PROKARYOTES

1. List unique characteristics that distinguish archaea from bacteria.

Archaea Evolved from the

earliest cells Inhabit only very

extreme environments

Only a few hundred species exist

Bacteria The “modern”

prokaryotes Over 10,000 species Differ structurally,

biochemically, and physiologically from Archaea

2. Describe the three domain system of classification and explain how it differs

from previous systems.

1. Domain Archaea Archaebacteria2. Domain Bacteria Eubacteria3. Domain Eukarya all eukaryotes

“domain” is above the Kingdom taxon, and includes all taxa below

3. Using a diagram, distinguish among the three most common shapes of

prokaryotes.

1. Spheres (cocci)

2. Rods (bacilli)

3. Helices (spirilla & spirochetes)

4. Describe the structure and functions of prokaryotic cell walls.

1. Maintain cell shape2. Protect cell3. Prevent cell from bursting (hypotonic) Differ in chemical composition and

construction than protists, plants and fungi

Made of peptidoglycan modified sugar polymers crosslinked by short polypeptides (archaea don’t have it)

5. Distinguish between the structure and staining properties of gram-positive

and gram-negative bacteria.

Gram stain a stain used to distinguish two groups of bacteria by virtue of a structural difference in their cell walls

Gram + simple cell walls with lots of peptidoglycan- these stain blue in color

Gram - more complex cell walls with less peptidoglycan- Outer lipopolysaccharide-containing membrane that covers the cell wall- these stain pink in color

6. Explain why disease-causing gram-negative bacterial species are generally more

pathogenic than disease-causing gram-positive bacteria.

The lipopolysaccharides:- these are often toxic and the outer membrane helps protect these bacteria from host defense systems- can impede the entry of drugs into the cells, making gram negative bacteria more resistant to antibiotics

7. Describe three mechanisms motile bacteria use to move.

1. Flagella2. Filaments characteristic of spirochetes

- spiral around cell inside cell wall and rotate like a corkscrew

3. Gliding glide through a layer of slimy chemicals secreted by the organism - movement may result from flagellar motors that lack the flagellar filaments

8. Explain how prokaryotic flagella work and why they are not considered to be

homologous to eukaryotic flagella.

Prokaryotic flagella are unique in structure and function

They lack the microtubular structure and rotate rather than whip back and forth

They are not covered by plasma membrane

They are 1/10 the width of eukaryotic flagella

9. Explain what is meant by geometric growth.

One cell divides into two, two divide into four, four into eight, etc…

Essentially, growth doubles with each generation

10. Distinguish between autotrophs and heterotrophs.

Autotrophs organisms that synthesize their food from inorganic molecules and compounds - Example: Plants, cyanobacteria

Heterotrophs organisms that require organic nutrients as their carbon source - Example: Animals, some bacteria

11. Describe four modes of bacterial nutrition and give examples of each.

1. Photoautotrophs use light energy to synthesize organic compounds from CO2 - examples: plants, cyanobacteria

2. Chemoautotrophs require CO2 as a carbon source and obtain energy by oxidizing inorganic compounds like H2S, NH3, Fe2+

- example: Archaea, Sulfobolus3. Photoheterotrophs use light to generate ATP from

an organic carbon source (unique to some prokaryotes)4. Chemoheterotrophs must obtain organic

molecules for energy and as a carbon source- examples: most bacteria and most eukaryotes

12. Explain how molecular systematics has been used in developing a classification of prokaryotes.

By comparing energy metabolism Ribosomal RNA comparisons show prokaryotes

diverged into Archaea and Bacteria lineages early – the RNA indicates the presence of “signature sequences” = domain-specific base sequences at comparable locations in ribosomal RNA or other nucleic acids

Bottom line they found that Archaea have at least as much in common with eukaryotes as they do with bacteria

13. List the three main groups of archaea, describe distinguishing

features among the groups and give examples of each.

1. Methanogens named for their unique form of energy metabolism

- important decomposers and in digestive system of termites and herbivores

2. Extreme halophiles like high salinity environments (15 – 20%)- have the pigment bacteriorhodopsin in the plasma membrane- absorb light to pump H+ ions out

3. Extreme thermophiles inhabit HOT environments (60 – 80 degrees Celsius)- one sulfur-metabolizing thermophile lives in 105 ‘C water by underwater hydrothermal vents

14. List the major groups of bacteria, describe their mode of nutrition, some characteristic

features and representative examples.

1. Spirochetes helical chemoheterotrophs; flagella; ex: Lyme disease

2. Chlamydias obligate parasites; gram – cell walls; most common STD – causes blindness

3. Gram positive some are gram – but grouped here due to molecular systematics; example – Clostridium

4. Cyanobacteria photoautotrophs; example – Anabaena5. Proteobacteria

1. Purple bacteria: photoautotrophs; Chromatium2. Chemoautotrophic: free-living and symbiotic; Rhizobium3. Chemoheterotrophic: in intestinal tracts; Ecoli, Salmonella

15. Explain how the presence of E. coli in public water supplies can be used as

an indicator of water quality.

E. coli is found in the intestines and excretion of animals and if found in drinking water or post-plant sewage, the sewage system is bad (leaking, etc)

16. Explain why all life on earth depends upon the metabolic diversity of

prokaryotes.

Earth’s metabolic diversity is greater among the prokaryotes than all of the eukaryotes

The diversity is a result of adaptive radiation over billions of years

Examples: cyanobacteria – make oxygen saprobes – decompose dead

materials

17. Describe how humans exploit the metabolic diversity of prokaryotes for scientific and commercial purposes.

The range of purposes has increased through recombinant DNA technology

1. Cultured bacteria to make vitamins and antibiotics 2. Used as simple models of life to learn about

metabolism and molecular biology3. Methanogens digest organic waste at sewage plants4. Decompose pesticides and other synthetic

compounds5. Make products like acetone and butanol6. Convert milk into yogurts and cheeses for

consumption

18. Describe how Streptomyces can be used commercially.

Many of the antibiotics that we now use are produced naturally by members of the genus Streptomyces