Download Microbial Polysaccharides

CLASS: Fundamentals I 11:00-12:00
DATE: 08-19-2010
PROFESSOR: Pritchard
I.
II.
III.
IV.
V.
VI.
LECTURE TITLE
Scribe: Lauren Morris
Proof: Spencer Terry
Page 1 of 7
MICROBIAL POLYSACCHARIDES [S1]
a. READ SLIDE
b.
c.
CLASSIFICATION OF BACTRIA BY GRAM-STAINING [S2]
a. This Danish physician, Christian Gram, about 120 years ago, was experimenting with some of these new
coal-tar dyes that became available. These German organic chemists about them were just churning out all
these neat so-called coal-tar dyes.
i. They were made by diazetizing analine with all these other compounds.
ii. And one of these was crystal violet. It’s a nice beautiful symmetrical molecule. If you’ve ever worked with
this, a tiny little speck of it gets on you, then it gets all over you
b. What he found is that he could group bacteria into two major groups on the basis of staining properties.
Many of you who had microbiology will have done this gram staining.
i. The idea is you first of all, put the bacteria on a slide, fix them there either by warming it briefly in a flame or
putting a little alcohol on it and letting it dry (thus attach bacteria to the slide)
ii. You then stain the bacteria with crystal-violet which makes everything purple
iii. Then you use a mordant, Iodide, to help fix the stain there.
iv. You put a little alcohol on the slide and let it run over the stained bacteria, and you’ll see it washes out the
stain of some bacteria
v. Since it’s hard to see colorless bacteria, usually people do a counter stain, and that counter stain usually is
safranin which turns the bacteria pink although some people use a stain that turns the bacteria green.
vi. The net effect is some bacteria end up being one color and other bacteria another color.
c. The blue bacteria are gram-positive, and the ones that are pink are gram-negative
d. This image is a mixture of streptococci. They are gram-positive; they are blue. The E.coli are gram-negative
so it’s real easy to tell them apart
e. For the first hundred years ago, people didn’t really know how this worked. They knew it had to do something
with the cell walls of the bacteria
GRAM-POSITIVE BACTERIA FIGURE [S3]
a. Gram-positive bacteria differ from gram-negative in that it has only one membrane. Gram-positive will have
this typical lipid bilayer, symmetrical bilayer by the way,
i. Then on the surface they’ll be this peptidoglycan layer
ii. Now this image is a schematic from your textbook and a lot of people are not sure they believe this
anymore, and in some cases they know it’s not true
iii. The basic idea is there is a thick layer of peptidoglycan on the outside of the membrane
GRAM-NEGATIVE BACTERIA FIGURE [S4]
a. In the Gram-negative bacteria there are two membranes
i. the symmetrical bilayer is the inner membrane
ii. then there is a layer of peptidoglycan
iii. then there’s this outer membrane, and the outer membrane is not symmetrical.
b. The bottom is the typical phopholipid, but the outer leaflet (they talk about leaflets sometimes) is something
called lipopolysaccharide
i. The lipid part is embedded in the membrane and then there are these long polysaccharide chains [points to
the tall grey lines on the outer membrane] and that’s lipopolysacchride – that’s very important in disease.
LIPOPOLYSACCHARIDE FIGURE [S5]
a. Ok, that’s showing you the same thing so I’ll skip along
PEPTIDOGLYCAN STRUCTURE FIGURE [S6]
a. Peptidoglycan, we’ll talk about it’s structure
i. Let me just remind you what peptidoglycan is: bacteria have an internal pressure of about 5 atm, and if they
weren’t in a strong little bag or sac, they would blow up and pop.
