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Bacteria
Chapter 24
Introduction
• Believed to be the oldest form of life
o Fossil evidence dates bacteria to 3.5 bya
• Can live in all environments on earth
o Deep ocean vents (archae)
• High temp, high pressure, highly acidic
o Extremely salty environments (archae)
• Great salt lake, dead sea
o Swamps/digestive tract (archae)
• Produce methane gas
o Others surround us at all times
(bacteria/eubacteria)
• Billions on your body at all time
Classification
• Broken into 5/6 kingdoms
o Monera = archaebacteria and eubacteria
• Microbiology uses 3 domains
o Archae, bacteria, eukarya
Kingdom
• All bacteria are considered Monera
o Includes bacteria and blue-green algae
• Blue-green algae also called cyanobacteria
• Archaebacteria (Domain Archaea)
o “Ancient” bacteria
o First broken off in 1977
• Eubacteria (Domain Bacteria)
o “Modern” bacteria
Prokaryotes
• Lack membrane
bound organelles
o No membrane
organelles = no nucleus
• Single circular strand of
DNA
o Makes replication,
transcription, translation
occur much more
rapidly
Unicellular
• All bacteria are unicellular
• All prokaryotes are bacteria= all prokaryotes are
unicellular
• Not all unicellular are prokaryotes
Phyla (3/1)
• Schizophyta: common bacteria
• Cyanophyta: Blue green algae
o Responsible for formation of current atmosphere
More Classification
• Bacteria classification in large part
determined by gram staining
o Gram positive have a thick cell wall that absorbs
purple dye
o Gram negative have a thin cell wall, do not
absorb dye and appear pink
o Knowing if bacteria is gram +/- is important
because of different succeptibilities to
antibacterial drugs and disinfectants
o Also release different toxins
o Very useful tool tool for grouping bacteria
Peptidoglycan
• Material that
absorbs the crystal
violet
• 20-80 nm in gram +
o 90% of dry weight
• 7-8 nm in gram –
o 10% dry weight
• Helps counter act
osmotic pressure
Linnaeus’s System of Classification
• Due to enormous number of living things of all types
a classification system was devised by a Swedish
naturalist named Carrolus Linnaeus (1707-1778)
• Used organisms morphology (structure and form) to
categorize it
Example of Levels of Classification
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Example
Animalia
Chordata
Mammalia
Carnivora
Felidae
Panthera
Leo (Panthera Leo)
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Level
Kingdom
Phylum
Class
Order
Family
Genus
Species
Binomial Nomenclature
• Scientific name of each organisms consist of
2 parts
o Genus and species
• Genus written first
• Species written second
o Examples
• Homo (genus) sapien (species), panthera (genus) leo
(species), panthera (genus) tigris (species)
o Members of the same genus share many
morphological similarities
Methods of Getting Food
• Heterotrophic
o Unable to make organic molecules from
inorganic molecules
o Saprophytic bacteria
• Autotrophic
o Organisms that can make organic molecules for
food
o Chemosynthetic
o Photosynthetic
Types of Reproduction/Genetic
Variation/Survival Adaptations
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Binary Fission
Endospores
Conjugation
Transformation
Transduction
Binary Fission
• Simplest form of
asexual reproduction
• Parent cell split into two
new cells
o Offspring are exact copies
o Very rapid
Endospores
• Help bacteria survive
harsh conditions
• Used by some gram
positive bacteria
• Protects the genetic
information
o Thick covering that is over the
genetic info
o Cell may die, but endospore
can survive
Transformation
• DNA from dead bacteria is taken in by living
bacteria
• Living bacteria may take on traits of the dead ones
• Major experiment done by Frederick Griffith (1928)
Griffith’s Experiment
Conjugation
• Bacteria join
and transfer
genetic
information
Transduction
• Virus transfers material between 2 bacterial cells
Size of Bacterial Cells
• Very small
• Simple cells, do not require much material
• Cell size measured in microns
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Also called micrometer
mm
1 micron = 1/1 000 000 m
1 000 000 micron = 1m
Size Scale
Shape: Coccus (KOK-us)
• Round or
spherical
• Plural term is
cocci
Shape: Bacillus (buh-SILLus)
• Rod shaped
• Plural is bacilli
• Some are
curved
(comma
shape) called
vibrio
Shape: Spirillum (spyRILL-um)
• Spiral shaped
• Plural is spirilla
• Also called
spirochetes
Prefix: Diplo• 2
• 2 cells linked
together
Prefix: Strepto- (STREPtoh)
• Twisted/chain
• Many cells
Prefix: Staphyl- (STAHfill-oh)
• Cluster/bunch
Structure of Bacterial
Cells
• All have
o Rigid cell walls
o Capsule – structure that surrounds cell wall
