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• Microscopic prokaryotes
• Most numerous
organisms on Earth
• Most ancient; earliest
forms of life
• Bacteria are part of every
environment on Earth
• Many are adapted to
places where nothing
else can live
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• Rock deposits in Australia contain fossils of
bacteria 3.5 byo; in relation:
– 1st Eukaryotic cells (protists) 2.5 bya
– Modern Humans only came about 100,000 years ago
• So, all modern organisms evolved from bacteria
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• PROKARYOTIC: single-celled; no nucleus or
membrane-bound organelles
• Few morphological differences between types of
bacteria
• Do not vary much in shape & size like other
organisms
• Grouped into taxa based on structure, physiology,
molecular composition, & reaction to specific types of
stains
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Bacteria used to be grouped into a single
Kingdom, called Monera
Today, we separate them into 2 kingdoms,
based on difference in ribosomal RNA
• Eubacteria
– Common “germs”
– Simply called “bacteria”
• Archaebacteria
– Ancient, extremophiles
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• Have a unique form of rRNA
• Cells walls characterized by absence of
peptidoglycan
– Peptidoglycan: protein-carb
compound found in cell walls
of eubacteria
• Thought to be the ancestral organisms
that gave rise to other (more modern)
forms of life
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• Found in extreme environments
• More common than once thought,
example:
• Methanogens: broad phylogenetic group of
archaebacteria
– Convert H2 & CO2 into food and methane CH4
gas
– Found anaerobic areas; oxygen is poison to
many of these
– Intestinal tracts of humans & cows
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• Extreme Halophiles: salt-loving
archaebacteria; live in high salt
concentration environments
– Great Salt Lake & Dead Sea
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Thermoacidophiles:
• live in extreme acidic environments,
high temp., low pH
• Deep sea hydrothermal vents
• Hot springs, geysers
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• Divided into MANY different phyla
according to evolutionary
relationships
• 4 generally recognized phyla are
– CYANOBACTERIA
– SPIROCHETES
– GRAM-POSITIVE
– PROTEOBACTERIA
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Eubacteria come in three basic
shapes:
• Bacilli (bacillus): rod-shaped
• Cocci (coccus): sphere-shaped
• Spirilla (spirillum): spiral-shaped
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Cell forms:
• Diplo- pairs
• Strepto: chains
• Staphylo: grapelike clusters
Identify this
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• Eubacteria cell walls
are made of
Peptidoglycan.
• Thickness of cell
wall and other
membranes protects
bacteria against
some kinds of
antibiotics by
preventing their
entry into the cell.
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• Most species of bacteria can be
grouped into 2 categories based on
their response to a laboratory
technique called Gram Staining
• Taxonomists divide bacteria
into various subgroups
including Gram-Positive
& Gram-Negative Bacteria
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• Technique involves staining bacteria with purple dye (Crystal
violet) & iodine
• Then rinsed with alcohol
• Then restained with a red dye (Safranin)
• Gram-Positive Bacteria will retain the PURPLE DYE and appear
Purple.
• Gram-Negative Bacteria will appear RED (pink) from the RED
DYE
• Depending on cell walls, bacteria absorbs either purple/red dye
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• Gram-Positive bacteria
have thicker layer of
peptidoglycan in cell wall
• Gram-Positive and
Negative differ
insusceptibilities to
antibacterial drugs,
produce different toxic
materials, & react
differently to
disinfectants.
Gram + (top), Gram – (bottom)
Note: Gram-negative bacteria
have cell wall including an outer
membrane composed of a layer of
lipids and sugars: “glycocalyx”
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• Composed of a
– Cell Wall
– Cell Membrane
– Cytoplasm
• Some bacteria have
distinctive structures,
such as flagella,
capsules, and outer
membranes
• Capsule: (glycocalyx) an additional (optional) outer
covering; protects against drying or harsh chemicals
& host body's white blood cells, which would
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otherwise engulf (eat) it
• Flagella: whip-like
structure used for
movement
• Pili: (pilus) short,
hair-like protein
structures found on
the surface of some
species of bacteria
– Help bacteria hold on
to host cells & can be
used to transfer
genetic material from
one bacterium to
another
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• Prokaryotes have lots •Have a single
of ribosomes, but no chromosome: DNA in
single closed loop
organelles with
membranes
•May also have small
loops of additional genes:
• Do not have
plasmids
mitochondria or
chloroplasts so use
cell membranes to
carry out cellular
respiration or
photosynthesis
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• A spore is a dormant structure
that is produced by Grampositive bacterial species that
are exposed to harsh
environmental conditions.
