Agricultural microbiology is an excellent career field for individuals with interests in both agriculture and microbiology. Included in the field of agricultural microbiology are studies of the beneficial and harmful roles of microbes in soil formation and fertility; in carbon, nitrogen, phosphorus, and sulfur cycles; in diseases of plants; in the digestive processes of cows and other ruminants; and in the production of crops and foods. Many different viruses, bacteria, and fungi cause plant diseases. A food microbiologist is concerned with the production, processing, storage, cooking, and serving of food, as well as the prevention of food spoilage, food poisoning, and food toxicity. A dairy microbiologist oversees the grading, pasteurization, and processing of
milk and cheeses to prevent contamination, spoilage, and transmission of diseases from environmental, animal, and human sources. Certain aspects of agricultural microbiology are discussed in Chapter 10.
Biotechnology (Industrial Microbiology)
Biotechnology (Industrial Microbiology)—the use of microorganisms in industry—is an excellent career field for individuals with interests in both industry and microbiology. Many businesses and industries depend on the proper growth and maintenance of certain microbes to produce beer, wine, alcohol, and organic materials such as enzymes, vitamins, and antibiotics. Industrial microbiologists monitor and maintain the microorganisms that are essential for these commercial enterprises. Applied microbiologists conduct research aimed at producing new products and more effective antibiotics. Biotechnology is discussed more fully in Chapter 10.
Environmental Microbiology and Bioremediation
The field of environmental microbiology, or microbial ecology, has become increasingly important in recent years because of heightened awareness and concern about potential dangers to the environment. Environmental microbiologists are concerned about water and sewage treatment. The purification of waste water is partially accomplished by bacteria in the holding tanks of sewage disposal plants, in which feces, garbage, and other organic materials are collected and reduced to harmless waste (discussed in Chapter 11). Some microorganisms such as the iron- and sulfur-utilizing bacteria even break down metals and minerals. Bioremediation involves the use of microorganisms to clean up after ourselves, that is, to clean up landfills and industrial and toxic wastes. The beneficial activities of microbes affect every part of our environment, including soil, water, and air. Environmental microbiology and bioremediation are excellent career fields for individuals with interests in both ecology and microbiology.
Microbial Genetics and Genetic Engineering
Microbial genetics involves the study of microbial DNA, chromosomes, plasmids, and genes. (Plasmids are small, circular molecules of extrachromosomal DNA; they are discussed in Chapter 3.) Genetic engineering involves the insertion of foreign genes into microorganisms (usually into bacteria or yeasts). These foreign genes may come from any other organism (e.g., another microorganism, an animal, or even a plant). The primary purpose of inserting a foreign gene into a microorganism is to create a microbe that is capable of either producing a product of importance to us or accomplishing some task of importance to us. Genetic engineering has applications in agricultural, environmental, industrial, and medical microbiology. The intestinal bacterium Escherichia coli has been used extensively in microbial genetics, genetic engineering, and microbial physiology. Microbial genetics and genetic engineering are excellent career fields for individuals with interests in both genetics and microbiology. Microbial physiology and genetics are discussed in Chapter 7.
Research in microbial physiology has contributed immensely to our understanding of the structure and functions of microbial cells. What microbiologists learn about microbial cells quite often applies to cells, in general, including human cells. Microbial physiology is an excellent career field for individuals with interests in both biochemistry and microbiology.
The field of paleomicrobiology involves the study of ancient microbes. Although life is thought
to have originated between 3.7 and 4 billion years ago, there are no cellular fossils available from that time period. But there are molecular fossils—molecules (usually lipids) known to be made only by organisms or, in some cases, only by particular organisms. Finding such molecular fossils in ancient rocks serves as evidence that life existed at that time. The earliest molecular fossils date back to between 3.7 and 4 billion years ago. Some paleomicrobiologists examine and study skeletons and mummified human remains to determine the infectious diseases that occurred in ancient civilizations. Such studies often involve the recovery of microbial DNA from bone and mummified tissue samples. For example, finding Mycobacterium tuberculosis DNA in Egyptian mummies has revealed that tuberculosis existed as far back as 3000 BC. Paleomicrobiology is an excellent career field for individuals with interests in anthropology, archaeology, and microbiology.
Technically, any organism that lives on or in another living organism is called a parasite. It would seem, then, that the term parasite would apply to all of the microbes of our indigenous microbiota—the viruses and bacteria that live on or in the human body. However, the field of parasitology involves only the following three categories of parasites: parasitic protozoa, helminths (parasitic worms), and arthropods (specifically, certain insects and arachnids). A parasitologist studies these organisms and their life cycles in an attempt to discover the best ways to control and treat the diseases that they cause. Chapter 21 contains a wealth of information about medical parasitology.
The field of sanitary microbiology includes the processing and disposal of garbage and sewage wastes, as well as the purification and processing of water supplies to ensure that no pathogens are carried to the consumer by drinking water. These topics are discussed in Chapter 11. Sanitary microbiologists also inspect food processing installations and eating establishments to ensure that proper food handling procedures are being enforced.
A wide variety of microbes—including viruses, bacteria, fungi, and protozoa—cause infectious diseases in animals. Control of such diseases is the concern of veterinary microbiologists. The production of food from livestock, the raising of other agriculturally important animals, the care of pets, and the transmission of diseases from animals to humans are areas of major importance in this field. Infectious diseases of humans that are acquired from animal sources are called zoonoses or zoonotic diseases. Zoonoses are discussed in Chapter 11. Veterinary microbiology is an excellent career field for a person who is fond of animals and microbiology