Prokaryotes and the Origins of Metabolic Diversity

1
Chapter 27 Prokaryotes and the Origins of
Metabolic Diversity
2
I.  The world of prokaryotes             A. 
Theyre everywhere!                         1. 
Collective prokaryote biomass outweighs all
eukaryotes combined by at least tenfold. 
                          2.  They exist almost
everywhere, including places where eukaryotes
cannot.   Figure 27.1 (p. 527) Heat-loving
prokaryotes.
3
(No Transcript)
4
                        3.  Most prokaryotes are
beneficial we couldnt live without them.  (e.g.
Nitrogen-fixing bacteria)                         
  4.  Some cause illness à bubonic plague,
diphtheria, salmonella                          
5.  Approximately 5000 species have been
identified.  Estimates of prokaryote diversity
range from 400,000 to 4,000,000 species.
            B.  Bacteria and archaea are the
two main branches of prokaryote
evolution                         1.  Archaea are
thought to be more closely related to eukaryotes
than to bacteria.    Figure 27.2, p. 527, Ed. 6)
The three domains of life. Figure 27.12, .
540, Ed. 7
5
(No Transcript)
6
II.  Structure, function, and reproduction of
prokaryotes             A.  Most prokaryotes are
unicellular.                          1.  Some
species form aggregates of two or more
individuals.   B.  Three (3) common shapes 
cocci (round) bacilli (rod) helical
(spiral)   Figure 27.3 (p. 528, edition 6) The
most common shapes of prokaryotes. Figure 27.2
(p. 535, edition 7)
7
(No Transcript)
8
C.  Prokaryotes are typically 1-5 µm in diameter,
but some can be seen by the naked
eye.                         - Eukaryotic cells
are typically 10-100 µm in diameter.   Figure
27.4 (p. 528) The largest known prokaryote.
9
(No Transcript)
10
(No Transcript)
11
D.  Almost all prokaryotes have cell walls
external to the plasma membrane.                  
       1.  Cell walls maintain cell shape.   2. 
Cell walls are composed of peptidoglycan.
12
 3.  There are two types of cell walls.  Bacteria
are grouped according to cell wall type. 
                                    a. 
Gram-positive bacteria have simple, thick cell
walls.  Their cell walls are composed of a
relatively large amount of peptidoglycan.   b. 
Gram-negative bacteria have less peptidoglycan
and are more complex.  They have a peptidoglycan
layer surrounded by the plasma membrane and an
outer membrane.                                   
                 - Gram-negative bacteria are
typically more resistant to host immune defenses
and antibiotics. Note that the two types of
bacteria can be stained to determine which is
gram-negative (pink) and gram-positive (purple)
using a Gram Stain. Figure 27.5 (p. 529, Ed. 6)
Gram-positive and gram-negative bacteria. (Fig.
27.3, Ed. 7)
13
(No Transcript)
14
(No Transcript)
15
4.  Most prokaryotes secrete sticky substances
that form a protective layer that enables them to
adhere to substrates.                             
        a.  The sticky protective layer secreted
by prokaryotes is called the capsule.   5.  Some
prokaryotes adhere to substrates using pili and
fimbriae.                                     
a.  Some pili are specialized for DNA transfer.
This process is called conjugation note for
later in class.   Figure 27.6 (p. 530, Ed. 6)
Pili.
16
(No Transcript)
17
(No Transcript)
18
 E.  Many prokaryotes are motile        - Some
exceed speeds 100 times their body length per
second.   1.  Modes of movement Note the three
types a.  Flagellum - basal apparatus rotates
the flagellum and propels the cell   Figure 27.7
(p. 530, Ed. 6) Form and function of
prokaryotic flagella. Figure 27.6, p. 536, Ed.
7   b.  Corkscrew movement of spirochetes
(helical) c.  Some prokaryotes glide over jets of
slimy secretions.  2.  Many prokaryotes move
toward or away from a stimulus à taxis. 
