Chapter 27 Reading Quiz

1. Which structure in bacteria contains “peptidoglycan”?

2. How do prokaryotes reproduce?3. What do aerobes utilize?4. Extreme halophiles like what substance?5. What term describes ecological

relationships between organisms of different species?

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 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 9 + 2 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. Indicate where photosynthesis and cellular respiration take place in

prokaryotic cells.

Photosynthesis prokaryotes have specialized metabolic machinery with internal membranes and a light-harvesting pigment system

Cellular respiration most prokaryotes use this, including saprobes and parasites

Occurs in infoldings of the plasma membrane, like mitochondria

10. Explain how the organization of the prokaryotic genome differs from that in

eukaryotic cells.

Lack diverse internal membranes of eukaryotes Genome has 1/1000 as much DNA as eukaryotes Has a genophore the bacterial chromosome

(one strand of circular DNA)- concentrates in the “nucleoid region” with no surrounding nuclear membrane

Has plasmids smaller rings of DNA with supplemental genes for functions like antibiotic resistance

11. 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

12. List the sources of genetic variation in prokaryotes.

1. Transformation the process by which external DNA is incorporated by bacterial cells

2. Conjugation the direct transfer of genes from one bacterium to another

3. Transduction the transfer of genes between bacteria by viruses

13. 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

14. 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

15. Distinguish among obligate aerobes, facultative anaerobes and

obligate anaerobes.

1. Obligate aerobe prokaryotes that need O2 for cellular respiration

2. Facultative anaerobe prokaryotes that use O2 when present, but in its absence can grow using fermentation

3. Obligate anaerobe prokaryotes that are poisoned by oxygen and live exclusively by fermentation- they use other inorganic molecules as electron acceptors (other than O2)

16. Describe, with supporting evidence, plausible scenarios for the evolution of

metabolic diversity of prokaryotes.

The 1st prokaryotes must have been anaerobes and simple

In the beginning, as ATP supplies were depleted, natural selection selected prokaryotes that could regenerate ATP from ADP, leading to glycolysis (no O2)

The 1st prokaryotes were probably chemoautotrophs (rare in today’s world)

17. 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

18. 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- use H2 to reduce CO2 to CH4 (strict anaerobes)- important decomposers and digestive system symbionts with 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

19. 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

20. Explain how endospores are formed and why endospore-forming bacteria are important

to the food-canning industry.

Endospore resistant cell formed by some bacteria; contains one chromosome copy surrounded by a thick wall

Original cell replicates chromosome and surrounds one copy with a durable wall

Endospores can survive boiling water for a short time- special precautions must be taken to kill endospores of dangerous bacteria

21. 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)

22. 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

23. Distinguish among mutualism, commensalism, and parasitism.

1. Mutualism symbiosis in which both symbionts benefit (+/+)

2. Commensalism symbiosis in which one symbiont benefits while neither helping nor harming the other symbiont (+/0)

3. Parasitism symbiosis in which one symbiont (the parasite) benefits at the expense of the host (+/-)

24. List Koch’s postulates that are used to substantiate a specific pathogen as the cause

of a disease.

1. Find the same pathogen in each diseased individual

2. Isolate the pathogen from a diseased subject and grow it in a pure culture

3. Use cultured pathogen to induce the disease in experimental animals

4. Isolate the same pathogen in the diseased experimental animal

25. Distinguish between exotoxins and endotoxins.

Exotoxins proteins secreted by bacterial cells - can cause disease without the organism being present

- these are among the most potent poisons (example: botulism & cholera)

Endotoxins toxic component of outer membranes of some gram – bacteria- usually induces fever and aches (example: Salmonella)

26. 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

27. Describe how Streptomyces can be used commercially.

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

The End!! Study for the Chapter 26 & 27 Quiz!