ii. The sac their in is composed of something called peptidoglycan that adds strength and shape to the
bacteria cell wall. It consists of these fairly long chains of polysaccharide
b. Here we have an N-acetylglucosamine [points to the pink and blue structures at top of slide]
i. Except it has this little ether group attached to it – and what this is called is N-acetylmuramic It is ether
linked to this 3-Carbon unit here
ii. These polysaccharide chains that go on are cross-linked with these peptide bridges
iii. The composition of these peptide bridges is a little different in different bacteria, but most cases, the 1 st
amino acid (AA) that this lactic acid group here is attached to is Alanine
CLASS: Fundamentals I 11:00-12:00
Scribe: Lauren Morris
DATE: 08-19-2010
Proof: Spencer Terry
PROFESSOR: Pritchard
LECTURE TITLE
Page 2 of 7
iv. Then it’s attached to something called Isoglutamate – that’s a glutamic acid, but normally in proteins a
glutamic acid would be linked through this alpha-carboxyl group. Here it is linked through the gammacarboxyl – that’s why they call it isoglutamate
c. By the way this is a D-AA
i. Normally in proteins, you never ever find a D-AA, but bacteria occasionally use D-AA
ii. For all other proteins there is just L-AA
d. Then it is linked to Lys, or a compound very similar to Lys in some bacteria, and finally a D-Ala
i. These things can then be cross-linked – this is called a Stem Peptide
ii. Stem peptides can be cross-linked by the so called bridge peptides, which differ in composition depending
on what the bacteria is
iii. Often in gram-neg there is no cross link peptide connected directly; but in things like Staph aureus, you
may recognize this as a Gly or you may not, but there’s 5 Gly in a row – that’s the bridge peptide in Staph
aureus
iv. For some reason textbooks always show this [indicating the part of slide above the arrow pointing towards
“in Staphylococcus aureus only”]. It’s different in different bacteria, but textbooks always use Staph aureus
as an example, probably because it was the first one to be figured out.
VII. N-ACETYLMURAMIC ACID FIGURE [S7]
a. A close up of N-acetylmuramic acid. Again, it’s the glucosamine structure with this lactic acid group linked
here
VIII. GRAM-POSITIVE/NEGATIVE CELL WALL FIGURES [S8]
a. Repeating stuff
b. The idea is these stem peptides can be cross-linked
c. Again, this is Staph aureus showing you the 5 Gly in a row
d. QUESTION: So Staph aureus is the only one with peptidoglycan stems cross-linked? ANSWER: No, almost
all gram-positives are cross-linked, but they’re not crosslinked with 5 Gly. Ex Group B Strep is cross-linked
with 2 Ala. Stem peptides are almost identical with gram positives. They’re a little different in gram neg.
e. QUESTION: What is the difference between linking of gram pos and gram neg? ANSWER: It depends on
the bacterias. In general, gram neg tend to be directly cross-linked. I’m gonna show you in a moment,
whereas gram pos often are cross-linked through a bridge peptide.
IX. TRANSPEPTIDASE REACTION [S9]
a. To answer your question; there’s a reaction called a Transpeptidase Reaction
i. It is a really important reaction and has been enormously studied
ii. The example shown here is for Staph aureus. See those 5 Gly?
iii. The idea is that this enzyme then causes the formation of a bond between this amino group and the
carboxylic acid group of this 2nd Ala and at the same time cleaves off this Ala [references the dotted line]
iv. Release an Ala to make a linkage there
v. So all these polysaccharide chains that have the stem peptides coming off, many will be cross-linked
vi. So basically the peptidoglycan of a bacteria is like one big cross-link bag or basket
X. BIOSYNTHESIS OF PEPTIDOGLYCAN [S10]
a. This is illustrating the biosynthesis of peptidoglycan
b. What happens to begin with, is when you make a UDP N-acetalglucosamine, and an enzyme catalyzes the
addition of a phospholino pyruvate to it, essentially what you do is you make UDP-N-acetalmuramic acid.
