GROWING ONE-CELLED MICROSCOPIC ORGANISMS- BACTERIA OF
Materials:A pieceofrawpotato(peeled), a few seedsofeither beans or
peas, two test tubes and a test tube holder, tap water.
Follow this procedure: Soak the small pieceofpotatoin a test tube of
water. Do the same with the bean or pea seeds. Leave the test tubes openand
exposed to air for three days. Then put a plug ofabsorbentcottonloosely
in each test tube. Keep the tubes in acomparativelywarm place for the next
Place a drop of the water from each test tube in the middle of a clean
glass slide. Carefully cover with a cover slip and observe, firstunderthe low
power ofyour microscope, then underhigh power.
You will observe: Hundreds of large, harmful bacteria. They will be
especially clearunderhigh power.
Bacteria thatcause the decay of dead plantand animalmatterlive as
spores(masses ofprotoplasmwith or withoutcell walls) in the air and even
on plants. When they getwarmthand moisture, they become active and feed
on dead plantor animal cells, actually breakingthem down. This process
results in decay.
Somebacteriaof decay are useful because they make soil rich forplanting
purposesbybreakingdown the cells of plants and animalsthathave died. The
materialsof which these cellshadbeen composedreturnto the soil to be used
asnourishmentby new growing plants. This isnature'smeansoffertilizing
soil. Theactionofbacteriainbreakingdown the cellsofdeadmatterprevents
the wasteofimportantminerals thatall living plants need in orderto grow
successfully. In turn, plants provide animals, including humanbeings, with
foodcontainingimportantminerals. All animals need minerals for thegrowth
OBSERVING BACTERIA OF DECAY
Materials: Driedlima beans, water, ajarwith a tight-fitting cover and
Soak some beans in a glass of water for several days. Thencover thejar
andkeep it in acomparativelywarm place for the next few days. Use your
medicinedropperand take off some of the fluid at the surface. Puta drop
or two on a clean slide. Cover carefully with a cover slip. Focusand observe,
firstunderlow power ofyour microscope and thenunderhigh.