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Eukaryote. Prokaryote. Archaebacteria & Bacteria. Classification. Old 5 Kingdom system Monera , Protists, Plants, Fungi, Animals New 3 Domain system reflects a greater understanding of evolution & molecular evidence Prokaryote: Bacteria Prokaryote: Archaebacteria Eukaryotes Protists

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classification

Eukaryote

Prokaryote

Archaebacteria&Bacteria

Classification
  • Old 5 Kingdom system
      • Monera, Protists, Plants, Fungi, Animals
  • New 3 Domain system
    • reflects a greater understanding of evolution & molecular evidence
      • Prokaryote: Bacteria
      • Prokaryote: Archaebacteria
      • Eukaryotes
        • Protists
        • Plants
        • Fungi
        • Animals
fig 27 2

Fig. 27-2

2 µm

5 µm

1 µm

(a) Spherical

(cocci)

(b) Rod-shaped

(bacilli)

(c) Spiral

structure and function
Structure and Function
  • 3 basic shapes: spherical (cocci), rods (bacillus) and spiral
  • Cell Wall
    • Peptidoglycan covers cell, anchors attachments
    • Archaea have no peptidoglycan
gram staining
Gram Staining

Gram + : simple walls, lots of PTG

Gram - : complex walls with lipopolysaccharides less PTG

  • Medical significance: Gram – lipids are toxic causing fever or shock and are resistant to our defenses
  • Gram –: antibiotic resistance (hard for drugs to penetrate)
  • Antibiotics often target peptidoglycan
slide5

outer membrane of lipopolysaccharides

Gram-negative bacteria

Gram-positive bacteria

peptide side

chains

outer

membrane

cell wall

peptidoglycan

cell wall

peptidoglycan

plasma membrane

plasma

membrane

protein

Prokaryote Cell Wall Structure

peptidoglycan = polysaccharides + amino acid chains

lipopolysaccharides = lipids + polysaccharides

capsule vs fimbriae
Sticky and covers entire cell

Protection from dehydration and shield from immune system

Hair like appendages that stick

Ex. Neisseria gonorrhoeae sticks to mucus membranes

Shorter and more numerous than sex pilli

Capsule vs Fimbriae
fig 27 5

Fig. 27-5

Fimbriae

200 nm

motility for most bacteria
Motility for most bacteria
  • propel themselves by flagella that are structurally and functionally different from eukaryotic flagella
  • PROK flagella are 1/10 the width of EUK
  • PROK flagella are not covered by plasma mem
motility
Motility
  • Different composition and propulsion
  • The motor of the flagella is the basal apparatus (rings embedded in the cell wall)
  • ATP proton pump generates power by turning hook attached
  • Hook is attached to chains of flagellin
  • In a heterogeneous environment, many bacteria exhibit taxis, the ability to move toward or away from certain stimuli

Video: Prokaryotic Flagella (Salmonella typhimurium)

slide11

Fig. 27-6

Flagellum

Filament

50 nm

Cell wall

Hook

Basal apparatus

Plasma

membrane

fig 27 8

Chromosome

Plasmids

Fig. 27-8

1 µm

slide13

mitochondria

chloroplast

Variations in Cell Interior

cyanobacterium(photosythetic) bacterium

aerobic bacterium

internal membranesfor respirationlike a mitochondrion(cristae)

internal membranesfor photosynthesislike a chloroplast(thylakoids)

reproduction and adaptation
Reproduction and Adaptation
  • Binary fission in optimal conditions every 1-3 hours (E.coli every 20 min usually 1/24 hr)
  • They are small, repro binary fission and short generation time
  • Endopsores (ability to endure hardship)
slide15

Fig. 27-10

EXPERIMENT

Daily serial transfer

0.1 mL

(population sample)

New tube

(9.9 mL

growth

medium)

Old tube

(discarded

after

transfer)

RESULTS

1.8

1.6

Fitness relative

to ancestor

1.4

1.2

1.0

10,000

0

5,000

15,000

20,000

Generation

rapid evolution high genetic diversity
Rapid Evolution: high genetic diversity
  • 2 strains of E.coli differ in an rRNA gene more than between a human and a platypus
  • Rapid reproduction
  • Mutation
  • Genetic recombination
mutation
Mutation
  • Probability of a spontaneous mutation in an E.coli gene is 1 in 10 million/division
  • 2x1010 new E.coli per day
  • About 2000 bacteria will have mutations
  • 4300 genes total in E.coli
  • 4300 x 2000 = 9 million mutation per day in the human intestines
genetic recombination
Genetic Recombination
  • Transformation: uptake foreign DNA
    • Ex. Competent cells, pneumonia
  • Transduction: a bacteriophage performs horizontal gene transfer
  • Conjugation
  • Plasmids
slide19

