Bacteria and our senses
Written by Dr. T. M. Wassenaar Tuesday, 23 December 2008
Bacteria are too small to see with the naked eye. With the development of the microscope, which is nothing but a set of strong optical lenses, Antony van Leeuwenhoek made it possible for the first time to "see the unseen". Photo gallery of bacterial pathogens. If you can't get enough of this, check out our special feature file: Images of bacteria.
- How a microscope works
- Electron microscopes give an even bigger magnification. But how can one measure things using a microscope?
- How many bacteria are living in total on earth do you reckon? Check it out!
Who said bacteria couldn't be seen with the naked eye? There only need to be enough of them. The water in a vase of flowers becomes cloudy when it is not daily refreshed...there you can see your bacteria! And minute as they are, they are with many. View a 520 k time lapse movie of two E. coli cells dividing into hundreds in just a few hours. Note that they grow in a circular way. When millions of bacteria grow from one single cell on a solid medium, the result will be a small round heap, which we call a colony. To a bacteriologist, the shape of bacterial colonies is very informative. To an artist, and with a bit of comupation, colonies are just beautiful. Here is an excellent website showing Microbial Art. Each sort, or species, of bacteria forms a particular shape and color colony (yes, bacteria can have colors too), and this was an early way of recognizing and describing bacterial species. To study bacteria (see our exhibit on bacteriology) we still use microscopy as an important tool of identification, with the use of diverse staining methods. Laboratory tests of their biochemical properties are also important identification tools.
Taste them
Can we taste bacteria? Maybe not, but we can taste their metabolic products. When milk has gone sour, it is because bacteria, such as Lactobacillus, are growing in it. Sometimes bacteria change the taste of our food for the better, as in cheese, yoghurt, or sourkraut. Check out our exhibit on good bacteria in food. And even the stale taste in your mouth when you wake up in the morning is mainly due to bacterial activity.
Smell them
Bacteria have a smell of their own, or, more correctly, their metabolic products have. A bacteriologist will smell the plate on which his bacteria grew to check, just as he looks at the colonies to inspect their form. And don't you check the smell of milk to make sure it has not gone sour? The smell of pond water of questionable quality which smells like rotten eggs is also produced by bacteria. The smell of earth in a forest, or the smell of a wet dog - you are exposed to the smells of various bacteria more often than you would think.
Feel them
Can you feel bacteria? Difficult, but when they are infecting your body, the pain they cause can be quite noticeable! However, it is often your bodies defense that causes the pain. For instance, during an ear infection, fluid is accumulating in the middle ear, and this causes pressure on the sensitive drum. So it may not be the bacteria themselves you are aware of, but the pain is nothing less serious!
But can we hear them?
If you can think of an example, the curator of this museum would be all ear!
Last Updated on Friday, 04 November 2011