o Genetic material- looks like a tangled bundle in
the nuclear area
• Some have
o Plasmids-extra genetic information
o 1 or more flagella- tail for movement (motile)
o Pili – tiny hairs used for attachment
Respiration: Aerobic
• Process that requires oxygen to break down
glucose
• These bacteria are similar to mitochondria
• Referred to as obligate aerobes
o Must have oxygen gas available
Respiration: Anaerobic
• Energy produced without oxygen
• Similar to the anaerobic process discussed earlier
o Obligate anaerobes cannot be exposed to oxygen
o Oxygen gas is actually a poison for them
Respiration: Facultative Anaerobic
Bacteria
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Can live in both types of conditions
Do not use oxygen gas for energy production
Oxygen gas is not a poison for them however
E. Coli is an example of this
o Lives in digestive tract (No O2)
o Lives outside the digestive tract (21% O2)
Life Style
• Most Bacteria are…
o Heterotrophic (very few autotrophic)
o Saprophytic-live on dead organic material
• Some bacteria are…
o Parasites
o In a symbiotic relationship: close association between 2 dissimilar
organisms
• Mutualism: both bacteria and host benefit
Classified According To:
• Size/shape
• Structure of cell wall
o Gram +/-
• Whether or not they need oxygen
• How they obtain food
More Terms
• Virulence – the ability to cause serious
disease
• Fermentation – production of alcohol/lactic
acid
• Pasteurization – a way to inhibit bacterial
growth in some foods
• Clostridium Botualinum – anaerobic bacteria
that cause food poisoning (also used for
Botox injections)
• E. Coli (Escherichia Coli)– Human intestinal
bacteria
• Anthrax- related to Botualism (Bacillus
anthracis)
Bacterial Infections
• Escherichia coli and Salmonella cause food poisoning.
• Helicobacter pylori cause gastritis and ulcers.
• Neisseria gonorrhoeae causes the sexually transmitted
disease gonorrhea.
• Neisseria meningitidis causes meningitis.
• Staphylococcus aureus causes a variety of infections in
the body, including boils, cellulitis, abscesses, wound
infections, toxic shock syndrome, pneumonia, and food
poisoning.
• Streptococcal bacteria cause a variety of infections in
the body, including pneumonia, ear infections, and strep
throat.
• Clostridium botulinum causes paralysis and decreased
muscle tone. It is a weapons grade neurotoxin, what
else is it used for?
Diseases
Importance of Monerans
• Food Production
o Buttermilk, cottage cheese, yogurt, sour cream, sauerkraut,
pickles
o Also cause food spoilage (milk, fruits, meats)
• Recycle the remains of dead/decaying plants and
animals
• Fix/produce important gases in our atmosphere
• Industrial chemical production
• Clean up the environment
• Genetic engeenring: because they are simple,
unicellular, very few mutaions; we can study an
predict genetic variablitiy
Factors affecting growth
• Temperature (39 degrees Celcius/79 degrees
Fahrenheit)
• Radiation (UV)
• Chemicals (disinfectants/alcohol)
• Available food
• Available O2
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Prevention of Bacterial
Refrigeration Growth
o Slows reproduction
• Boiling
o Sterilizes
• Pasteurizing food
o High heat for a defined period of time, followed by
rapid cooling
• Drying
o All living things need water
• Salting
o Similar to drying, will draw water out of bacterial
cells
• Canning
Control of Bacterial Growth:
Physical Agents
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Dry Heat (passed through a flame)
Moist heat/steam
Boiling (100 degrees Celsius (212F) for 15 min
Freezing: -20 C
Radiation energy: UV light or x-rays
Chemical Agents
(Disinfectants)
• Acid (low pH) or base (high pH)
o All organisms have an optimal range for homeostasis
• Alcohol: 70% isopropyl (rubbing alcohol)
o Other types of alcohol work as well
• Phenol lysol: Popular household cleaner
• Detergents, or surfactants which are popular in
antibacterial hand soaps
Antibiotic Drugs
• Grouped based upon their mode of action
o Cell wall synthesis inhibitors (CWSI)
• Penicillin
o Ampicillin, Amoxicillian, and G and V
• Cephalosporins
o Keflex, Ceftin, Cefzil
• Bacitracin
o Used in antibiotic ointments
Protein Synthesis
Inhibitors
• PSI
• Tetracycline
o Used in treatment of acne/skin infections
• Erythromycin
o Derivative is Azithromycin
o Come in a Z-pak
• Known as zithromax
o Clarithromycin
• Known as biaxin
Nucleic Acid Synthesis
Inhib.
• NASI
• Cipro
o Block synthesis of bacterial DNA
o Only drug that can be used to treat inhalation anthrax
Cell Metabolism Inhib.
• CMI
• Sulfa drugs
o Synthetic antibiotics
o Most other antibiotics produced form chemicals released
by living organisms
• Fungi and bacteria in most cases