Prokaryotes Life Science. What are Prokaryotes? Single-celled organisms Very tiny Cannot be seen without a microscope Our microscopes are not.

ProkaryotesLife Science

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)

Bacterial shapes

Baccili: Rod shaped

Cocci: Sphere-shaped

SpirilliSpiral-shaped

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

Structure of Bacterial Cells

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