These bacillus thuringensis species of bacteria secrete protein crystals that are toxic to most insects hence used in agriculture to kill pests that attack the crops. This is also the reason the genes responsible for this protein crystal is incorporated in crops (transgenic crops) to make them resistant to pests.
B. subtilis is important in the nutrient cycle and availing nutrient to plants hence promote plant growth
Both species are able to survive harsh conditions and remain dormant for long periods of time as spores hence their suitability in application in agriculture