Applications of Bacillus thuringiensis for Prevention of Environmental Deterioration

Abstract

The indiscriminate use of chemical insecticides for the control of insect pests over the years has led to serious environmental problems such as persistence of toxicity, which can in turn lead to the acquisition of resistance in target pests. These broad-spectrum insecticides, in addition to target pests, also kill non-target predators and parasites that otherwise check the pest populations. Furthermore, these pesticides keep on accumulating throughout aquatic and terrestrial food webs, creating ecological imbalances, and impairing human health. Growing concerns regarding insect resistance, environmental degradation, and human health problems paved the way for the development of biological, target-specific, low-persistent pesticides with no or fewer long-term hazards. One of the most successful biological pesticides over the last century is Bacillus thuringiensis. Bt is a Gram-positive, spore-forming aerobic bacterium having the characteristic ability to produce proteinaceous insecticidal crystals during sporulation. These proteins, more popularly known as Cry and Cyt proteins, are toxic to certain groups of insect pests; the latter cause major losses to crops and many act as vectors of human and animal diseases. Owing to their specific mode of action, Bt products are unlikely to pose any hazard to humans or other vertebrates or to the great majority of nontarget invertebrates. Besides being effective against insect pests of agricultural and horticultural crops, Bt products are also safe for use in aquatic environments for the control of mosquitoes. The growing importance of bacterio-insecticides in insect control activities has encouraged many research programs aiming to discover new bacterial strains with improved insecticidal properties. This chapter deals with the basic biology of Bt and the ways in which this entomopathogenic bacterium can be used for prevention of environmental deterioration and improvement of human health.