Effect of strain and medium variation on mosquito toxin production by Bacillus thuringiensis var. israelensis

The effect of strain variation and culture medium on production of toxin lethal to mosquito larvae by Bacillus thuringiensis var. israelensis serotype H-14 was investigated. Shake flask culture of B. thuringiensis H-14 strains showed varied ability to produce toxins lethal to mosquito larvae dependent upon the particular strain and growth medium used. Buffered media demonstrated no better mosquito toxicity than did unbuffered media that ranged in pH from 5.7 to 8.1 at harvest. Although toxin production is associated with sporulation, spore count was generally not proportional to toxin produced for those strains and media evaluated.