i. And then you add sequentially, you know building up the stem peptide now, an Ala, a Glutamine, a Lys
ii. And the interesting thing is you don’t add one Ala after another, you add them two at once,
iii. Notice they’re D-Ala, not L-Ala. It’s real critical that they’re D
iv. Then this is linked to a Dolichol-phosphate. We talked dolichol when we talked about glycoproteins –
bacteria make dolichols too, usually either shorter than the ones that animals make
v. And then you add another GlcNAc to make this basic subunit of peptidoglycan
vi. Then you buildup the cross-link. Remember this only happens in Staph – different AA are used in gram
pos
XI. BIOSYNTHESIS OF PEPTIDOGLYCAN (CON’T) [S11]
a. You have this basic subunit it can then be, as I said, cross-linked to another subunit, and again, so on and so
on
b. you build up this big cross-linked network or mesh of peptidoglycans
XII. LYSOSZYME [S12]
a. There’s the peptidoglycan there
b. This man, Alexander Fleming, is doubly famous for a couple discoveries he made
CLASS: Fundamentals I 11:00-12:00
Scribe: Lauren Morris
DATE: 08-19-2010
Proof: Spencer Terry
PROFESSOR: Pritchard
LECTURE TITLE
Page 3 of 7
i. There’s a “myth”, maybe not a myth – one day, back in 1922, he had a bad cold and his nose was running
and he was working on his cultures and his nose dripped in his culture plate petri dish
ii. Instead of throwing it out he put it in the incubator to see what would happen. The next day he came back
and found that the bacteria had all lysed where his nose had dripped into the plate – there’s something in
his nasal secretion that killed all the bacteria.
iii. He thought this was a way to cure disease, so he started testing different bacteria – some bacteria lysed
readily with this component in the nasal secretion, and other bacteria didn’t
iv. He was disappointed because not all human pathogens were harmed by whatever this substance was –
“lysozyme” – it’s a small protein, studied extensively
v. Then he thought, “maybe that’s why the bacteria aren’t pathogens” - We have lysozyme in our saliva, in
our tears, nasal secretions, and all secretions, in our blood and everywhere
vi. So if a bacteria was dissolved by lysozyme, it wouldn’t be a human pathogen. Bacteria that are pathogens
for us all modify their peptidoglycans so they are not attacked by lysozyme.
c. They have neat tricks for changing this peptidoglycan, like taking off this acetyl group, and then lysozyme
doesn’t cut it anymore
i. Where lysozyme cuts is right after this NAM here [references the lysozyme cleavage point] – if you cleave
the peptidoglycan, then this sac that’s holding the bacteria with this 5 atm pressure inside isn’t intact
anymore, and the bacteria blows up and lyses
d. Most bacteria out there doesn’t make people sick, you could probably eat a handful of dirt with thousands of
different bacteria and you are not gonna get sick. Only a relatively small number of bacteria are human
pathogens. The ones that are have got to defeat our defenses, things like lysozyme.
XIII. PENICILLIN [S13]
a. Another discovery the man made and another “myth”:
i. a mold in the air fell into one of his dishes, and instead of throwing it out, let it grow through the weekend,
came back and found something like this [references petri dish]
ii. that’s staph aureus there, there’s the mold [white circle]. Notice that clear zone – the mold is obviously
secreting something that’s dissolving/killing the bacteria
iii. that substance turned out to be Penicillin
iv. originally he couldn’t isolate this, so not much was done for several years because they couldn’t get
enough of it
b. this substance did kill human pathogens, unlike lysozyme
c. later they worked out the structure of Penicillin – 5 membered ring with S, C, N, 2 methyl groups and a C, and
then this really unusual 4 member ring – there’s a carbonyl group attached to a N (that’s an amide) that’s
cyclic (special name = beta-lactam)
XIV.
