Download Cell Wall

The old way:
When scientists first started to classify life, everything was
designated as either an animal or a plant (Aristotle). But as new
forms of life were discovered and our knowledge of life on Earth
grew, new categories, called "Kingdoms," were added (Linnaeus).
There eventually came to be five Kingdoms in all - Animalia, Plantae,
Fungi, Protista, and Bacteria. These were all categorized as either
Eukarya, or Prokarya.
The new way:
New insight into molecular biology changed this view of life. A type of
prokaryotic organism that had long been categorized as bacteria
turned out to have DNA that is very different from bacterial DNA.
This difference led microbiologist Carl Woese of the University of
Illinois to propose reorganizing biological taxonomy into three
separate Domains: Eukarya, Eubacteria (true bacteria), and Archaea.
Depending upon the resource, you still may see these
referred to in the “old” way. Sometimes, the
eubacteria and archaebacteria are classified
together in the “old” kingdom, Monera.
Today, as already stated, science recognizes three
Domains. Within those three, bacteria comprise two!
All other life forms (kingdoms Protista, Fungi,
Plantae, and Animalia) are from the Domain Eukarya.
The single unifying characteristic of all organisms
within this bacterial “group” is that they are all
prokaryotes.
• They lack true nucleus, and other
membrane-bound organelles
• They contain a single,
“naked” chromosome
consisting of a DNA molecule
•Some contain “plasmids”
(small, circular DNA
molecules, in addition to the
major chromosome)
•Most have a cell wall containing peptidoglycans (a
polysaccharide modified with polypeptides)
(Most other organisms containing this structure, have cellulose/chitin-based cell
walls.)
The cell wall distinguishes two broad groups of
bacteria.
Gram-Positive
Contain a thick peptidoglycan cell wall, which stains
darkly when subjected to gram-stain
A: E.coli (gram negative)
B. Staphylococcus
epidermidis (gram
positive)
c. Bacillus cereus (gram
positive)
Gram-Negative
Contain a thin peptidoglycan wall covered with a layer
of lipopolysaccharides, which doesn’t absorb the
gram-stain
Capsule: a sticky
gelatinous coating
surrounding the cell wall.
A bacterium with a
capsule more than likely
causes disease.
Flagellum: Some have
long whiplike protrusions
that enable them to move
Nucleoid: Central region where the bacterial cell’s DNA is
generally located…not a true nucleus
Pilus: Extensions of the plasma membrane, help bacterium to
stick to a surface, and sometimes used in the exchange of genetic
material during sexual reproduction
Cell Wall: surrounding the plasma membrane, it gives the cell its
shape.
The cell wall also prevents the osmosis of water into the cell, as
bacteria typically live in a hypotonic environment.
Contains less dissolved particles than inside the bacteria…so which way would water flow?
Many bacteria have the ability to move.
•Flagella:
Consists of globular protein flagellin, arranged in helical
chains (not tubulin found in eukaryotes with flagella) that
rotate like screws
Some species of bacteria (such as
Spirochetes) have a specialized type
of flagellum called an "axial
filament" that is located in the
periplasmic space, the rotation of
which causes the entire bacterium to
move forward in a corkscrew-like
motion.
Still others glide through slimy
material that they secrete…called
slime-gliding appropriately enough!
• Flagella: the most common mechanism for movement.
Flagella can be spread over the entire cell or concentrated at
one or both ends.
What globular protein
makes up bacterial
flagella?
• Spiral Motion: In helix shaped bacteria. Moves similar to a
cork screw.
• Slime gliding: Cells secrete slimy threads that anchor to the
host. As the cell continues to secrete a slime layers build up and
the bacteria is able to glide around.
• Some bacterial have no
movement
Autotrophs: manufacture their own organic
compounds.
• photoautotrophs: use sun’s energy
• chemoautotrophs: use energy obtained from
chemical substances (chemosynthesis)
Hydrogen sulfide (H2S), ammonia (NH3), nitrite
(NO2), and nitrate (NO3)
• Heterotrophs: obtain their energy by consuming
organic substances produced by autotrophs.
• parasites: obtain energy from living host
• saprobes: (saprophytes) obtain energy from
dead and decaying matter.
(decomposers)
Obligate aerobes: Bacteria which require an
oxygen environment to live
Mycobacterium tuberculosis
Obligate anaerobes:
Bacteria which are killed in an
oxygen environment.
Clostridium tetani
Facultative anaerobes:
Grow in the presence of
oxygen, but when oxygen is
absent, can switch to
anaerobic metabolism
Staphylococcus aureus
Archaebacteria
Extremists: habitats where little else can live.
