Download LESSON 1.3 WORKBOOK Bacterial structures

LESSON 1.3 WORKBOOK
Bacterial structures
DEFINITIONS OF TERMS
Colonize — the ability of bacteria
to adapt to permanently inhabit
our bodies.
Capsule — an external layer
made of sugars that surrounds
some bacteria.
Cell wall — an external layer surrounding the plasma membrane
of most bacteria.
Before we can discuss processes used to identify
infectious diseases, details about specific diseases, and
immune responses, we need to become familiar with the
structures of bacteria, viruses, and immune barriers. In
this lesson we will focus on the structures of bacteria that
directly relate to their ability to cause infection. As we will
see, these structures in disease-causing microbes are
often precisely adapted for survival in a host.
The bacterial envelope
Plasma (cell) membrane — a
membrane that separates the
internal cell contents from the
outside environment.
For a complete list of defined
terms, see the Glossary.
Wo r k b o o k
Lesson 1.3
When bacteria attempt to grow in, or colonize, an organism,
the immune system responds to the foreign invader
immediately. The first bacterial component that the immune
system recognizes as foreign, is its outer surface called the
envelope. The bacterial envelope is composed of a capsule,
cell wall, and plasma membrane (Figure 2). Since the
immune system is so vigilant, pathogenic bacteria must try
to stay one step ahead by continually modifying their surface
components, so as to go undetected.
The capsule is camouflage and protection from the
environment
Figure 1: The envelope of
the bacteria helps to keep it
camouflaged from the immune
system.
The capsule is not essential to bacterial life and not all
bacteria have one, but those that do, have an advantage in
infecting their hosts. The capsule is composed of long chains
of sugar molecules. It plays two roles: First, it is durable and
1. The bacterial envelope is
composed of all of the following
EXCEPT
aa. sputum
bb. capsule
cc. plasma membrane
dd. cell wall
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
27
LESSON READINGS
so can protect the bacterium from physical stresses such as osmotic pressure. Second, it camouflages
the bacteria from the immune system. A strategy that some bacteria use, is to make their capsule with the
same sugars that are found in the host, and thus avoid being detected as foreign. The immune system
therefore doesn’t recognize the bacterium as a foreign interloper and doesn’t target it for death. Examples
of bacteria that use a capsule to evade immune system recognition are Streptococcus pyogenes
which causes both strep throat and ‘flesh eating’ disease, Streptococcus pneumoniae which causes
pneumonia, and Neisseria meningitidis which causes meningitis.
DEFINITIONS OF TERMS
Osmotic pressure — the
pressure on the plasma
membrane as the result of
water flowing from a dilute
outside environment into more
concentrated internal cell content.
Pneumonia — inflammation of
the lung caused by microbes.
Meningitis — inflammation of the
membranes covering the brain
and the spinal cord.
Transport channels ­— protein
complexes in the cell membrane
used to transport ions and
molecules across the membrane.
For a complete list of defined
terms, see the Glossary.
Wo r k b o o k
Lesson 1.3
The cell wall protects the bacteria from environmental stresses
In contrast to the capsule, most bacteria have some kind of cell wall. It is located internal to the capsule
(if there is one) and external to the plasma
membrane. The cell wall reinforces the cell
membrane and protects it from environmental
stress, and particularly osmotic pressure. If we
think about the stresses bacteria face in their
natural environment, the reasons they need a
cell wall becomes clear. For example, intestinal
bacteria, such as E. coli, are constantly
exposed to bile salts that have detergent-like
properties able to dissolve a lipid-containing
cell membrane. The cell wall also plays a key
role in causing infection, as we will see later in
the course.
As in eukaryotic cells, the plasma
membrane in bacteria separates the
cell from the environment
Figure 2: The bacterial envelope is made
up of the capsule (if present), the cell wall,
and the plasma membrane.
The bacterial plasma membrane, also called the cell membrane, lies internal to the cell wall. It is the
definitive structure of a cell since it sequesters the molecules of life in a unit, separating it from the
environment. Its main function is that of a selective permeability barrier that regulates the passage
of substances into and out of the cell. The bacterial membrane allows passage of water and small
uncharged molecules, but does not allow passage of larger nutrients or ions, except through special
transport channels. One key way in which the bacterial plasma membrane is different from the
eukaryotic plasma membrane, is that it carries out functions of energy generation, since bacteria
don't have mitochondria.
