passages. The transformant population exhibited a generation time comparable to that of the wild type strain with a copy number of approximately 1 plasmid per rickettsia. These results demonstrate for the first time that a plasmid can be maintained in R. prowazekii, providing an important genetic tool for the study of this obligate intracellular pathogen.
Insights
Researchers have successfully introduced a replicating plasmid into Rickettsia prowazekii, the bacterium causing epidemic typhus. This breakthrough provides a crucial genetic tool for studying this obligate intracellular pathogen.
Area of Science:
- Microbiology
- Genetics
- Pathogen Biology
Background:
- Rickettsia prowazekii causes epidemic typhus and is an obligate intracellular bacterium.
- Its intracellular lifestyle limits genetic analysis and the development of essential tools like replicating plasmids.
- Existing plasmids in related rickettsial species offer a potential avenue for developing genetic systems for R. prowazekii.
Purpose of the Study:
- To establish a functional plasmid-based genetic system for Rickettsia prowazekii.
- To overcome limitations in the genetic manipulation of this important human pathogen.
Main Methods:
- Transformation of competent R. prowazekii with a plasmid vector (pRAM18dRGA) derived from R. amblyommii.
- Selection of transformed bacteria using antibiotic pressure.
- Maintenance and characterization of the plasmid-containing R. prowazekii population through multiple passages.
Main Results:
- Successful introduction and stable maintenance of the plasmid vector (pRAM18dRGA) in R. prowazekii.
- The plasmid was maintained extrachromosomally in the host cell.
- The transformant strain showed a generation time comparable to the wild-type, with approximately one plasmid copy per bacterium.
Conclusions:
- Demonstrates the feasibility of maintaining a plasmid in Rickettsia prowazekii for the first time.
- Provides a foundational genetic tool for future research on this obligate intracellular pathogen.
- Opens new avenues for understanding R. prowazekii pathogenesis and developing potential interventions.
