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Ch. 23 Bacteria
AP Biology
Intro to Bacteria
 Anton van Leeuwenhoek
 Pathogen
 Decomposer, recycler, producers,
agriculture
Prokaryotes
 Archaeabacteria
 Eubacteria
 Smaller than eukaryote
 Exception = Epulopiscium fishelsoni
 Most unicellular
 Some colonies/filaments
Bacteria
on Pin
Shapes of Bacteria
 Spherical =
 Twos –
 Long chains –
 Bunches –
 Rod-shaped =
 Single rods or chains
 Helical –
 Short helix =
 Rigid, longer helix =
 Flexible, longer helix =
Fig. 27-2
1 µm
(a) Spherical
(cocci)
2 µm
(b) Rod-shaped
(bacilli)
5 µm
(c) Spiral
Lack membrane-bound organelles
 No nuclei, mitochondria, chloroplasts, ER,
Golgi, lysosome
 Cytoplasm –
 ribosomes and storage granules
 Metabolic enzymes
 Plasma membrane may be infolded
Bacterial Cell Wall
 Support, shape
 Hypotonic
 Hypertonic
 High sugar/salt (jams, salted fish)
Bacterial Cell Wall continued
 Eubacteria – peptidoglycan
 Peptidoglycan = complex polymer consisting
of amino sugars linked with short
polypeptides
Gram Staining
 Gram +
 Thick cell wall – mostly peptidoglycan
 Absorb and retain crystal violet dye
 Gram –
 2 layers = thin peptidoglycan +thick outer membrane
 Do not retain crystal violet dye when rinsed with alcohol
Fig. 27-3
Carbohydrate portion
of lipopolysaccharide
Peptidoglycan
Cell
wall
Cell
layer
wall
Outer
membrane
Peptidoglycan
layer
Plasma membrane
Plasma membrane
Protein
Protein
Grampositive
bacteria
(a) Gram-positive: peptidoglycan traps
crystal violet.
Gramnegative
bacteria
20 µm
(b) Gram-negative: crystal violet is easily rinsed away,
revealing red dye.
Fig. 27-3a
Cell
wall
Peptidoglycan
layer
Plasma membrane
Protein
(a) Gram-positive: peptidoglycan traps
crystal violet.
Fig. 27-3b
Carbohydrate portion
of lipopolysaccharide
Outer
membrane
Cell
wall Peptidoglycan
layer
Plasma membrane
Protein
(b) Gram-negative: crystal violet is easily rinsed
away, revealing red dye.
Fig. 27-3c
Grampositive
bacteria
Gramnegative
bacteria
20 µm
Gram-Positive Bacteria
• Gram-positive bacteria include
– Actinomycetes
– Bacillus anthracis
– Clostridium botulinum
– Some Staphylococcus and Streptococcus
– Mycoplasms, the smallest known cells
5 µm
Fig. 27-18m
Streptomyces, the source of many
antibiotics (colorized SEM)
1 µm
Fig. 27-18n
Hundreds of mycoplasmas
covering a human fibroblast
cell (colorized SEM)
The Bacterial Glycocalyx
 Around cell wall
 Some bacteria
 Free-living
 Add protection against phagocytosis by
microorganisms
 Disease-causing
 Protect against phagocytosis by WBCs
 Ex: Streptococcus pneumoniae
 Attachment
 Rocks, plant roots, human teeth
Fig. 27-4
200 nm
Capsule
Bacterial Pili (Pilus)
 Protein
 Adhere
 Transmission of DNA between bacteria
Fig. 27-5
Fimbriae
200 nm
Motile Bacteria
 Water = viscous
 Flagella rotate
 # and location – classify
 3 parts
 1. basal body – motor; anchors flagellum
 2. hook – curved; connects basal body to long, hollow
filament
 3. single filament
Bacterial Flagellum
 Basal Body motor
 ATP energy -pump protons out of cell
 Diffusion of protons back powers motor –
spins flagellum like a propeller
 Rotary motion pushing the cell
Fig. 27-6
Flagellum
Filament
50 nm
Cell wall
Hook
Basal apparatus
Plasma
membrane
Fig. 27-6a
Filament
Cell wall
Hook
Basal apparatus
Plasma
membrane
Fig. 27-6b
50 nm
Prokaryotic flagellum (TEM)
Bacterial Flagella
Genetic material in bacteria
 Single circular DNA molecule
 Cytoplasm
 Little protein
 Plasmids
 Small circular fragment of DNA
 Can replicate independently of genomic DNA
 Become integrated in genomic DNA
Fig. 27-8
Chromosome
Plasmids
1 µm
Reproduction in Bacteria - Asexual
 Binary fission
 1 cell  2 cells
 1st – circular bacterial DNA replicated
 2nd – transverse wall is formed
 Fast
 <20min.