PENICILLIN (con’t) [S14]
a. These guys, before WWII, an awful lot of soldiers were wounded died from infections that they got after they
were wounded. It was enormously important to come up with antibiotics that would kill things like Staph and
strep that cause so many deaths, so there was a big push to try to purify the penicillin
b. Fleming originally used bedpans from a hospital trying to grow the mold – didn’t work well. England was
being bombed (1940s) so they moved the research to the States. Here they discovered that they could grow
this mold in enormous fermentors on an enormous scale in something called corn-steep liquor.
i. Corn can be dry milled or wet milled and the wet milling has a by-product called corn-steep liquor which is
either thrown away or dried up and fed to cattle
ii. It turns out it was a wonderful substrate for growing penicillin – so they made vast quantities of penicillin
and that turned out to be a wonder drug, killing all strep and all staph and worked great for several years
until bacteria figured out a way to defeat it.
XV. PENICILLIN FUNCTIONS BY… [S15]
a. Let me just tell you how penicillin works
i. This is a transpeptidase reaction I’m showing you now for the 3rd or 4th time.
ii. The amino group binding to the carboxyl group of a nearby stem peptide
iii. The way the enzyme, transpeptidase, does that is in two steps
1. Makes an acyl-enzyme intermediate where this D-Ala (remember there’s 2 D-Ala in a row, the
terminal is cleaved off, and then you get this intermediate – see this particular part of the
peptidoglycan is linked to the enzyme)
2. It then reacts with the Gly residue (if this was Staph) to form the complete cross-linking
XVI.
PENICILLIN MIMICS THE… [S16]
a. Here’s how penicillin works
b. this is an illustration of the structure of penicillin. This is an illustration of the 3D structure of the two D-Ala.
CLASS: Fundamentals I 11:00-12:00
Scribe: Lauren Morris
DATE: 08-19-2010
Proof: Spencer Terry
PROFESSOR: Pritchard
LECTURE TITLE
Page 4 of 7
i. They are very similar, so similar they fool the enzyme
ii. So the enzyme thinks it is binding to the 2 D-Ala on the peptidoglycan, but it instead binds penicillin
iii. This causes this beta-lactam ring here to open up, and you get a covalent linkage of the penicillin to a Ser
on the transpeptidase enzyme active site. That wrecks an enzyme
iv. One tiny molecule of penicillin totally wrecks the whole transpeptidase enzyme
c. If the bacteria can’t cross-link the peptidoglycan, they’re gonna swell up and pop from the osmotic pressure.
d. Penicillin mimics D-ala-D-ala, and one molecule of penicillin inactivates one enzyme
XVII. PENICILLIN RESISTANCE [S17]
a. Bacteria unfortunately develop resistance. Almost all Staph have become resistant to penicillin. Fortunately
most strep have not, but most other bacteria are now resistant because they make something called a betalactamase.
b. Beta-lactamase cleaves beta-lactams. Another name for beta-lactamase is penicillinase. Clinical labs
typically get a pathogen isolated from a patient, they will check to see if it makes beta-lactamase. This
enzyme cleaves beta-lactam right here and you end up getting this carboxyl group here
c. This is penicillanoic acid, there is no antibiotic activity. So virtually every staph aureus that is isolated from a
patient now makes that enzyme unfortunately. So people design penicillins that look different so that this
enzyme no longer works and that works for a few years until the bacteria become resistant.
XVIII. TEICHOIC AND LIPOTEICHOIC ACIDS [S18]
a. For completion I want to tell you about teichoic acids
b. teichoic acids are polysaccharides on the surface of cells that are involved in adherence of bacteria to cells
c. what makes then a teichoic acid is that they will have Phosphate groups every few residues
i. here there is a phosphated glycerol, phosphated glycerol, and so on
ii. very often there will be things attached to the glycerol at the hydroxyl
iii. it can be other things than glycerol
XIX.
