Prokaryotes

Three domains of life

Bacteria, Archaea, Eukarya  

The estimated time of LUCA (Last Universal Common Ancestor)

3 billion years ago 

Which domains of life contain prokaryotes?

Bacteria & Archaea

What do all three domains have in common?

• have cell membranes and ribosomes

• share some metabolic pathways 

• use DNA as a genetic material

• replicate DNA 

What features are unique to prokaryotes?

• small, unicellular 

• lack membrane bound organelles

• divide by binary fission

• circular DNA, plasmids, no nucleus, haploid

Where are prokaryotes are found?

• every habitat on the planet

• our bodies (intestinal tract) 

How do prokaryotes reproduce?

binary fission: single cell divides into two identical daughter cells after replicating DNA (asexual reproduction) 

What shape is cocci?

round, ball shaped 

What is an example of cocci?

Staphylococcus and Streptococcus 

Where is cocci found? (diseases)

Strep throat, pink eye, meningitis, pneumonia, swiss cheese

What shape is bacilli?

rod shaped 

Where is bacilli found?

soil, fermented foods, bubonic plague

Endospore

Heat resistant, dormant resting state

What bacteria produces endospores?

bacilli

What causes endospores?

They are environmentally induced when key nutrients are scarce

How are endospores formed?

The bacterium replicates its DNA, encapsulates one copy and some cytoplasm in a tough cell wall with extra peptidoglycans

What infection does spirilli cause?

Leptospirosis: common infection in dogs

What are the cell walls of bacteria made up of?

peptidoglycan

What is peptidoglycan?

Polysaccharide made up of amino acids and sugars

How does peptidoglycan help categorize bacteria?

helps categorize between gram positive and gram negative bacteria

gram positive

thick multi layered peptidoglycan, retains dye and stains purple

gram negative

thin single layered peptidoglycan, stains red

obligate anaerobic

oxygen is poisonous. anaerobic metabolism

obligate aerobic

oxygen is required for cellular respiration

facultative anaerobe

can switch between fermentation and cellular respiration depending on if oxygen is available or not

Photoautotroph

• gets energy from light

• gets carbon from CO₂

Photoheterotroph

• gets energy from light 

• gets carbon from organic compounds made by other organisms 

Chemoautotroph

• gets energy from inorganic compounds

• gets carbon from CO₂

Many Archaea are what? (photoautotrophs, photoheterotrophs, chemoautotrophs, chemoheterotrophs)

chemoautotrophs

Chemoheterotroph

• need to eat other organisms

• both energy and carbon from organic compounds

Phototrophs

gets energy from light

Chemotrophs

gets energy from chemical compounds

Autotrophs

make their own food

Heterotrophs

consumes food made by autotrophs

Examples of types of Archae

• Halophiles: live in high salt environments

• Thermophiles: live in high temperatures

• Methanogens: produce methane by reducing carbon dioxide

Biofilm

Cells bind to surfaces and secrete sticky polysaccharides. Become much harder to kill

Examples of where biofilm is found

plaque, contact lenses, artificial joints, corrode metal pipes