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67 Cards in this Set

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usually haploid, with a single chromosome and extrachromosomal plasmids. Lack nuclei and other internal membrane-bound organelles
prokaryotes (e.g. bacteria)
three general demands made on microbes
nutrition, occupancy and resistance to damaging agents
Ultimately, the rate of biochemical reactions is limited by what?
diffusion, the smaller the cells, the less limiting is diffusion
Gram stain method (4 steps):
1. Stain with crystal violet (purple)
2. Modify with potassium iodide
3. Decolorize with alcohol; only Gram-positives remain purple
4. Counterstain with safranin: Gram (-) become pink; Gram (+) remain purple
Acid-fast stain (3 steps):
1. Stain with hot carbolfuchsin (red)
2. Decolorize with acid alcohol; only acid-fast remain red
3. Counterstain with methylene blue: acid-fast remain red; others become blue
This type of bacteria is protected by a thick cell wall composed of a polymer unique to bacteria, composed of sugars and amino acids called murein, or peptidoglycan.
Gram positive
Murein is composed of glycan chains that are cross-linked via peptides and can form the following shapes:
rods (bacilli), spheres (cocci) or helices (spirilla)
a murein-hydrolytic enzyme present in many human and animal tissues
lysozyme
This feature of gram (+) bacteria allows many of them to withstand certain noxious hydrophobic compounds, including bile salts
thick, hydrophobic, murein cell wall
chains of ribitol or glycerol linked by phosphodiester bonds found in the walls of gram pos bacteria
teichoic acids
these bacteria contain an outer membrane outside the murein cell wall
gram neg
A complex molecule found in the outer membrane of gram neg bacteria that is not found elsewhere in nature
lipopolysaccharide (LPS)
Three components of LPS
1. Lipid A: anchors LPS in the outer leaflet of the membrane.
2. Core: short series of sugars that include two characteristic sugars, ketodeoxyoctanoic acid and heptose
3. O antigen: the hydrophilic carbohydrate chains of the O antigen cover the bacterial surface and exclude hydrophobic compounds
porins
small channels in the outer membranes of gram neg bacteria that allow the entry of certain necessary hydrophilic compounds
How do larger hydrophilic compounds cross the outer membrane?
By specially designed proteins that translocate the particular compound
This compartment, on the outside of the cytoplasmic or inner membrane of gram (-) bacteria, contains the murein layer and a gel-like solution of components that facilitate nutrition.
periplasmic space, or periplasm
List several functions that occur in the periplasmic space:
1. degradative enzymes break down large and impermeable molecules to "digestible size"
2. binding proteins help soak up sugars and amino acids
3. B-lactamases are present
an example of an acid-fast bacteria. Characterized by the waxy coat, interlaced with murein, polysaccharides, and lipids.
Tubercle bacillus
Penicillins, cephalosporins, and carbapenems are collectively known as what?
the B-lactams
The step in murein synthesis in which disaccharides are linked to a growing chain of murein is inhibited by what drug?
vancomycin
Regeneration of the lipid carrier in the cytoplasmic membrane is inhibited by what drug?
bacitracin
The cross-linking between D-alanine on one chain and the free N terminus of a lysine or a diaminopimelic acid on the other chain is inhibited by what two drug classes?
penicillins and cephalosporins
Explain how B-lactams cause cell lysis.
B-lactams bind to and inhibit the enzyme transpeptidase (PBP). Because the enlarged cytoplasm is not restrained by a properly cross-linked murein sac, as the cell continues to grow the cell contents extrude and the cells lyse. Cells that are not growing are not lysed because they are not increasing in mass.
What is the explanation for persisters or tolerant bacteria (to penicillins)?
Autolysin deficiency. Autolysin is an enzyme used to break open some bonds of murein at the septum. Normally, the activity of autolysin is tightly controlled. Treatment with penicillin may arouse it to more unrestrained action.
This group of bacteria have no murein and consequently are not rigid and are resistant to penicillin.
mycoplasmas
Permeases
Carrier proteins located in the cytoplasmic membrane that facilitate the entry of most metabolites.
Three main versions of transport across the cytoplasmic membrane:
1. facilitated diffusion: down its concentration gradient
2. group translocation: phosphorylation linked transport.
