1. Prokaryotes
Biology

2. What are Prokaryotes? Single-celled organisms
Very tiny
Cannot be seen without a microscope
Our microscopes are not powerful enough
Lack a nucleus and most other organelles
Most numerous organisms on Earth
Extremely important organisms.

3. Classification and Evolution
Prokaryotes are split into 2 Domains
Domain Bacteria
Domain Archaea
Everything else on Earth is in Domain Eukarya
Prokaryotes were the first living things to evolve, around 3.8 billion years ago
Only living things on earth until 2 billion years ago
Until 1970s, Archaea were considered to be bacteria (called Archaebacteria)
As more was learned about them, they were given their own domain because they are VERY different from bacteria

4. Domain Bacteria Made up of bacteria Only 1 kingdom-Bacteria
Most abundant living things on Earth.
Live in almost every environment
Air
Ocean
Soil
Intestines
Estimated number of bacteria on earth: 5x1030
You have 10 times more bacterial cells than human cells!

5. Classification of Bacteria
Thousands of bacterial species exist.
Many are classified by shape.
Others are classified based on the color that they stain (Gram staining)

6. Bacterial shapes Baccili: Cocci: Spirilla Rod shaped Sphere-shaped
Spiral-shaped

7. Structure of Bacterial Cells
Bacterial cells are surrounded by a plasma membrane
Most also have cell walls
Surrounding the membranes and cell wall (if present) is a capsule, which further protects the cells
Inside of the bacterial cell is cytoplasm, similar to eukaryotic cells
Floating in the cytoplasm are ribosomes and plasmids (small sections of DNA)
There is no nucleus
Instead, there is a Nucleoid (area with DNA) and may be plasmids (circular DNA) to be exchanged with other bacteria
Bacterial cells also may contain whip-like structures called flagella
Also have hair-like protrusions called pili that allow them to attach to objects

8. Structure of Bacterial Cells

9. How do bacteria get energy?
Some are photosynthetic
Others decompose organic matter
Some can use chemicals from the environment to do a process similar to photosynthesis (called chemosynthesis)
Mutualism
Getting resources from other species, while providing some service to that species (+/+)
Parasitism
Stealing resources from host organisms (+/-)

10. Bacteria and People
You may think that bacteria’s purpose is to make us sick
For some bacteria, this is true
For many others, it is not
Benefits of Bacteria
Create medicine, such as vaccines
Help us digest foods and get vitamins
Decompose wastes
Fix Nitrogen into usable forms for plants
Make foods such as cottage cheese, yogurt, cheese, and many more.

11. Dark side of Bacteria Some bacteria can lead to disease
Clostridium tetani
Tetanus aka Lockjaw
Affects muscles (including the heart). Leads to muscle spasms, and can be fatal.
Escherichia coli (E. Coli)
Many strains exist in human intestines in a commensalism relationship. However, some can cause food poisoning.
Transmitted by fecal-oral route. WASH YOUR HANDS AFTER USING THE BATHROOM!!!
Salmonella bongori & Salmonella enterica
Salmonella
Cause Typhoid fever (very fatal) and Food Poisoning

12. Dark side of Bacteria Continued
Staphylococcus (many species)
Sinus infections, ear infections, skin infections, food poisoning
Streptococcus (Many species)
Pneumonia, necrotizing fasciitis (flesh-eating bacteria), pink eye, strep throat
Mycobacterium tuberculosis (Tuberculosis)
Second deadliest infectious disease (After HIV/AIDS).
Yersinia pestis
“The Bubonic Plague” or “The Black Death
Killed over 1/3 of the European Population between 1347 and 1353

13. A child and a portrait of a soldier affected with tetanus

16. If you have a weak stomach, please look away now…

18. Spread of the Black Death

19. Artist drawing of a typical street during the spread of the black death.

21. At least the Plague is over… Right?

22. Controlling Bacteria
Bacteria in food and water can be killed by cooking at a high temperature
Bacteria on surfaces can be killed with cleaning products such as bleach or Lysol
Antibiotics can be used to kill bacteria that are harming humans
Effective against bacterial infections such as strep throat, sinus infections, ear infections, pneumonia, etc.
However, there is a problem

23. Antibiotic Resistance in Bacteria
Some bacterial species are evolving resistance to antibiotics.
The antibiotic kills those that are not resistant, but leaves the one that are resistant
Example: Clostridium difficile
A common bacteria that causes diarrheal disease in hospitals. Hospitals, due to their obsessive cleaning procedures, have selected for resistant strains. Patients are being infected at a high rate, while staying in hospitals.

24. Even more alarming…
Remember how we just learned that Tuberculosis is the 2nd most deadly infectious disease… Well…
Tuberculosis is spreading due to becoming resistant to the antibiotics typically used to treat it.
One strain is totally resistant to ALL drugs currently used
Another is resistant to 3 of the 6 drugs used to treat it.

25. Genetic Diversity in Bacteria
Bacteria reproduce asexually (without sex)
Called binary fission
One bacteria replicates its DNA and then splits
Makes clones-identical copies
Benefit: Quick, little energy used, don’t need a mate
Disadvantage: No genetic diversity
Susceptible to extinction
Conjugation is a way bacteria can increase genetic diversity
Exchanging all or part of a plasmid with another bacteria
No longer identical

26. Antibiotic Resistance and Evolution by Natural Selection
Organisms must adapt to changing environments or they will die off
Called natural selection
As organisms adapt, the frequency of alleles (traits) in the population change
Evolution
Bacteria, because they reproduce asexually, are able to quickly adapt
The antibiotic kills the weak ones and eliminates them as competition for strong ones.
They will rapidly reproduce

28. Domain Archaea Only 1 Kingdom Prokaryotes
Called Archaea (Surprised?)
Prokaryotes
First discovered in extreme environments
Originally classified as bacteria
As more was learned about them, they were found to be VERY different from bacteria
Their cell wall is more similar to Eukaryotes than bacteria
They were given their own Domain and Kingdom
Very little is known about these organisms

29. Archaea: Tiny but Tough
Many archaea are extremophiles
Organisms that have evolved to live in extreme conditions.
Example: Hydrothermal vents in the ocean (picture) are very acidic and hot.
Would kill most organisms, yet archaea thrive.
4 types of extremophiles
Halophiles-Survive in very salty water (Dead sea)
Hyperthermophiles- Survive at high heats
Some archaea can survive up to 122° C (252° F)
Acidophiles-Live in highly acidic environments (like near volcanoes)
Alkaliphiles-Live in very basic environments

30. Where else do they live?
Archaea do not only live in extreme environments
They are found nearly everywhere on Earth.
Including in humans (many are found in the human belly button!)
Around 4 % of human microbiome
The microorganisms that live on or in us
They are also important decomposers, and part of Nitrogen cycle
Many archaea also form symbiotic relationships
None are known parasites
Most form mutualistic relationships
Archaea in cattle gut help break down grass and straw, and get nutrients in return