Post on 25-Dec-2015
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.
Classification and Evolution
Prokaryotes are split into 2 Domains (Recall Taxonomic Levels?) 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
Your textbook still has them listed as bacteria…
Domain Bacteria
Made up of bacteria (surprised?)
Only 1 kingdom-Can you guess what it’s called?
Most abundant living things on Earth.
Live in almost every environment
Air
Ocean
Soil
Intestines
Estimated number of bacteria on earth: 5,000,000,000,000,000,000,000,000,000,000
You have 10 times more bacterial cells than human cells!
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)
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 (circular DNA)
Bacterial cells also may contain whip-like structures called flagella
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) Example: Nitrogen fixation
Mutualism Getting resources from other species, while providing some service
to that species (+/+)
Parasitism Stealing resources from host organisms (+/-)
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 produce vitamins
Decompose wastes
Fix Nitrogen into usable forms for plants
Make foods such as cottage cheese, yogurt, cheese, and many more.
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
Transmitted by fecal-oral route. WASH YOUR HANDS AFTER USING THE BATHROOM!!!
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
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
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
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 is 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.
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.
Domain Archaea
Only 1 Kingdom 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
They were given their own Domain and Kingdom
Very little is known about these organisms
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
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
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