Prokaryotes
(Bacteriology)
Laboratory 2
Biology 171
Three domains of life: two are prokaryotic
Prokaryotes
An organism that lacks a membrane-enclosed nucleus
and other membrane-enclosed organelles
Prokaryotes
An organism that lacks a membrane-enclosed nucleus
and other membrane-enclosed organelles
Prokaryotes
These organisms have circular DNA with very simple
transcription processes
Domain Archaea – thermophiles
(extremophiles)
Today in Lab
• Exercise 1: General Features of Bacteria
– Lab Study A: Colonies
– Lab Study B: Individual morphologies
– Lab Study C: Gram Stain
• Exercise 4: Investigating Microorganisms
– Lab Study A: Controlling bacterial growth
• Observing Cyanobacteria
– Anabaena, Oscillatoria, Nostoc
Bacteria
• Unicellular microorganisms
• a few micrometers in length
• Numbers…
– 40 million bacterial cells in a gram of soil
– 1 million in a milliliter of freshwater
– Approximately 10x as many bacterial cells as human cells
in the human body – most on skin & digestive tract
– Approximately 5 nontrillion (5 x 1030) on earth!
5,000,000,000,000,000,000,000,000,000,000
Where are bacteria found?
• EVERYWHERE!
– In the soil and water
– On and in our bodies
– In the air we breathe
• Critical to nutrient cycling as decomposers
• Some cause disease
– Vast majority are harmless, but half of all human diseases
are caused by bacteria
Anatomy of a Bacterium
• Some examples of
differences between
bacteria and
eukaryotic cells?
– Cell wall
– Capsule
– Ribosomes
• How could these
differences help fight
disease?
Activity A: Bacterial Colonies
• the population of bacteria derived
from one or a few cells, visible
with the unaided eye
• Exponential growth
– For example, if we start with only
one bacteria which can double every
hour, by the end of one day we will
have over 16 million bacteria.
– At the end of 24 hours, there are
16,777,216 bacteria.
Colony Shape
Colony Color
Diversity of Bacterial Colonies
Source
Number of Different Types of Colonies
Activity B: Bacterial Shapes
Spirilla
Activity C: Gram Stain
• Invented by Hans Christian Gram in
1884 to discriminate between two
types of bacteria that had similar
symptoms.
• Gram-positive bacteria tend to be
more sensitive to most antibiotics.
• Other antibiotics work better on
gram-negative bacteria.
• Broad-spectrum antibiotics work on
both types.
Exercise 4: Controlling bacterial growth
Antibiotics – drugs that either kill or inhibit the
growth of bacteria. They assist the immune
system…blocks cell division (peptidoglycan
synthesis)
Antibiotics in Healthcare
• Antibiotics such as penicillin and
tetracycline have helped save millions of
people around the world.
• Penicillin was discovered in 1941, before
this there was no cure for diseases such
as pneumonia, strep throat, and
gonorrhea.
• Patients with infected wounds often had
to have limbs amputated or risk infection
spreading to the rest of the body.
Cyanobacteria (not in manual)
• Def: photosynthetic, oxygen-producing bacteria,
formerly called blue-green algae
– Anabaena
– Oscillatoria
– Nostoc
Genus
• Observe these bacteria by making a wet mount slide
and observing with a compound microscope.
• Draw pictures, record their behaviors, colors, etc.
Anabaena
Filamentous – grows in long strings of many cells
Heterocysts – involved in nitrogen fixation - which is the process
where gaseous nitrogen is “fixed” into ammonia, necessary for
building many parts required for life, e.g. DNA and proteins
Oscillatoria
Filamentous – grows in long strings of many cells
Nostoc
Colonial filamentous – grows in long strings of many
cells that cannot function (i.e. survive) individually
Heterocyst – anoxic environment…nitrogen fixation
cannot happen in the presence of oxygen