Prokaryotes
They’re Everywhere!
References
••
Bergey’s Manual of
Determinative Bacteriology
•Provides identification schemes
for identifying bacteria and
archaea
•• Bergey’s Manual of Systematic
Bacteriology
•Provides phylogenetic
information on bacteria and
archaea
•• Approved Lists of Bacterial
Names
•Lists species of known
prokaryotes
•Morphology,
differential
staining, biochemical tests
•Based
on rRNA sequencing
•Based
on published articles
Pokaryota Overview


They’re (Almost) Everywhere!
Most prokaryotes are microscopic


But what they lack in size they more than
make up for in numbers
The number of prokaryotes in a single
handful of fertile soil

Is greater than the number of people who
have ever lived
Prokaryotes thrive almost everywhere

Including places too acidic, too salty, too cold, or too hot for
most other organisms
Figure 27.1
Themes in the Diversification of
Bacteria and Archaea


Morphological Diversity
Metabolic Diversity
 Cellular Respiration: Variation in Electron
Donors and Electron Acceptors
 Fermentation
 Photosynthesis
 Pathways for Fixing Carbon
Numbers
Total
number alive today
5  1030
 As much carbon in these cells as
in all of the plants on Earth
 More living on a single person
than number of people alive in the
world

Prokaryotic Cells

Size

Smallest of living cells
0.2 to 2.0 μm in diameter
 2 to 8 μm in length

Most eukaryotes bigger
 Viruses much smaller

Two of the Three Domains
Prokaryote vs Eukaryote
Overview

Prokaryote or “before
nucleus”






no membrane-bound
nucleus
no other membrane-bound
organelles
DNA not associated with
histones
cell walls almost always
contain peptidoglycan
70s ribosomes
Largest about size of
smallest eukaryote

Eukaryote or “true
nucleus”






membrane bound nucleus
many other membranebound organelles
DNA associated with
histones
cell walls never contain
peptidoglycan
80s ribosomes
Smallest about size of
largest prokaryote
Bacteria
Cell
walls made of peptidoglycan
 Plasma membranes similar to
those of eukaryotes
 Distinct ribosomes and RNA
polymerase.
Archea

Extreme environments
High
heat
High Salt Concentration
High Acid Concentration

Call walls made of polysaccharides

unique plasma membranes
Ribosomes and RNA polymerase similar to those of
eukaryotes.

Major nutritional modes in
prokaryotes
Table 27.1
The Requirements for Growth:
Chemical Requirements

Oxygen (O2)
obligate
aerobes
Faultative
anaerobes
Obligate
anaerobes
Aerotolerant
Microaerophiles
anaerobes
Cyanobacteria

Photosynthetic bacteria
first
organisms to perform
oxygenic (oxygen-producing)
photosynthesis
Once oxygen was common in
the oceans, aerobic respiration
became possible.

Changed the Earth’s Atmosphere
From one dominated by
nitrogen gas and carbon dioxide

To one dominated by nitrogen
gas and oxygen.

Nitrate Pollution

Use of ammonia fertilizers
serious

pollution problems
Releasing nitrate
by-product
metabolism
Nitrate
of bacterial ammonia
may cause
cancer
decrease
oxygen of aquatic systems
anaerobic
“dead zones” to develop
Study of Bacteria
and Archaea
Our understanding of the
Bacteria and Archaea domains is
advancing more rapidly now than
at any time during the past 100
years—and perhaps faster than
our understanding of any other
lineages on the tree of life.

Enrichment
Culture
•Media with
specific
growing
conditions
• Used to
isolate new
bacteria and
archea
Direct Sequencing
a strategy for documenting the presence of
bacteria and archaea that cannot be grown in
culture
Direct sequencing has been used to
discover a new lineage of Archaea called
the Korarchaeota
Bacteria NOT Closely Related to
Archea
The first lineage to diverge from
the common ancestor of all living
organisms was the Bacteria
Archaea and Eukarya are more
closely related to each other than to
the Bacteria.