 Soon – lack of food, accumulation of waste
products
Reproduction continued
 Budding
 Bulge (bud)
 Bud enlarges, matures, separates
 Fragmentation
 Walls develop within cell  separates into
several new cells
No Sexual Reproduction – INSTEAD:
Genetic Exchange of Material
 1. Transformation –
 2. Transduction –
 3. Conjugation –
 E. coli – donor cells (“male” cells)
 Plasmids can be transmitted to recipient “female” cells
 Pilus on donor recognizes recipient cell and makes the 1st
contact
 Cytoplasmic bridge forms btw. 2 cells and DNA is transferred
from donor to recipient
Fig. 27-11-1
Phage DNA
A+ B+
A+ B+
Donor
cell
Fig. 27-11-2
Phage DNA
A+ B+
A+ B+
Donor
cell
A+
Fig. 27-11-3
Phage DNA
A+ B+
A+ B+
Donor
cell
A+
Recombination
A+
A– B–
Recipient
cell
Fig. 27-11-4
Phage DNA
A+ B+
A+ B+
Donor
cell
A+
Recombination
A+
A– B–
Recipient
cell
A+ B–
Recombinant cell
Fig. 27-12
Sex pilus
1 µm
Fig. 27-13-1
F plasmid
Bacterial chromosome
F+ cell
Mating
bridge
F– cell
Bacterial
chromosome
(a) Conjugation and transfer of an F plasmid
Fig. 27-13-2
F plasmid
Bacterial chromosome
F+ cell
Mating
bridge
F– cell
Bacterial
chromosome
(a) Conjugation and transfer of an F plasmid
Fig. 27-13-3
F plasmid
Bacterial chromosome
F+ cell
F+ cell
Mating
bridge
F– cell
Bacterial
chromosome
(a) Conjugation and transfer of an F plasmid
F+ cell
The F Factor in the Chromosome
• A cell with the F factor built into its chromosomes functions as a
donor during conjugation
• The recipient becomes a recombinant bacterium, with DNA from
two different cells
• It is assumed that horizontal gene transfer is also important in
archaea
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
Endospores
 Unfavorable environment
 Some bacteria 
 Endospores
 1 endospore/original cell
 Can survive extreme conditions
 Favorable conditions 
Endospores continued
 Medical importance –
 Clostridium tetani – tetanus
 Bacillus anthracis - anthrax
Fig. 27-9
Endospore
0.3 µm
Metabolic diversity
 Heterotrophs
 Must obtain organic compounds from other organisms
 Most  free-living saprotrophs
 Autotrophs
 Can make own organic molecules from simple raw
materials
 Photosynthetic autotrophs (photoautotrophs)
 Chemosynthetic autotrophs (chemoautotrophs)
Table 27-1
Aerobes Vs. Anaerobes
 Aerobic –
 Anaerobic
 Facultative anaerobes –
 Obligate anaerobes –
 Certain bacteria killed by low O2 level
Archaea
 Produce methane gas from simple C
 Extreme environments
 No peptidoglycan
 Methanogens, halophiles, thermophiles
Methanogens
 O2 free environments
 Strict anaerobes
 Produce methane gas
 Important in recycling organic products of
organisms in swamps
Extreme Halophiles
 Heterotrophs
 Saturated brine solutions
 Some – capture energy of light with a
purple pigment (bacteriorhododpsin)
similar to pigment rhodopsin involved in
animal vision
 Different from photosynthesis
Halophile
Salt Ponds
Extreme Thermophiles
 Hot, acidic environments
 Sulfur springs –Yellowstone
