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Microbiologists perform a wide range of jobs and activities, and the tools they use are just as diverse. The instruments and techniques that microbiologists use range from the simplest to the most complex.
Microscopes are to microbiology what telescopes are to astronomy.
The earliest microscopes were simple instruments consisting of one or more crude glass lenses similar to those used to make early spectacles. The invention of the first true microscope is credited to the Jansen family of Middleburg, Holland, around 1595.
Later, in the 17th century, Dutch cloth merchant and amateur scientist Anton van Leeuwenhoek enlightened the world to what he dubbed “animacules” such as protozoa found in standing water. Using microscopes he made himself, Leeuwenhoek wrote up what he viewed in pond water, plant material, even gunk scraped off his teeth. He was the first to identify sperm and red blood cells.
There are two basic types of microscopes: light microscopes and electron microscopes.
Light microscopes may be familiar to you from biology classes.
Light microscopes can magnify an object up to 1,000 times. Good light microscopes are powerful enough to view most algae, fungi, and protozoa.
High-quality light microscopes (pictured right) generally allow viewing of bacterial cells, too. They can’t view viruses, however, as these tiny objects are smaller than a wavelength of visible light (about 0.2 microns). Nor can they readily allow scientists to examine individual tiny parts of cells in detail.To view extremely tiny objects, scientist use electron microscopes.
There are three types of electron microscopes: transmission electron microscopes (TEM), scanning electron microscopes (SEM) and scanning-tunneling electron microscopes (STM).
TEMs transmit electron beams through a thin section or slice of a specimen to create an image. TEMs are particularly useful for studying the insides of cells.
With SEMs, the specimen is usually coated with an ultra-thin layer of gold atoms. The electron beam scans over the surface of the specimen, exciting electrons on the surface. When these surface electrons are emitted (as secondary electrons), they are collected by special devices that create an image out of them.
SEMs are especially useful for studying the surfaces and structures of cells. With their great depth of field, SEMs produce 3-D images.
STMs can display things as infinitesimal as the individual atoms on an object’s surface. They scan specimen surfaces in the same way as SEMs, but they use an electrically charged tip that is placed within nanometers of the surface of the specimen. Electrons “jump” between the tip and the specimen surface in what’s called the tunneling current, hence the name of this kind of microscope.
As the tip is moved back and forth across the specimen, the current varies according to whether the tip is right over an atom or over the space or trough between atoms. A computer creates an image based on these differences in current.
When microbiologists want to identify microbes in a sample or study microbes in-depth, they often try to culture, or grow, the microbial cells in their labs. The scientists can then manipulate the cells or their environments to see what effects these changes have on the organisms.