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146 Cards in this Set
- Front
- Back
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what allows bacteria to have a high metabolic rate?
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high surface to volume ratio
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what limits bacteria metabolic rate?
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diffusion
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do prokaryotes have nuclei?
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no; lack membrane bound organelles, no endocytosis
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are prokaryotes haploid or diploid?
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haploid; single chromosome +/- plasmids
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what is the biofilm made by dental bacteria made of? and why?
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polysaccarides; to allow bacteria to stick to teeth
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what color do gram pos bacteria stain and what is the stain called?
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purple; crystal violet +iodine
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what color do gram neg bacteria stain and what is the stain called?
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red; safranin
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what makes the gram pos bacteria different?
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thick cell wall made of murein (peptidoglycan) and teichoid acids
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murein:
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glycan sugars cross linked to each other by peptides
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what can be used to remove the cell wall of gram pos bacteria?
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lysosyme (murein-hydrolytic enzyme)
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what is the role of the cell wall in the survival of gram pos bacteria?
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allows stability of the cell in presence of hypo/hypertonic solution
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what makes gram neg bacteria different?
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2 membranes; outer membrane bilayered containing LPS; periplasm between inner mem and cell wall (murein); porin in outer membrane
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what are the 3 components of LPS?
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lipid A (glycolipid), sugar core (ketodeoxyoctanoic acid and heptose) and O antigen chain (carb chain up to 40 C)
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what is another term for lipid A?
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endotoxin
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what is the role of O antigen?
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excludes hydrophobic compounds like bile salts and antibiotics
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how do nutrients like B12 and Fe get across the outer membrane of gram neg?
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specific transporters
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what is the role of porin proteins in gram neg?
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allows passage of molecules of 600-700 daltons into cell while excluding hydrophobic molecules
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what exists in the periplasm? (murein layer and gel-like solution)
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enzymes to break particles into digestible size, binding proteins, enzymes to inactivate antibiotics
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what color do acid-fast bacteria stain? what is the name of the stain?
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red; hot carbolfuchsin
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what is used as a counterstain in acid fast staining?
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methylene blue-stains all other cells that aren't acid-fast
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what is special about the cell wall of acid-fast bacteria?
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it's waxy due to long chain hydrocarbons and sugars (interlaced with murein, polysaccharides, and lipids)
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what are the advantages and disadvantages of the waxy cell wall of acid-fast bacteria?
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advantages: impervious to chemicals and acids, avoids killing by WBCs…disadvantages: slow growth, place of attachment for infecting bacteriophages
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with what do the beta-lactams interfere?
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transpeptidation causing the formation of penicilloyl-enzyme complex instead of D-Ala-enzyme complex
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what is required for bacterialcidal action of beta-lactams?
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cell growth
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MOA of vancomycin
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inhibits addition of subunits to growing murein chain
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MOA of fosfomycin
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inhibits creation of NAM-UDP
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MOA of cycloserine
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inhibits creation of monometric peptide units in cytoplasm to be added to NAM (NAM-UDP)
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MOA of bacitracin
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inhibits regeneration of lipid carrier=no transfer from cyto to periplasm/murein layer
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what makes mycoplasms resistant to penicillins?
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lack of murein with no defined shape
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what makes antrax bacillus resistant to penicillins?
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tough protein layer (S-layer) on outside
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what occurs in group translocation?
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chemical altering of the molecule; phosphorylation-linked transport
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siderophores are required for the uptake of what?
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Fe; are chelating compounds
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where does oxidative metabolism take place?
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bacterial cytoplasmic membrane; cytochromes located there=performs role of mitochondria
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what is the structure of bacteria genome?
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numerous tightly twisted supercoils make up a central nucleoid
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what causes supercoiling of genome?
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DNA gyrase
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what causes relaxation of supercoils in genome?
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topoisomerase I
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what are the 3 stages of DNA replication in bacteria? and at what 2 stages do antibiotics work?
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initiation, elongation and termination; initiation or elongation
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what causes regulation of DNA replication?
