Tiny organisms critical to life processes

Amy Burgin

What do cheese production, sewage treatment, and insect-resistant corn have in common? Without microbes, none of these things would be possible. Microbes are an important part of our daily lives, yet few of us consider what they do for us on a day-to-day basis.

Microbes are microscopic organisms that generally have a single cell. This includes bacteria, fungi and protists. They carry out all of the same functions of life that higher-order organisms do, but with their own twist. For example, microbes reproduce, but generally this is through splitting one cell into two cells that are exactly the same, a process called binary fission.

Microbes also "breathe" and "eat" (respire and metabolize), except they aren't restricted to oxygen as we are, and their food includes sugars and starches, as well as rocks and chemicals. Some are similar to plants in that they make their own food through photosynthesis. Others can even communicate very primitively by sending chemical signals, a process called quorum sensing.

The human body houses 10-20 times more bacterial cells than human cells. But because microbial cells are much smaller than human cells, they don't account for much of our body weight. In addition to being a large part of us, microbes are a very large part of the environment. There are few places where they do not live.

The hidden bodies of fungi can be quite large, in spite of the fact they are made of small threads of cells. Based on the area it covers, an individual Armellaria ostoyae fungus in Oregon's Malheur National Forest is said to be the largest organism in the world. It is estimated to cover 2200 acres and may be more than 2,000 years old.

Even extreme environments, such as the Yellowstone's hot springs and Antarctic ice sheets, are home to flourishing microbial communities. Their abundance and diversity increases in more hospitable areas. A single teaspoon of soil from your lawn or garden can hold more than a billion microbes.

Microbes do very mundane things few of us think about. Fermentation is a microbe-driven process responsible for many of the foods we enjoy, including beer, yogurt, bread and cheese. Microbes also play a role at water treatment plants, where they help process our waste by decomposing organic matter in sewage.

Many fruits and vegetables wouldn't be possible without assistance from microbes. Through a process called decomposition, microbes break complex organic substances into smaller units that plants can more readily absorb. Other specialized microbes form a symbiosis with plants that can help them acquire nutrients. An example is members of the group rhizobium, which take up residence in soybean roots, giving the plants increased access to nitrogen and boosting plant growth.

In addition to everyday tasks, microbes also perform some unique processes that humans have capitalized on for technological advances. For example, many microbes produce chemicals that compete with and fight off other microbes. We know these mainly as antibiotics. Penicillin, for example, was first extracted from bread molds.

Transgenic crops, such as Bt corn, are another example of how humans have tapped into microbial chemical warfare. The "Bt" stands for Bacillus thur-ingiensis, a bacterium that produces a toxin poisonous to insects. By borrowing genes from this microbe and putting them in corn, scientists have created a strain of genetically modified corn that can fight off predatory insects.

The next time you are washing your hands with anti-bacterial soap, consider all of the things a microbe may have done for you today. In their absence, plants would not grow, food would be scarce and the world would be filled with waste and garbage.

Cary Institute of Ecosystem Studies | Millbrook, New York 12545 | Tel (845) 677-5343

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