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Updated: Dec 11, 2025
Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43
Published on: September 11, 2020
Advancing Genetic Tools in Streptococcus pneumoniae
1Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
Abstract:
Streptococcus pneumoniae is the causative agent of a multitude of diseases, and further study into its pathogenies is vital. The pneumococcus is genetically malleable, and several tools are available to manipulate this pathogen. In this study, we attempted to utilize one such tool, the Sweet Janus cassette, to replace the capsule locus with other capsule loci in our strain background and found that the efficiency of allelic replacement was low and the number of revertant false-positive colonies was high. We determined that the capacity to recombine capsule varied by the initial isolated colony, suggesting that frequency of reversion is dependent on the bacterial clone. Alternative selection markers may further expand the application of Sweet Janus. We created novel cassettes that utilized chlorinated phenylalanine as an alternative counter-selection agent in conjunction with the Janus or Sweet Janus cassette, providing a new dual or triple selection marker. Moreover, we created cassettes that do not require engineered resistance in the background strain, including both single and dual selection markers. We were able to utilize all constructs in allelic replacement of the capsule loci. These novel constructs provide a new means for generating gene deletions in S. pneumoniae that expand experimental applications.
Insights
Researchers improved genetic tools for studying Streptococcus pneumoniae. Novel constructs enhance gene deletion efficiency, aiding research into pneumococcal diseases and pathogen manipulation.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Streptococcus pneumoniae causes numerous diseases, necessitating further study of its pathogenesis.
- Genetic manipulation tools exist for S. pneumoniae, but their efficiency can be limiting.
Purpose of the Study:
- To evaluate the efficiency of the Sweet Janus cassette for allelic replacement in S. pneumoniae.
- To develop novel genetic constructs for improved gene deletion and allelic replacement in S. pneumoniae.
Main Methods:
- Utilized the Sweet Janus cassette for capsule locus replacement.
- Developed and tested novel cassettes with alternative selection markers, including chlorinated phenylalanine.
- Created constructs with single and dual selection markers, some not requiring engineered resistance.
Main Results:
- Initial attempts with Sweet Janus showed low allelic replacement efficiency and high false-positive revertants.
- Reversion frequency was found to be dependent on the bacterial clone.
- Novel dual and triple selection marker cassettes were successfully created and utilized for allelic replacement.
Conclusions:
- The efficiency of allelic replacement in S. pneumoniae is influenced by bacterial clone and selection methods.
- Novel selection marker cassettes improve gene deletion capabilities in S. pneumoniae.
- These new tools expand experimental applications for studying pneumococcal genetics and pathogenesis.
