More than 200 types of bacteria can cause plant diseases in Australia, though some bacteria are beneficial in controlling pests and diseases or through symbiotic relationships with plants. Scientists had battled Agrobacterium, which causes crown gall disease in plants for decades, but in 1969 a strain called K84 was discovered that produced an antibiotic deadly to the pathogenic strain but was immune itself. K84 was genetically modified to strain K1026, which could control the disease without transferring resistance and was commercialized as No Gall pesticide. Various forms of Bacillus thuringiensis are used to control insects like caterpillars and beetles by producing proteins that paralyze their digestive systems. Rhizobia form nodules on legume roots