Selective medium based on tyrosine metabolism for the isolation and enumeration of Brevibacillus brevis (Bacillus brevis)

AIMS: To develop a selective medium for the enumeration of Brevibacillus brevis Nagano spores from soil and plant material. METHODS AND RESULTS: Tyrosine agar was developed as a selective medium and compared with nutrient agar for the enumeration of B. brevis Nagano spores from sterile and non-sterile plant and soil extracts. Brevibacillus brevis Nagano colonies could be easily identified only on tyrosine agar due to their clear halo and distinct colony morphology. Identification was confirmed by thin layer chromatography of the antibiotic, gramicidin S, produced by this strain. CONCLUSIONS: Tyrosine agar was shown to be a suitable selective medium for the enumeration of B. brevis Nagano. SIGNIFICANCE AND IMPACT OF THE STUDY: The medium developed, tyrosine agar, can be used to monitor the population of the biological control agent, B. brevis Nagano, and will allow detailed studies within the crop environment.