Fig. 27-11-4

Phage DNA

A+

B+

A+

B+

Donor

cell

A+

Recombination

A+

A–

B–

Recipient

cell

A+

B–

Recombinant cell

conjugation and plasmids
Conjugation and Plasmids
  • Conjugation is the process where genetic material is transferred between bacterial cells
  • Sex pili allow cells to connect and pull together for DNA transfer
  • A piece of DNA called the F factor is required for the production of sex pili
  • The F factor can exist as a separate plasmid or as DNA within the bacterial chromosome
slide21

Fig. 27-12

1 µm

Sex pilus

the f factor as a plasmid
The F Factor as a Plasmid
  • Cells containing the F plasmid function as DNA donors during conjugation
  • Cells without the F factor function as DNA recipients during conjugation
  • The F factor is transferable during conjugation
slide23

Fig. 27-13

F plasmid

Bacterial chromosome

F+ cell

F+ cell

Mating

bridge

F– cell

F+ cell

Bacterial

chromosome

(a) Conjugation and transfer of an F plasmid

Recombinant

F– bacterium

A+

Hfr cell

A+

A+

A+

F factor

A–

A+

A–

A+

A–

A–

F– cell

(b) Conjugation and transfer of part of an Hfr bacterial chromosome

r plasmids and antibiotic resistance
R Plasmids and Antibiotic Resistance
  • R plasmids carry genes for antibiotic resistance
  • Antibiotics select for bacteria with genes that are resistant to the antibiotics
  • Antibiotic resistant strains of bacteria are becoming more common
bacterial diversity
Bacterial Diversity

Major nutritional modes

Role of oxygen in metabolism

Nitrogen metabolism

nitrogen fixation: converting N2 from the atmosphere into ammonia NH3

Metabolic Cooperation

colony of cyanobacterium Anabaena (filaments) genes for photosynthesis (most cells) and N fixation)few heterocytes) but one cell cannot perform both

Biofilms

slide27

Fig. 27-14

Photosynthetic

cells

Heterocyte

20 µm

prokaryotic phylogeny
Prokaryotic phylogeny
  • Horizontal gene transfer (ring instead of a tree)
  • Archaea more closely related to eukaryotes than bacteria
  • polyphyletic

Eukarya

Archaea

Bacteria

Eukarya

Bacteria

Archaea

slide29

Fig. 27-16

Domain

Eukarya

Eukaryotes

Korarcheotes

Euryarchaeotes

Domain Archaea

Crenarchaeotes

UNIVERSAL

ANCESTOR

Nanoarchaeotes

Proteobacteria

Chlamydias

Spirochetes

Domain Bacteria

Cyanobacteria

Gram-positive

bacteria

proteobacteria
Proteobacteria
  • These gram-negative bacteria include photoautotrophs, chemoautotrophs, and heterotrophs
  • Some are anaerobic, and others aerobic
slide32

Fig. 27-18a

Subgroup: Alpha Proteobacteria

Alpha

Beta

Gamma

Proteobacteria

Delta

2.5 µm

Epsilon

Rhizobium (arrows) inside a

root cell of a legume (TEM)

Subgroup: Beta Proteobacteria

Subgroup: Gamma Proteobacteria

1 µm

0.5 µm

Thiomargarita namibiensis

containing sulfur wastes (LM)

Nitrosomonas (colorized TEM)

Subgroup: Delta Proteobacteria

Subgroup: Epsilon Proteobacteria

B. bacteriophorus

5 µm

2 µm

10 µm

Fruiting bodies of

Chondromyces crocatus, a

myxobacterium (SEM)

Helicobacter pylori (colorized TEM)

Bdellovibrio bacteriophorus

attacking a larger bacterium

(colorized TEM)

subgroup alpha proteobacteria
Subgroup: Alpha Proteobacteria
  • Many species are closely associated with eukaryotic hosts
  • Scientists hypothesize that mitochondria evolved from aerobic alpha proteobacteria through endosymbiosis
slide34
Example: Rhizobium,which forms root nodules in legumes and fixes atmospheric N2
  • Arrows in the next slide are Rhizobium
  • Example: Agrobacterium,which produces tumors in plants and is used in genetic engineering
slide35

Fig. 27-18c

2.5 µm

Rhizobium (arrows) inside a root

cell of a legume (TEM)

cyanobacteria
Cyanobacteria
  • These are photoautotrophs that generate O2
  • Plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis

Two species of Oscillatoria,

filamentous cyanobacteria (LM)

concept 27 6 prokaryotes have both harmful and beneficial impacts on humans
Concept 27.6: Prokaryotes have both harmful and beneficial impacts on humans
  • Some prokaryotes are human pathogens, but others have positive interactions with humans
  • Prokaryotes cause about half of all human diseases
  • Lyme disease is an example
slide39
Pathogenic prokaryotes typically cause disease by releasing exotoxins or endotoxins
  • Exotoxins cause disease even if the prokaryotes that produce them are not present
  • Endotoxins are released only when bacteria die and their cell walls break down
  • Many pathogenic bacteria are potential weapons of bioterrorism