Download Bacteria

Bacteria
Learning Targets:






Describe the structure and function of a typical
bacterial cell
Classify bacteria based on shape and
arrangement
Describe how bacteria reproduce
Summarize the history and adaptations of
bacteria
Evaluate the importance of bacteria
Identify diseases cause by bacteria
What are bacteria?

Prokaryotes
–
–

unicellular
lack a nucleus and
membrane-bound
organelles
classified in 2 kingdoms
–
–
archaebacteria
eubacteria
What are archaebacteria?

live in extreme habitats
–
–
–
Methanogens = oxygenfree environments
Halophiles = very salty
environments
Thermoacidophiles = hot,
acidic environments
What are eubacteria?


Heterotrophs
Found everywhere
– parasites obtain
nutrients from
living organisms
– saprophytes feed
on dead
organisms/organic
waste
Autotrophic eubacteria
Cyanobacteria

photosynthetic
autotrophs

Obtain energy from
light

Make own food
Chemosynthetic autotrophs
–
break down &
release the energy
of inorganic
compounds
containing S & N
to make organic
molecules that are
their food
Anatomy of a bacterium?






Cell wall gives shape & prevents
osmosis from bursting the cell
Capsule surrounds cell wall
Circular chromosome (single DNA
molecule) not enclosed in a
nucleus contains most of the
genes
Few genes are located in a small
circular plasmid
Plasma (cell) membrane regulates
what enters & leaves the cell
Hair-like pilus helps a bacterium
stick to a surface
–

helps exchange DNA
Whip-like flagellum enable them to
move
Flagellum

Clip 1

Clip 2
Bacterial culture techniques




Carefully & thoroughly swab selected surface
Transfer bacteria from broth culture to nutrient agar plate
by touching swab to agar surface in a single spot
Isolate bacterial colonies by streaking the plate, being
careful not to tear agar
Incubate plate
Pure culture

population of bacterial
cells growing in the
absence of other types
–
–
streak plate technique is
used to spread millions of
cells so that some are
deposited a distance from
all others
these cells grow &
reproduce, forming an
isolated colony
(represents a pure culture)
How can bacteria be identified?

Gram staining checks for
differences in the
structure of their cell
walls
–
–
–
gram-positive bacterial
cells turn purple
gram-negative cells turn
pink
doctors know which
antibiotics to use based
on the results
Antibiotics

Bacteria live in hypotonic
environments
–
–

Penicillin inhibits Stapylococcus
higher concentration of
water outside than inside
cell
water is always trying to
enter cell
A bacterial cell remains
intact & doesn’t burst
open as long as its cell
wall is intact
–
scientists used this need to
develop antibiotics
Disc diffusion




antibiotic discs release
antibiotic into
surrounding medium
zone of growth inhibition
Area of no bacterial
growth
around the disc will
occur if the bacteria are
susceptible to the
antibiotic
Antibiotic resistant bacteria
Shapes of bacteria

another way to identify bacteria
–
–
–
sphere = coccus
rod = bacillus
spiral = spirillium
Growth pattern of bacteria

also used to identify bacteria
–
–
–
pairs = diplogrape clusters = staphylolong chains = strepto-
Draw the following…



Diplococcus meningitidis causes
meningitis
Streptococcus pneumoniae causes
pneumonia
Staphylococcus aureus causes
toxic shock syndrome and boils
2 kinds of Reproduction
How do bacteria asexually
reproduce?

Binary fission
–
–
–
–
–
makes a copy of its
chromosome
cell grows larger
chromosomes move to
opposite ends of the cell
a wall begins to form in
the middle
2 new cells are genetically
identical
Binary fission video clip

Clip 1

Clip 2
How do bacteria sexually
reproduce?

Conjugation
–
–
–
–
pilus = bridge-like structure
that one bacterium uses to
connect to another
1st bacterium transfers all or
part of its chromosome to the
second through the pilus
2nd bacterium has a mix of
genetic material &
reproduces by binary fission
produces bacteria with a
whole new genetic
combination
Conjugation video clip
Diversity of metabolism

Obligate aerobes require
oxygen for respiration
–
Mycobacterium
tuberculosis causes
tuberculosis
Mycobacterium tuberculosis

Obligate anaerobes are
killed by oxygen
–
–
Treponema pallidum
causes syphilis
Clostridium botulinum
causes botulism
Clostridium botulinum
Facultative anaerobes

Bacteria that prefer
an aerobic condition

Can make ATP with
no oxygen if put into
that situation
Ex’s
 Staphylococcus (g+)
 E. coli (g-)
 Listeria (rare food
borne illness-25%
lethal)
 Corynebacteria- skin
flora
Which tube flourishes in O2?
Whats up?
A survival mechanism

Endospore
–
–
–
tiny structure that contains
bacterium’s DNA & small
amount of cytoplasm
encased by tough outer
covering that resists
drying out, temperature
extremes, & harsh
chemicals
bacterium rests & doesn’t
reproduce
The importance of bacteria

Disease-causing bacteria are few in number
compared with the number of harmless &
beneficial bacteria on Earth
–
–
–
help to fertilize fields
help to recycle nutrients
help to produce foods & medicine
Food Safety
Nitrogen fixation


All organisms need
nitrogen, yet few can
directly use it from air
nitrogen fixation –
process of converting
nitrogen gas into
ammonia
–
Rhizobium on plant nodules
convert nitrogen gas into
ammonia
–
other bacteria convert
ammonia into nitrate &
nitrite which plants can
use
Animation
Recycling of nutrients

Life could not exist if
decomposing bacteria
didn’t break down
organic materials in
dead organisms and
wastes
–
returns nutrients to the
environment
Food and medicines

During respiration,
different bacteria
produce diverse
products which have
distinctive flavors &
aromas
–
–
–
–
vinegar
yogurt & cheeses
sauerkraut
sour cream

Some bacteria produce
important antibiotics that
destroy other types of
bacteria
–
–
–
–
streptomycin
erythromycin
bacitracin
neomycin
What diseases do bacteria
cause?
Diseases Caused by Bacteria
Disease
Transmission
Symptoms
Treatment
Strep throat
inhale/ingest
fever, sore throat, swollen glands
antibiotic
Tuberculosis inhale
fatigue, fever, night sweat, cough,
chest pain
antibiotic
Tetanus
puncture
wound
stiff jaw, muscle spasms,
paralysis
antibiotic,
antitoxin
Lyme
disease
tick bite
rash, chills, body aches, joint
swelling
antibiotic
Cavities
bacteria
toothache
fillings
Diphtheria
inhale/contact
sore throat, fever, heart/breathing
failure
vaccine,
antibiotics
Bacteria and Disease
50% of all diseases are thought to be caused from
bacteria
 In 1900, tuberculosis and pneumonia were the two
most common diseases
 Factors that increased life expectancy:
Less poverty, better health systems, increased water and
sewage systems, increased nutrition, better medical
care

Are there bacteria on cell phones?
Controlling Bacteria

Cooking Foods

Referigeration/freezing

Drying foods

Pickling