Oxolinic acid-resistant mutants of Bacillus subtilis

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Oxolinic acid is an inhibitor of DNA gyrase, crucial for bacterial DNA replication.
• Understanding resistance mechanisms is vital for antibiotic development and bacterial genetics.

Purpose of the Study:

• To characterize two newly selected Bacillus subtilis mutants resistant to oxolinic acid.
• To elucidate the genetic basis and phenotypic properties of oxolinic acid resistance.

Main Methods:

• Selection of oxolinic acid-resistant mutants (oxr-1, oxr-2) in Bacillus subtilis.
• Genetic mapping of mutations relative to DNA gyrase genes.
• Phenotypic analysis including sensitivity to nalidixic acid and oxolinic acid effects on DNA synthesis in toluenized cells.

Main Results:

• The oxr-1 and oxr-2 mutations are distinct from known DNA gyrase mutations.
• Mutants exhibit wild-type sensitivity to nalidixic acid and oxolinic acid inhibition of DNA synthesis.
• DNA gyrase enzyme from a gyrA mutant showed resistance, unlike the oxr mutants.

Conclusions:

• Oxolinic acid resistance in these mutants is not caused by altered DNA gyrase.
• Resistance is likely due to impaired uptake of oxolinic acid.
• The oxr-1 and oxr-2 mutations define a new genetic locus in B. subtilis, useful as genetic markers.