likely that more individuals will have new mutations at any particular ...

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16 Δεκ 2012 (πριν από 4 χρόνια και 10 μήνες)

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How do bacterial cell walls differ from plant cell walls?


Plants


made of cellulose (polysaccharide)







Bacteria


made of
peptidoglycan










Archaea



lack
peptidoglycan
, made of a variety of





polysaccharides and proteins

Simpler cell wall, large
amounts of
peptidoglycan

More complex, less
peptidoglycan
, outer layer of
lipopolysaccharides

Capsule


sticky layer of polysaccharide or protein covering the cell wall
of many prokaryotes



enables them to adhere to substrate





or other cells
(colony)



prevent dehydration



protects from host’s immune system



Fimbriae



hair
-
like protein appendages






(aka “attachment
pili
”)




Sex
pili



appendages that pull two cells




together prior to DNA transfer from one





cell to the









other.

Bacteria Locomotion



Flagella



Slimmer than Eukaryotic flagella



Not covered by plasma membrane as Eukaryotic flagella a


Different molecular composition and Eukaryotic flagella



Mechanism of propulsion is different than Eukaryotic







Taxis


movement towards or away from a stimulus




Positive taxis


towards stimulus


Negative taxis


away from stimulus


Examples:


Chemotaxis


Phototaxis




Transformation


pGLO

lab


genotype and




possibly phenotype is changed by the uptake




of foreign DNA from its surroundings.



pGLO


Griffins experiment








Transduction


Bacteriophages

(viruses) carry



bacterial genes from one host cell to another



(accidents during viral replication)


Conjugation


DNA transfer from





one bacterial cell to another






(same or different species)


Binary Fission


asexual
reproduction of bacteria

What is the difference between and F plasmid and an R plasmid?


F plasmid


contains genes that enable cell to form a “mating

bridge” with a cell that does not have the plasmid.




R plasmid


contains genes that make it resistant to antibiotics

What is the difference between F
+

cells and F
-

cells?


F
+

cells contain the F plasmid and therefore are donors during

conjugation




F
-

cells do not contain the F plasmid and therefore are recipients

during conjugation

Questions from 27.2 pg. 564


1.
What features of prokaryotes make it likely that considerable genetic
variation will be added to their populations in each generation?



Large population size (more likely that more individuals will have new mutations at




any particular gene…adding diversity)



Short generation time.

2.
Distinguish between the three mechanisms of transferring DNA from
one bacterial cell to another.



Transformation








Transduction








Conjugation

3.
If a nonpathogenic bacterium were to acquire resistance to
antibiotics, could this strain pose a health risk to people? Explain.



Yes. Genes for antibiotic resistance could be transferred from the nonpathogenic

bacterium to a pathogenic bacterium, which could then harm the population.

(MRSA). The processes listed in #2 increase the spread of resistance genes.

Photoautotroph


vs.


Chemoautotroph

Energy source is light




Energy source is inorganic






compounds (H
2
S or NH
3
)



Photoheterotroph


vs.


Chemoheterotrophs

Energy source is light




Energy source is organic
but obtain carbon in organic form


compounds and obtain






carbon in organic form






(animals, fungi, and most






protists
)



The role of Oxygen in metabolism




1. Obligate Aerobes


use O
2

for CR, can’t live
wo
/it




2. Obligate Anaerobes


poisoned by O
2
, some live by




fermentation while others go through anaerobic respiration


using nitrate ions or sulfate ions



3. Facultative Anaerobes


use O
2

if it is present but can also


carry out anaerobic respiration or fermentation if needed


Nitrogen fixation


converting atmospheric nitrogen to ammonia (NH
3
)
Benefit: can then use ammonia to make amino acids and nucleotides

Filamentous colonies


cooperation between the same species


majority of cells in the colony carry out photosynthesis


there are a few cells (“
heterocytes
”) that carry out nitrogen fixation (have a thicker cell wall to
keep O
2

out)


cells can’t do both because the O
2

inactivates the enzymes involved in nitrogen fixation.


products from both reactions get transported via intercellular connections between the cells

Biofilms



cooperation between different species


cells in colony secrete signaling molecules that recruit nearby cell.


cells also produce proteins that stick the cells together and to a substrate.


channels
wi
/
biofilm

allow nutrients and waste to be transported

Causes of tooth decay, damage to industrial
and medical equipment, contamination of
products

Ecological Significance of Prokaryotes:


Recycling:


Symbiosis:


Pathogens:


Bioremediation:


Genetic Engineering





Identify 2 ways Prokaryotes have affected you positively today…