Download Bacteria

Prokaryotes
Or 100 Trillion Friends That
You Didn’t Know You Had
The Human Microbiome
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We are actually a giant ecosystem of microbes
Prokaryotes comprise between 1-3% of the mass
of a human body
- up to 6lbs of a 200 lb person can be microbes
Bacteria
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Earth’s oldest life forms
– between 3.5 and 3.8 billion years old
Most abundant life form – up to 2.5 billion
individual bacteria in 1 gram of fertile soil
Very adaptable – found in all of Earth’s
ecosystems
Bacteria Characteristics
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Unicellular
Circular DNA
No organelles
1/10th the size of eukaryotic cells
Flagella-long hair-like structure used for
movement
Reproduce asexually –Binary Fission
Bacterial Shapes
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3 main shapes
- coccus – sphere
- bacillus – rods
- spirillum - spiral
Bacterial Characteristics
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Metabolic diversity –
Bacteria can produce
energy in a variety of circumstances
autotroph – (self-feeding) – some bacteria can
produce their own food
- some use photosynthesis – get energy from
light
- some use chemosynthesis – get energy from
chemicals
Heterotroph - (other feeding) – many bacteria
are unable to produce their own
food and are required to eat other
things
Bacterial Characteristics:
Metabolic diversity continued
obligate aerobe – like us these bacteria need oxygen
obligate anaerobe - these bacteria need to be in an oxygen
free environment – human gut
facultative anaerobe – these bacteria can live in either an
oxygen or oxygen free environment
Bacterial Structure
Cell Wall
Cell Membrane
Pilus
chromosome
nucleoid
capsule
plasmid cytoplasm
flagellum
ribosome
Bacterial Structure: Cell Wall
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Made of peptidoglycan – a combination of protein and
polysaccharides
Some bacteria called Gram negative bacteria have an additional
layer of membrane that contains lipopolysaccharide
- this extra layer inhibits the uptake of antibiotics – protecting
the bacteria
cell wall
cell
membrane
cell
membrane
lipopolysaccharide
cell wall
Outer membrane
Gram + vs. Gram The type of cell wall is used by
doctors to help diagnose disease
The bacteria are stained with a
special stain called Gram stain
Bacteria without the extra membrane,
appear purple. These are Gram positive
(Gram +) bacteria
Absorb stain appear purple
Bacteria with the extra membrane
appear pink. These are Gram negative
( Gram -) bacteria
Don’t absorb stain appear
pink
Bacterial Structure continued
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Pili – hairlike structures usually found
in Gram neg. bacteria. Help the
bacteria stick to surfaces.
Also forms conjugation bridge
Chromosome – a single loop of DNA
that is folded on itself
- controls the cell’s function
Nucleoid – the region of the cytoplasm
where the DNA is found
Plasmid – an accessory loop of DNA – small contains only a few
genes - can be responsible for: conjugation, antibiotic
resistance, unique metabolic properties – like the ability to
use hydrocarbons
Capsule – found outside some bacteria stores nutrients and protects
the bacteria from changing environmental conditions
Reproduction - Binary Fission
Bacterial cells undergoing binary fission
Reproduction - Binary Fission
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Asexual reproduction
- offspring are genetically
identical to parent – no
new genetic combinations
- under ideal conditions
can occur every 20 min
- creates large numbers
of bacteria in a short
time
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Each spot represents
a single bacterial
cell that reproduced
by binary fission to
produce millions of
genetically identical
cells.
Genetically identical,
good or bad?
Exchanging Genetic Information
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Bacterial cells need to be able to exchange genetic
information
- creates new genetic combinations which increases the
ability of the bacteria to survive
Bacteria have 3 methods for exchanging DNA
-Transduction – viruses carry DNA from one bacterial
cell to another
-Transformation – bacteria can absorb “naked” DNA
released by dead bacteria from
the environment
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Conjugation – two bacteria join at a conjugation
bridge, one bacteria passes on a
copy of its plasmid or chromosome
Exchanging Genetic Information
Transduction – DNA is carried from one
bacteria to another by a virus
Transformation: Bacteria absorb
“naked” DNA from the
environment
Conjugation
Conjugation-
one cell passes a copy of
its plasmid or chromosome to another
Donor Cell
Recipient
Cell
A special pilus forms
a connection called
a conjugation bridge
between 2 bacterial
cells
Plasmid
Conjugation bridge
The donor cell
copies its plasmid
or chromosome and
passes the copy
through the
conjugation bridge
Cells separate
Bacteria Play Important Roles in
Ecosystems
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Decomposers
– recycle dead organisms releasing their
nutrients back to the environment for
use by other organisms – SPONCH
Without decomposers,
the elements on earth
would have remained
locked up in dead
organisms and life
would have ceased
Bacterial Roles: Nitrogen Fixation
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some bacteria contain enzymes which allow them to
convert (or fix) nitrogen from the air into a useable form
- they are nitrogen fixing bacteria
Why do living things use nitrogen?
