Go back in time. Put yourself in 1900, for that is when this took place. Sophomore Mary Lou breezed into lab only to find her nemesis Cheryl too closely associating with her senior colleague "Jimmy-the-Bod". Mary Lou has had her eyes on Jim for some weeks now. But Mary Lou just did not have the terrific intellectual and morphological genes that Cheryl had. Anyway, while the pair's backs were turned, she took a live culture of relatively small, aerobic Bacillus subtilis from her rack and poured a little into each of the three cultures standing on Jim's sunny desk next to the window. Ooops, they were turning around! The tube of B. subtilis was hastily put into a rack on Jim's desk. With considerable satisfaction at not getting caught, Mary Lou slipped away and out of the room. Cheryl and Jim set about to inspect their three cultures under the microscope. They were studying 'very large' microbes: Bacillus megaterium is one of the largest true bacteria, and also a few of its cells possesses a round spore as does the one shown below; Centimeter-long Beggiatoa is a 'higher bacterium' which is photosynthetic and converts sulfide to sulfur;* huge Spirogyra is eucaryotic with a distinctive helical single chloroplast. The students made "wet-mount" slides of each under cover-slips, and set them on their desk as they set up their microscope.

    Two hours later Mary Lou returned to the scene of her crime to find that Prof. Bengston had joined Cheryl and Jim as all three were whooping it up and excitedly discussing what they were seeing. Remember that this happened back in 1900. (Below are 5 microscope views, and one of a test-tube.)

    You will note that the rod-shaped B. megaterium has a spore in this view. The Beggiatoa has blue-greenish cylinders as well as some sulfur granules that look like little black diamonds. The helical chloroplast of the Spirogyra is very distinctive, and its nucleus is only slightly visible. Samples were also taken for microscopic viewing from the tube that had been sitting for awhile.

    From these pictures and background information, discuss the tremendous significance of all this. (Hints: remember that the group had done this around 1900, and you are looking at this from that time-perspective. This exercise is to help you escape the memorize-and-regurgitate routines of school. Expand your powers of observation, as well as draw on information you have stored at the back of your mind!)

*     Plants are known to do this in light:

CO₂ + H₂O → carbohydrate + O₂ (elemental O).

    Beggiatoa are known to do this in light:

CO₂ + H₂S → carbohydrate + S₆ (elemental S).

    Note that S lies directly below O on the periodic table. Thus you should expect somewhat similar reactions.