Genetic analysis of Staphylococcus aureus RNA polymerase mutants

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Antibiotic resistance is a growing public health concern.
• Staphylococcus aureus is a common pathogen.
• Rifampin and related antibiotics target bacterial RNA polymerase.

Purpose of the Study:

• To investigate the genetic basis of spontaneous resistance to rifampin, rifamycin SV, streptovaricin, and streptolydigin in Staphylococcus aureus.
• To characterize the cross-resistance patterns and underlying mutations.
• To propose a model for antibiotic binding to RNA polymerase.

Main Methods:

• Isolation and characterization of spontaneous antibiotic-resistant mutants.
• Determination of spontaneous mutation rates and genetic cotransduction rates.
• In vitro sensitivity studies of bacterial lysates and purified RNA polymerase.

Main Results:

• Resistance was attributed to chromosomal mutations, not plasmids.
• Four distinct antibiotic cross-resistance patterns were identified.
• Genetic markers for resistance were separable by transduction.
• Mutant RNA polymerase activity mirrored whole-cell resistance phenotypes.

Conclusions:

• Mutations conferring resistance to these antibiotics are chromosomal and affect RNA polymerase.
• A model of overlapping binding sites on RNA polymerase is proposed.
• Understanding these interactions can inform the development of new antibiotics.