 Volcanoes under sea
 Deep sea vents
Fig. 27-17
Eubacteria
 Ecological importance
 Photosynthesis –
 Soil –
 Mutualism –
 Agriculture:
 Roots of legumes
 Fixing nitrogen
2.5 µm
Fig. 27-18c
Rhizobium (arrows) inside a root
cell of a legume (TEM)
Eubacteria continued
 Causing disease
 Normal microbiota
 Prevent harmful bacteria
 Human intestine – Vit. K, some B vitamins
 Opportunistic bacteria –
Robert Koch – showed bacteria
cause infectious disease
 Koch’s postulates
 1. pathogen must be present in every individual
with the disease
 2. sample of the microorganism taken from the
diseased host can be grown in pure culture
 3. when a sample of pure culture is injected into a
healthy host, it causes the same disease
 4. microorganism can be recovered from the
experimentally infected host
Pathogens
 Enter by food, dust, droplets, wounds, bites
 To cause disease  adhere to specific cell
type, multiply, produce toxin
2 µm
Fig. 27-18h
Helicobacter pylori (colorized TEM)
Cause Stomach Ulcers
2.5 µm
Fig. 27-18j
Chlamydia (arrows) inside an
animal cell (colorized TEM)
•Parasites in animal cells
•Causes blindness and nongonococcal urethritis by sexual transmission
5 µm
Fig. 27-18k
Leptospira, a spirochete
(colorized TEM)
•helical heterotrophs
•Some, such as Treponema pallidum, which causes syphilis, and Borrelia
burgdorferi, which causes Lyme disease, are parasites
Fig. 27-21
5 µm
Exotoxins
 = strong poisons either secreted from the cell or
leak out when the bacterial cell is destroyed
 Ex:
 Diphtheria – toxin kills cells/causes
inflammation
 Botulism – food poisoning – paralysis/death
 Destroyed by heat
Commercial Uses of Bacteria
 Fermentation – Tasty Bacteria
 Lactic acid bacteria –
 cheese, salami, vinegar, soy sauce
 Antibiotics
 Soil bacteria
 G-bacillus
 Molds
Commercial uses continued
 Reproduction rates high
 Make biomolecules
 Genetic engineering
 Vaccines, HGH, insulin, insect resistance
 Sewage treatment
 Landfill – break down solid waste
 Bioremediation
Fig. 27-22
(b)
(c)
(a)
0.5 µm
Fig. 27-18e
Thiomargarita namibiensis
containing sulfur wastes (LM)
Endotoxins
 Not secreted; components of cell walls of
most G Affect host when released from dead
bacteria
 Bind to macrophages and stimulate them to
release substances causing fever/other
symptoms
 Not destroyed by heating
Cyanobacteria
 Photosynthesize
 1st oxygen
Antibiotics
 2 classes
Inhibit protein biosynthesis
Inhibit cell wall biosynthesis
 Resistance
You should now be able to:
1. Distinguish between the cell walls of gram-
positive and gram-negative bacteria
2. State the function of the following features:
capsule, sex pilus, nucleoid, plasmid, and
endospore
3. Explain how plasmids are important in
genetics
4. Distinguish among the following sets of terms:
photoautotrophs, chemoautotrophs,
photoheterotrophs, and chemoheterotrophs;
obligate aerobe, facultative anaerobe, and
obligate anaerobe; exotoxins and endotoxins