GROUP-SPECIFIC POLYSACCHARIDES OF -HEMOLYTIC STREPTOCOCCI [S19]
a. An important group of polysaccharides is group-specific polysaccharides
b. Rebecca Lancefield is kind of the patron saint of streptococci. She worked in the Rockefeller University for
70 years. She figured out a procedure for grouping streptococci into 20 different groups.
i. The way they did that, is they’d get a streptococcus from an infection, heat kill it, inject a rabbit and make
antibodies to it
ii. Then when they go an unknown strep, they’d treat it with hot acid to release the polysaccharides to the
surface of the strep, cool it, then mix it with different antiserum
iii. If you get a different precipitate, you’d recognize it was a particular group of strep.
iv. All group A strep make this polysaccharide – 2 rhamnoses with a GlcNAc linked to every 2nd Rhamnose
c. The way they’d do the test is they’d suck up a little of the extract of the unknown bacteria then wipe it, stick it
in a little antiserum, usually rabbit antiserum, and see whether they get a precipitate at the junctions of these
tubes – that’s called capillary precipitate reaction
d. She grouped strep into A,B,C,D, etc. and that’s important to know for epidemiologic purposes
i. This same type of reaction is done in your doctor’s office on these little devices – swab the back of your
throat, stir it in a little liquid and put a drop on these plates and you get a positive blue plus sign showing up
if you have group A strep infection. You normally shouldn’t have group A strep in the back of your throat.
e. So these polysaccharides are used typically all over the world, usually identified immunologically, and they
allow you to group strep into different groups. Group B strep has a particular characteristic, Group B
polysaccharide.
XX.
SEROTYPE-SPECIFIC POLYSACCHARIDES OF GROUP B STREPTOCOCCI [S20]
a. In addition to group polysaccharides, many bacteria like Group B make another polysaccharide.
b. The way you look at these structures, you see where the dotted lines are, imagine this whole structure, with
these 5 sugars, being repeated over and over and over again, this end will be linked to this position of
another oligosaccharide - So these are called the repeating units, and these can be from 2-6 sugars long, and
they’re repeated over and over again – immunologics allows you to categorize these in different groups
XXI.
PNEUMOCOCCAL POLYSACCHARIDES [S21]
a. Here’s a bacteria you should be aware of – Strep pneumoniae, kills millions of people, serious infection, the
#1 reason for pediatrician visits in the country, kid’s infections are almost always caused by strep pneuoniae,
b. it always causes pneumonia, meningitis
c. there are 90 different serotypes – a specific antibody will identify unique polysaccharide on the surface of
strep pneumonia. Most of these structures have been worked out, but not all of them, and some worked out
were wrong.
XXII. PNEUMOCOCCAL VACCINES [S22]
CLASS: Fundamentals I 11:00-12:00
Scribe: Lauren Morris
DATE: 08-19-2010
Proof: Spencer Terry
PROFESSOR: Pritchard
LECTURE TITLE
Page 5 of 7
a. Several years ago we discovered if you immunized with these isolated polysaccharides, say to type 14
pneumococci, it would elicit antibodies in people that would protect them from an infection from type 14.
Type 14 is one of the most serious pneumococcal serotypes
b. Type 19F, Type 14 – referring to the type of polysaccharide on the surface of that bacteria.
c. These antibodies work pretty well with adults, but they didn’t work very well with young children b/c young
children don’t make antibodies to polysaccharides
i. more recently they’ve learned that they can purify the polysaccharide from the bacteria and attach it to an
immunogenic protein , like munengococcal outer membrane protein, they could then get a conjugate
vaccine that elicits antibodies in very young children
XXIII. CAPSULAR POLYSACCHARIDE OF HAEMOPHILUS INFLUENZAE TYPE B (HIB) [S23]
a. There’s another infection you might be aware of- H flu – it’s really gram-neg, but is an “honorary gram-pos”
b/c it makes a teichoic acid which is normally just done in gram pos bacteria –
i. this teichoic acid consists of a ribose, a ribitol, a phosphate, repeated over and over again
ii. vaccines made with this pure polysaccharide protect adults against H flu but didn’t protect children very
well
b. Pediatrician friend said that in children’s hospital there would be about 50 cases of children coming in with H
flu and 5 would typically die a year (10% mortality rate), and of the survivors, more than half would have
permanent neurological damages, deafness, blindness, learning disabilities - it’s important to try to protect
children against it
c. The 1st vaccines were just the polysaccharide and they didn’t work well in children
d. But then they learned they could attach this to an immunogenic protein to make a conjugate vaccine and that
worked very well.