• Cell is encased in a protective
covering.
• Makes them VERY hard to kill!
• When conditions improve they
break open & resume
producing new bacteria cells
This bacterium has
formed an
ENDOSPORE
Difference between
“disinfect” and “sterilize”?
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• Most Prokaryotes are heterotrophs;
get their energy by consuming
organic matter as a source of
nutrition.
• Some are autotrophs; obtain
energy by making their own food.
– Phototrophs: from sunlight
– Chemotrophs: from minerals
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Bacterial Reproduction
• Bacteria cell goal: to
grow and multiply
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• Many can double
number every 20
minutes!
Binary fission
•Use binary fission to
reproduce asexually,
quickly
• Process: chromosome
is replicated, then the
cell divides
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Bacteria can also
combine genes
3 ways:
• Conjugation --
• Transformation
(uptake of naked DNA
from outside the cell)
• Transduction (virus
inserts new genes
into cell)
Conjugation
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Eubacterial Phyla:
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• Nitrogen-Fixing Bacteria
• Earth's atmosphere is 80% nitrogen
but plants and animals cannot use
nitrogen in gaseous state
• We require nitrogen to make
nitrogen-containing compounds like
proteins and nucleic acids
• Rhizobium are essential to the
nitrogen cycle
Legumes have lots of root nodules, filled with
these bacteria
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• Gram-Negative bacteria that perform
plant-like photosynthesis & release
oxygen as by-product (waste)
• Once classified as blue-green algae
• Now considered eubacteria, because they
lack a membrane-bound nucleus &
chloroplasts
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• “Eutrophication”: Population Bloom
of bacteria = sudden increase in # of
cyanobacteria due to high availability
of nutrients.
• After many cyanobacteria die;
decomposed by heterotrophic
bacteria.
• Consume available oxygen
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• Actinomycetes: Gram-positive
bacteria that form branching
filaments; used to make
antibiotics.
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• Used in sewage treatment
• Decomposers, breaking down the remains of
organic matter in dead plant & animal waste
• Recyclers, returning nutrients back to the
environment
• Food production: Bacteria help us make
buttermilk, sour cream, yogurt, some cheese,
sauerkraut and pickles
http://www.innvista.com/health/microbes
/bacteria/foodprod.htm
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• Industrial chemical production
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• Help clean up environmental
disasters caused by humans, such
as chemical & oil spills
• Useful in genetic engineering (gene
splicing) to produce medicines and
drugs.
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• Spoil food
• Cause odor
• Some cause illness/disease,
death
• "Toxins" substances released by
bacteria the make you ill
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• Pathology: scientific study of disease
• Pathogens: bacteria that cause
disease
• Some bacteria cause disease by
producing toxins (poisons)
• Exotoxins: bacterial proteins;
produced by Gram-positive Bacteria
– Secreted into the surrounding environment
– Tetanus is a disease caused by an
Exotoxin. Ever cut yourself or step on a nail
and had to take a shot? That was to
prevent Tetanus
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• Endotoxins: made of lipids &
carbohydrates
• associated with the outer membrane
of Gram-negative bacteria, such as
E. coli
– Not released until bacteria dies
– Cause fever, body aches, & weakness,
& they damage the vessels of the
Circulatory System
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• Pathogenic bacteria are a major cause of human
death and disease and cause infections such as
tetanus, typhoid fever, diphtheria, syphilis, cholera,
foodborne illness, leprosy and tuberculosis,
pneumonia, Lyme disease, etc.
– http://biology.clc.uc.edu/courses/bio106/bact-dis.htm
• Bacterial diseases are also important in agriculture,
with bacteria causing leaf spot, fire blight and wilts in
plants, as well as Johne's disease, mastitis,
salmonella and anthrax in farm animals.
– http://en.wikipedia.org/wiki/Bacterial_diseases
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• Many antibiotics are derived from chemicals
that bacteria or fungi produce;
• 3 ways that antibiotics kill bacteria:
– interferes with cell wall synthesis, ex: Penicillin
– interferes with protein synthesis; ex: Tetracycline
– inhibits RNA synthesis; ex: Rifampin
• They affect only the growth of bacteria without
harming the body cells of humans
• Antibiotic Resistance
– Overuse of antibiotics encourages drug-resistant
strains to evolve through selection
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– Mutant bacteria continue to grow