Topic 7 - Prokaryotic and Viruses

Question 1

what are prions?

Answer 1

• prions are proteins that are misfolded relative to their normal structure.
• they are able to induce similar misfolding in proteins that they come in contact with. (They are able to reproduce themselves with error, but lack other features of being alive)
• a buildup of misfolded proteins can cause disease.

-prions from different species may induce disease if ingested; prions cannot be destroyed at normal cooking temperatures.

Question 2

What is the first fossil evidence of life on earth of prokaryotes?

Answer 2

• For 2.5 billion years ago

Question 3

what are the two domains?

Answer 3

• bacteria
• archaea
• only forms of life for 1.5 billion years.

Question 4

Do prokaryotes dominate the biosphere numerically and are second to plants in total biomass?

Answer 4

True

Question 5

where can prokayotes live?

Answer 5

• they live in places where eukaryotes do and many places they cannot, such as oil sands.

Question 6

Prokaryotic Diversity

Answer 6

• the # of described species of prokaryote sis is much less than the number of described eukaryotic spp.
• the # of prokaryote species and higher taxa are increasing very rapidly due to DNA- and RNA-based descriptions.

-because of this rapid increase in names, it is
difficult to get a count of validly described taxa

• there are a total of 23865 valid spp. of prokaryotes.

Question 7

how many phyla in domain bacteria?

Answer 7

40 phyla

Question 8

how many phyla in domain archaea?

Answer 8

4 phyla

Question 9

what is a prokaryote?

Answer 9

• organisms whose cells lack a nucleus and other organelles.

Question 10

what is the first feature of prokaryotes?

Answer 10

• they do not have a nucleus.
• nucleus = membrane-bound organelle
  containing genetic material structured as
  dense linear chromosomes

-pro = first/before
- karyon = kernel (i.e.,
nucleus; nucle = little nut )
– eu = true

• instead have a diffuse, circular ring of
  DNA not enclosed by membrane
  – the nucleoid region

Question 11

what is the second feature of prokaryotes?

Answer 11

• in addition to nucleoid regions, prokaryotes have plasmids.

-plasmids are small rings of DNA containing a few extra genes.

Question 12

what is the third feature of prokaryotes?

Answer 12

• reproduction and transfer of genetic
  material in prokaryotes take several
  forms, none using mitosis or meiosis.

Question 13

what are the different forms of reproduction?

Answer 13

1. Binary Fusion:
   
   • new DNA synthesized almost constantly
     - when a chromosome duplicated, the cell splits

-fission rate depends on the environment, can be divided once every 20
minutes

2. Transformation:
   
   • involves uptake of
     ‘naked’ DNA released from dead
     prokaryote by a living prokaryote
3. Transduction:
   
   • involves the transport of
     DNA between prokaryote cells by
     viruses (bacteriophages [phag = eat]
     and prophages)*
4. Conjugation:
   
   • when one
     prokaryote latches on to another with
     a string-like structure (called a pilus
     in bacteria) and transfers DNA
     i. One cell attaches its pilus to another and
     then retracts it, pulling cells together

ii. transfer of genetic material in bacteria*
is unidirectional, from pilus-producer to
receiver

iii. plasmids are often transferred during conjugation.

Question 14

what are transformation, transduction and conjugation are modes of?

Answer 14

• horizontal transfer of genetic material, and because of this antibiotic resistance can spread so rapidly.

Question 15

what is horizontal?

Answer 15

• means
  transfer between individuals
  within the same generation
• individuals need not be
  related

Question 16

what is vertical?

Answer 16

-means transfer
from parent to offspring
between generations
- e.g., binary fission

Question 17

widespread use of
antibiotics has sped up
selection for —————— in most medically important bacteria.

Answer 17

resistance

Question 18

what is the fourth feature of prokaryotes?

Answer 18

• bacterial cell wall.
• includes peptidoglycan (no cellulose in cell wall or chitin in fungi)
• archaeans lack peptidoglycan.
• cell wall prevents cell from exploding when
  placed in hypotonic solution:

– hypotonic = lower in solutes than cell contents
(hypo = below); water enters cell [low solute out of cell, and high solute in cell] –> LYSIS

– hypertonic = higher in solutes than cell contents
(hyper = above, beyond); cell wall usually doesn’t
prevent plasmolysis, when water leaves cell [high solute out of cell, low solute in cell] –> SHRINK OR PLASMOLYZE

– (lys = release, usually in the sense of dissolve)

Question 19

How does a bacterial cell wall determine whether the cell is Gram + or Gram -

Answer 19

• Gram + = have peptidoglycan wall in contact with
  external medium which traps purple stain
• Gram - = have lipopolysaccharide layer outside of cell
  wall, and thus do not absorb stain readily
• Gram - are more pathogenic, as out LPS layer can contain toxins also resist
  action of antibiotics

Question 20

what is the fifth feature of Prokaryotes?

Answer 20

• they lack membrane enclosed organelles.-no nucleus, mitochondria,
  chloroplasts
• however, prokaryotes may have structures that are highly complex.

Question 21

what is the sixth feature of prokaryotes?

Answer 21

• prokaryotic smaller in size than eukaryotic cell.
• prokaryotic are 1-5 micrometre
• eukaryotic are 10-100micrometer.

Question 22

what is the seventh feature of prokaryotes?