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frequency of initiation; coupled with growth and cell division
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where does DNA replication begin?
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replicative origin-bidirectional replication
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MOA of metronidazole
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anaerobic bacteria (and amoebas) partially reduces the drug which causes incorporation into its DNA which makes it unstable --> death; no or full reduction=inactive
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MOA of nalidixic acid
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inhibits DNA gyrase --> death; bactericidal
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MOA of fluoroquinolones
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inhibits DNA gyrase and topoisomerase to cause double strand DNA breaks
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what is the principal biosynthetic activity of bacteria?
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protein synthesis
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MOA of rifampin
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binds free-floating RNA polymerase to inhibit transcription; bacteriostatic-does not affect bound polymerase (****useful in TB and leprosy-nontoxic)
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MOA of chloramphenicol and macrolides (erythromycin)
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binds 50S subunit to block the formation of peptide bonds near tRNA binding sites to cause truncated ribosome cycles (*****ribosomally active antibiotics); bacteriostatic, reversible when stop tx
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MOA of aminoglycosides (streptomycin, gentamicin, neomycin)
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bactericidal; binds 30S;enhances interaction between 50S and 30S subunits to cause an accumulation of 70S --> death due to inhibition of elongation; irreversible, can not be removed from cell
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MOA of tetracycline
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prevents addition of tRNA to the ribosome
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MOA of linezoid
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prevents creation of initiation complex
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allows bacteria to change pilin or flagella to avoid killing by Ab
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phase variation=flagellar
antigenic variation=pili |
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what movement of flagella causes straight swimming?
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association into a bundle and counterclockwise motion (clockwise=tumble)
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law of growth, Nt =
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Nt = No * e^kt
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CFU =
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# colonies * dilution factor
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what is the string of genes needed for enzyme production called?
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operon
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3 types of cell membranes to protect bacteria
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gram +, gram -, acid fast
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Cell walls of gram positive bacteria are made heavily of ...
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murein (peptidoglycan), that absorbs the gram staining = purple
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LPS is characteristic of Gram (+ or -) bacteria?
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LPS is on gram - bacteria
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3 parts of LPS
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Lipid A, sugar core (heptose, ketodeoxyoctanoic acid), O antigen (sugar chain)
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Broadly speaking, which class of bacteria are more antibiotic resistant? Gram - or +
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Gram negative are less affected by most antibiotics, especially penicillin. most antibiotics work to inhibit murein synthesis (in gram +) anyways
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What makes up the cell wall of acid fast bacteria?
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waxes (long hydrocarbon chains), very impervious to acid so acid doesn't wash the strong dye out
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Vancomycin inhibits murein synthesis at what step?
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prevents growing chain of murein by inhibiting disaccharide linking
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How does bacitracin inhibit murein synthesis?
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prevents regeneration of lipid carrier = monomeric units of murein cannot cross membrane into periplasm for further synthesis
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Penicillin and cephalosporin inhibit what step of murein synthesis?
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transpeptidation; prevents peptide linkages
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Bacteria treated with penicillin die by lysis. Even though only murein synthesis has been blocked, why does lysis occur?
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with no murein, the cell walls are very weak. as growth continues in the bacterial cell, it will exert pressure on the weaker wall and lyse eventually
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Why do we not want to give a patient penicillin and a drug that inhibits cell growth concurrently?
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penicillin will inhibit murein synthesis, synthesis occurs during cell growth
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Penicillin resistant bacteria are deficient in autolysin. Explain why they might be resistant.
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penicillin may arouse autolysin to a more-unrestrained action
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What are siderophores?
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chelating agents used by bacteria to take up as much free iron out of the blood as possible to use for its own growth; usually specific to each bacteria
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Function of DNA gyrase
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wind DNA back up after replication; introduce supercoils
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Function of topoisomerase I
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unwind DNA for replication
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FACT: rate of DNA polymerase movement is INdependent of the cell's growth rate
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chromosome replication regulated by frequency of initiation of DNA synthesis
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Metronizadole mechanism
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inhibit DNA synthesis; incorporates into DNA making DNA unstable
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Why is metronizadole a safe drug for human use?
