Spectinomycin resistance and associated DNA amplification in Streptomyces achromogenes subsp. rubradiris

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Streptomyces achromogenes subsp. rubradiris exhibits complex responses to antibiotic stress.
• High concentrations of spectinomycin induce genetic changes in bacterial populations.

Purpose of the Study:

• To investigate the genetic basis of spectinomycin resistance in Streptomyces achromogenes.
• To characterize the DNA sequence responsible for high-level spectinomycin resistance.

Main Methods:

• DNA cloning in Escherichia coli and Streptomyces lividans.
• Physical characterization of DNA fragments using restriction enzyme digestion and Southern blotting.
• Transformation experiments to assess antibiotic resistance conferred by cloned DNA.

Main Results:

• An 8-kilobase (kb) DNA sequence amplification (200-300 fold) was observed in spectinomycin-resistant colonies.
• This 8-kb sequence, cloned as an 8.8-kb amplifiable unit, confers spectinomycin resistance independently of orientation.
• A 1.7-kb subfragment contains the spectinomycin resistance determinant.

Conclusions:

• The amplifiable unit containing the spectinomycin resistance determinant is crucial for high-level resistance in S. achromogenes.
• Loss of this unit correlates with loss of resistance, confirming its role.
• The identified resistance mechanism provides a model for bacterial adaptation to antibiotics.