can be thought of as a parade of many very tiny creatures. How decomposition
proceeds in your column depends on which bacteria and fungi inhabit
it, what ingredients you have put inside, and environmental factors
such as light, temperature and moisture.
The first decomposing organisms that go to work attack the most
available food molecules, such as sugars, carbohydrates and proteins.
As they grow, these first bacteria and fungi also change the environment.
For example, they produce heat, change the pH and consume oxygen.
You will see these changes in your column as plant parts become
dark and slimy.
As they change their own environment, these organisms can create
conditions that favor competing microbes. The biological definition
of succession is the replacement of one
type of organism by another, often caused by environmental changes
wrought by the first organism.
In your Decomposition Column, for example, one type of bacteria
might flourish, changing the pH and raising the temperature of the
column in the process. These new conditions may be favorable for
a more heat tolerant type of bacteria, which will take over the
A Decomposition Column will show you the dynamic process of decay:
strange white fuzz may appear and cover your column for a few days
before suddenly disappearing to be replaced by a dark fuzz that
climbs up one side. You might see something orange and slimy moving
slowly along a rotting twig. You may also observe nonmicrobial life
such as fruit flies, mites and millipedes.
Bacteria, fungi, algae, protozoa and other organisms that live
on dead or decaying matter are collectively known as saprophytes.
Saprophytes often secrete enzymes onto material they want to eat.
Enzymes are biochemicals, responsible for all kinds of chemical
reactions including the breakdown of matter into digestible parts
for the decomposers. A crumbling log lying on the forest floor,
for example, shows the work of enzymes made by saprophytes.
are the most numerous of the decomposers. Good soil may have 100
to 1,000 million bacteria per gram. You may see bacterial colonies
as round spots, ranging from white, to cream, to brown in color.
There are many types of bacteria. You might identify one type by
its odor. These bacteria, called actinomycetes,
live in the soil and are responsible for that fresh, earthy smell
that accompanies newly plowed soil, or a long awaited summer rain.
might appear in your column as a fuzzy blanket of mold covering
some delectable rotting thing. Mold fungi form mazes of tiny threads
called mycelium. If you look closely,
you may see tiny dots along the threads. These dots are fruiting
bodies, which release fungal spores. A particularly common mold,
Rhizopus, has a cottony appearance with
black dots, and often shows up on bread, fruits and other food.
molds are organisms that move, feeding on microorganisms
such as bacteria. They are often brightly colored and have the appearance
and consistency of pudding. Slime molds often move toward light,
leaving snail-like tracks behind, and producing numerous tiny fruiting
bodies, some resembling tiny mushrooms.
might show up in your column as a green tinge on the soil surface
or on a moist twig. You have probably seen algae, like Spirogyra,
growing on the banks of a river, a lake, or perhaps the sides of
a fish tank, or as seaweed in the ocean.
Protozoans are another organism with
a role in the decomposition drama. These single-celled organisms,
such as amoebas, vary widely in size, shape and the manner in which
they move. You might see protozoa swimming if you mix a little water
with some decomposing material and examine it under a microscope.
Although much of the action takes place on a microscopic scale,
decomposition is an exciting process even to the naked eye. By studying
your Decomposition Column you can get a sense of the great diversity
and activity of microbial life. Bacteria, fungi, algae and protozoa
may be small but they are responsible for a great deal of change.