chp 9 MICRO

The bacterial cell wall is a protective barrier against:
?Osmotic pressure changes
?Other environmental stresses
allow pathogens to evolve structures that can help with the requirements for infection.
Bacterial structures play a significant role in the five steps required for infection
The primary structure of the cell wall is __________ which is composed of repeating sugar molecules.
?N-acetyl glucosamine (NAG)
?N-acetyl muramic acid (NAM)
the bacterial cell wall is a mesh work held together w/ small ________
peptide chains
11The linking together of NAG and NAM subunits is facilitated by several
1 enzymes
Cytoplasmic phase
?Membrane-associated phase
?Extra-cytoplasmic phase
There are three phases of peptidoglycan assembly of a new wall:
1NAG and NAM building-blocks are formed in the cytoplasm of the cell.
?The enzymes coded for by these genes attach 5 amino acids to each molecule of NAG and NAM.
1The cytoplasmicphase is an important target for ________

they prevent the formation of the peptidoglycansubunits

1Specific enzymes link the NAG and NAM subunits with the lipid portion of the bacterial cell plasma membrane.
?The first step in the cycle is the formation of a bond between peptidoglycan and the side of the plasma membrane facing the cytoplasm
1Subunits are then moved from one side of the membrane to the other.
?This is done by membrane associated enzymes.
?It allows new components to be integrated into the growing wall.
?It is an important target for antibiotics
ScienceBUILDING THE BACTERIAL CELL WALL: The Extra-Cytoplasmic Phase
?The last step in the formation of the meshwork is the binding together of the peptidoglycan layers.
?This is done with polypeptide chains.
?These connections give the wall many layers and an increased strength.
The __________ cell wall is rich in peptidoglycan with multiple layers of meshwork
gram positive
1contains very littie peptidoglycan
the gram negative cell wall
1In addition to many layers of peptidoglycan, the cell wall of ____________ bacterials cells also contain:
?Teichoic acid
?M protein
?Mycolic acid.
gram positive
1There are two forms
?Wall _______–
?Both forms protrude above the wall, which gives the bacterial cell a negative charge.
?Teichoic Acid
1go completely through the wall and link to the plasma membrane
Lipoteichoic acids
1go part way through the wall.
1teichoic acids
This is a virulence factor.
?It protrudes from the cell wall.
?It is required for infection.
?It is highly susceptible to mutations.
?M Protein
This is found in the Mycobacterium species.
?It consists of a waxy lipid incorporated into the cell wall.
?It makes cells extremely resistant to environmental stress.
?It acts as a barrier against antibiotics and host defenses.
?Mycolic Acid
only have a thin peptidoglycanlayer.
?They also have an outer membrane, known as the lipopolysaccharidelayer (LPS).
Gram-negative bacteria
of gram negative bacteria is composed of lipids, proteins, and polysaccharides.
The LPS layer
__________ molecules fasten the outer membrane to the peptidoglycan layer of gram negative bacteria
the outter membrane of the gram neg bacteria is composed of (instead of phospholipids molec) which serves as a barrier for the gram neg cell
the outter membrane of gram neg bacteria contains _____________ systems:
Some are found in the outer layer of the membrane and break down nutrients for transport.
?Some are found in the periplasmic space (the space between the outer membrane and the cell wall) and move substances out of the cell
translocation protien
gram neg bac contains speacilized proteins called __________:
These form a channel through the outer layer.
?This channel is responsible for passage of molecules and ions into and out of the Gram-negative cell
porin proteins
has a thick layer of peptidoglycan
teichois acid is present
has very little lipids
no outter membrane
uses exotoxins
very sensitive to antibiotics
gram positive bacteria
has a thin peptidoglycan layer
teichoic acid is absent
has a lipopolysaccharide layer
has an outter membrane
uses endotoxins
moderately sensitive to antibiotics
gram negative bacteria
can cause colonization of the nasal epithelium.
teichoic acid
causes an inflammatory response
lipoteichoic acid
cell wall is a complex structure involved in infection in many ways.
?The outer layer is a barrier to antiseptics, disinfectants, and antibiotics.
?Porinproteinsexcludelarge molecules
The gram-negative
the ________ of gram neg bacteria functions as endotoxin, with two parts having clinical relevance
?Lipid A
?O polysaccharide
outter layer
of gram neg bac cell wall
Anchors the lipopolysaccharide part of the outer layer
?Is released when the cell dies.
?Lipid A:
______ of the gram neg cell wall are
Carbohydrate chains that are part of the outer layer
?Variable from one bacterial species to another
?Recognized by the adaptive immune response
?Sometimes used as a diagnostic marker -E. coli O157: H7 is designated by O polysaccharide 157
?O Polysaccharides are:
the are 5 structures that can found outside the cell wall

