Under a Microscope; Seeing Is Truly Believing

Article excerpt


Scott Whittaker magnifies unseen worlds. Small details become a big deal when they are seen through a scanning electron microscope.

Mr. Whittaker, the scanning electron microscopy lab manager at the Smithsonian National Museum of Natural History, brings items into focus, aiding the many researchers who need increased visualization for their work.

"We are a visual species," Mr. Whittaker says. "Inevitably, one of the first questions we will ask is what something looks like."

The field of microscopy has come a long way since 17th-century pioneers such as Anton van Leeuwenhoek and Robert Hooke first peered at cells. Today, scanning electron microscopy is used in a number of fields, with artists and scientists alike benefiting from the technology.

The scanning electron microscopes at the National Museum of Natural History can magnify external structures on objects up to 150,000 times, Mr. Whittaker says.

"Nowadays, we can see such things as flagella and cilia on the outside of the cell," he says. "We can see the three-dimensional details on single-celled organisms, such as dinoflagellates, which are crucial to distinguish between species."

A botanist studying a tree can walk into the forest and adequately describe its morphological characteristics, he says. With the scanning electron microscope, much smaller organisms, even those that can't be seen with the naked eye, can be magnified for study.

A scanning electron microscope works by creating a cloud of electrons similar to how an incandescent light bulb creates light, he says. In this case, a thin wire filament is heated to make a cloud of electrons, he adds.

The cloud of electrons is accelerated toward the item to be viewed. The cloud is condensed into a beam and focused with a series of electromagnetic lenses onto the item. The electrons generate a signal, which is displayed onto a computer screen.

In contrast to the scanning electron microscope, under an optical microscope, which uses light and glass lenses with about 1,000 times magnification, only a small portion of the organism is in focus at any one time, he says.

When studying an organism such as the dinoflagellates that cause red tide, the scanning electron microscope enhances the overall information collected, says Maria Faust, research scientist in the department of botany at the museum.

For instance, she can distinguish the cell wall structure and numerous other structures that are present on the surface of an organism, all useful in descriptive taxonomy, in which the museum specializes.

The research at the Smithsonian is used by countless other researchers around the world in their own studies on morphology, toxicity or ecology and by professionals doing applied science, Ms. Faust says.

"Without the SEM, you couldn't identify all the details of any kind of organism," Ms. Faust says. "You have to describe the organisms to name them."

Examining viruses, fungi, insects, mites and nematodes under the scanning electron microscope makes the country's crops safer, says Eric Erbe, research scientist in electron microscopy at the Henry A. Wallace Beltsville Agricultural Research Center, which is part of the Agricultural Resource Service in the U.S. Department of Agriculture.

Because hundreds of pests invade crops, Mr. Erbe says his department studies healthy plants and learns how to grow them more effectively.

"We look at the host plant to see how it looks in the healthy and infected state," Mr. …