Prokaryotes - lecture 8

Three domains

Bacteria, Archaea, Eukarya

rRNA sequences

Used to reveal evolutionary relationships of domains

Microbes

Virtually all unnamed and undescribed species

500 species

Number of species in the human mouth

One trillion species

Estimated number of microbes on Earth

Thermophiles

Most ancient prokaryotes that originated in a hot environment

Extremophiles

Prokaryotes that can survive in extreme conditions

Habits

Different types of prokaryotes based on their preferred environment (hot, salt, acid)

Methanogens

Produce methane in the guts of herbivorous animals

Cell size

Varies a lot in prokaryotes

Cocci, bacilli, spirilla

Different forms of prokaryotes (round, rod, spiral)

Multicellular prokaryotes

Rare, but myxobacteria is an example

Lack of 'stuff' inside

Prokaryotes lack nuclei, membrane-enclosed organelles, and cytoskeletons

Circular chromosome DNA

DNA in prokaryotes is circular

Plasmids

Additional DNA in prokaryotes

Flagella

Used by prokaryotes for movement

Prokaryotic cell walls

Contain peptidoglycan or polysaccharides

Asexual reproduction

Prokaryotes reproduce by binary or cell fission

Plasmids

Prokaryotes can exchange genetic info via pieces of DNA

Metabolism

How organisms obtain their energy and carbon

Photoautotrophs

Use light energy and CO2 for carbon

Chemoautotrophs

Use chemical energy and CO2 for carbon

Photoheterotrophs

Some bacteria that use light energy and other sources of carbon

Chemoautotrophs

Some bacteria and archaea that use chemical energy and CO2 for carbon

Metabolic diversity

Bacteria and archaea produce ATP

Bacteria

Prokaryotes with peptidoglycan cell walls and plasma membrane-like eukaryotes

Archaea

Prokaryotes with polysaccharide cell walls and unique plasma membrane

Prokaryotes in environments

Bacteria play a key role in global nitrogen and sulfur cycles

Pathogenic bacteria

Some bacteria cause diseases

Toxic prokaryotes

Prokaryotes that can be highly toxic (e.g., tetanus, cholera)

Bioremediation

Use of bacteria and archaea to degrade pollutants

Benefits of bacteria in colon

Training the immune system, preventing growth of harmful bacteria, producing vitamins

Mycoplasma

Smallest living things that lack cell walls