3. Microbes and Environment

Microbes are omnipresent in the biosphere, and their presence invariably affects the environment in which they grow. The effects of microbes on their environment can be beneficial or harmful or inapparent with regard to human measure or observation. The most significant effect of the microbes on earth is their ability to recycle the primary elements that make up all living systems, especially carbon, oxygen, and nitrogen (N). Primary production involves photosynthetic organisms which take up CO₂ from the atmosphere and convert it to organic (cellular) material. The process is also called CO₂ fixation, and it accounts for a very large portion of organic carbon available for synthesis of cell material. Decomposition or biodegradation results in the breakdown of complex organic materials to other forms of carbon that can be used by other organisms. There is no naturally occurring organic compound that cannot be degraded by some microbe, although some synthetic compounds such as Teflon, plastics, insecticides, and pesticides are broken down very slowly or not at all. Through the microbial metabolic processes of fermentation and respiration, organic molecules are eventually broken down to CO₂ which is returned to the atmosphere for continuous process of primary production. Biological nitrogen fixation is a process found only in some bacteria which remove N₂ from the atmosphere and converts it to ammonia (NH₃), for use by the plants and animals. Nitrogen fixation also results in replenishment of soil nitrogen removed by agricultural processes. Thus along with all these benefits, microbes greatly contribute in maintaining sustainability of environment. This chapter mainly focuses on beneficial and harmful impacts of microbes on environment and their role to maintain quality, health, and sustainability of environment.