Analysis of the DNA gyrase genes ofAcholeplasma laidlawii PG-8B

A 5-kb region of theAcholeplasma laidlawii PG-8B genome was sequenced. The region contained the genes for RecF, DNA gyrase subunits A and B (GyrA and GyrB), and a fragment of the ATP-binding subunit of the hypothetical ABC transporter. In phylogenetic analysis,A. laidlawii GyrA and GyrB formed statistically significant, stable clusters with the corresponding proteins ofClostridium acetobutylicum, Staphylococcus aureus, Bacillus subtilis, andStreptococcus pneumoniae. A laidlawii PG-8B clones resistant to fluoroquinolone (FQ) antibiotic ciprofloxacin (Cff) were obtained on a selective medium. The clones carried mutations in the quinolone resistance-determining region (QRDR) ofgyrA, which resulted in substitutions Ser83→Ala, Ser83→Phe, or Asp91→Asn. No mutations were found ingyrB QRDR of the resistant clones.