2. Most bacteria have some kind
of cell wall. The cell wall is an
important structure for bacteria
because
aa. it reinforces the cell
membrane and protects it from
environmental stress
bb. it exports toxins to the plasma
membrane
cc. it provides camouflage
dd. it contains waxes that makes it
impervious to many chemicals
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
28
LESSON READINGS
The acid-fast solution to membrane protection: slow
growing but very tough and well-camouflaged bacteria
DEFINITIONS OF TERMS
Murein (peptidoglycan) — a
complex molecule (polymer)
made of sugars and amino acids,
that is the building block of the
bacterial cell wall.
For a complete list of defined
terms, see the Glossary.
Wo r k b o o k
Lesson 1.3
Acid-fast bacteria have cell walls that contain large amounts of waxes.
This protective cover makes them impervious to many chemicals and
able to avoid being killed by immune cells. The cost of this protection,
is that they grow very slowly, probably because they cannot take up
nutrients very rapidly. Only a few pathogenic bacteria are acid-fast. One
notable example is the tuberculosis causing agent, Mycobacterium
tuberculosis, which divides only once every 24 hours. This is very slow
growth rate! For comparison, E. coli divides every 20 minutes. The
acid-fast coating allows the Mycobacterium to wall itself off from the
immune system when it infects the lungs. Its slow division rate, coupled
with resistance to immune attack, results in infections that can persist for
a long time.
Figure 3: Acid-fast
bacteria have a waxy,
durable coating, and they
grow slowly.
The Grampositive solution
to membrane
protection
Most bacteria protect their cell
membranes with a thick exterior
cell wall that plays a critical role in
maintaining rigidity. But the cell walls
Figure 4: Gram-positive bacteria have a rigid,
differ in structure and organization
external cell wall made of murein layers (purple
among different bacteria and there are
rectangles) and LTA (cells with thin green protrutwo major types of cell wall. A staining
sions up through cell wall). The larger red bodies
in the cell membrane are membrane proteins.
technique, called Gram staining
(named after the microbiologist who
designed it), is used to determine the
type of cell wall: Gram-positive or Gram-negative. In Gram-positive bacteria the wall is made of many
layers of a polymer composed of sugars and amino acids, called murein. Bacteria are the only organisms
to have murein, and so bacterial cell walls are easily recognized as foreign by the immune system. The
murein on the surface of a Gram-positive bacterium can absorb and retain a purple dye during staining,
hence the term ‘Gram-positive’. This technique is used to identify Gram-positive bacteria from an infected
person.
3. Which statement represents the
advantage and disadvantage of
being acid-fast?
aa. it has a cell wall; it separates
the cell from the environment
bb. it separates the cell from the
environment; it has a cell wall
cc. it contains waxes; it
reproduces slowly
dd. it reproduces slowly; it
contains waxes
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
29
LESSON READINGS
How does murein work?
Murein is composed of sugar chains that are cross-linked to one another
and to chains of peptides in an organization resembling a chain link
fence. Layers of murein are wrapped around the length and width of
the bacterium to form a sac. The murein sack is critical in maintaining
bacterial shape such as bacilli or cocci.
DEFINITIONS OF TERMS
Peptides — small proteins made
of a few amino acids.
Bacilli — rod-like bacteria.
Cocci — sphere shaped bacteria
Lipoteichoic acid (LTA) — a
polymer of modified lipids used
to strengthen the Gram-positive
cell wall.
Lipopolysaccharides (LPS)
— large molecules composed
of lipids and polysaccharides,
critical in the making of the Gramnegative outer membrane.
Figure 5: Murein
The thick dense layer of murein allows bacteria to survive in
is the target for many
environments where the osmotic pressure (pressure on the membrane
antibiotics.
either from the inside or the outside) is high. This allows the bacteria to
live in solutions that have a low or high salt concentration. However, if the
murein is breached the cells may burst or shrink depending on the outside environment.
