Tuesday, January 4, 2011


The new class is going OK so far. I have very little formal training as a microbiologist, and I'm more of a molecular biologist who happens to work in Bacteria than an actual microbiologist. So, until today, I've never used a microscope for work. Today, though, I had to teach a lab class, using microscopes--phase contrast, Gram stain, and so on. Fortunately, it was all review for the students, and the TAs did most of the work. I spent most of the time looking at all the groovy things that grow when you make herbal tea using hay.

"Hay infusion" is close to the roots of microbiology--after Leeuwenhoek, who looked at rain water and water that had pepper in it, most of the early discoveries in microbiology were done looking at the things that grew after you soaked hay in boiled water--a hay infusion. In the early days of the field, when it was still unclear whether the critters seen in the microscope were alive, or plants, or fungi, or whatever, scientists dodged the issue by calling them "infusoria."

So, here's some video of a couple of ciliated eukaryotes found in hay infusion. This first one is happily waving his cilia (or "paws," as Leeuwenhoek called them).

This second video shows the organism's "contractile vacuole" at work. Look for it at seven o'clock on the cell, getting larger then suddenly contracting every four seconds.

This organelle solves the difficult problem of osmosis: water is constantly flowing into the cell, trying to dilute the contents of the cell so they are at the same concentration as the surrounding liquid. If the cell doesn't want to explode from the inrushing water, it has to get rid of it. So, it spends lots of energy sucking water out of its cytoplasm and concentrating pure water in the contractile vacuole--then discharging that pure water back out into its surroundings.

Technical notes: Zeiss optics, 10X60 or 10X100 with phase contrast and oil immersion, and the video was shot using a Canon PowerShot SD 880 held up to the eyepiece.

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