How the Major Clades are
Related
Themes in the Diversification of Bacteria
and Archaea

Bacteria and Archaea diversified
Hundreds of thousands of distinct species
 3.4 billion years


Metabolic Diversity
Produce ATP in different ways
 Obtain carbon in diverse ways

Microbial Growth and Cell
Division


Increase in mass
Increase in cell numbers
Mitosis in most eukaryotes
 Budding in yeasts
 Fragmentation in filamentous fungi
 Binary fission in bacteria and archea

Steps in Binary Fission




Chromosome replication
Chromosome attachment to cell
membrane.
Chromosomal segregation
Septum formation


Inward movement of cell wall and cell membrane dividing
daughter cells
Wall Elongation
Binary Fission
Plasmids
Figure 8.29
Conjugation
Figure 8.27a
Conjugation
Figure 8.27b
Conjugation
Figure 8.27c
Cellular Respiration
A molecule with high potential
energy serves as an electron donor

is
oxidized,
A molecule with low potential
energy serves as a final electron
acceptor

is
reduced
Potential energy difference is
converted into ATP

Exploit a Wide Variety of
Electron Donors and Acceptors
Typical Bacterial Cell
Common Bacterial Shapes

Cocci - spherical

Bacilli – rods

Spirillum - spiral
Other, Less Common Shapes

Vibrio – comma

Coccobacillus -

Square

Star
Common Cell arrangements

Cocci

Bacilli
Bacterial Anatomy from the
Outside In





Glycocalyx
Appendages
Cell Wall
Bacterial Cell Membranes
Inside the Cell
Glycocalyx


Sticky substances that surround cells
 Firmly attached = capsule
 Loosely attached = slime layer
Composition varies with species




Polysaccharides
Polypeptides
Both
Function



Protect cell from phagocytosis and dehydration
Aid in attachment to various surfaces
May inhibit movement of nutrients from cell
Appendages

Flagella
Tail-like structures extending out from
glycocalyx
 Functions in movement of the bacterial cell
 Complex structure

Structure of Flagella

Filament




Hook


Long tail-like region
Constant diameter
Made of protein
Filament attachment
Basal body

Small central rod
inserted into a series
of rings
Cell Wall


Rigid
Composed mostly of peptidoglycan
Found only in bacterial cell walls
 Amount differs in gram+ and gram- cells


Protects cell in environments with
osmotic pressures
Peptidoglycan

Glycan portion

NAG


NAM



N-acetylglucosamine
N-acetylmuramic acid
Linked in rows of
10-65 sugars
Peptide portion

Adjacent rows are
linked by
polypeptides
Gram+ Cell Wall
Gram – Cell Wall
Gram Stain



The Gram Stain is the single most important test in microbiology. The
principal utility of the Gram Stain rests on its speed and simplicity.
Most bacteria may be divided in two groups by this procedure
developed by the Danish physician Hans Christian Gram to
differentiate pneumococci from Klebsiella pneumonia
difference between Gram-positive and Gram-negative bacteria is in the
structure of the cell wall
Results
G+ cocci
G- rods
Websites with more samples of gram stained bacteria
GRAM STAINED IMAGES OF MEDICALLY IMPORTANT BACTERIA
Loyola University Medical Center
http://www.meddean.luc.edu/lumen/DeptWebs/microbio/med/gram/slides.htm
GRAM STAIN TUTORIAL
http://www.courses.ahc.umn.edu/pharmacy/5825/GSPage05.html
Atypical Cell Walls

Mycoplasmas



Archea



Lack cell wall
Smallest known bacteria
Cell walls contain pseudomurein rather than
peptidoglycan
Lacks D-amino acids found in bacteria
L-forms


Tiny mutant bacteria with defective cell walls
Just enough material to prevent lysis in dilute
environments
Bacteria
There are at least 14 major
lineages (phyla) of bacteria.

