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Micro Chapter 1


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Gram-positive organisms absorb ____a____ and therefore appear to be colored ___b___.

Gram-negative organisms appear ___c___ because of the counter-stain __d___.
a. crystal-violet
b. blue
c. red
d. safranin
Both gram-positive and gram-negative organisms have an extra cytoplasmic layer called the cell wall, or _______a______.

The amino-acid chains of the peptidoglycan covalently bind to other amino acids from neighboring chains, with the help of a
a. peptidoglycan
b. transpeptidase
How does penicillin work?
It binds to and inhibits the transpeptidase enzyme (also called "penicillin binding protein") that catalyzes the formation of cell wall linkages.
What polysaccharide present in the gram-positive cell wall acts as an antigenic determinant and is thus important for serologic identification of many gram-positive species?
Teichoic acid
Do bacterial cytoplasmic membranes contain cholesterol or other sterols?
Gram-negative bacteria have a ___a____ space between the cytoplasmic membrane and the peptidoglycan layer, which is very __b___.

What is the space filled with?
a. periplasmic
b. thin
c. gel with proteins and enzymes
Does the thin peptidoglycan layer of gram-negative bacteria contain techoic acid?
What is the important lipoprotein present in gram-negative peptidoglycan layers? Why is it important?
Murein lipoprotein. It is important because it extends outward to bind the unique third outer membrane.
What is unique about the outer third membrane of gram-negative bacteria?
It contains lipopolysaccharide.
What carbohydrate chains are antigenic determinants in gram (-)?

Where are they found?
O-specific side chains, O-antigen

Found in the outermost layer of LPS
What is the center of LPS composed of?

What makes up the interior layer of LPS? What is another name for this substance?
1. water soluble core polysaccharide

2. Lipid A, aka gram (-) ENDOTOXIN
Name 3 possible sequelae of gram (-) bacterial lysis in the human
fever, diarrhea, and possible fatal endotoxic shock (septic shock)
What class of gram organisms are vulnerable to lysozyme and penicillin attack?
Gram (+) are vulnerable, because their thickly meshed peptidoglycan layer does not block diffusion of low molecular weight compounds.
What are the four major bacterial shapes? Name one example of each.
1. Cocci: strep, staph, neisseria (diplococci)
2. Bacilli/rods: listeria, e.coli (and most gram neg)
3. Spiral forms: treponema
4. Pleomorphic: chlamydia, rickettsiae
What are the 6 classic gram (+) bugs?
1. streptococcus (strips of cocci)
2. staphylococcus (clusters of cocci)
3. bacillus (bacillus with spores)
4. clostridium (bacillus with spores)
5. corynebacterium (bacillus without spores)
6. listeria (bacillus without spores)
what is unique about LISTERIA as a gram (+) organism?
Listeria is gram (+) but HAS endotoxin!
What is the only group of gram (-) cocci?
Neisseria (kissing coffeebeans diplococci)
What is the best way to stain mycobacteria?

Name two diseases caused by mycobacteria
acid-fast stain.

tuberculosis and leprosy.
what is the best way to visualize spirochetes?

what STD is caused by a spirochete?
darkfield microscopy. spirochetes are tiny gram (-) bacteria that are too small to be seen with the light microscope.

syphilis, caused by Treponema pallidum
what group of bacteria are neither gram (+) nor gram (-)? why?
Mycoplasma don't have a cell wall to hold on to any dye.
Where can you usually find antibiotic resistant genes in bacteria?
In PLASMIDS, smaller adjacent circles of double-stranded DNA.
How do erythromycin and tetracycline act like magic bullets?
They INHIBIT PROTEIN SYNTHESIS preferentially at the bacterial RIBOSOMAL subunits while leaving the animal ribosomes alone.

This is possible beacuse procaryotes have smaller, different ribosomes than eucaryotes.
What 3 enzymes can bacteria possess to break down reactive oxygen products?
1. CATALASE: breaks down H2O2

2. PERODIDASE: breaks down H2O2

3. SUPEROXIDE DISMUTASE: breaks down superoxide radical
What enzymes do OBLIGATE AEROBES possess to help defend themselves?

Name 3 obligate aerobes
They have catalase, peroxidase, and superoxide dismutase.

NOCARDIA and bacillus cereus (gram pos)
NEISSERIA, pseudomonas, bordetella, legionella, brucella (gram neg)
What two enzymes do FACULTATIVE ANAEROBES possess? Name 3 facultative anaerobes
Catalase and Superoxide dismutase.
They are aerobic, but have the capacity to be anaerobic.

1. STAPH, Bacillus anthracis, corynebacteria, listeria, actinomyces (gram pos)

2. MOST Gram negative RODS

What enzyme allows microaerophilic bacteria to tolerate low amounts of oxygen?

Name 3 aerotolerant anaerobes
SUPEROXIDE DISMUTASE (no catalase like facultative anaerobes)

2. SPIROCHETES (treponema, borrelia, letpospira)
3. CAMPYLOBACTER (gram neg)
Name two obligate anaerobes
What are chemoheterotrophs and why are they important?
All the medically important bacteria are CHEMOHETEROTROPHS, meaning they use chemical and organic compounds (like glucose) for energy.
What is the most common fermentation pathway for the breakdown of glucose to pyruvate?

Why do we care about this in micro?

Following fermentation the pyruvate must broken down, and the different end products formed in this process can be used to classify bacteria.
Why must obligate intracellular organisms always live in their host cell?
Because they lack the metabolic machinery to utilize oxygen for ATP synthesis and must therefore steal their host's ATP.

Examples: CHLAMYDIA and RICKETTSIA (pleomorphic gram - )

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