Gram positive cell wall components can cause illness
Gram-positive bacterial cell walls contain other unique polymers such as the lipid (fat) molecule
lipoteichoic acid (LTA). Both murein and LTA are recognized as foreign by the immune system. The
Gram-positive bacterium Staphylococcus aureus for instance, has a capsule that cannot always
camouflage it from the immune system. The cell wall murein and LTA that lie beneath the capsule, are
easily recognized by the immune system which then initiates a response to the invading bacteria. This
gives rise to typical symptoms of bacterial infection such as fever.
The Gram-negative solution to membrane protection
For a complete list of defined
terms, see the Glossary.
Wo r k b o o k
Lesson 1.3
Figure 6: Gram-stained
cells: Gram-positive
bacteria stain purple and
Gram-negative bacteria
stain pink.
Gram-negative bacteria have adopted a radically different solution to
the problem of how to protect their plasma membranes. Their cell wall
also has a murein component for rigidity, but it is far less elaborate
than in the Gram-positive cell wall. Instead, Gram-negative bacteria
build a second membrane external to the murein wall (figure 7).
This outer membrane is just like other typical biological membranes,
except it contains molecules called lipopolysaccharides (LPS), that
are unique to Gram-negative bacteria. The composition of this outer
membrane doesn't allow Gram-negative bacteria to keep the purple
Gram dye during the decolorization step. Instead they turn pink when
the last pink dye is added after decolorization.
4. The following are true about the
differences between Gram-positive
and Gram-negative bacteria
EXCEPT
aa. Gram-positive bacteria can
keep a purple dye while Gramnegative bacteria cannot
bb. Gram-positive bacteria have
an additional outer membrane
external to the murein cell wall
while Gram-negative bacteria
have a rigid external cell wall
made from murein
cc. Gram-positive have LTA while
Gram-negative have LPS
dd. Gram-positives use their cell
wall components to cause
illness while Gram-negatives
use their cell wall to inhibit
antibiotics
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
30
LESSON READINGS
The unique LPS of Gram-negative bacteria can cause symptoms of disease
Since LPS is the major component of the Gram-negative outer membrane, just like Gram-positive LTA,
it is recognized as foreign and stimulates a strong immune response. LPS is very potent — even small
amounts of LPS in the bloodstream will cause the host to become severely ill. Each Gram-negative
species has its own unique LPS. As a consequence, the immune system's response to the different kinds
of LPS is specific as well.
DEFINITIONS OF TERMS
Enzymes — proteins produced
by living organisms that are used
to speed up chemical reactions.
For a complete list of defined
terms, see the Glossary.
Figure 7: Gram-negative bacteria have an additional outer membrane, external
to the murein cell wall. The outer membrane contains LPS. The red shapes in the
inner and outer membranes are membrane proteins.
The Gram-negative cell wall can inhibit antibiotics
Wo r k b o o k
Lesson 1.3
Between the inner and outer membrane of Gram-negative bacteria, in addition to the thin murein cell
wall layer, there is a gel-like solution of enzymes. These enzymes can play important roles in infection.
One enzyme in particular, beta-lactamase, can inactivate certain types of antibiotics like penicillins and
cephalosporins, which interfere with the synthesis of the bacterial cell wall. This is one of the reasons why
Gram-negative bacteria are somewhat more resistant to antibiotics than Gram-positives. Examples of the
many disease-causing bacteria with Gram-negative cell walls are Escherichia coli O157:H7 that causes
intestinal diarrhea (hamburger disease), and Haemophilus influenzae that causes flu-like symptoms.
The complex architecture of the Gram-negative cell wall must work very well because in nature (but not
necessarily in the human body) Gram-negatives outnumber Gram-positives!
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
31
LESSON READINGS
Flagella — How bacteria get around
Why bacteria need to move
Bacteria, just like other organisms, need to move in order to obtain food and to escape predators. Some
bacteria are carried passively by fluid or air currents. Others have special long, whip-like appendages
on their outer surface, called flagella, that allow them to be actively motile. Depending on the species,
bacteria may have one or several flagella.
DEFINITIONS OF TERMS
Chemotaxis — the targeted
movement of an organism
towards or away from a stimulus.
For a complete list of defined
terms, see the Glossary.
