prokaryotes (bacteriology) laboratory 2 biology 171

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