[Selective medium with nalidixic acid for isolating antibiotic-producing Actinomyces].

Area of Science:

• Microbiology
• Antibiotic Discovery
• Actinomycetes Isolation

Background:

• Actinomycetes are crucial for producing novel antibiotics.
• Contaminating bacteria, like Bacillus species, hinder pure actinomycete isolation.
• Nalidixic acid exhibits inhibitory effects on common contaminating bacteria.

Purpose of the Study:

• To evaluate nalidixic acid as a selective agent for isolating soil actinomycetes.
• To develop an enhanced method for increasing actinomycete isolation efficiency.
• To screen isolated actinomycetes for antibiotic properties and determine taxonomic classification.

Main Methods:

• Utilized a selective medium containing nalidixic acid to inhibit contaminating bacteria.
• Implemented a preliminary soil treatment with calcium carbonate under moist conditions.
• Combined pre-treatment with inoculation onto the nalidixic acid selective medium for mass isolation.

Main Results:

• Nalidixic acid-containing medium increased actinomycete isolation by 20% compared to standard methods.
• The complex method (calcium carbonate pre-treatment + nalidixic acid medium) enhanced isolation by up to 100-fold.
• Successfully isolated 495 actinomycete cultures, characterized their antibiotic potential, and determined genus-level taxonomy.

Conclusions:

• Nalidixic acid is an effective selective agent for isolating soil actinomycetes.
• The developed complex method significantly improves the efficiency of actinomycete isolation.
• This efficient method is recommended for screening novel antibiotic-producing microorganisms.