Microbes have been used to produce products for thousands of years. Even in ancient times, vinegar was made by filtering alcohol through wood shavings, allowing microbes growing on the surfaces of the wood pieces to convert alcohol to vinegar. Likewise, the production of wine and beer uses another microbe — yeast — to convert sugars to alcohol. Even though people did not know for a long time that microbes were behind these transformations, it did not stop them from making and selling these products.
Both of these are early examples of biotechnology — the use of microbes for economic or industrial purposes. This field advanced considerably with the many developments in microbiology, such as the invention of microscope. Once scientists learned about the genetics of microbes, and how their cells produce proteins, microbes could also be altered to function in many new, and useful, ways. This sparked the application of biotechnology to many industries, such as agriculture, energy and medicine.
Genetic Engineering of Microbes
Genetic information in organisms is stored in their DNA. This molecule holds instructions for how the organism looks and functions. DNA is broken into sections called genes, each of which contains the template for a single protein molecule. Proteins serve as building blocks for the cell, and also carry out other activities. By studying microbes, scientists learned how to cut pieces out of a DNA molecule, and move them to another part. This changes how the cell looks or acts. Scientists can also take genes from one organism and insert them into the DNA of another. This gives the organism entirely new abilities.
This type of genetic engineering — the altering of an organism’s genetic information — has enabled scientists to use microbes as tiny living factories. One example of this is the production of insulin. In humans, the pancreas creates a protein called insulin that regulates glucose — sugar — levels in the blood. People with one type of diabetes cannot produce insulin, so they inject it into their blood throughout the day. To produce cheaper insulin, scientists inserted the human gene for insulin into the DNA of a common intestinal bacterium. This change enabled the bacterium to produce a new product — human insulin.
Food and Agriculture & Microbes
As with the production of vinegar, microbes are used widely in the agricultural and food industries. Bacteria are used in the production of many food products, such as yogurt, many types of cheese and sauerkraut. Farmers also use a bacterium that produces a natural fertilizer. This type of bacterium is normally associated with bean plants, growing in nodules on the roots in a symbiotic — mutually beneficial — relationship. The bacterium converts nitrogen gas in the air to a form that plants can use — like fertilizer. By adding bacteria to the soil, farmers can increase the productivity of the plants.
Genetic engineering can also be used to produce plants with new abilities, such as enhanced resistance to pesticides, or increased nutritional content. In this case, microbes are used to insert new genes into the DNA of the plants. This results in genetically modified — GM — foods. Humans have long modified the genetics of agricultural plants and animals by breeding them to enhance specific traits. Genetical engineering, however, allows scientists to add genes that exist in totally unrelated organisms.
Energy & Microbes
During vinegar production with wood chips, bacteria grow on the surface of the wood, forming what is called a biofilm. Bacteria attached to a surface like this can produce many compounds, as well as block the flow of a fluid. The latter behavior has been used to increase the amount of oil extracted from an oil field. Bacteria growing in the wells block areas that are more open. When water is then pumped into the ground, the biofilms drive the water into other areas that still contain oil. This then forces the oil to the surface.
Microbes can also be used to create fuels directly. Certain bacteria ferment glycerol to form ethanol, a biofuel that can be used in automobiles. The glycerol is a byproduct of biodiesel production, but it is more valuable if converted to fuel. With genetic engineering, microbes can also be altered to produce fuels that they don’t usually make. One company has modified the DNA of yeast to create biofuel from sugarcane feedstock. The challenge to all of these methods is creating a process that produces fuels more easily — and cheaply — than conventional methods.
Crime and Security & Microbes
Certain types of bacteria thrive in high temperatures. These extremophiles — organisms that prefer extreme conditions — have cell components designed to withstand heat. One of these is a bacterium, Thermus aquaticus, that lives in hot springs and near thermal vents. It contains an enzyme that is involved in the copying of DNA inside the cell. This type of enzyme occurs in other organisms, but the one from T. aquaticus can withstand higher temperatures. Scientists use this enzyme to multiply very small amounts of DNA, such as from samples found at crime scenes.
Other techniques are used to identify disease-causing microbes released by terrorists. The microbes can be identified from their DNA. These tests are extremely sensitive, and can find the DNA equivalent of a drop of water in a swimming pool. The U.S. Postal used microbe-detection techniques after letters contaminated with a dangerous microbe — anthrax — were sent through the mail. The tests identified the microbe as coming from the same source, meaning that a single person sent all of the letters.
Medical Application of Microbes
In addition to vaccines and antibiotics, microbes have been essential for many important contributions to medicine. Like diabetes, many diseases can be treated with compounds derived from microbes: cystic fibrosis, cancer, growth hormone deficiency and hepatitis B. In addition, genetic methods that were first developed in microbes now allow scientists to study genetic diseases in humans. This has resulted in the ability to test fetuses for genetic diseases.
There have also been research studies of gene therapy in humans. This technique uses a microbe — often a virus — to insert new genes into cells. In theory, this could correct a condition caused by a genetic disease. Microbial genetics has also led to the ability to determine the sequence of DNA more rapidly, like reading a book. With this information, scientists can look for genes in individuals that cause — or contribute to — diseases.