Wo r k b o o k
Lesson 1.3
Flagella allow bacteria to move toward substances that they need, such as nutrients, and away from those
that they want to avoid such as toxins or immune cells that might kill them. This process of movement in
response to the concentration of chemicals in their environment is called chemotaxis.
How flagella help bacteria move
When a bacterium has a single flagellum, its counter-clockwise rotation propels the bacterium forward,
and a flicking motion causes reorientation. If the bacterium has several flagella, they form a bundle
when all of them spin counterclockwise, and this propels the bacterium forward. This forward propulsion
is called swimming. However, if any of the flagella begin to rotate clockwise, the bundle unwinds and
movement becomes erratic causing the bacterium to tumble randomly and reorient its direction.
Figure 8: Swimming allows bacteria to chemotax towards or away from a stimulus.
5. Flagella is to ____________ as
pili is to ______________.
aa. movement; attachment
bb. clockwise; counterclockwise
cc. counterclockwise; clockwise
dd. attachment; movement and
immunity
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
32
LESSON READINGS
These two types of motion, swimming and tumbling, both occur during chemotaxis. When moving in a
favorable direction such as towards nutrients, swimming predominates and tumbles are suppressed.
However, when the bacterium's direction of motion is unfavorable (e.g., movement towards immune cells),
tumbles are no longer suppressed and occur much more often, with the chance that the bacterium will
thus be reoriented in a more favorable direction and then proceed to swim.
How flagella impact infection
DEFINITIONS OF TERMS
Antigen — a structure which can
be recognized by the immune
system as foreign.
For a complete list of defined
terms, see the Glossary.
Flagella can aid in the movement of pathogenic bacteria and
their spread through the host. An example is Helicobacter
pylori, which uses multiple flagella to propel itself through the
mucus lining to reach the stomach epithelium. Flagella are
also a target of the immune system, since their constituent
protein flagellin, also called the bacterial H antigen, is a potent
immune stimulator. Bacteria therefore have to continually
modify their flagella in an attempt to camouflage themselves.
For example, one of the Salmonella species that causes food
Figure 9: Vibrio cell with
poisoning (Salmonella enterica) has two different kinds of H
flagella.
protein, types 1 and 2. When S. enterica infects a host, the
immune system will recognize and start building a response to
the current H protein of the flagella, e.g., type 1. However, the
bacteria have the ability to switch and start building their flagella with protein type 2 which the immune
system has not recognized yet, giving the bacteria more time to replicate.
Pili — How bacteria stick around
Some sites in the host are very inhospitable to infection. For
instance the nasal cavity is continually being cleansed by
sneezing, while swallowing washes contents of the mouth
down into the harsh acid environment of the stomach. Bacteria
that need to survive these challenges use special structures
— pili to attach to cells of the host or other bacteria to avoid
being washed away.
Wo r k b o o k
Lesson 1.3
Figure 10: Pili are hair-like
structures on the bacterial
surface, used for attachment to
surfaces.
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
33
LESSON READINGS
Pili are used to stick to surfaces
DEFINITIONS OF TERMS
Gonoccoci — Gram-negative
bacteria which cause gonorrhea.
Gonorrhea —
­ sexually
transmitted disease caused by
gonoccoci, also called Neisseria
gonorrhoeae.
For a complete list of defined
terms, see the Glossary.
Figure 11: Gonorrhea
causing bacteria use pili to
adhere to the genital tract.
Like flagella, pili also protrude from the cell wall, but unlike flagella
they are usually used to attach to specific surfaces and rarely for
movement. Pili are shorter than flagella and often distributed in
large numbers over the entire surface of the bacteria, like little hairs.
During attachment the tip of the pilus attaches to cells or other
bacteria, in a process that resembles the use of grappling hooks or
Velcro. In addition to these “common pili” some bacteria also use
"sex pili" to form a tube between donor and recipient cells through
which DNA is transferred between them.
How pili impact disease
Like flagella, pili are often recognized by the immune system, and therefore many bacteria also continually
vary the types of pili they produce. This enables them to keep one step ahead of the immune system.