Chemotaxis is the movement toward or away from a
chemical.
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
F.  Cellular and genomic organization of
prokaryotes is different from that of
eukaryotes                         1. 
Prokaryotes have no nucleus.   2.  The nucleoid
region in a prokaryotic cell consists of a
concentrated mass of DNA. This mass of DNA is
usually one thousand times less than what is
found in a eukaryote.   3.  A prokaryote may have
a plasmid in addition to its major chromosome.  A
plasmid is a small ring of DNA that carries
accessory genes. Usually these genes are for
antibiotic resistance!
23
G.  Prokaryotes grow and adapt rapidly - The
doubling time for E. coli is 20 minutes.  Start
with one E. coli cell.  After 48 hours of
doubling every 20 minutes, the mass of E. coli
would be 10,000 times the mass of the
earth. Bacteria do not have gene transfer by
sexual reproduction, but do transfer genes. Why?
This is an aid in adapting (evolving).   1. 
Three (3) ways for genes to be transferred
between cells a.  Transformation cell takes
up genes from the surrounding environment. b. 
Conjugation direct transfer of genes from one
prokaryote to another. Use the sex pilus to
conjugate. c.  Transduction viruses transfer
genes between prokaryotes.
24
2.  Endospores are resistant cells formed by some
bacteria as a way to withstand harsh conditions.
The cell replicates its chromosome and wraps it
in a durable wall that can protect the chromosome
from adverse conditions, e.g. boiling water,
desiccation. When the environment is good again,
the cell will revive to a new vegetative
(growing) state.   Figure 27.10 (p. 532) An
anthrax endospore.
25
(No Transcript)
26
(No Transcript)
27
III.  Nutritional and metabolic
diversity             A.  All prokaryotes (and
eukaryotes too) are grouped into four (4)
categories according to how they obtain energy
and carbon ? Table 27.1 (p. 533, Ed. 6 p. 339,
Ed. 7) Major Nutritional Modes   1. 
Photoautotrophs                                   
  - Photosynthetic à use light as the energy
source                                     - CO2
is the carbon source                              
       Example  Cyanobacteria plants
(eukaryotic). Figure is of Anabaena Genus of
photosynthetic cyanobacterium that fixes N2 in
specialized cells called heterocysts ? A major
source of organic nitrogen in the world.
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
(No Transcript)
34
2.  Chemoautotrophs      - Energy from oxidation
of inorganic substances (e.g. NH4, and S)      -
CO2 is the carbon source          Example 
Sulfolobus, Beggiatoa (shown on
slide)                                            
                    
35
(No Transcript)
36
3.  Photoheterotrophs      - Light as energy
source      - Organic compounds are source of
carbon   4.  Chemoheterotrophs       - Organic
compounds are energy source and source of carbon
(this includes humans)   Examples  Many
prokaryotes animals (eukaryotic) fungi
(eukaryotic)
37
(No Transcript)
38
(No Transcript)
39
(No Transcript)
40
 B.  Metabolic relationships to
oxygen                         1.  Obligate
aerobes       - Use O2 for respiration cannot
grow without it. (Humans are obligate
aerobes)                         2.  Facultative
aerobes       - Use O2 when available ferment
when O2 isnt available.   3.  Obligate
anaerobes       - Poisoned by O2 use
fermentation or live by anaerobic respiration. 
In anaerobic respiration, inorganic molecules
like SO4, NO3, and Fe3 are used instead of
oxygen.
41
C.  Photosynthesis evolved early in prokaryotic
life                         1.  Cyanobacteria
started to produce O2 about 2.7 billion years
ago  
42
IV.  A survey of prokaryotic diversity            
   Figure 27.13 (p. 536, Ed. 6) Some major
groups of prokaryotes. Figure 27.12, p. 540, Ed.
7.