3. active transport: proton motive force
Chelating compounds that bind iron with great avidity
siderophores. Note: each organism can take up its own particular form of complexed iron; individual complexes are unique enough to be less digestible for other organisms.
The location of cytochromes and oxidative metabolism and performs the role of mitochondria
cytoplasmic membrane
The genome of most bacteria consists of what?
single circular chromosome of double-stranded DNA
Nucleoid
central irregularly coiled structure of bacterial DNA
Supercoiling depends on balancing the actions of two what?
topoisomerases
Name the two topoisomerases and their functions:
1. DNA gyrase - introduces supercoils into circular DNA.
2. topoisomerase I - relaxes the supercoils by making single-strand nicks.
Bacterial DNA replication takes place bidirectionally, starting at a precise place on the chromosome known as what?
replicative origin
T/F At a given temperature, the rate of DNA polymerase movement is nearly independent of the growth rate of the cells.
True. Replication takes 40 mins, whether the cells are growing slowly or quickly.
This inhibitor of DNA replication is inert, but can be selectively modified to an active form by some bacteria.
metronidazole
This drug inhibits DNA gyrase and is bactericidal.
Nalidixic acid. This is the prototypical first-generation quinolone.
These drugs interfere with DNA gyrase or topoisomerase and cause double stranded DNA breaks.
fluoroquinolones
The synthesis of the principal macromolecules of bacteria is regulated mainly by what?
the frequency with which each chain is initiated and not so much by altering their rate of manufacture of each molecule
This powerful inhibitor of bacterial transcription acts at the initiation step.
rifampin. It binds strongly to molecules of RNA polymerase that are floating freely in the cytoplasm but much less strongly to polymerase molecules that are bound to DNA.
These drugs block the formation of peptide bonds by binding at or near the aminoacyl transfer RNA binding site.
chloramphenicol and macrolides (such as erythromycin)
Are ribosomally active antibiotics bacteriostatic or bacteriocidal?
bacteriostatic. EXCEPT for Aminoglycosides which inhibit the 30S subunit and are bactericidal and sometimes try to make you buy them meals because they think they are right.
streptomycin, gentamicin and neomycin are examples of what?
aminoglycosides
These drugs bind to the 30S ribosomal subunit and are bactericidal.
aminoglycosides
Long, helical filaments that endow bacteria with motility.
flagella
These are involved in the attachment of bacteria to cells and other surfaces.
pili (fimbriae)
When flagella rotate in this motion they swim in a straight line.
counterclockwise
When flagella rotate in this motion they tumble in random fashion.
clockwise
A good example of a bacteria containing genes coding for many varients of the protein pilin.
gonococci
phase variation
change in flagellar synthesis, based on the control of a gene for flagellar protein
these bacteria must have oxygen to grow
strict aerobes
bacteria that cannot grow in the presence of oxygen
strict anaerobes
final electron acceptor in aerobes
oxygen
final electron acceptor in fermentation
organic molecule (e.g. pyruvate, acetyle coenzyme A)
these bacteria have never been cultured in artificial media and only replicate inside host cells
obligate intracellular parasites (e.g. clamydia)
The time it takes for a bacterium to become two is called
generation time or doubling time
body count of bacteria with no discrimination between living and dead bacteria
total count
The number of living or viable bacteria
colony count
The number of colonies multiplied by the dilution factor
colony-forming units (CFUs)
The stage of the culture where growth stops
stationary phase
Stopping the flow of substrates at the very beginning of the pathway
feedback or end-product inhibition
Site where RNA polymerase binds to initiate the synthesis of mRNA
promoter site
Mechanism by which, in the presence of a desired substance, the transcription of desired biosynthetic enzymes for that substance is terminated.
attenuation
In the presence of a required substance (the inducer), a transformational change occurs in a repressor protein rendering it incapable of binding to what location, and therefore allowing transcription to take place?
operator
These enzymes are made on demand.
inducible enzyme (e.g. B galactosidase)
These enzymes are made at all times
constitutive enzymes (e.g. RNA polymerase)
T/F The synthesis of enzymes and proteins are ALWAYS regulated within the cell?
False. The energy cost of making regulatory devices is weighted against the greater disadvantage that cells would have in not being able to switch major biosynthetic pathways on and off.