For example, gonococci that cause gonorrhea can make many different types of pili proteins. However,
they only make a few at any given time. If the types of pili proteins that the bacteria make at a given time
during infection, are easily recognized by the immune system, then the bacteria will be attacked and
killed. In response to this immune pressure, the gonococci constantly switch pili, so that the immune
system doesn't get a chance to recognize them. In this quick-change scenario the bacteria keep one step
ahead of the immune system. This is why attempts to immunize against gonococci using a vaccine that
recognizes only one kind of pilus protein have failed so far.
Spores — How bacteria survive
hostile conditions
Wo r k b o o k
Lesson 1.3
When environmental stresses become too harsh, simply
sticking to a surface is not enough. Some bacteria wait
out harsh stresses, such as starvation, by forming spores.
Spores are formed when bacteria lose their cellular content,
form a protective coat around their DNA, and enter a
dormant state. Each bacterium usually makes only one
spore. When the spore finds that conditions have become
favorable again, it gets reactivated and forms a live bacterium
that can grow and divide.
Figure 12: Spores are first
formed inside the cell and are
then released to the outside.
6. Spores help bacteria stay alive by
aa. allowing bacteria to be
constantly active in harsh
conditions.
bb. allowing bacteria to be
dormant in harsh conditions
and active in better ones.
cc. causing food poisoning.
dd. none of the above
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
34
LESSON READINGS
How spores impact disease
DEFINITIONS OF TERMS
Tetanus — an infection
caused by Clostridium tetani
characterized by muscle spasms
due to toxins produced by the
bacteria.
Botulism — illness that results
from toxins produced by the
bacterium Clostridium botulinum.
For a complete list of defined
terms, see the Glossary.
Wo r k b o o k
Lesson 1.3
Some particularly important pathogenic bacteria form spores. The Clostridium species that cause
tetanus and botulism are key examples. Spores are highly resistant to desiccation, heat, and radiation.
Tetanus spores can lie dormant in the soil for many years before becoming reactivated when they enter
the body through a cut in the skin. Botulinum spores, on the other hand, are resistant to heat and can
survive food canning processes. They can cause food poisoning when the food is eaten even years after
preparation if the preservation method used was insufficient to kill them. When swallowed they can get
reactivated in the intestines, and start growing and multiplying.
Bacterial chromosome and plasmids — bacterial genes
Bacterial genes are in the nucleoid
Bacteria do not have a nucleus like eukaryotic
cells. Instead there is a DNA-rich area in the
cytoplasm called the nucleoid, where the DNA
is present in a compacted form. Also unlike
eukaryotic cells, where the DNA is in the form of
genes arranged on linear chromosomes; bacteria
usually have their genes arranged on one or
two circular chromosomes. Since the DNA is not
Figure 13: Nucleoid, the dense,
enclosed in a membrane-bound nucleus, once
whitish area of DNA packing in the
transcription begins, the translational machinery in
cytoplasm.
the cytoplasm has instant access to the transcript,
and can start protein synthesis simultaneously.
This is in contrast to eukaryotes where there is a
delay, because the transcript has to be exported from the nucleus to the cytoplasm for translation to occur.
Bacteria are thus better equipped to deal with changes in their environment, by making rapid changes in
the proteins that are synthesized.
Bacterial genes obviously play a key role in their ability to cause disease because they determine
every single characteristic of the bacterium, such as whether they are Gram-positive or negative,
have multiple types of flagella or pili, and whether they can form spores.
7. Plasmids
aa. are DNA molecules that are
distinct and can replicate
independently from
chromosomal DNA.
bb. can transfer advantageous
genes between bacteria
through sex pili.
cc. are involved in the production
of toxins.
dd. all of the above
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
35
LESSON READINGS
Bacterial genes are also found in plasmids
Unlike eukaryotic cells, whose genes are solely confined
to chromosomes, bacteria have additional genes located
on small circular pieces of DNA called plasmids.
DEFINITIONS OF TERMS
Toxins — molecules (usually proteins) produced by bacteria that
are toxic to the host's cells, and a
major reason for the symptoms of
an infectious disease.
Antibiotics — molecules,
produced usually by bacteria
and fungi, that have the ability to
suppress the growth of microbes
or kill them.
For a complete list of defined
terms, see the Glossary.