Microbial Diversity

PCR indicates up to 10,000 bacteria/gm of
soil. Many bacteria have not been
identified or characterized because they:
Haven't been cultured
 Need special nutrients
 Are part of complex food chains requiring the
products of other bacteria
 Need to be cultured to understand their
metabolism and ecological role

Spirochetes
Spirochetes are distinguished
by their corkscrew shape and
unusual flagella




Borrelia
Leptospira
Treponema
Spirochaetes
Figure 11.23
Chlamidiae
Chlamydiaeare spherical and
very tiny.
They live as parasites inside
animal cells

Chlamydiae

C. trachomatis
Trachoma
 STD, urethritis



C. pneumoniae
C. psittaci

Causes psittacosis
In Bergey's Manual, Volume 5
Figure 11.22b
In Bergey's Manual, Volume 5
Figure 11.22a
High-GC (guanine and cytosine)
Gram-positive bacteria have
various shapes, and many soildwelling species form mycelia
(branched filaments)

Actinobacteria








Actinomyces
Corynebacterium
Frankia
Gardnerella
Mycobacterium
Nocardia
Propionibacterium
Streptomyces
Figure 11.20b
Cyanobacteria
Cyanobacteria dominate many
marine and freshwater environments.
They produce much of the oxygen
and nitrogen, as well as many organic
compounds, that feed other
organisms in freshwater and marine
environments

Cyanobacteria



Oxygenic
photosynthesis
Gliding motility
Fix nitrogen
Low-GC Gram-positive bacteria
cause a variety of diseases
including anthrax, botulism,
tetanus, gangrene, and strep
throat.
Lactobacillus is used to make
yogurt.

Clostridiales

Clostridium
Endosporeproducing
 Obligate
anaerobes

Figure 11.14 & 15
Bacillales

Bacillus

Endospore-producing
rods
Figure 11.16b
Bacillales

Staphylococcus

Cocci
Figure 1.17
Lactobacillales

Generally
aerotolerant
anaerobes, lack an
electron-transport
chain
 Lactobacillus
 Streptococcus
 Enterococcus
 Listeria
Figure 11.18
Mycoplasmatales



Wall-less,
pleomorphic
0.1 - 0.24 µm
M. pneumoniae
Figure 11.19a, b
Proteobacteria

Large group
Cause
Legionnaire’s disease,
cholera, dysentery, and
gonorrhea.
 Certain species can produce
vinegars.
Rhizobium can fix nitrogen.
The  (alpha) Proteobacteria

Human pathogens:
Bartonella
 B. hensela Cat-scratch disease
 Brucella
Brucellosis

The  (alpha) Proteobacteria

Wolbachia.
Live in
insects and
other
animals
The  (alpha) Proteobacteria

Nitrogen-fixing
bacteria:

Azospirillum
Grow in soil, using
nutrients
excreted by
plants
 Fix nitrogen


Rhizobium

Fix nitrogen in the
roots of plants
Figure 27.5
The  (alpha) Proteobacteria

Produce acetic acid from ethyl alcohol:
Acetobacter
 Gluconobacter


The  (beta) Proteobacteria
Thiobacillus


Chemoautotrophic, oxidize sulfur: H2S 
SO42–
Sphaerotilus

Chemoheterotophic, form sheaths
Figure 11.5
The  (beta) Proteobacteria

Neisseria
Chemoheterotrophic,
cocci
 N. meningitidis
 N. gonorrhoeae


Spirillum

Chemoheterotrophic,
helical
Figure 11.4 & 6
The  (beta) Proteobacteria

Bordetella
Chemoheterotrophic, rods
 B. pertussis



Burkholderia. Nosocomial infections
Zoogloea. Slimy masses in aerobic sewagetreatment processes

The  (gamma) Proteobacteria
Pseudomonadales:
 Pseudomonas
 Opportunistic
pathogens
 Metabolically
diverse
 Polar flagella
 Azotobacter and
Azomonas.
Nitrogen fixing
Moraxella.