43
(No Transcript)
44
(No Transcript)
45
A.  Great diversity of Archaea in extreme
environments and oceans   1.  Two taxa of
archae         a.  Euryarchaeota most
archae         b.  Crenarcheota most
thermophilic species    2.  Examples of
extremophiles         a.  Methanogens produce
methane             - Energy is from hydrogen
gas             - Strictly anaerobic             -
Inhabit swamps and animal intestines  
b.  Extreme halophiles   - Live in
salty environments (Great Salt Lake)              
                                     Figure
27.14 (p. 537) Extreme halophiles.
46
(No Transcript)
47
   c.  Extreme thermophiles       - 60- 80 C
optimum temperatures (hot springs)       - 105 C
for deep-sea hydrothermal vents
48
(No Transcript)
49
            B.  Most prokaryotes are in the
Domain Bacteria. ?Table 27.3 (p. 537) A
Comparison of the Three Domains of Life - There
are five clades to remember  1. 
Proteobacteria       - Gram-negative
bacteria       - Broad, diverse group that has
five subgroups REMEMBER THE FOLLOWING BACTERIA
WITHIN THIS CLADE AND WHAT THEY DO!!!
50
(No Transcript)
51
(No Transcript)
52
Rhizobium N2-Fixing, Lives in Plant Roots of
Legumes
53
Chromatium Example of a chemoautotroph Note
the sulfur granules
54
Bdellovibrio Bacterial predator
55
Myxobacterium Produces cell aggregates and
fruiting bodies
56
Heliobacter Causes stomach ulcers
57
The remaining four clades and examples for each
are
58
 2.  Chlamydias - Parasitic survive only within
cells of animals  - Some cause STDs e.g.
chlamydia
59
 3.  Spirochetes       - Helical
heterotrophs      - Some cause STDs e.g. syphilis
60
 4.  Gram-Positive Bacteria        - Broad,
diverse group          - Antibiotic producing
bacteria are in this group - Example shown is
Streptomyces (streptomycin) - And (next slide)
61
Mycoplasma shown covering a human cell some
species of mycoplasmas cause walking pneumonia
62
 5.  Cyanobacteria          - Oxygenic
photosynthesis Remember these because
chloroplasts evolved from them.
63
V.  Ecological impacts of prokaryotes 
            A.  Prokaryotes are links in the
recycling of chemical elements   B.  Many
prokaryotes are symbiotic (2 organisms living in
direct contact with each other). There are
three types of symbioses                      1. 
Mutualism both symbiotic organisms
benefit                          - e.g.
Nitrogen-fixing bacteria like Rhizobium plant
obtain organic nitrogen, Rhizobium gets energy in
the form of sugars that the plant produces.
Another example   Figure 27.15 (p. 540, Ed. 6,
p. 545, Ed. 7) Mutualism  bacterial
headlights.
64
(No Transcript)
65
2.  Commensalism one organism benefits and the
other is not harmed.                              
       - e.g. Bacteria on our skin   3. 
Parasitism parasite benefits and the host is
harmed.               C.  Pathogens cause human
diseases                         - Some
pathogens are opportunistic.  They may be normal
residents of the host, but if the host is
weakened, then they cause disease.   Figure 27.16
(p. 541) A very harmful germ Haemophilus
influenza (causes bacterial pneumonia NOT the
flu).
66
(No Transcript)
67
Lyme disease Caused by a spirochete
68
(No Transcript)
69
Most pathogens cause disease by producing
poisons, these are either - Exotoxins proteins
secreted by the pathogen that cause illness.   -
Endotoxins poisons that are part of the pathogen
that causes illness.  (e.g. bacteriums outer
membrane)
70
  D.  Humans use prokaryotes in research and
technology                         1.  Bacteria
clean wastewater, landfills, brownfields.   Figure
27.18 (p. 542) Putting prokaryotes to work in
sewage treatment facilities.  
71
(No Transcript)
72
Figure 27.19 (p. 542) Bioremediation for an oil
spill.