Which microbe does this describe: Smallest infectious particles; 18-600 nanometers; True parasites – require host cells for replication?
Viruses
Once again, how large are viruses?
18-600 nanometers
Describe bacteria. How do they reproduce?
Simple unicellular organisms – no nuclear membrane, mitochondria, Golgi or ER
**asexual reproduction
T/F Bacteria are eukaryotes.
FALSE!! They are prokaryotes.
How large are bacteria?
1-20 micrometers
What does prokaryote mean?
primitive nucleus
What does eukaryote mean?
true nucleus
T/F Fungi are eukaryotes.
True!! Whoa
Which microbe does this describe? More complex – well-defined nucleus, mitochondria,; Golgi bodies and ER; Membranes contain a unique sterol - ergosterol
Fungi
Describe the replication of fungi.
Unicellular (yeast) – asexual
Filamentous (mold) – can replicate sexually or asexually
Once again, what is the name of the sterol in the membrane of fungi?
ergosterol
Are parasites prokaryotic or eukaryotic? How large are they?
1-2 micrometers (protozoa) to 10 meters (tapeworms)
Eukaryotes!
Are parasites multicellular or unicellular?
They can be either! They are the most complex of the microbes. And the largest potentially!
What is the most common sterol in our membranes?
cholesterol!
What are the some of the ways that you can classify bacteria?
Shape Arrangement Cell Wall Structure Antigenic Metabolism Ability to lyse erythrocytes fermentation of sugars
What are the 3 shapes of bacteria?
Spherical - coccus
Rod - bacillus
Spiral - spirillum
What are the 2 arrangements of bacteria?
Chains – single division plane
Clumps – multiple division planes
What are the different cell wall structures of bacteria?
Gram positive
Gram negative
Acid fast-mycobacterium
H1N1 is what type of classification?
antigenic–presence of absence of specific antigens
Which is the least helpful way to classify bacteria?
based off of arrangements
What are different types of metabolism of bacteria?
Aerobic
Facultative anaerobe
Anaerobic
What are the options for classification of bacteria based off of ability to lyse erythrocytes?
hemolytic or NOT
What are the options for classification of bacteria based off of ability to ferment sugars?
fermenter or NOT
What are different ways to classify microbial pathogens in general?
Taxonomic (textbook)
Growth Habit
System Affected
Means of Acquisition (food borne, etc)
What are different examples of growth habit classification?
Extracellular
Intracellular
Toxin Producer
Pyogenic Cocci (pus former)
What’s the deal with extracellular pathogens?
Cannot survive inside phagocytes
Often controlled by antibody
What’s the deal with intracellular pathogens?
Grows inside phagocytes
Often controlled by T-cell based immunity
Differences from mammalian cells provide targets for antimicrobial agents
Give examples of these differences that can be targeted.
Cell wall Cytoplasm Nucleic acid synthesis Protein synthesis Metabolic pathways
Give examples of bacterial structure giving rise to pathogenesis.
Sometimes their structures can cause these things…
Inflammation
Resistance to host factors
Adherence to cells and tissues
What is the structure of a bacterial chromosome?
Single double-stranded circle
No nucleus or nuclear membrane
Bacteria have plasmids. What are these? What info do they carry?
Small, extra chromosomal DNA
May encode extra, non-essential functions, e.g., toxins or antibiotic resistance
Streptococci & diplococci have what arrangement?
chains-single division plane
staphylococci have what arrangement?
clump-multiple division plane
What are some examples of toxin producers?
tetanus & botulinim–symptoms at distant sites
How does the bacterial ribosome differ from the human ribosome?
Human: 80S
Bacterial: 30S + 50S–>70S
different proteins than eukaryotes have.
Describe the cytoplasmic membrane of a bacteria?
there aren’t any sterols, like cholesterol
What is the exception to the rule that bacteria don’t have sterols in their membranes?
mycoplasma
they actually have cholesterol b/c as they move around they pick up stuff from other people’s membranes.
Is staph aureus gram positive or negative?
gram positive
What is the peptidoglycan layer for bacteria? Which types of bacteria have it?
this is the cell wall of bacteria.
All types have it.
Gram negative: it is thinner & is sandwiched b/w the outer membrane & inner membrane.
Gram positive: it is thick & right outside the inner membrane
What is periplasm? Which type of bacteria exhibit this?
this is the space b/w the inner membrane & peptidoglycan thin cell wall of gram negative bacteria. Enzymes etc are found there.
