Introducing mutations into a chromosomal rRNA gene using a genetically modified eubacterial host with a single rRNA...

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Eubacterial organisms typically possess multiple ribosomal RNA (rRNA) operons.
• The presence of multiple rRNA operons complicates the isolation of recessive rRNA mutations due to recessivity, hindering studies on drug resistance.
• Developing methods to study single rRNA operons is crucial for understanding ribosome function and developing novel antimicrobial strategies.

Purpose of the Study:

• To construct a Mycobacterium smegmatis mutant with a single functional rRNA operon.
• To establish a system for isolating and characterizing drug-resistant rRNA mutants.
• To investigate the potential of this system for studying rRNA structure and function.

Main Methods:

• Gene-inactivation techniques were used to create a single rRNA operon mutant.
• Homologous recombination was employed to replace the chromosomal rRNA operon with a plasmid-borne rDNA segment containing resistance markers.
• Allelic exchange experiments were performed to validate the drug resistance phenotype.

Main Results:

• A viable Mycobacterium smegmatis strain with a single functional rRNA operon was successfully constructed.
• The single-operon system enabled the isolation of rRNA mutants exhibiting a drug-resistant phenotype, overcoming the issue of recessivity.
• Allelic exchange experiments confirmed that the identified rRNA mutation confers in vivo drug resistance.

Conclusions:

• The developed single-rRNA operon system in Mycobacterium smegmatis is effective for isolating drug-resistant rRNA mutants.
• This system circumvents the challenge of recessivity associated with multiple rRNA operons.
• The platform offers significant potential for advancing research into ribosomal RNA structure, function, and the development of novel therapeutics.