XXIV. HAEMOPHILUS INFLUENZAE [S24]
a. This is illustrating the incidence of H flu disease in Finland
b. arrows shows when the conjugate vaccine was introduced. – dramatic drop in the cases of H flu
c. Unfortunately, some people around the world don’t believe in vaccines, so they don’t have their children
immunized
i. Children will carry H flu in their throats without getting sick, and the immunized children don’t carry it
anymore
ii. So by immunizing most of the population, there are far fewer children that are carrying H flu
iii. So even the people who didn’t get immunized are partly protected because there is less bacteria out there
XXV. LIPOPOLYSACCHARIDES (ENDOTOXINS) [S25]
a. Remember that the outer membrane of a gram neg bacteria has this typical phospholipid bilayer innerleaflet
of the outer membrane, but this unusual outer membrane that is composed of lipopolysaccharides.
i. These are the long fatty acid chains that are hydrophobic and are on the interior of the membrane
ii. Then there’s a core region of these unusual sugars
iii. Then a long polysaccharide – not short, go way up
iv. There’s different polysaccharides – this part is called the O-antigen, this is called the core region (there’s
an inner and outer core), and the part that’s embedded in the membrane (the hydrophobic part) is called
lipid A.
XXVI. SOME BIOLOGICAL PROPERTIES OF LIPOPOLYSACCHARIDE [S26]
a. Lipopolysaccharides, also called endotoxins, are important in medicine because they do people real harm.
i. They are pyrogenic – means they cause a fever, they do this effectively, nanogram amounts in the
bloodstream will cause a high fever – you don’t want gram neg bacteria in your bloodstream
XXVII. DRUGS THAT ARE INJECTED… [S27]
a. If you’re in the lab and you pick up a syringe and you read the package, it’s likely to say pyrogen-free – that
means it doesn’t have any endotoxin
b. it’s real important for things like needles and scalpels to not have even the tiniest trace of endotoxin
i. presumably you are working on a sick person, and they could get even sicker if they get
lipopolysaccharide in their blood
ii. solutions you put into a person, like albumin, you can’t have any endotoxin – and it’s really hard making
any solution that doesn’t have endotoxin in it – there are special ways and columns that people try to use
to get endotoxins out of something
iii. when you do certain types of animal experiments, mice, you don’t want to have endotoxin there – you’re
trying to determine whether you can protect a mouse with a vaccine that you made, you cannot have
endotoxin there – there are special toxins that remove it
c. The key thing you will learn in other classes is that sterile is not good enough
i. you can autoclave something and it’s sterile, but autoclaving does not destroy the endotoxin
CLASS: Fundamentals I 11:00-12:00
Scribe: Lauren Morris
DATE: 08-19-2010
Proof: Spencer Terry
PROFESSOR: Pritchard
LECTURE TITLE
Page 6 of 7
ii. you have to have it cleaned first so there is no bacteria residue at all, then you sterilize
d. How do you measure endotoxin? You need a really sensitive way
XXVIII. DETECTION OF ENDOTOXIN [S28]
a. All over the world they use Limulus Lysate – this is a horseshoe crab
i. they don’t have blood – they have hemolymph and this is blue – it’s blue because the Oxygen carrying
pigment contains a copper (instead of an Fe)
ii. limulus lysate is harvested from these crabs, (don’t kill the crabs), and it will have these cells called
amebocytes which they can spin down from the hemolymph
iii. when they add water, the cells swell up and pop and you get limulus lysate – if you add a tiny tiny bit of
endotoxin, the whole thing will form a gel – protective mechanism the crabs use to keep from getting
infected
iv. people use all kinds of different versions of limulus lysate and check solutions for endotoxin
XXIX. LIIPID A [S29]
a. I told you endotoxin has all these potent bad effects, the part of the endotoxin that is responsible for it’s