Answer 22

• many prokaryotic cells are motile, and they can move on their own.
• they use a g flagella (flagellum = whip)
• Prokaryotes perform taxes (plural) or taxis (singular)
  • movement away from or towards stimulus
    – e.g. positive phototaxis is movement towards
    light (light receptor)
    – note: motility and taxic behaviour not restricted
    to prokaryotes

Question 23

Do prokaryotes differ from eukaryotes in
having a higher diversity of metabolic
pathways? (True or False)

Answer 23

True

Question 24

what is metabolism?

Answer 24

-chemical pathways used by living organisms to build molecules (anabolism) or break down molecules to release energy (catabolism)

• meta = change

Question 25

what is anabolism?

Answer 25

• building up molecules using energy.

-ana =up

Question 26

what is catabolism?

Answer 26

• break down molecules to release energy
• cata=down

Question 27

what are the three needs for metabolic activity?

Answer 27

1. water
2. carbon (comes form co2 or other organisms)
3. energy (comes from sunlight, inorganic chemicals, organic chemicals. )

Question 28

what is a phototroph?

Answer 28

• use light energy and co2 to make their own carbohydrates.

-photo = light

• auto=self

-troph =eat.

Question 29

what is a chemoautotrophs?

Answer 29

• use energy obtained by
  oxidizing inorganic chemicals, and CO2

Question 30

what is a photoheterotroph?

Answer 30

• use light energy, but
  get carbon from organic molecules

-hetero =different

Question 31

what is chemoheterotroph?

Answer 31

• use organic
  molecules for both energy and carbon
  source

Question 32

What are the two different linages of prokaryotes that are now placed in the rank of Domain?

Answer 32

1. bacteria (eubacteria, eu=true)
2. Archaea (Arch=ancient or orginal)

There are three domains but two of these are prokaryotic (3rd is eukarya)

Question 33

How does Archaea differ from Eubacteria?

Answer 33

• RNA structure
• archaea lack peptidoglycan in cell wall.
• archaea do not respond to antibodies that inhibit eubacterial growth.

Question 34

what are extremophiles?

Answer 34

• phil =love, prefer, attached to.
• an organism that thrives or lives in extreme environments or conditions.

Question 35

what re methanogens?

Answer 35

• they live in oxygen -free habitats.
• in swamps, cow gut

-produce methane as a waste product.

-gen =to generate

Question 36

what are halophiles?

Answer 36

• they live in very salty habitats.
• halo = salt.
• it can be any type of salt, dosn’t just have to be NaCl.

Question 37

what are thermophiles?

Answer 37

• live in very hot habitats.

-therm=heat

-many thermophiles are autotrophs.

Question 38

what are the 5 major clades?

Answer 38

1. Proteobacteria
2. Chlamydias
3. Spirochaete
4. Gram + Bacteria
5. Cyanobacteria

Question 39

What is Proteobacteria?

Answer 39

• large and
  metabolically diverse group of Gram–
  bacteria
• include endosymbiotic mutualists* like
  Rhizobium
  (rhizos = root)
  a. libe in roots nodules of leguminous plants.
  b. fix atmospheric nitrogen.
  c. host plants gives Rhizobium
  carbohydrates
• include causative agents of cholera and gastric
  ulcers, Escherichia coli
  a. e. coli harmless commensal in human intestine.
  b. tested in drinking water b/c of presence in fecal matter.
  c. some strains can be toxic.

Question 40

what is chlamydias?

Answer 40

• they live only within the cells of animals.
• no peptidoglycan in cell walls, perhaps
  because they live within other cells
• common STD , can cause blindness

Question 41

what is spirochaetes?

Answer 41

• quite long helical bacteria that swim by spiraling.
• causative agents of syphilis (STD) and Lyme
  disease (bite from infected tick)
• passed on from pregannt women to child

Question 42

what is Gram + Bacteria?

Answer 42

• includes number of gram
  (-) taxa

-include decomposers in soil and sources for many antibiotic

• include mycoplasmas (any of a group of small typically parasitic bacteria that lack cell walls and sometimes cause diseases.), which are the
  smallest known cells
• include Bacillus anthracis
  (anthrax),
  which can enter a resistant endospore
  state

-include Clostridium botulinum, a Gram+
bacterium that causes botulism (disease caused by neurotoxins
produced by bacteria)

Question 43

what does type C toxin devastate?

Answer 43

• devastates waterfowl.
• fly larvae can accumulate toxin by eating
  decomposing matter with C. botulinum
  -waterfowl that feed on larvae die

Question 44

what is Botox?

Answer 44

• cosmetic agent.
• a sterile lyophilized form of botulinum toxin type A

Question 45

what is cyanobacteria (blue-green algae)?

Answer 45

• the only
  prokaryotes that produce oxygen
  through photoautotrophy, like
  plants

-some species also fix nitrogen
from the atmosphere
-most cyanobacteria are benign (not harmful),
but some contain toxins that
impair liver function or act as
neurotoxins

Question 46

What are the ecological and economic importance of prokaryotes?

Answer 46

• vital decomposers in all terrestrial
  and aquatic systems

-important producers of oxygen and
fixers of nitrogen

-some situations, prokaryotes rather
than plants are primary producers
that support food webs
a. hydrothermal vents (bacteria in sea water) b. acid caves

• many prokaryotes are beneficial inhabitants
  of eukaryotes (to an areas where eukaryotes occupy)
• many prokaryotes cause diseases.

Question 47

what is a Thermus aquaticus (“Taq”) ?

Answer 47

• it is an extremophile eubacterium from hot springs.
• enzymes retain activity at very high
  temperatures used in PCR (polymerase chain
  reaction - produces millions of copies of a specific segment of DNA) to amplify DNA for sequence
  analysis