Conjunctivitis
Figure 11.7
The  (gamma) Proteobacteria

Legionellales:

Legionella
Found in streams,
warm-water pipes,
cooling towers
 L. pneumophilia


Coxiella

Q fever
transmitted via
aerosols or milk
Figure 24.15b
The  (gamma) Proteobacteria

Vibrionales:

Found in coastal
water
Vibrio cholerae causes
cholera
 V. parahaemolyticus
causes gastroenteritis

Figure 11.8
The  (gamma) Proteobacteria

The  (gamma) Proteobacteria

Enterobacteriales (enterics):

Peritrichous flagella, facultatively anaerobic









Enterobacter
Erwinia
Escherichia
Klebsiella
Proteus
Salmonella
Serratia
Shigella
Yersinia
The  (delta) Proteobacteria



Bdellovibrio. Prey on other bacteria
Desulfovibrionales. Use S instead of O2 as
final electron acceptor
Myxococcales. Gliding. Cells aggregate to
form myxospores
The  (delta) Proteobacteria
Figure 11.10a
The  (delta) Proteobacteria
Figure 11.1b
The  (epsilon)
Proteobacteria

Campylobacter
One polar flagellum
 Gastroenteritis

Figure 11.1a
The  (epsilon)
Proteobacteria

Helicobacter
Multiple flagella
 Peptic ulcers
 Stomach cancer

Figure 11.1b
Extremophiles

Some archaea


Extreme thermophiles



Live in extreme environments
Thrive in very hot environments
hot springs at the bottom of the ocean, where
water as hot as 300°C emerges
Extreme halophiles



Live in high saline environmentsMethanogens
Live in swamps and marshes
Produce methane as a waste product
Extremophiles

Methanogens
Live
in swamps and marshes
Produce methane as a waste product
 Low-temperature

High-pressure habitats

Are of commercial interest
 enzymes that function at low temperature or high temperature
may be useful in industrial processes

Model organisms in the search for extraterrestrial life
Extreme Halophiles
Figure 27.14
Prokaryotes play crucial roles in the
biosphere

Prokaryotes are so important to the biosphere
that if they were to disappear



Continual recycling of chemical elements
function as decomposers


The prospects for any other life surviving would be
dim
Corpses, dead vegetation, and waste products
Symbiotic Relationships

mutualism, commensalism, parasitism
The Nitrogen Cycle
Molecular nitrogen (N2) is
abundant in the atmosphere
most organisms cannot use
All eukaryotes and many bacteria
and archaea must obtain their
nitrogen from ammonia (NH3) or
nitrate (NO3).

Nitrogen Metabolism

Prokaryotes can metabolize nitrogen


In a variety of ways
In a process called nitrogen fixation
Some prokaryotes convert atmospheric
nitrogen to ammonia
 Redox reactions

Nitrogen Fixing Organisms


Species of cyanobacteria
bacteria
Land
 Live in close association with
plants

often
in nodules
Pathogenic Prokaryotes

Prokaryotes cause about half of all
human diseases

Lyme disease is an example
Figure 27.16
5 µm
Pathogenic Prokaryotes

Pathogenic prokaryotes typically cause
disease


Many pathogenic bacteria


By releasing exotoxins or endotoxins
Are potential weapons of bioterrorism
Also cause other animal and plant diseases
Bioremediation

Prokaryotes are the principal agents in
bioremediation

The use of organisms to remove pollutants from
the environment
Figure 27.17
Bioremediation
 Some of the most serious pollutants in soils, rivers, and
ponds
 organic compounds


originally used as solvents or fuels
leaked or were spilled into the environment
Sediments where these types of compounds accumulate
become anoxic


Use bacteria and archaea to degrade pollutants
 fertilizing contaminated sites to encourage the growth of
existing bacteria that degrade toxic compounds
adding
specific species of bacteria to contaminated sites
Prokaryotes in Research and
Technology

Experiments using prokaryotes

Have led to important advances in DNA
technology
Other Contributions

Prokaryotes are also major tools in
Mining
 The synthesis of vitamins
 Production of antibiotics, hormones, and
other products
