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Prokaryotes Biology 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..

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Prokaryotes Biology What are Prokaryotes?

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What are Prokaryotes?

Single-celled organisms

Very tiny

Cannot be seen without a microscopeOur microscopes are not powerful enoughLack a nucleus and most other organellesMost numerous organisms on EarthExtremely important organisms.Slide3

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 agoOnly living things on earth until 2 billion years ago

Until 1970s, Archaea were considered to be bacteria (called


) As more was learned about them, they were given their own domain because they are VERY different from bacteriaSlide4

Domain Bacteria

Made up of bacteria

Only 1

kingdom-BacteriaMost abundant living things on Earth.Live in almost every environmentAirOceanSoil


Estimated number of bacteria on earth: 5x10

30You have 10 times more bacterial cells than human cells!Slide5

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) Slide6

Bacterial shapes



Rod shapedCocci:




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 cellsInside of the bacterial cell is cytoplasm, similar to eukaryotic cellsFloating 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 objectsSlide8

Structure of Bacterial CellsSlide9

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)MutualismGetting resources from other species, while providing some service to that species (+/+)Parasitism

Stealing resources from host organisms (+/-)Slide10

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 notBenefits of BacteriaCreate medicine, such as vaccinesHelp 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.Slide11

Dark side of Bacteria

Some bacteria can lead to disease


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






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, strep throat

Mycobacterium 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 1353Slide13

A child and a portrait of a soldier affected with tetanus Slide14

If you have a weak stomach, please look away now…Slide17

Spread of the Black DeathSlide19

Artist drawing of a typical street during the spread of the black death.Slide20

At least the Plague is over… Right?Slide22

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 humansEffective against bacterial infections such as strep throat, sinus infections, ear infections, pneumonia, etc.However, there is a problemSlide23

Antibiotic Resistance in Bacteria

Some bacterial species are evolving resistance to antibiotics.


www.youtube.com/watch?v=znnp-Ivj2ek The antibiotic kills those that are not resistant, but leaves the one that are resistantExample: 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.Slide24

Even more alarming…

Remember how we just learned that Tuberculosis is the 2


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 usedAnother is resistant to 3 of the 6 drugs used to treat it.Slide25

Genetic Diversity in Bacteria

Bacteria reproduce asexually (without sex)

Called binary fission

One bacteria replicates its DNA and then splitsMakes clones-identical copiesBenefit: Quick, little energy used, don’t need a mateDisadvantage: No genetic diversity

Susceptible to extinction

Conjugation is a way bacteria can increase genetic diversity

Exchanging all or part of a plasmid with another bacteriaNo longer identical Slide26

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 changeEvolutionBacteria, because they reproduce asexually, are able to quickly adaptThe antibiotic kills the weak ones and eliminates them as competition for strong ones.

They will rapidly reproduceSlide27

Domain Archaea

Only 1 Kingdom

Called Archaea (Surprised?)

ProkaryotesFirst discovered in extreme environmentsOriginally classified as bacteriaAs more was learned about them, they were found to be VERY different from bacteriaTheir cell wall is more similar to Eukaryotes than bacteria

They were given their own Domain and Kingdom

Very little is known about these organismsSlide29

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)


-Live in very basic environmentsSlide30

Where else do they live?


chaea 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 parasitesMost form mutualistic relationshipsArchaea in cattle gut help break down grass and straw, and get nutrients in return