• oxygen-free environments, producing methane
Methanogens
Anaerobic, living in mud and
swamps, the guts of cows,
humans, termites, and others
• concentrated salt water
Halobacterium salinarium
Halophiles can cause spoilage in
salted foods, and while most are
heterotrophic, some are
autotrophic and contain the
pigment bacteriorhodopsin
• hot acidic waters of sulfur springs
and hydrothermal vents
Thermophiles, and thermoacidophiles
Eubacteria
• True bacteria
•Heterotrophs/parasites
•Saprobes or saprotrophs
•Autotrophs
• cyanobacteria
• chemosynthetic
bacteria (Nitrifying
bacteria, which turn nitrite
into nitrate)
•nitrogen-fixing
bacteria (living
mutualistically with plants)
•spirochetes
(use their internal
flagella to move in a spiral, or
corkscrew motion)
Cocci: spherical shaped
Bacilli: rod shaped
Spirillum: spiral shaped
Diplo: Arrangements of two
Diplococcus
Strepto: Arrangements of long chains
Streptococcus
Stroptobacillus
Staphylo:
Arrangements of
grape-like clusters
Staphylococcus
Bacterial Shapes and
Arrangements
Bacteria have evolved the ability to reproduce in
many different ways.
• Binary Fission: A means of asexually
reproducing whereby each of the two daughter
cells are genetically identical to the parent
Would you rather have $10 every 20 minutes for 13 hours, or one
penny, doubled every 20 minutes for 13 hours?
The first choice will get you $400
The second choice will get you $5 million!
The growth rate for bacteria as they undergo
asexual reproduction is like the second example.
This kind of growth pattern is
known as exponential
Binary Fission in bacteria
In addition to binary fission, bacteria can sexually recombine their
genetic material, in a process known as conjugation.
Conjugation: is NOT sexual reproduction, as one
bacterium transfers all or part of its genetic
material to another bacteria through the pilus.
Usually, a bacterial plasmid (circular DNA) is conferred to
the recipient, which benefits that bacteria. Often the
plasmid contains the code for antibiotic resistance.
Then, the bacteria
receiving the new
genetic code can
reproduce by binary
fission.
Some bacteria, when faced with unfavorable
environments produce endospores.
Endospores are tiny
structures that contain a
bacterium’s DNA and a
small amount of its
cytoplasm, enclosed by a
tough outer covering that
is resistant to drying out,
extreme temperatures,
and chemical conditions.
Bacillus anthracis
• Nitrogen Fixation
Bacteria have the ability to convert N2
into ammonia (NH3) in this process.
Then other bacteria convert the
ammonia into nitrite (NO2) and nitrate
(NO3). Plants can use these forms of
nitrogen.
Humans and other heterotrophs eat the plants
and receive the nitrogen in that way.
Nitrogen is important because it is a component
in protein, DNA, and RNA.
If it weren’t for these nitrogen-fixing bacteria, all
the nitrogen in the atmosphere would be
unusable to life on Earth.
• Recycling of nutrients
Without the action of
decomposing bacteria, organic
materials would never break
down. We would be buried in
waste.
As a decomposer, bacteria play a vital role in the
food chain. Autotrophic bacteria also help to
replenish the oxygen in Earth’s atmosphere.
• Food and medicines
• Streptomycin
• Erythromycin
Cheeses, pickles, and yogurt all rely
on the action of bacteria for a
variety of distinctive flavors and
aromas
Many types of bacteria also produce
antibiotics that destroy other types
of bacteria.
• Neomycin
Completely by accident, in 1928 Sir Alexander
Fleming discovered that the airborne mold,
Penicillium notatum inhibited the growth of the
bacterium he was culturing. He never knew how
it worked.
Years later, it was discovered that the penicillin
interfered with the ability of some bacteria to
make cell walls.
• During reproduction, cell walls
developed holes
• Osmosis occurred, and cells burst,
killing the bacterium
Don't be alarmed about the bacteria in yogurt. Everyone has
bacteria inside their bodies; especially in the stomach and
intestines where food is broken up and digested. When you eat
yogurt, it encourages the good types of bacteria to multiply in
your digestive track. These "friendly" bacteria also protect your
body systems against harmful microorganisms which cause
digestive upset and other infections.
To put the size of the big bacterium in perspective, it is
a true giant in the world of the very small. It is a huge
(for the bacterial world) ¾ mm in size. Scientists,
drawing an analogy, said if the largest of the newly
discovered bacteria was the size of a blue whale, the
typical bacterium would be the size of a new-born
mouse.
Into what category
would you place this
newly discovered
bacterium?
Streptococcus
Thiomargarista namibiensis