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11/15/2011
Chapter 27: Bacteria and Archaea
Outline
I. Categories of life
A. Domains
B. Eukaryote vs Prokaryote
II. Domain Bacteria
A.
B.
C.
D.
cell walls, structure
Bacterial reproduction
Nitrogen fixation
Pathogenic bacteria
III. Domain Archaea
Why care about the small stuff
 Bacteria are important “nitrogen fixers”
 Bacteria and fungi are decomposers
 Some bacteria and algae can produce
oxygen
 They are everywhere!!
 Some can produce disease
 Good website:
http://www.bacteriamuseum.org/cms/
Prokaryotes
 Prokaryotes thrive almost everywhere, including
places too acidic, salty, cold, or hot for most
other organisms
 Most prokaryotes are microscopic, but what
they lack in size they make up for in numbers
 There are more in a handful of fertile soil than
the number of people who have ever lived
 Prokaryotes are divided into two domains:
bacteria and archaea
© 2011 Pearson Education, Inc.
Bacteria in our bodies
 Bacteria are found naturally in our bodies
including in our:
 Nasal cavity (nose)
 Large intestine
 On our skin
Staphylococcus
in the human
nasal passage
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Do prokaryotes have a nucleus
Ye
 Photo courtesy of Margaret McFall-Ngai.
The First Cells
Are Domain Bacteria and Domain Archaea
prokaryotic or eukaryotic?
50%
50%
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Microfossils are fossilized forms of microscopic
life
-Oldest are 3.5 billion years old
eu
ar
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1. prokaryotic
2. eukaryotic
pr
ok
50%
o
50%
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1. Yes
2. No
N
Euprymna Scolopes have a symbiotic
relationship with luminescent bacteria.
The First Cells
Stromatolites are mats of cyanobacterial cells
that trap mineral deposits
-Oldest are 2.7 billion years old
Prokaryotes
 Domain Archaea – live in extreme
environments
 Domain Bacteria (Eubacteria)
 Microorganisms are any small organism – too
small to see with the naked eye include
 Pathogens – cause disease
 Most bacteria are not pathogens
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Prokaryotic Characteristics
1. Unicellular
2. No membrane-bound nucleus, single
chromosome and histone-like proteins found
in nucleoid region
3. Lack membrane bound organelles
4. Contain ribosomes
Prokaryotic Characteristics
5. Many have flagella
6. Cell wall present in many species
Prokaryotes
 No membrane bound organelles including:
nucleus, mitochondria, chloroplasts,
endoplasmic reticulum, golgi complex,
lysosomes.
7. Have plasma membrane
8. Reproduction by prokaryotic fission
 They do contain small ribosomes, storage
granules, plasma membrane may be folded
9. Great metabolic diversity
Domain Bacteria
 Prokarotes
 Categorized by
1. Shape
2. Cell wall type
3. Where they get their energy and their
nutrients from.
4. Motility
Molecular Classification
 Based on these molecular data, several
prokaryotic groupings have been proposed
 Bergey’s Manual of Systematic Bacteriology
 Contains about 7,000 bacterial and
species
archaeal
 The three-domain (Woese) system of phylogeny
is based on rRNA sequences
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Molecular Classification
Categories by shape
 Cocci – spherical (round ball) shaped, may
be singly or in groups
 Bacilli – rod shaped, may occur as a single
rod or as chains of rods
 Spirilla – helical, spiral shaped
Prokaryotic Shapes
Figure 27.2
Diverse nutritional and metabolic
adaptations have evolved in prokaryotes
 Prokaryotes can be categorized by how they obtain
energy and carbon




Phototrophs obtain energy from light
Chemotrophs obtain energy from chemicals
Autotrophs require CO2 as a carbon source
Heterotrophs require an organic nutrient to make
organic compounds
© 2011 Pearson Education, Inc.
1 m
1 m
3 m
Most prokaryotes have one of 3 basic shapes
 Bacillus = Rod-shaped
 Coccus = Spherical
 Spirillum = Helical-shaped
(a) Spherical
(b) Rod-shaped
(c) Spiral
Diverse nutritional and metabolic
adaptations have evolved in prokaryotes
 Energy and carbon sources are combined to give
four major modes of nutrition:




Photoautotrophy
Chemoautotrophy
Photoheterotrophy
Chemoheterotrophy
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Table 27.1
The Role of Oxygen in Metabolism
 Prokaryotic metabolism varies with respect to O2
– Obligate aerobes require O2 for cellular
respiration
– Obligate anaerobes are poisoned by O2 and use
fermentation or anaerobic respiration
– Facultative anaerobes can survive with or without
O2
© 2011 Pearson Education, Inc.
Nitrogen Metabolism
 Nitrogen is essential for the production of amino
acids and nucleic acids
 Prokaryotes can metabolize nitrogen in a variety
of ways
 In nitrogen fixation, some prokaryotes convert
atmospheric nitrogen (N2) to ammonia (NH3)
Nitrogen Fixation
 Some bacteria are able to take nitrogen gas and
fix it in the form that can be used by plants
 Rhizobium fixes nitrogen for plants like
legumes.
 Legumes and Rhizobium live in a mutualistic
relationship
 Rhizobium provide usable nitrogen
 Legumes provide sugar
 Rhizobium live inside legume cells in nodules
© 2011 Pearson Education, Inc.
Metabolic Cooperation
 Cooperation between prokaryotes allows them
to use environmental resources they could not
use as individual cells
 In the cyanobacterium Anabaena,
photosynthetic cells and nitrogen-fixing cells
called heterocysts (or heterocytes) exchange
metabolic products
© 2011 Pearson Education, Inc.
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Figure 27.14
Eutrophication
 Cyanobacteria like Anabaena are nitrogen fixers
(use heterocysts)
 Phosphorus and nitrogen are the main limiting
mineral in natural ecosystems
Photosynthetic
cells
Heterocyst
 Ph & N sources include sewage, agricultural
runoff (fertilizers), and industry
20 m
 Ph & N that enters rivers, lakes and estuaries can
produce blooms of cyanobacteria
Eutrophication
Eutrophication
 This bloom of bacteria covers the top of the
pond, blocking light from reaching the water
plants below.
 Oxygen is depleted by decomposers, and
blooms block out light which decreases
photosynthesis
 The water plants are not able to
photosynthesize so they can’t produce oxygen
 End result – oxygen depletion, fish need
oxygen and will die.
 Cyanobacteria have a short life and die,
decomposers break them down. Decomposers
use oxygen.
Photoautotroph - cyanobacteria
These organisms use the energy from the sun to fix
carbon into a sugar from CO2
25% 25% 25% 25%
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Photoheterotrophs
Chemoheterotrophs
Photoautotrophs
Chemoautotrophs
hs
1.
2.
3.
4.
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These organisms use the energy from inorganic
compounds to fix carbon into a sugar from CO2
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Photoheterotrophs
Chemoheterotrophs
Photoautotrophs
Chemoautotrophs
hs
1.
2.
3.
4.
Cell-Surface Structures
Cell Wall
 An important feature of nearly all prokaryotic cells is
their cell wall, which maintains cell shape, protects
the cell, and prevents it from bursting in a hypotonic
environment
 Prokaryotic cell plasma membranes are
usually covered with a cell wall. Keeps cell
from bursting in hypotonic solutions
 Eukaryote cell walls are made of cellulose or chitin
 Eubacteria cell walls contain peptidoglycan,
a combination of amino acids and sugars.
 Bacterial cell walls contain peptidoglycan, a
network of sugar polymers cross-linked by
polypeptides
© 2011 Pearson Education, Inc.
Cell Wall
 Some species have a capsule surrounding the
cell wall. The capsule can provide protection
against immune system cells (phagocytes)
 Some bacteria have pili – hair like structures
made of protein, help bacteria to adhere to
surfaces
 Some pili are involved in transmitting DNA
between bacteria
Cell Walls
 Archaea contain polysaccharides and
proteins but lack peptidoglycan
 Scientists use the Gram stain to classify
bacteria by cell wall composition
 Gram-positive bacteria have simpler walls
with a large amount of peptidoglycan
 Gram-negative bacteria have less
peptidoglycan and an outer membrane that
can be toxic
© 2011 Pearson Education, Inc.
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Cell Wall Types
The Bacterial Cell Wall Types
 There are two main cell wall types. The
differences have important implications in
treating the bacteria with antibiotics
 Gram Positive
 Gram Negative
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Gram positive
Figure 27.3a
(a) Gram-positive bacteria: peptidoglycan traps crystal violet.
 Gram positive cells have thick cell walls,
consisting mainly of peptidoglycan.
 Gram positive cells absorb the violet “gram
stain”
Cell
wall
Peptidoglycan
layer
Plasma
membrane
Fig. 28.8-1
Gram Negative
 Gram negative cells have two layers:
 A thin peptidoglycan layer
 A thick outer layer made of polysaccharides bound
to lipids, similar to plasma membrane
 Gram negative cells do not retain the gram
stain, they counter-stain pink
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Figure 27.3b
(b) Gram-negative bacteria: crystal violet is easily rinsed
away, revealing red dye.
Carbohydrate portion
of lipopolysaccharide
Cell
wall
Outer
membrane
Peptidoglycan
layer
Plasma membrane
Gram Stain
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External Layers
Motility
 Capsule
 A gelatinous layer found in some bacteria
 Aids in attachment
 Protects from the immune system
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 Most motile bacteria propel themselves by
flagella scattered about the surface or
concentrated at one or both ends
 Flagella of bacteria, archaea, and eukaryotes
are composed of different proteins and likely
evolved independently
© 2011 Pearson Education, Inc.
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Figure 27.6
Flagellum
Filament
Hook
Motor
Cell wall
Video: Prokaryotic Flagella (Salmonella typhimurium)
Plasma
membrane
20 nm
Rod
Peptidoglycan
layer
© 2011 Pearson Education, Inc.
Flagella
Motility
 Most prokaryotes have a flagella
 Flagella
 These flagella are not like eukaryotic flagella,
they are not composed of microtubules
 Long, helical structures
 Composed of the protein flagellin
 Involved in locomotion
 Instead it has:




