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Prokaryotes (Bacteriology) Laboratory 2 Biology 171.

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1 Prokaryotes (Bacteriology) Laboratory 2 Biology 171


3 Three domains of life: two are prokaryotic

4 Prokaryotes An organism that lacks a membrane-enclosed nucleus and other membrane-enclosed organelles

5 Prokaryotes An organism that lacks a membrane-enclosed nucleus and other membrane-enclosed organelles

6 Prokaryotes These organisms have circular DNA with very simple transcription processes

7 Domain Archaea – thermophiles (extremophiles)


9 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

10 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 10 30 ) on earth! 5,000,000,000,000,000,000,000,000,000,000

11 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

12 Anatomy of a Bacterium Some examples of differences between bacteria and eukaryotic cells? – Cell wall – Capsule – Ribosomes How could these differences help fight disease?


14 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.

15 Colony Shape

16 Colony Color

17 Diversity of Bacterial Colonies SourceNumber of Different Types of Colonies

18 Activity B: Bacterial Shapes Spirilla


20 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.



23 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)

24 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.

25 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

26 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

27 Oscillatoria Filamentous – grows in long strings of many cells

28 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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