Bacterial Roles: Producers
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In some ecosystems
chemosynthetic and
photosynthetic bacteria
serve as the basis of
the food chain
– chemosynthetic bacteria in deep ocean vents
convert hydrogen sulfide (H2S) gas into energy
- cyanobacteria are photosynthetic bacteria
which act as producers in many aquatic
ecosystems
Bacterial Roles: Symbiotic Bacteria
Many bacteria live in or on other organisms
(including humans) and aid their host
- some live in the gut of herbivores helping to
digest cellulose
- bacteria in the gut of humans
aid digestion and produce
vitamins
- bacteria on skin and in body
openings help prevent infection
by harmful organisms
Antibiotics
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Antibiotics are chemicals which either kill bacteria or
prevent their growth and reproduction
Bacteria and other microbes produce antibiotics to
reduce competition from other organisms
Penicillin was the first to be use to fight disease
- discovered accidently by Alexander Fleming in 1928
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Two scientists Walter Florey and Ernst Chain determined
how to use penicillin to
treat disease in 1939.
The discovery of
antibiotics revolutionized
the treatment
of disease
Antibiotic Action
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Antibiotics effect bacteria, but not eukaryotic cells
Antibiotics attack bacteria in 5 ways
- some damage the cell walls or prevent new cell wall from forming
- some damage the cell membrane
- some prevent protein synthesis
- some prevent DNA from being copied
- some interfere with bacterial metabolism
Antibiotic Resistance
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Some bacteria have developed a resistance to the effect
of some antibiotics
- the number of resistant bacteria is growing
The problem is increased by overuse and misuse of
antibiotics
- use of antibiotics to treat viral infections – antibiotics don’t effect
viruses
- the use of antibiotics in livestock (cattle, chickens, pigs)
antibiotics show up in the meat and milk
- people take the antibiotics until they feel better, but stop before all
of the bacteria are destroyed
- this kills the most susceptible bacteria, but leaves the more
resistant bacteria
Black Plague-Yersinia pestis
Syphilis--Treponema
pallidum/Bacterial
Mycobacterium leprae/Bacteria
Clostridium perfringes/Bacteria
Vocabulary
Microbiome
autotroph
heterotroph
peptidoglycan
plasmid
Gram Gram +
binary fission
conjugation
transduction
transformation
biofilm
Archea
pili
nucleoid
capsule
conjugation bridge
obligate aerobe
obligate anaerobe
facultative anaerobe
nitrogen fixing bacteria
cyanobacteria
pathogens
Tooth Decay
Causative Agent:
Bacteria
Name of bacteria:
Streptococcus mutans
Symptoms:
Destruction of tooth
enamel
Tetanus
Causative Agent:
Bacteria enters thru a
break in skin
Name of bacteria:
Clostridium tetani
Symptoms:
Severe muscle spasms,
paralysis, death
Tuberculosis
Causative Agent:
Bacteria particles
inhaled
Name of bacteria:
Mycobacterium
tuberculosis
Symptoms:
Fatigue, weight loss,
mild fever, chills, night
sweats, chronic cough
Bacterial Meningitis
Causative Agent:
Bacteria inhaled by
someone
coughing/sneezing, contact
w/ an infected individual
Name of bacteria:
Neisseria meningitdis
Symptoms:
High fever, headache, stiff
neck, nausea, fatigue,
death if not treated in early
stages
Strep Throat
Causative Agent:
Bacteria, direct contact
w/ mucus of infected
person
Name of bacteria:
Streptococcus pyrogenes
Symptoms:
Fever, soar throat swollen
glands, if left untreated
bacteria will move to the
heart and destroy tissues
Botulism
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Botulism is a rare
but serious
paralytic illness
caused by a nerve
toxin that is
produced by the
bacterium
Clostridium
botulinum
Common Cold
Causative Agent:
Virus
Mode of Transmission:
Contact or inhalation
Symptoms:
Sneezing, soar throat,
fever, mucus, headache
and muscle aches
West Nile
Causative Agent:
Virus
Mode of Transmission:
Bite fr/ infected mosquito
Symptoms:
Fever, headache, body
ache
inFLUenza
Causative Agent:
Virus
Mode of Transmission:
Contact or inhalation
Symptoms:
Body aches, fever, soar
throat, nasal congestion,
headache dry cough
fatigue
Autoimmune Deficiency Syndrome
Causative Agent:
Virus
Mode of Transmission:
Contact w/ blood or body fluids,
pregnant women to babies
during delivery or breast feeding
Symptoms:
Helper T Cells, which are
needed for normal immune sys
function are destroyed
Chicken Pox
Causative Agent:
Virus
Mode of Transmission:
Contact w/ rash or
inhalation
Symptoms:
Fever & weakness, red,
itchy rash
Hepatitis B
Causative Agent:
Virus
Mode of Transmission:
Contact w/ contaminated
blood or body fluids
Symptoms:
Jaundice, fatigue,
abdominal pain, nausea,
vomiting, & joint pain