Bacillus (Lec 25)

Bacillus thuringiensis and Other Microorganisms

• Bt products represent about 1% of the total agrochemical market worldwide, including fungicides, herbicides, and insecticides.
• The toxin genes are plasmid encoded and have been genetically engineered into crop plants such as Bt corn and Bt cotton.
• Bt products have a specific mode of action, with crystals that must be activated before having any effect.
• The toxin is safe for humans, higher animals, and most insects, and it is solubilized in the high pH conditions found in the mid-gut of lepidopteran larvae.
• Once solubilized in the insect gut, the protoxin is cleaved by a gut protease to produce an active toxin called delta-endotoxin.
• Recent studies on the delta-endotoxin structure reveal that it has three domains with specific functions.
• Bacillus thuringiensis was first discovered in 1911 in Thuringia, Germany, and has different strains with varying insect host ranges.
• Specific Bt strains are highly effective against certain insects, such as B.t. var kurstaki for lepidoptera and B.t. var israelensis for blackfly and mosquito control.
• Bacillus anthracis primarily affects domesticated and wild animals, with humans becoming infected incidentally.
• U.S. military forces have been vaccinated against anthrax due to concerns about the use of anthrax spores in biological warfare.
• Clostridium botulinum is an anaerobic, Gram-positive, spore-forming rod that produces a potent neurotoxin and can cause botulism.
• Clostridium acetobutylicum played a critical role in the production of acetone and butanol during World War I, affecting the outcome of the war.