What is the repeating disaccharide that makes up the peptidoglycan cell wall?
NAG-NAM
**the poly AA chain is attached to NAM
What is NAG?
N-acetyl glucosamine
What is NAM?
N-acetyl muramic acid
What is the stem peptide of the peptidoglycan cell wall?
4 AA that are attached to NAM.
Alanine-Glucose-Lysine-Alanine
**w/ 2 alanines at the end. I think one gets chopped off with cross linking
Stem peptides are linked with a transpeptide bridge composed of ______. This is accomplished by which enzyme?
glycine (pentaglycine)
**transpeptidases; also D-alanine carboxypeptidases
aka penicillin binding proteins b/c they are the target of antibiotics.
**lysine on one (3rd residue) is attached to the alanine (4th residue) of the other
What is the purpose of the peptidoglycan cell wall?
to give a rigid & protective structure to the bacteria.
to resist osmotic pressure
Describe the process of peptidoglycan biosynthesis.
- form the precursor in the cytoplasm (water soluble)
- attach the precursor to the inside of the membrane
- flip the precursor to the other side of the membrane
- attach precursor to disaccharide chain & cross link the AA chains. Form a strong matrix!!
Does NAM or NAG have a lactyl group?
NAM
What is the role of bactoprenol-phosphate in peptidoglycan synthesis?
it carries precursors across the membrane to become a part of the cell wall
How do beta lactam antibiotics target bacterial cell walls?
they bind the transpeptidases & prevent cross linking.
then the bacteria burst under the osmotic pressure
**vancomycin also has a way of targeting this step (but not a beta lactam antibiotic)
Which part of peptidoglycan biosynthesis involves transglycosylation?
transglycosylation: linking together the disaccharide units into a linear polymer (NAG & NAM)
Which part of peptidoglycan biosynthesis involves transpeptidation?
transpeptidation: linking together the polyAA chains. cross linking!
Describe the process involved in a gram stain.
- use heat or alcohol to fix cells onto the slide
- use crystal violet to stain the cell wall
- gram’s iodine
- Decolorizer (alcohol or acetone)
- safranin
What is the purpose of the gram’s iodine?
it precipitates the crystal violet into the gram positive cell wall
Gram positive bacteria appear how during the gram stain?
they appear colorless before the crystal violet & then they appear blue/purple the rest of the time.
Gram negative bacteria appear how throughout the gram stain?
They appear blue during the crystal violet & gram’s iodine steps. After the decolorizer they are colorless. Then, they are RED after the safranin.
What does this mean: I’m positively blue over you.
Gram positive bacteria=blue.
Then you know–gram negative is red.
T/F Sometimes a gram negative bacteria will stain gram positive–blue.
False. It never will. The decolorizer will always take away the blue.
T/F Sometimes a gram positive bacteria will stain gram negative-red.
True. B/c the gram positive cell wall can become compromised.
What are some of the factors that can compromise the gram positive cell wall & cause it to stain gram negative?
penicillin & other antibiotics that affect a cell wall
old age-autolytic enzymes
too much heat fixation
Why is it advised (unless there is an emergency) to take a sample of the bacteria infecting a patient before administering antibiotics?
b/c if you are going to do a gram stain & you have already given penicillin or something–you could think you have gram negative bacteria when you really have gram positive.
Once again, describe the cell wall of gram positive bacteria.
thick, multilayered
mainly made up of peptidoglycan
the cell wall surrounds the cytoplasmic membrane
contains teichoic & lipoteichoic acids
What degrades the cell wall of gram positive bacteria? What results from this degradation?
lysozyme (found in tears)
results in protoplasts
What are protoplasts?
this is what results from a gram positive bacteria losing its cell wall entirely. You are left with intracellular contents
What are the 2 types of teichoic acids?
Teichoic acid
Lipoteichoic acid
What is the structure of teichoic acid? How is it found?
polymer of polyol phosphates
linked covalently to the peptidoglycan of the cell wall
What is the function of teichoic acid?
affects virulence (increases i think)
What is the structure of lipoteichoic acid? How is it found?
structure of teichoic acid (polymer of polyol phosphates) + fatty acid
it is anchored in the cytoplasmic membrane
What is the function of lipoteichoic acid?
