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Bacteria
Chapter 24
Classification
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Structure
Physiology
Molecular composition
Reactions too stain
rRNA sequences
Archaebacteria
aka: ancient bacteria
• Unusual lipids in cell membrane- no
petoglycan
• Introns in DNA
• Cell walls lack peptidoglycan
• Genes closely related to early eukaryotes
• Extreme environments
Archaebacteria
Archaebacteria
• Methanogens
– Convert H2 and CO2 into methane gas
– Live in anaerobic environment
– Found in intestinal tracts of humans and other
animals
• Extreme halophiles
– Salt lovers
– Use salt to generate ATP
– Found in Dead Sea
Archaebacteria
• Thermoacidophiles
– Live in acidic environments pH <2
– Live in high temperatures up to 230
– Live near volcanic vents and cracks in the
ocean floor
Gram staining
pg 471
• Gram-positive - appear purple under a
microscope
– Thicker peptoglycan
– Causes different resistance to antibiotics
– Produce different toxins
• Gram-negative - do not retain stain
appearing pink under a microscope
Gram Staining
Eubacteria
aka: new bacteria
• Three basic shapes
– cocci
– bacilli
– Spirilla
• Strepto= Chains
• Staphlo= Grape like clusters
• 12 different phyla according to evolutionary
relationships
Cocci
Bacilli
Spirilla
Eubacteria
• Cyanobacteria
– Autotrophic
• Makes its own food
• Photosynthetic
– “Blue-green algae”
– Often cling in colonies
– Thrive on nitrates and phosphates in a body of
water
• Population bloom or eutrophication
Cynobacteria
aka: blue green algae
Eubacteria
• Spirochetes
– Gram-negative
– Spiral shaped
– Heterotrophic
• Cannot make its own food
• Example- Treponema pallidium (Syphilis)
Spirochetes
Eubacteria
• Gram-Positive Bacteria
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Not all are gram-positive
Cause tooth decay
Turn milk into yogurt
Causes strep throat
Eubacteria
• Proteobacteria- largest most diverse group
– Enteric bacteria
• inhabit animal intestines (E. Coli)
– Chemoautotrophic
• Gram-negative bacteria
• Oxidizes chemicals
– Nitrogen-fixing bacteria
• Convert nitrogen into ammonia
E. Coli
Nitrogen-fixing Bacteria
pg 467-475
Structure
• Cell Wall
– Eubacteria - peptidoglycan
• Cell Membrane
– Acts like mitochondria in cells
– Contains enzymes that speed up cellular
respiration
• Cytoplasm
– Contains DNA, ribosomes, & organic
compounds
Structure
• Capsules
– Outer covering that protects the cell and assist
in attaching the cell to other surfaces
• Pili- used for adhesion
– Hairlike protein structures that transfer genetic
material from one bacterium to another
• Endospores
– Dormant structure protecting against harsh
conditions
– When conditions are right, bacteria emerge.
Yogurt
Nutrition and Growth
• Saprophytes - feed on dead and decaying
material
• Photoautotrophic – uses the sun to make its
own food (blue-green algae)
• Obligate anaerobe - cannot live in presence
of oxygen (Tetnus)
• Facultative anaerobe - Can live with or
without oxygen (E.coli)
Nutrition and Growth
• Obligate aerobes - Cannot live without
oxygen (Turberculosis)
• Thermophilic - Grow between 104 - 230
Bacteria and Disease
• Pathology - Studying diseases
• Toxins = poisons
• Exotoxins = Toxins made of proteins
(Gram-Positive Bacteria)
• Endotoxins = Toxins made of lipids and
carbohydrates (Gram-Negative Bacteria)
– Not released till bacteria die
– Cause fever, aches, weakness
Antibiotics
• Combat bacteria by interfering with various
cellular functions
• Resistance
– Mutated bacteria that is resistant to antibiotics
can continue to grow and reproduce
Example- Penicillin attacks bacteria cell walls
Body’s Defense
Useful Bacteria
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Insecticides
Clean up environmental disasters
Produce and process food
Turn sewage into simpler organic
compounds
Bacteria Replication
Binary fission
• Divides a prokaryotic cell into 2 off spring
cells
Binary fission cont.
• DNA is copied
Binary fission cont.
• Cell begins to divide
Binary fission cont.
• Two identical haploid cells (original # of
chromosomes)
Binary Fission
More terms to know
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Population bloom
Capsule
Saprophytes
Pathogen
Conjugation
– 2 bacteria connect and transfer genetic material
to each other.