27 Prokaryotes Abbreviated 20120130

8/3/2019 27 Prokaryotes Abbreviated 20120130

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Bacteria on the point of a pin

Chapter 27:Bacteria and Archaea

1/30, 31/2012


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26.21. The three domains of life. Branch lengths areproportional to the amount of genetic change in each lineage.Lineages with multi-cellular organisms shown in red


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Harmful Haemophilus influenza, the bacteria that causes pneumonia

(shown on human nose cells)


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27.21. Lyme disease, a bacterial disease transmitted by ticks.([)


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Bacillus anthracis. Gram stain. The cells have characteristic squared ends.The endospores are ellipsoidal shaped and located centrally in thesporangium. The spores are highly refractile to light and resistant to staining.


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Without prokaryotesecosystems wouldcollapse!

54.11


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55.4 An overview of energy and nutrientdynamics in an ecosystem.

Decomposition connects all

trophic levels in an ecosystem


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If all the bacteria on Earth suddenlydisappeared, which of the following would

be the most likely direct result?

A. Human populations would thrive in the absenceof disease.

B. The Earth's total photosynthesis woulddecline markedly.

C. The number of organisms on Earth woulddecrease by 10 to 20 percent.

D. There would be little change in the Earth'secosystems.

E. Recycling of nutrients would becatastrophically reduced.


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27.16.

A simplified

phylogeny of

prokaryotes.


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Table 27.2.

A comparison of the three

domains of life

Antibiotic target


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27.17 Some Archaea: Thermo-acidophile (heat-acid loving) prokaryotes


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Some Archaea: Hot springs, home of thermophiles ()


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Methanogens () in Peat

and the gut of cows


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Some Archaea:

Extreme halophiles

()

Halobacterium:

32%


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Common Features of the Domain Bacteria

May be classified according to their shape (just like Archaea)

Many are motile using flagella

No membrane-enclosed organelles (prokaryotic!)

Peculiar cell wall containing peptidoglycan (a combination ofsugars and polypeptides)

Smaller and simpler genome (than eukaryotes)

A sexual or sexual reproduction

Diversity of nutritional modes

Often live in close association (symbiosis) with eukaryotes


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27.2 The most common shapes of prokaryotes


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Common Features of the DomainBacteria

May be classified according to their shape



Peculiar cell wall containing peptidoglycan (acombination of sugars and polypeptides)


A sexual or sexual reproduction Diversity of nutritional modes

Often live in close association (symbiosis) witheukaryotes


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27.6. Prokaryotic flagellum with the basal apparatus as a motor.

Taxis/chemotaxis


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27.7 Specialized membranes of prokaryotes


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Figure 27.3 Gram-positive and gram-negative bacteria

Gram staining: Apply crystal violet dye to bacterial smear, treat with

iodine, rinse with alcohol and counterstain with safranin.


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Gram-positive and gram-negative bacteria


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Staphylococcus aureusStreptococcus pneumoniae

Actinomycete

Gram Positive


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Escherichia coliNeisseria gonorrhoeae

Yersinia pestis

Gram Negative


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27.4. Capsule

The cell wall of may prokaryotes

is covered with a sticky layer ofpolysaccharides or proteins.

27.5. Fimbriae

Hair-like protein appendages

that allow a prokaryote to

attach itself to their substrate

or to each other.


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27.8. A prokaryotic chromosome and plasmids.

A single ring ofDNA surrounding a ruptured E. colicell.


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Asexualreproduction:

Fission(see also Fig 12.11)


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Genetic recombination in prokaryotes

No meiosis and fertilization, but

Transformation:

Uptake and incorporation of foreign DNA from the

environment

Conjugation:

Direct transfer of genes from one prokaryote to

another

Transduction:

Transfer of genes between prokaryotes by viruses


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27.12. Prokaryotic conjugation.

Donor cell transfersDNA to recipient.

j Flagella, fimbriae, pilus


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27.13. Conjugation: Direct transfer of genes from one prokaryote to another

(have only been studied in Bacteria)

The F factor is responsible for producing the mating bridge. It can either

exist as a plasmid (a small circularDNA molecule with accessory genes)

or as a segment ofDNA within the bacterial chromosome.


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27.11. Transduction:

Transfer of genes between

prokaryotes by viruses.

Phages may carry pieces of

bacterial chromosome from

one bacterium (donor) to a

recipient bacterium.


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Endospores

27.9. Bacillus anthracis endospore (TEM)


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A sexual or sexual reproduction Diversity of nutritional modes Taxis/chemotaxis



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Prokaryotes can evolve rapidly because of theirshort generation times

Cooper and Lenski,Michigan State University E coli, 12 populations, 20,000 generations (8 years) of evolution

Fig. 27.10 Can prokaryotes evolve rapidly in response to environmental change?

CONCLUSION

Asexual populations ofE. colicontinued to accumulate beneficial mutations for 20,000

generations, allowing rapid evolution of improved performance in theirnew environment.

Low-glucose


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Table 27.1 MajorNutritionalModes

- H2S,S-, Fe-comp.,NH3


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Figure 27.14. One of the most independent organisms on earth:

Cyanobacteria (in this case Anabaena) or blue-green algae


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Symbiotic relationships

Mutualism bothsymbiotic organismsbenefit

Commensalism onebenefits, the otheris neutral

Parasitism onebenefits at theexpense of the other

27.20. Bacterial headlights. Glowing oval below the

eye of the flashlight fish contains bioluminescent

bacteria that receive nutrients from the fish. The fishuses the light to attract prey and signal potential mates

SEM ofEscherichia coli, very common in the lower

intestine of warm-blooded animals where it produces a

vitamin and protect against pathogenic bacteria.


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37.9. The role of bacteria in the nitrogen cycle

Nitrogen fixing bacteria in root nodules

(mutualism) and in cyanobacteria (heterocysts)


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Putting prokaryotes to work in sewage treatment facilities


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Figure 27.17 (a) Bioremediation of an oil spill, (b) bacteria

synthesizing biodegradable plastics, and (c) bacteria used to

produce ethanol from plants.


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AlexanderFleming18811955

1928(Penicillin)1938

:


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1945


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, , , ,

, :

14%53.7%


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In which of the following ways are prokaryotes

more successful on Earth than humans?

A. Prokaryotes often parasitize humans in many ways.

B. Prokaryotes are much more numerous than

humans.

C. Prokaryotes occupy more diverse habitats than

humans.

D. Prokaryotes have survived on Earth for billions ofyears longer than humans have.

E. All of the above are true.

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27 Prokaryotes Abbreviated 20120130