Stimulate innate host responses in manner similar to endotoxin of gram negative bacteria
**has proinflammatory properties
What is the endotoxin we are talking about found in gram negative bacteria?
lipopolysaccharide
Describe the structure of the gram negative cell wall.
cytoplasmic membrane
outside of that is a thin cell wall
then an outer membrane (not found in gram positive)
What is found in the peptidoglycan layer of gram negative bacteria?
so…similar peptidoglycan structure with cross linking etc. It is just thinner than the cell wall of gram +. Also, it doesn’t have teichoic acids.
It is separated from the cytoplasmic membrane by a periplasmic space (not found in gram +).
Describe the structure of the outer membrane of gram negative bacteria.
inner layer: normal phospholipid layer
outer layer: mainly lipopolysaccharide endotoxin
How do things get thru this crazy outer membrane of the gram negative bacteria?
there are porins present that allow small cytophilic particles (<700Da) to get thru.
Which attackers work on gram negative bacteria? Which don’t?
Don’t Work: lysozyme!; hydrophobic or large antibiotics
Work: small & cytophilic to get thru the porin.
Lipolpolysaccharide (LPS) found in the outer membrane of gram negative bacteria is highly toxic & is shed into the body during infection. What are its 3 components?
Lipid A
Core polysaccharide
O antigen
What’s the deal with Lipid A?
this is what is responsible for the endotoxin activity
**it is bound to the core polysaccharide
What’s the deal with the core polysaccharide of LPS?
It is 9-12 sugars.
it includes an unusual sugar: 2-keto-3-deoxy-octanoate (KDO)
Which antibiotic binds Lipid A of LPS?
polymyxin B
Describe the O antigen that is attached to LPS. What is an example of gram negative bacteria that lack this O antigen?
50-100 repeating units of 4-7 sugars
- *a means of classifying bacteria
- *Neisseria produce LOS (lipooligosaccharide–LPS minus the O antigen).
Which have a cell wall? Outer membrane? LPS? Teichoic acids? Gram negative/Gram positive
Gram Negative–thin cell wall; outer membrane present; LPS present; teichoic acids absent
Gram Positive–thick cell wall; outer membrane absent; LPS absent; teichoic acids present
Which have spores? Capsules?
Gram negative/Gram positive
Gram negative–no spores; sometimes have a capsule
Gram positive-some spores; sometimes have a capsule
Which is sensitive to lysozyme? Penicillin sensitive? Which make exotoxins?
Gram negative/Gram positive
Gram negative–lysozyme resistant; penicillin resistant; sometimes make exotoxins
Gram positive–lysozyme sensitive; penicillin sensitive; commonly make exotoxins
Describe the structure of bacterial capsules.
usually composed of polysaccharides
makes the bacteria anti-phagocytic
common vaccine target (T-independent antigens)
What is an exception to bacterial capsules being made of polysaccharides?
Bacillus anthracis is exception – poly-glutamic acid in the capsule
What are the flagella that are sometimes found on bacteria? What is their fcn?
rope-like propellers
they are coiled protein subunits
fcn: provide motility
What are the fimbriae found on bacteria? What is their fcn?
they are hair-like structures
composed of protein subunits (pilin)
fcn: adherence factors
special fcn: F-pili (sex pili) used to transfer bacterial chromosomes between cells
There are bunch of reasons why mycobacterial cell walls (including mycobacterium tuberculosis) are different. What are the differences?
peptidoglycan (intertwined w/ arabinogalactan) cell wall also has... wax like lipid coat w/ mycolic acid cord factor wax D
What do these differences in the mycobacterial cell wall cause? Are mycobacteria considered gram negative, positive?
these differences cause resistance to disinfectants. Ex: hard to disinfect a room of a TB patient.
Weakly gram positive. Really: acid fast
What does it mean to be acid fast?
these bacteria are resistant to the decolorizing procedure in gram staining
often use Ziehl-Neesen stain
What’s the deal with mycoplasma? What are they resistant to?
they lack a peptidoglycan layer
resistant to penicillins or beta lactam antibiotics b/c of this lack of cell wall
**they incorporate their host sterols into their membranes–like cholesterol.
What is the function of spores? Which types of bacteria make them?
Fcn-allows bacteria to survive harsh environments
Gram positive (never negative) make them!