Basal body that acts like a motor
Hook
Filament
Protein is flagellin
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Prokaryotic DNA
 Prokaryotes usually have a single, circular
DNA molecule.
 Most prokaryotes also have plasmids, small
circular fragments of DNA.
 Plasmids can replicate independently or
integrate into the main DNA
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Reproduction in Bacteria
 Most bacteria undergo asexual reproduction =
binary fission
 Occasionally some bacteria will undergo a
form of sexual reproduction – the plasmid of
one bacteria will be transferred to another
bacteria through the pilus
Internal Organization
 Prokaryotic cells usually lack complex
compartmentalization
 Some prokaryotes do have specialized
membranes that perform metabolic functions
 These are usually infoldings of the plasma
membrane
© 2011 Pearson Education, Inc.
Figure 27.7a
Pathogenic bacteria
 Some E. coli cause health problems
0.2 m
 Clostridium botulinum bacteria produce the
toxin botulism
Respiratory
membrane
(a) Aerobic prokaryote
 Clostridium tetanus cause tetanus
 Borrelia burgdorferi – bacteria that uses deer
ticks to move from host to host, causes Lyme
disease
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Cause of Disease
 Disease caused by bacteria are often
caused by either a toxin released by the
bacteria, or by the response of the host
Commercial Uses
 Lactobacillus – used to make yogurt,
pickles, sauerkraut.
 Bacteria populations can rapidly mutate,
antibiotic resistance can result
 The few bacteria that mutate and are
resistant to antibiotics will repopulate the
area with antibiotic resistant bacteria
Prokaryotic Domains
 Domain Archaea and Domain Bacteria
(Eubacteria)
 Differences in ribosomes
 Archaea does not have peptidglycan in cell wall
 Archaea have isoprene units and ether linkages
in the cell membrane.
 Domain Bacteria have ester linkages in the cell
membrane and fatty acids
Plasma membrane
Table 27.2
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Domain Archaea
 Prokaryotic – no nucleus
 Extreme bacteria
Methanogens example
Discovered in 1983 contains methanococcus jannaschii
Pacific Ocean thermal vent
 Methanogens (methane makers)
 Extreme halophiles (salt loving)
 Extreme thermophiles (heat lovers)
[©Stan Watson, Woods Hole Oceanographic Institute]
Halophile example
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Thermophile example
Yellowstone NP
Dunaliella salina
Important Concepts





Know the vocabulary in the lecture
What are auto/hetero/photo/chemo-trophs
What are the characteristics of prokaryotes
Which domains are prokaryotic
Know the parts of a prokaryotic cell and their
functions
 Know the structure of prokaryotic cell walls,
what they are made of, and the difference
between gram negative and positive,
understand how the gram stain technique works
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Important Concepts
 Know how many chromosomes a prokaryote
has and what plasmids are
 How do prokaryotes reproduce
 What is nitrogen fixation, why is it important
 Domain Archaea – three main types
 What are the differences between Domain
Archaea and Domain Bacteria (Eubacteria)
 How does bacteria cause disease
 Antibiotic resistance
 Understand eutrophication, including the causes
and effects
To Know for Lab Practical
 Be able to identify the three shapes of bacteria,
know their latin names
 Be able to identify anabaena.




what are the causes and effects of eutrophication,
What are heterocysts, be able to identfy them
Characteristics of anabaena
What domain does it belong in
 Identify Rhizobium and know what element it
fixes, What domain does it belong in
 Identify lactobacillus and why is it beneficial,
What domain does it belong in
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