Download Microorganisms and Their Environment

Microorganisms and
Their Environment
October 11, 2004
What are Microorganisms?

A microorganism is any living thing of
microscopic size or smaller.
Bacteria
Yeasts
Protists
40,000x Mag.
10,000x Mag.
200x Mag.
Also Viruses, some Algae, and some Animals
The Importance
of Microorganisms

Microorganisms have positive and
negative effects on humanity.
– Many foods, beverages, and medicines
are made with the help of bacteria and
yeast.
– The spoilage of food and many diseases
are caused by microorganisms.
The Benefits
of Microorganisms
Beer made with yeast.
Bread made with yeast.
Champagne made with yeast.
Cheese made with bacteria.
Pickles made with bacteria.
Sauerkraut made with bacteria.
Soy Sauce made with bacteria.
Yogurt made with bacteria.
The Drawbacks
of Microorganisms




Some bacteria cause infections and diseases
like tuberculosis and bubonic plague.
Some protists cause diseases like malaria
and sleeping sickness.
Some viruses cause diseases like the flu,
measles, chicken pox, polio, and HIV.
Some yeasts also cause infections.
An Experimental Question

What conditions are suitable for growing
microorganisms for our benefit?
Or

What conditions are necessary to prevent
the growth of microorganisms?
Our Experimental Organism


Baker’s Yeast (S. cerevisiae) is found
naturally growing on grapes and
other fruits.
It has been used for thousands of
years for baking and brewing.
Characteristics of
Baker’s Yeast




Readily available in the grocery store.
Can grow in temperatures ranging from 8 to
40 degrees C. (46 to 104 degrees F.)
Can survive pH levels between 2.4 and 7.4
Reproduces quickly, optimally doubling
every hour.
Metabolism of Baker’s Yeast

In the absence of oxygen, yeast will
undergo anaerobic respiration.
C6H12O6
Glucose

 2 C2H6O + 2 CO2
Ethanol
Carbon
Dioxide
Yeast can also use sucrose (cane sugar) and
fructose (fruit sugar) as a sugar source.
Characteristics of
Various “Liquids”
Liquid
pH (Acidity)
Main Sugar
Water
7.0
None
Sugar
per 10 ml
None
Grape Juice
3.4
Fructose
1.667 g
Lipton Tea
2.5
Fructose
0.875 g
Lemonade
2.4
1.125 g
Gatorade
3.2
Fructose /
Sucrose
Fructose /
Sucrose
0.583 g
Independent (Input)
Variables



What conditions should we test in our
experiment?
We will grow our yeast in liquid to
easily deliver the sugar source.
But what liquids should we pick?
Dependent (Output)
Variables


Remember that we want to determine what
conditions are most suited to growing
yeast cells.
How can we use the reactants and / or
the products of yeast metabolism to
answer our experimental question?
Yeast Incubation Tube
Grape Juice
Time = 0 hours
Sealed Yeast
Incubation Tube
Apple Juice
Time = 24 hours
A Pair of Sealed Yeast
Incubation Tubes
Apple Juice
Milk
Time = 24 hours
The Complete
Experimental Set-Up
CO2 Collection Tubes
Incubation Tubes
CO2 Collection Tubes
Time = 0 hours
0 ml CO2 Collected
CO2 Collection Tubes
Time = 24 hours
1 ml CO2 Collected
CO2 Collection Tubes
Time = 48 hours
5 ml CO2 Collected