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must be PARTIALLY reduced to be active (to inhibit DNA synthesis); only anaerobic bacteria and amoebas can partially reduce it, humans fully reduce is (making it inactive again)
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Nalidixic acid mechanism
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inhibits DNA synthesis by inhibiting DNA gyrase. bactericidal
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Mechanism of fluoroquinolones
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inhibit DNA synthesis by inhibiting DNA gyrase or topoisomerase, can lead to double strand DNA breaks
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RNA production rate is proportional to # of RNA polymerases. True or False.
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TRUE
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Rifampin mechanism
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inhibits bacterial transcription at initiation; only binds to free RNA polymerases unbound to DNA
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Why is rifampin safe for humans? (used in TB and leprosy)
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mammalian free RNA polymerases don't bind rifampin
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Chloramphenicol and macrolides (erythromycin) inhibit which part of bacterial life?
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Protein synthesis, bind at tRNA site on large ribosomal subunit; ribosomally active antibiotic; reversible/bacteriostatic
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Why is chloramphenicol's action reversible?
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binds to tRNA site on large (50S) ribosomal subunit. when cycle is finished, the complex disassociates and can bind to a new mixture of subunits = chloramphenicol/erythromycin must be continued to be effective
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Mechanism of aminoglycosides (streptomycin, gentomycin, neomycin)
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inhibit protein synthesis; bind to small 30S ribosome subunit; inhibits elongation of peptide chains; bactericidal
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Accumulation of 70S ribosomes is characteristic of bacterial cell death after being treated with which class of antibiotics?
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aminoglcosides (streptomycin, gentomycin, neomycin)
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Aminoglycosides are (bactericidal or bacteriostatic)?
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bactericidal. irreversible death
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Chloramphenicol/erythromycin are (bactericidal or bacteriostatic)?
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bacteriostatic, because they are reversible if treatment is discontinued
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Clock-wise spinning of flagella is associated with travel (in straight line or tumble)?
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tumble; counter-clockwise = streamlined
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Sex pili exchange information via what process?
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conjugation
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Why is it difficult to vaccinate against gonococci? (related to pili)
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their pili can express many different antigens
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All pathogenic microbes are (photosynthetic/chemosynthetic or rely on preformed organic compounds)?
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rely on preformed organic compounds
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TB is a (strict aerobe or obligate anaerobe)?
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strict aerobe, thats why its in the lungs
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Botox and tetanus are (strict aerobe or obligate anaerobe)?
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obligate/strict anaerobe, dont want oxygen at all
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FACT: Facultative anaerobes are the most medically relevant and hardest to treat since they can live most places.
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E. coli and other intestinal microbes are most common
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Fermentation uses what organic compounds as a final electron acceptor mostly?
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pyruvate, reduced to lactate in lactic acid fermentation
acetyl CoA, reduced to alcohol in ethanol fermentation |
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What does it mean if a bacteria is nutritionally fastidious?
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has high, specific nutrient requirements
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What is the bacterial SOS response?
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when DNA damage is detected (from UV light), genes are expressed to repair them
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Strep makes their hemolysins mainly in the stationary phase. Why does this make sense?
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when growing they must have enough nutrients; use hemolysins and get more nutrients from host RBCs in stationary phase
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A bacteria is growing in culture. leucine is added to the culture and bacterial production of endogenous leucine stops and uses the exogenous source. This is an example of...
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Parsimony/efficiency
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Where does RNA polymerase bind on an operon?
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promoter; initiates synthesis of mRNA
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A repressor would bind where on an operon?
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operator, just past the promoter
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What is an inducible enzyme vs. a constitutive enzyme?
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inducible = only made when needed. constitutive = always made
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In the presence of lactose, how are B-galactosidase genes transcribed.
