The Impact of Microbes on the Environment and Human Activities
Beneficial Effects of Microorganisms
Microbes are everywhere in the biosphere, and their presence invariably affects the environment that they are growing in.
The effects of microorganisms on their environment can be beneficial or harmful or inapparent with regard to human
measure or observation. Since a good part of this text concerns harmful activities of microbes (i.e., agents of disease) this
chapter counters with a discussion of the beneficial activities and exploitations of microorganisms as they relate to human
The beneficial effects of microbes derive from their metabolic activities in the environment, their associations with plants and
animals, and from their use in food production and biotechnological processes.
Nutrient Cycling and the Cycles of Elements that Make Up Living Systems
At an elemental level, the substances that make up living material consist of carbon (C), hydrogen (H), oxygen (O), nitrogen
(N), sulfur (S), phosphorus (P), potassium (K), iron (Fe), sodium (Na), calcium (Ca) and magnesium (Mg). The primary
constituents of organic material are C, H, O, N, S, and P. An organic compound always contains C and H and is symbolized
O (the empirical formula for glucose). Carbon dioxide (CO
) is considered an inorganic form of carbon.
The most significant effect of the microorganisms on earth is their ability to recycle the primary elements that make up all
living systems, especially carbon (C), oxygen (O) and nitrogen (N). These elements occur in different molecular forms that
must be shared among all types of life. Different forms of carbon and nitrogen are needed as nutrients by different types of
organisms. The diversity of metabolism that exists in the microbes ensures that these elements will be available in their
proper form for every type of life. The most important aspects of microbial metabolism that are involved in the cycles of
nutrients are discussed below.
involves photosynthetic organisms which take up CO
in the atmosphere and convert it to organic
(cellular) material. The process is also called CO
fixation, and it accounts for a very large portion of organic carbon
available for synthesis of cell material. Although terrestrial plants are obviously primary producers, planktonic algae and
account for nearly half of the primary production on the planet. These unicellular organisms which float in
the ocean are the "grass of the sea", and they are the source of carbon from which marine life is derived.