________ bacterium has all 5 of these structures

Three structures (outside the bac cell wall) are involved primarily with adherence (staying in)
Two structures (outside the bac cell wall) are involved primarily with motility (defeating host defenses and damaging the host)
?Axial filament
is a sticky substance composed of polypeptides, polysaccharides or both.
?It is produced in the cytoplasm and secreted to the outer part of the cell wall.
?It provides a protective element against environmental stress.
?It can be used for nutrition
the glycocalyx
if the glcocalyx is attached to the wall it is called a _______

if adhered tightly to the wall its called a ________

slime layer
both variations , the slime layer and the capsule of the glococyle gives an __________ capibility to the organsim
is a major part of infection (staying in), especially in respiratory and urinary tract infections.
?The glycocalyx is a primary factor of this
The slime layer form is associated with some forms of ____________.
dental decay
inhibits phagocytosis
many organisms arent infectious w/ it
its genes can be tranferred between organisms
the capsule form
Both are involved in adherence.
?Both appear as sticky projections which are shorter than flagella.
?They are found on Gram-negative organisms.
?Both are composed of pilin protein subunits.
?Genes for these can be transferred from one organism to another.
fimbriae and pili
help pathogens fulfill the staying in requirement through adherence
fimbriae and pili
are only used for adherence, particularly in the urinary and intestinal tracts.
can give bacteria motility in two ways
?Twitching or gliding movements
?Through extension and retraction of the _____
are involved in the development of biofilms
fimbrae and pili are potential targets for
use antigenic variation to change or mask their structure and avoid host defenses
They can form fragments (S pili) that bind antibody molecules and inactivate them.
fimbriae and pili
are also clinically important because they facilitate the transfer of genetic material from one bacterial cell to another
Genes that have been transferred by the facilitation of pili can be used for:
?Antibiotic resistance
?Toxin production
?Defense against host defenses
are flagellum-like structures that are found on spirochetes.
?They wrap around the bacterial cell and are confined to the space between the plasma membrane and cell wall.
?They are used for motility and cause the entire organism to rotate like a corkscrew
axial filaments
The corkscrew motion of axial filaments gives the bacterium the ability to ___________.
they allow organisms to get into the ________ as well as other tissues (damage the host)
?They allow organisms to get into the blood as well as other tissues (damage the host).
bore holes through the tissue )staying in)
are used only for motility.
?They are long structures that extend far beyond the cell wall and even beyond the glycocalyx.
?They make it possible for bacteria to move from their point of origin to other places in the body.
E. coli can move from the large intestine, where it is harmless, to the urinary tract, where it can cause serious infection by the use of
?A flagella consists of the following three parts:
?Basal body
the ___ of the flagella is made of flagellin protein.
they join to form a twisted helical chain of subunits
This gives the flagellum a hollow core.
?It is only seen in bacilli.
?It is flexible
the _____ of the flagella links the flexible filaments to the basal body
the _______ of the flagella is compossed of paired ring structures that anchor the flagella to the cell
basal body
there are two different arrangents in for the basal body:

–uses only one pair of ringed structures fastened to the plasma membrane
–uses two pairs of ringed structures: one is fastened to the plasma membrane and one to the outer layer

gram positive
gram negative
one flagellum located at the end of the cell
–two flagella, one at each end of the cell
–two or more flagella located at the same end of the cellELLA CONFIGURATIONS
–flagella surround the entire cell.
The _______ allow movement which allows:
?Opportunistic infections
?Escape from host defense (defeat of host defense)
?Systemic infection (damage to the host
There are six major structures found inside the bacterial cell well:
?Plasma membrane
?Nuclear region
?Inclusion bodies
surrounds the internal cellular matrix and organelles.
It is involved in:
?DNA replication
?Generation of energy
?Transport and secretion
plama membrane
?There are two basic types of membrane protein:
–found on either side of the membrane
–penetrate the membrane completely
?Some form pores in the membrane.
peripheral proteins
integral proteins
Categories: Microbiology