This includes clostridium & bacillus
Clostridium is an anaerobe that causes _____.
tetanus
Bacillus can cause what?
one form can cause anthrax
one form can cause food poisoning
What triggers sporulation?
depletion of nutrients, harsh environments
What triggers germination?
some form of stressor, water and a triggering nutrient
What are the contents of spores?
Complete copy of chromosome
Minimal proteins and ribosomes
High concentration of dipicolinic acid (unique to spores) bound to Ca++
What are some of the nutritional requirements for bacterial growth?
Carbon Nitrogen Growth factors, e.g., B complex vitamins Inorganic ions Oxygen
Oxidation reduction potential is important for bacteria to grow b/c of _____.
the electron transport chain!
Bacteria have certain preferences–conditions where they grow best. Give examples of these preferences.
certain temps
certain osmotic conditions
certain pHs
What do you call bacteria that thrive at low temps (-5–30dC)? (10-45dC)? 25-80dC?
Low Temp (-5-30dC): psychrophilic Medium Temp (10-45dC): Mesophilic High Temp (25-80dC): thermophilic
What are the 3 forms of energy production? List them from most efficient to least efficient.
Most Efficient 1. Aerobic Respiration 2. Anaerobic Respiration 3. Fermentation Least Efficient
What’s the deal with aerobic respiration?
oxygen is used as the terminal electron acceptor
What’s the deal with anaerobic respiration?
inorganic compounds are used as the terminal electron acceptors
**like nitrate, sulfate, carbonate
What’s the deal with fermentation?
organic molecule is used as the final electron acceptor
not very efficient
a last resort for bacteria
What’s the deal with obligate aerobes?
they can only use O2
produce H2O2 & superoxide radicals which are toxic to them so they also produce superoxide dismutase & catalase to deal with this problem.
What’s the deal with facultatively anaerobic bacteria?
they prefer O2 as the electron acceptor but if it’s not there no big deal–they’ll use something else. Maybe fermentation.
What’s the deal with obligate anaerobes?
oxygen is actually toxic to these guys
inorganic compounds are the terminal electron acceptor
**don’t use fermentation.
If obligate aerobes aren’t using their enzymes…what’s another way for them to get rid of their superoxide radicals etc?
by pumping them out of the cell!
What are 2 ways to determine bacterial mass?
dry weight
turbidity-measure optical density
What are different ways to determine cell number?
direct counting by microscopy
quantitative culture
What are the steps involved in quantitative cultures?
Prepare serial dilutions
Culture in petri plates
Directly count colonies
What are the different parts of the bacterial growth curve?
lag phase
exponential growth
stationary phase
death or decline
What happens during the lag phase of the bacterial growth curve?
Increase in cell size
Little or no cell division
adjustment to the new environment
What happens during the exponential growth phase of the bacterial growth curve?
Cell number and mass increase simultaneously
Growth rate expressed by natural exponential function (doubling time)
Growth rate depends on bacterial species and environment
**as it runs out of nutrients or accumulates radicals–it hits the stationary phase.
Bacteria may differ greatly in the efficiency of their energy production. Which of the following terminal electron acceptors is on a pathway that would maximize total ATP production? A) Nitrate B) Sulfate C) Oxygen D) Acetyl CoA E) Pyruvic acid
C. Oxygen
Transpeptidases are targets of the beta lactam class of antibiotics. What is the function of transpeptidases in cell wall synthesis? A) Catalyze formation of the pentapeptide that is attached to N-acetyl muramic acid B) Catalyze formation of the N-acetyl glucosamine – N-acetyl muramic acid disaccharide transglycosylase C) Cross-link a N-acetyl glucosamine – N-acetyl muramic acid disaccharide to a growing polysaccharide chain--transglycosylase D) Generate cross-linking between the peptides on peptidoglycan to produce a complex matrix E) Facilitate re-incorporation of lipid carriers into the lipid carrier pool
D!! It connects the peptides.
Transpeptidases are also called penicillin binding proteins. they both affect the vancomycin & penicillin actions.
Porins have been identified as potential vaccine targets for Neisseria meningitidis and Neisseria gonorrhoeae. What is the location of porins in the bacterial cell wall?
A) The outer membrane of gram positive bacteria
B) The outer membrane of gram-negative bacteria
C) Peptidoglycan of the gram-positive cell wall
D) Peptidoglycan of the gram-negative cell wall
E) Cytoplasmic membrane
B!!