Wo r k b o o k
Lesson 1.3
Although these plasmids are not critical to the life of the
bacterium itself, they may confer key advantages. In fact,
the two most potent toxins known to man, tetanus and
botulinum toxins, are produced from plasmids that are
found in different Clostridium species.
Figure 14: Plasmids (the
pale yellow loops) are circular
pieces of DNA found in the
cytoplasm.
Plasmids can also contain genes that make the bacteria
resistant to specific antibiotics. The advantage of plasmid
DNA, rather than chromosomal DNA, is that plasmids are relatively easy to transfer between bacteria,
using their sex pili. This exchange of advantageous genes is of great benefit to the bacteria but causes a
public health nightmare. Bacteria acquiring drug resistance genes from other bacteria can rapidly become
problematic. Vibrio cholerae, which causes cholera, routinely acquires new genes via plasmids. If such
species exchange genes they can give rise to a highly infectious species that is resistant to many more
antibiotics.
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
36
STUDENT RESPONSES
Bacterial structure
Description
How is it advantageous?
■■ Capsule
■■ Gram-positive cell wall
■■ Gram-negative cell wall
■■ Plasma membrane
■■ Murein
■■ LTA
■■ LPS
■■ Flagella
■■ Pili
■■ Spore
■■ Nucleoid
■■ Plasmid
Wo r k b o o k
Lesson 1.3
37
STUDENT RESPONSES
Some bacteria use pili "like Velcro". Sketch what Velcro looks like up close —how could hair-like structures with a similiar
shape help bacteria infect hosts? Would you expect the capsule to perform this same function? Why or why not?
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
____________________________________________________________________________________________________
Remember to identify your
sources
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
Why do you think it is important to organize bacteria based on the different structures they have (e.g cell wall type, presence of
capsule, etc.)?
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
Wo r k b o o k
Lesson 1.3
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_______________________________________________________________________________________________
38
TERMS
TERM
Wo r k b o o k
Lesson 1.3
DEFINITION
Antibiotics
Molecules, produced usually by bacteria and fungi, that have the ability to suppress the growth of microbes or
kill them.
Antigen
A structure which can be recognized by the immune system as foreign.
Bacilli
Rod-like bacteria.
Botulism
Illness that results from toxins produced by the bacterium Clostridium botulinum.
Capsule
An external layer made of sugars that surrounds some bacteria.
Cell wall
An external layer surrounding the plasma membrane of most bacteria.
Chemotaxis
The targeted movement of an organism towards or away from a stimulus.
Cocci
Sphere-shaped bacteria
Colonize
Ability of bacteria to adapt to permanently inhabit our bodies.
Enzymes
Proteins produced by living organisms that are used to speed up chemical reactions.
Gonoccoci
Gram-negative bacteria which cause gonorrhea.
Gonorrhea
Sexually transmitted disease caused by gonoccoci, also called Neisseria gonorrhoeae.
Lipopolysaccharides
(LPS)
Large molecules composed of lipids and polysaccharides, critical in the making of the Gram-negative outer
membrane.
Lipoteichoic acid (LTA)
A polymer of modified lipids used to strengthen the Gram-positive cell wall.
Meningitis
Inflammation of the membranes covering the brain and the spinal cord.
Murein (peptidoglycan)
A complex molecule (polymer) made of sugars and amino acids, that is the building block of the bacterial cell
wall.
39
TERMS
TERM
Wo r k b o o k
Lesson 1.3
DEFINITION
Peptides
Small proteins made of a few amino acids.
Plasma (cell) membrane
A membrane that separates the internal cell contents from the outside environment.
Pneumonia
Inflammation of the lung caused by microbes.
Tetanus
An infection caused by Clostridium tetani characterized by muscle spasms due to toxins produced by the
bacteria.
Toxins
Molecules (usually proteins) produced by bacteria that are toxic to the host's cells, and a major reason for the
symptoms of an infectious disease.
Transport channels
Protein complexes in the cell membrane used to transport ions and molecules across the membrane.
Turgor pressure
The pressure caused by the plasma membrane on the cell wall as the result of water flowing from a dilute
outside environment into more concentrated internal cell content.
40