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allolactose (inducer; indicates presence of lactose) binds to the repressor. this acts as an allosteric modifier and inactivates the repressor. the repressor now does not bind the operator and B-galactosidase is transcribed
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genetics of prokaryotes
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haploid with extrachromosomal plasmids
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genetics of eukaryotes
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diploid + many chromosomes
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what is unique about protein transcription in prokaryotes
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translation and transcription can occur at the same time due to the lack of a nuclear membrane
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three demands made on microbes
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nutrition, occupancy and resistance
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two ways how bacteria adapt to nutrient availability
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efficiency and adaptability
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polysaccharide buildup that allows for bacterial growth
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biofilm
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when does urine become cloudy
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when bacteria get 1 million to 10 million per mililiter
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outer structures can amount to what percent of the dry weight of the cell
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20%
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where is the strongest antibody response to bacterial antigens directed
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surface antigens
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gram positive
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purple
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gram negative
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red
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what makes up the cell wall of a gram positive cell
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murein/peptidoglycan
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what is murein composed of
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glycan (sugar) cross-linked together via peptides
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rod
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bacilli
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spheres
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cocci
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helices
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spirilla
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how does murein protect against osmotic gradients
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allows to live in media of lesser osmotic pressure than cytoplasm, does not let it burst
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spheroplasts
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gram positive treated with lysozyme kept in a isoosmotic medium
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what cant pass through gram positive cell wall
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hydrophobic compounds, because of polar layer of charged murein
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why can gram positive bacteria withstand bile salts
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because they are hydrophobic compounds, naturally repelled by cell wall
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why are most inhibitors of DNA synthesis too toxic for clinical use
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they bind directly to the nucleic acid strains
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what is unique about metronidazole
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inert but can become selecticely modified to an active form by selective reduction of a nitro group, usually done by anaerobic bacteria and amoebas
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how does metronidazole work
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partially reduced metronidazole is incorporated into the DNA of the bacteria rendering it unstable
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what is metronidazole effective against
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anaerobic bacteria and amoebas
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how does nalidixic acid work
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inhibits DNA gyrase and is bactericidal
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how do fluoroquinolones work
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interfere with DNA gyrase or topoisomerase and cause dsDNA breaks
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how do bacterial ribosomes differ from eukaryotic ones
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smaller subunits and smaller RNA molecules
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what rate is RNA made
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proportional to the number of RNA polymerase molecules
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when does rifampin work
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inhibits bacterial replication at the initiation step
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to which ribosomes does rifampin bind to
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free floating ribosomes in the cytosol, does not effect ribosomes already engaged in translation
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what is rifampin used to treat
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tuberculosis and leprosy, because it is non toxic to mamalian RNA polymerases
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what class of antibiotics is the most clinically useful
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those that inhibit protein synthesis
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which antibiotics bind at the tRNA binding site on the large ribosomal subunit
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amphenicol and macrolides (erythromycin)
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are the preceeding drugs reversible?
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yes, because once they detach from the subunit, they return to normal action
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which antibiotic is bactericidal
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aminoglycosides (class)
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which drugs are in the aminoglycoside class
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streptomycin, gentamycin and neomycin
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aminoglycosides bind to what subunit of the ribosome
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30s
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how do aminoglycosides work
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inhibit elogation of the peptide chains
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what is the method of cell death for aminoglycosides
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blocking of 30s causes build up of 70s particles, causes cell death
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how does linezolid work
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blocks the assembly of the initiation complex
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how does tetracycline work
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inhibits aminoacyl transfer RNA binding (tRNA)
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which antibiotics are cell wall inhibitors
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B lactams, glycopeptides, imadazoles, and echinocandins
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which antibiotics are inhibitors of membrane function
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lipopeptides and polyenes
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which antibiotics are folate antagonists
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sulfonamides and trimethoprims
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which antibiotics are protein synthesis inhibitors
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aminoglycosides, macrolides, ketolides, streptogramins and chloraphenicol
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which antibiotics are RNA synthesis inhibitors
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rifampin
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which antibiotics are DNA synthesis inhibitors
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metronidazole, fluoroquinolones and nalidixic acids
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memorize page 30
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racks on racks on racks
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