Prokaryotes(Bacteriology)
Laboratory 2Biology 171
Three domains of life: two are prokaryotic
ProkaryotesAn organism that lacks a membrane-enclosed nucleus
and other membrane-enclosed organelles
ProkaryotesAn organism that lacks a membrane-enclosed nucleus
and other membrane-enclosed organelles
ProkaryotesThese 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 ColoniesSource 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
• Observe these bacteria by making a wet mount slide and observing with a compound microscope.
• Draw pictures, record their behaviors, colors, etc.
Genus
Anabaena
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
Filamentous – grows in long strings of many cells
OscillatoriaFilamentous – grows in long strings of many cells
Nostoc
Heterocyst – anoxic environment…nitrogen fixation cannot happen in the presence of oxygen
Colonial filamentous – grows in long strings of many cells that cannot function (i.e. survive) individually
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