toxicity is the lipid A part
b. Lipid A has a glucosamine (not N-acetyl), that is amide linked to this fatty acid
i. The fatty acids can be branched, there’ll be a beta-hydroxyl group here, (beta b/c it’s two carbons away
from this carbonyl)
ii. Tiny amounts of this will cause a high fever in a person and all kinds of other undesirable effects
XXX. EXAMPLES OF LIPOPOLYSACCHARIDE CORE OLIGOSACCHARIDES [S30]
a. I told you about the core polysaccharides – people have been studying those b/c they might be able to
exploit the presence of the very odd shape here sometimes and use it to develop antibiotics, but they haven’t
had a lot of success with it so far
b. there are weird sugars often in the core regions (7,8 carbons)
XXXI. THE LIPOPLYSACCHARIDE CORE OLIGOSACCHARIDE FREQUENTLY… [S31]
a. That’s showing you some of the unusual sugars present in the core region
XXXII. EXAMPLES OF SOME O-POLYSACCHARIDE REPEATING UNITS [S32]
a. Now the old polysaccharides are really important too – there are thousands of them (E.coli, salmonella,…)
b. people can group these bacteria by immunologically detecting the polysaccharide
c. An antibody will recognize only a particular structure polysaccharide – sometimes all you have to do is
change one bond, change an alpha to a beta, and the antibody won’t work on it anymore – so antibodies are
good way of detecting polysaccharide
d. The different strains will have different polysaccharides, and that’ll be the O-antigen, the O-type
e. the real importance of these is for epidemiological purposes
i. if there’s an outbreak of diarrhea/throwing up and it turns out they’ve all gone to the local Sam’s Big Burger,
the public health authorities will check the food and determine whether or not this particular serotype of E.
coli the people have come down with is in the hamburger at that place
ii. so epidemiologists use O-antigens all the time
f. you can make antibodies to them that are protective, but no one’s gonna do it because it’s impractical to make
antibodies to all the different types
XXXIII. IDENTIFICATION OF BACTERIAL O-POLYSACCHARIDES… [S33]
a. What I just said, the importance is epidemiological
XXXIV. E.COLI O157:H7 [S34]
a. Japanese poster from internet
b. you heard about E.Coli O157 on the news reported causing thousands of infections –
c. the bacteria that’s carried in the large intestine of cows – when they slaughter the cow, it ends up in the meat
causing really serious infections
i. #1 cause of kidney failure in children
ii. it’s called O157 – O antigen #157, H means it contains this protein that causes severe cell damage to
intestine, hemotoxin
iii. this bacteria tends to be carried in cattle litter and kept in feed lots
1. cattle that eat grass tend not to have it
2. almost all cattle are kept in feed lots before they’re slaughtered
XXXV. O-POLYSACCHARIDE OF ENTEROHEMORRHAGIC E.COLI O157:H7 [S35]
a. What people are doing in several places around the country are experimenting with vaccines against this
particular bacteria
i. Remember the bacteria is O157 because it makes a particular polysaccharide – it’s 4 sugars
ii. This is a repeating unit, so the final things is hundreds of thousands of molecular weight
CLASS: Fundamentals I 11:00-12:00
Scribe: Lauren Morris
DATE: 08-19-2010
Proof: Spencer Terry
PROFESSOR: Pritchard
LECTURE TITLE
Page 7 of 7
iii. Antibodies against this will protect the cow from carrying this particular E.Coli
iv. They may carry other E.colis but they won’t hurt us
b. The reason it’s almost always hamburger –
i. if you cook a steak or roast, you heat the outside and kill all the bacteria
ii. hamburger is ground up thousands of pounds at once, and just a little bit infected spreads to all the
hamburger in the batch
iii. if it’s not cooked thoroughly, the people get the disease
XXXVI. MICROBIAL POLYSACCHARIDES [S36]
a. End here
XXXVII. PSYCHADELIC SPACE OUT [S37]
[End 44:37 mins]