Viewing microbes through a microscope provides much information about these small living organisms. Most microbes are composed of 70-90% water, so light passes easily through the cells. To assist the student to better view the microbe, stains or dyes are used to color the cells and/or cell structures (organelles). Staining cells kills the microbes and limits our observation of "life processes" in the microbes.

Staining the microbes and selection of a good microscope are important in the studying of microbes. Robert Koch spread microbes on a slide (prepared a smear) and permitted the microbes to dry. Today we use this same beginning procedure, and then we fix (attach by heating the slide) to kill and secure the microbe to the slide. Colored dyes called stains are then added to the smears. Basic stains like methylene blue, safranin (red), and crystal violet are attracted to the acidic contents of cells and are called positive stains because these stains color the microbe. Other acidic stains like Nigrosin and India ink are repelled by the chemical charge on the microbes and stain the background or environment.

How small are micro-organisms? Among the answers are tiny, too small to see, very little, microscopic, one-half an inch, one-tenth of a millimeter, etc. Yes, microscopic means too small to see clearly without the help of a microscope and is a good answer. By the way, macroscopic means large enough to see with "naked eye." I guess a naked eye is not clothed with a contact lense or microscope. But how big is small? Microbiologists use the metric system so one-tenth of a millimeter is microscopic. The unit of measurement used in microbiology is the micron. A micron is 1/1000 of a millimeter or 1000 microns equal one millimeter. Now, how small is microscopic? Most microbiology students can visualize that 250-300 microns is microscopic. So living organisms that are larger than 500 microns (0.5 mm.) are usually considered macroscopic. The "big one" is a microbe found recently in a sturgeon (fish) and measured about 600 microns. To read about the "big one" search for Epulopiscium fishelsoni on the Internet.

Imagine the excitement of Leeuwenhoek when he first saw the amazing variety of organisms in rainwater; the feeling of achievement when Louis Pasteur confirmed that microbes produced acids during fermentation; the thrill experienced by Robert Koch when he isolated the bacteria causing anthrax; the sense of accomplishment when agronomists identified Phytopthora and the potato famines of Europe could be eliminated; the sense of relief when Schaudin and Hoffman identified Treponema as the microbe causing syphilis; the great feeling when Ruska improved the electron microscope; and Enders, Weller, and Robbins's feeling of success when they cultured the polio virus.

How big are these microbes? Among the smallest microbes are viruses even though viroids that attack plant cells and prions which attack animal brain cells are smaller. Viruses are less than a micron in size. In fact the small polio virus is 28 nanometers and the large smallpox virus is 200 nanometers. (A nanometer is 1/1000 of a micron.) Bacteria usually range in size between 0.5 and 20 microns; yeast cells are similar to small bacteria and often measure 1-5 microns; the protists have extreme size variation with some algae including Chlorella (15 microns) and protozoans including Paramecium (200 microns); and worm eggs range in size from 50 microns (Taenia = tapeworm) to 100 microns (Fasciola= fluke).

The classroom microscope is a great tool for studying micro-organisms. With a typical magnification including 1000x, classroom microscopes help microbiology students observe organisms like Streptococcus (2 microns), E.coli (5 microns), and Amoeba (150 microns). The electron microscope (EM) has been used by microbiologists since the 1930s. Using beams of electrons which travel in waves that are 100,000 times shorter than waves of visible light, this EM has tremendous resolution (ability to separate) and magnification from 5000x to 750,000x. The electron microscope has been extremely beneficial in helping us better photograph and understand concepts like entry and ecape from cells by viruses. The black and white photograhs are called micrographs.

The microscope helps us recognize the shapes of bacterial cells. The three main shapes of cells are round, rod, and twisted. Round shaped bacteria cells are called cocci (singular= coccus). Examples of bacteria with round cells include Staphylococcus, Streptococcus, and Neisseria (causes gonorrhea). Rod-shaped cells are called bacilli (singular = bacillus); and examples of rod-shaped bacteria include E.coli, Salmonella, and of course Bacillus. Note that "bacillus" is a shape and Bacillus is a genus name of rod-shaped bacteria like Bacillus anthracis which is the bacterium that causes anthrax in cattle. Rod-shaped bacteria include bent or curved rods; so Vibrio is a curved bacillus that causes cholera. Can you identify the shape of Vampirovibrio chloravoris? That is an interesting genus name for an organism that devours (voris) Chlorella (green algae) by "sucking" (vampiro) out the cytoplasm. Even though some generic names are lengthy, most microbiology students can understand their names; however, genus names like Giardia lamblae simply indicate the names of the microbiologists who discovered this protozoan that causes severe intestinal disorders if consumed in water. Giardia has been identified in the lakes of Minnesota. The twisted or helical cells are called spirilla (singular =spirillum). These twisted cells can be flexible (Treponema which causes syphilis) or rigid corkscrew shape like Campylobacter (bacterium that causes food-borne illness). Some species of bacteria vary in shape; this is called pleomorphism. Variations and/or lack of rigid cell walls cause microbes like Mycoplasma, Corynebacterium, and Rhizobium to appear swolllen, curved, or club-shaped.