Lecture 1 part 2 Flashcards
Identify the structures labeled:
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- ) Teichoic acid
- ) Cell wall specific polysaccharide
- ) Lipoteichoic acid
- ) Peptidoglycan layer
- ) Cytoplasmic membrane
What is Teichoic acid and what is its function?
It is a polyribitol or polyglycerol phosphates, attached to NAM.
They are important in phage attachment and regulation of cell growth. They provide rigidity to the cell wall and are a dominant cell antigen in some bacteria
Only found in gram POSITIVE bacteria.
In which species is the teichoic acids highly substituted and serve as specific cell surface antigens?
Staphylococcus, Streptococcus, Lactobacillus, and Bacillus
What is Lipoteichoic acid and what is its function?
It is attached to glycolipids in the cell membrane; may serve as an anchor for the peptidoglycan.
The lipoteichoic acids are amphiphiles, and exhibit at higher concentrations many of the less toxic properties of endotoxins.
They induce IL6 and IL10 production in monocytes and stimulate nitric oxide release from macrophages.
Which organism is lipoteichoic acid the dominant antigen?
The Group D Streptococci
Do gram positive bacteria have a rigid structure?
If so, why?
Yes
Due to the multiple layers of peptidoglycan as well as the many other components associated with the wall: proteins, carbohydrates, and capsules.
How are the Teichoic acid-like polymers are found in a number of bacteria linked together?
phosphodiester-linked
Describe the structure of a gram negative bacteria.
They have three layers in their cell walls and much less peptidoglycan: may be only one layer thick in some E. coli.
The bonding between the components of the peptidoglycan is quite variable and more loosely arranged.
There is a large amount of lipoprotein that is associated with the peptidoglycan. The lipoprotein extends into the outer membrane (OM) and serves to anchor the OM to the cell.
The lipoprotein also associates with the OMP A (outer membrane protein A) and both are essential for membrane integrity.
Identify the following structures labeled in this gram negative bacteria:
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- ) Lipoprotein
- ) Porin
- ) Lipid A
- ) Phospholipid
Identify the following structures labeled in this gram negative bacteria:
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- ) Peptidoglycan layer
- ) Membrane protein
- ) Outer membrane
- ) Inner membrane
- ) “O” antigen side chain
Lipoproteins serve as major surface antigens in which gram negative species?
Borrelia, Treponema, and Mycoplasma
What are the important functions of the outer membrane (OM) of gram negative bacteria?
Specific transport proteins for large molecules, eg. B12 and nucleoside.
Contain Porins
Contains receptors for phages
Carrier of surface antigens.
May contain proteases and other enzymes, aggressins, evasins and toxins for host cells
Releases vesicular blebs of LPS and protein that may serve secretory functions.
Shields from lysozyme
Less permeable to hydrophobic and amphipathic molecules thus making Gram-negative bacteria less susceptible to antibiotics.
LPS = endotoxin (Actually some protein is associated with endotoxin.)
Describe porins and their role in gram negative bacteria.
They are composed of a protein trimer in the OM forming a large channel in each of the porin protien sub units.
This allows for the passage of small hydrophilic molecules.
The size of the molecules excluded varies greatly. Most porins are non-specific, but some only transport one or a limited number of substrates and some are inducible and only produced when the substrate is present.
Some of the porins are readily recognized by mammalian immune systems.
True/False: The outer membrane in gram negative bacteria is less permeable to hydrophobic and amphipathic molecules thus making them less susceptible to detergents, enzymes, many chemicals and macromolecules.
True
Identify the following structures of a lipopolysaccharide (LPS) labeled:
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Which is the toxic portion of the LPS?
- ) Lipid A
- ) Core
- ) O-Antigen side chain
Lipid A is the toxic portion of a LPS
What is the term for an absent O-Antigen side chain (O-Ag) portion of an LPS?
Give an example of a bacteria that has this.
lipooligosaccharides (LOS)
Note: The outer surface corresponds most closely to the core polysaccharides
Neisseria and Haemophilus
True/False: In other bacteria, production of the O-Antigen side chain of an LPS can be lost upon subculture in the laboratory or by specific mutational events.
True
Bacteria growing on an agar plate with a complete O-Antigen side chain (of their LPS) will be _____ in appearance?
Bacteria that lack the O-Antigen side chain (of their LPS) will produce colonies that are ______ in appearance.
Smooth
Rough
Describe the core region of the LPS (labeled 2)
The core region is arbitrarily separated into inner and outer core areas.
The inner core contains 2-keto-3-deoxy-octulosonic acid (KDO) that is unique to Gram-negatives and plant cell walls.
KDO is bound to lipid A and is important in formation of ligands in the cell wall that stabilize the outer membrane.
Label the following structures of a flagella:
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- ) Hook
- ) Filament
- ) Basal Body
- ) Outer membrane
- ) Peptidoglycan layer
- ) Cytoplasmic membrane
Describe the structure and function of a flagella.
In at least one instance, the location of the flagella is important:
Thin, several times the length of the cell
Composed of flagellin (protein) filaments
Motion by rotation
Arrangement and numbers of flagella are of some importance in identification: Peritrichous, Polar
Highly antigenic: H antigen.
Chemotaxis
Periplasmic flagella: Spirochetes have their flagella within a sheath and the cell essentially winds around the flagella.
Describe the structure and function of pili/fimbriae.
shorter, thinner than flagella
pilin, fimbrin
variety of types within a species
roles as receptors, adherence
Almost all capsules are composed of what?
exopolysaccharides
Describe the structure and function of bacterial capsules.
Most are more like a slime layer.
polypeptides
hyaluronic acid
can be fairly large (Klebsiella, Rhodococcus)
can be highly antigenic or poorly antigenic
antiphagocytic
masks other cell antigens (Streptococci with hyaluronic acid capsule)
True/False: Some organisms can become cemented together by their capsules or slime (glycocalyx) and form microcolonies on or in tissues. This greatly assists their survival.
True
List the various functions of bacterial spores.
Important for survival: Resist drying.
Resist heat-Can be boiled.
Resist disinfectants.
Relatively impervious (not susceptible to antibiotics)
Germination of spores is brought about by aging, heat, damage to the coat and the presence of adequate moisture.
