These are bacteria that I found recently in a water sample. They are spiral shaped, and move like cork screw. Bacteria are the smallest organisms on earth. These here are comparatively large, however, and I had no problems seeing them with my 40x objective. Bacteria are generally quite difficult to see. They are not only quite small, but also transparent. I am therefore using phase contrast to make them better visible.
I did also notice a somewhat unusual behavior. The bacteria were not randomly moving around the slide. Most of them were in a swarm, moving collectively into one direction. I therefore had to recenter the slide several times. I have seen this phenomenon already a few times before. I think it might have to do something with the oxygen concentration under the cover glass. Maybe the heat from the microscope lamp also plays a role. They might be moving towards edge of the cover glass, where the oxygen concentration is highest. But this is a “working hypothesis”.
I am sometimes asked if it is possible to identify the bacteria that can be seen under the microscope. What are the names of these bacteria now? Are they harmful, are they beneficial? Or neither?
Unfortunately it is not possible to say that using microscopes alone. The diversity among bacteria is simply too high. Bacteria that look similar or even identical, can be completely unrelated to each other. As a matter of fact, the majority of bacteria can not even be cultured in the laboratory for further analysis. So the chances are very good, that we are now seeing bacterial species, that have never been studied before. To this date, scientists characterized several thousand bacterial species, but know that there must probably be millions.
There are some amateur microscopists that want to test their equipment also by looking at bacteria. Here I recommend that you use a safe source. Put a bit of yogurt on the microscope slide and you might be lucky. Make sure that you close the condenser of the microscope completely to increase contrast.