Figure 1. Dental plaque stained with iodine. Used by permission of J.D. Ruby and V.F. Gerencser.
NAME, ID #:_______________________________________________.
REVISION DATE: 08/04/99
Figure 1. Dental plaque stained with iodine. Used by permission of J.D. Ruby and V.F.
Gerencser.
Recall the last time you waded barefooted into a pond, lake or stream and you stepped on the rocks and felt that "SLIMY" stuff squish between your toes? You were probably warned that it was slippery and to be careful not to slip. That slime is composed of a layer of microbes that grow ATTACHED to the rocks and other material under water. Microbes find it DESIRABLE to attach themselves to solid surfaces for a variety of reasons, the most importance of which is to keep from being washed away by a flow of liquid. Consider the problem a mouth or urethra microbe faces. Every time a person takes a drink any unattached microbes are likely to be washed into that LETHAL ACID BATH called the stomach; not a FUN trip. Similarly, a microbe in the urethra faces IMMEDIATE EXPULSION every time the person urinates if it is not firmly attached to the wall of the urethra (think of the pictures you've seen on TV of people caught in floods clinging desperately to a tree etc. to keep from being washed away). Obviously microbes in streams face the same serious problem, as do those in Trickling Filter sewage treatment plants, of being washed away by the continuous flow of water. To deal with this predicament microbes, like oysters and barnacles, have evolved elaborate systems for gluing themselves to things; like the cells they want to feast on.
Among the most important attachment structures produced by bacteria are #PILI and CAPSULES. These, and other attachment components, act to bind or stick bacteria to solid surfaces with the expressed purpose of keeping them in place against some force which would otherwise FLUSH them away. In the case of pathogens we are discovering that the attachment components are important VIRULENCE FACTORS and 100s of hard working graduate students, like your lab instructors, are laboring long hours at lab benches all over the world studying attachment. Incidentally, the US NAVY spends millions of your tax dollars/year trying to find ways to keep microbes and organisms like barnacles from attaching to the hulls of their ships. The effect of all these organisms clinging to the hull of an atomic carrier for example is to SLOW it down to a crawl.
The plaque on your teeth (Fig. 1) that contributes to tooth decay is the result of microbes, acting in concert to form a glue that attaches them tightly to the surface of your teeth and gums (remember that "scrapping sound" the last time you had your teeth cleaned?). Also consider what keeps that scum in place that forms on your tongue at times (which, incidentally, is where bad breath originates)?
In this exercise you will view slides that have been immersed in aquarium water for a time. You will stain these slides and observe the organisms fixed on them. It may be of interest to you to know that many of the organisms you will be seeing have probably never been cultivated and you could be the first one to ever see them.
Click here to see some fresh-water algae.
Visit this site for more information and pictures on biofilms
SAMPLE QUESTIONS: You should be able
to answer these questions at the conclusion of this laboratory. 
Copyright © Dr. R. E. Hurlbert, 1999.
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