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Micro Block 2 Pt. 1

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ptheodore's version from 2015-10-12 13:38

Bacteria Structure & Function

Question Answer
Peptidoglycan, Teichoic acid & Lipoteichoic acidCell wall of Gram + Bacteria
Lipopolysaccharide (LPS) & Porin are components of theOuter Membrane of Gram - Bacteria
Part of Lipopolysaccharide (LPS) that has toxic effectLipid A
Lipopolysaccharide (LPS) functions as aEndotoxin
Site of action of Beta-lactam drugs (penicillins & cephalosporins)Peptidoglycan
Site of action of of VancomycinPeptidoglycan
Bacterial enzymes essential for this cross-linkingTranspeptidases & Carboxypeptidases (PBPS)
Penicillin (and all other beta-lactam drugs) bind to _________to prevent cross-linking, hence called “penicillin binding proteins” (PBPs)Transpeptidases & Carboxypeptidases (PBPS)
Interferes with peptidoglycan synthesis by binding to D-ALA – D-ALA and preventing cross-linkingVancomycin
Gives rigidity, shape, and helps bacteria resist low osmotic pressure Peptidoglycan
Mostly made of Polysaccharides and prevents phagocytosis of bacteriaCapsule
Site of action of inhibitors of cell wall synthesis (beta-lactams & vancomycin)Peptidoglycan
Site of action of inhibitors of DNA synthesis (Quinolones)Nucleoid
Contains variety of genes coding for antibiotic resistance and toxinsPlasmid
Mediates bacterial attachmentPilus/Fimbria/Adhesins
Mediates bacterial motilityFlagellum
Highly resistant to desiccation, chemicals, hot/cold temps (Bacterial endospores)Bacillus & Clostridium
Medical supplies must treated to kill all spores usingAutoclave (steam under pressure)
True or False, Antibiotics are ineffective against sporesTrue (contin Endospore Coat)
Which Stages of Bacterial growth cycle does Beta-lactam drugs act onLog Phase
When oxygen is used for generation of energy, 2 toxic molecules are generated. In order to deal with these toxic radicals, bacteria that utilize O2 usually produce the following 2 enzymesSuperoxide Dismutase & Catalase
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Bacteria structures

Question Answer
Bacteria with no cell wallMycoplasma
Mycolic acid in cell wallMycobacteria
Lipid A portion of LPS hastoxic effect
LPS functions asEndotoxin
Unique to Gram (-) bacteriaLPS, Outer cell wall
These inhibit transpeptidase-carboxypeptidase enzyme that cross-links the peptide chainsBeta-lactam drugs
Because penicillin acts on this bacterial enzyme it is also called Penicillin-binding protein (PBP)
Vancomycinbinds to D-Ala – D-Ala interfering with cross-linking
What is the function of Pilus or fambriaMediates attachment
Highly resistant to dessication, chemicals, hot/cold tempsBacterial endospores
What are the two important genera that can form sporesBacillus & Clostridium
Bacteria reproduce bybinary fission
Bacteria grow byExponential
Beta-lactam drugs act at this phaseLog phase
When oxygen is used for generation of energy, 2 toxic molecules are generatedSuperoxide radical O2 & Hydrogen peroxide H2O2
In order to deal with these toxic radicals, bacteria that utilize O2 usually produce the following 2 enzymesSuperoxides dismutase & Catalase
Obligates aerobesPseudomonas, Mycobacterium
MicroaerophilesCampylobacter, Helicobacter
Facultative anaerobesEnterobacteriaceae
Obligate anaerobesClostridium, Bacteroides
Extracellular bacteriaVibrio cholerae
A facultative intracellular bacteria that grows inside macrophages, induces its’ own uptake & blocks lysosomal fusionLegionella
A facultative intracellular bacteria that grows inside macrophages, destroys phagosome, inhibits lysosomal fusion, escapes and grows in cytoplasm of macrophageMycobacterium tuberculosis
Obligate intracellular bacteria that cannot survive outside host cellsChlamydia
Obligate intracellular bacteriaRickettsia
Gram positive cocci in clusters Staphylococcus
Gram positive cocci in chains Streptococci
Gram positive cocci in pairs Streptococcus pneumoniae
Gram positive bacteria in chainBacilli anthrax
Gram positive bacilli with terminal spores Clostridium tetani
Gram positive bacilli with spores Bacillus anthracis
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Branching filamentous bacteria : Actinomyces & Nocardia
Question Answer
Pleomorphic gram negative bacilliHemophilus influenzae
Gram negative cocci in pairs Neisseria
Gram positive “budding” organismCandida fungus
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Aerobic & Anaerobic Bacteria

Question Answer
Obligate aerobesPseudomonas, Mycobacterium
MicroaerophilesCampylobacter, Helicobacter
Facultative anaerobesEnterobacteriaceae
Obligate anaerobesClostridium, Bacteroides
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BACTERIAL GENETICS

Question Answer
genes directing transfer of plasmid to other cellsFertilized plasmid
genes for antibiotic resistance Resistance plasmid
Chromosomal genetic element that carries gene resistance for multi-drug resistanceTransposons
Extra-chromosomal elements that carry a variety of genes such as fertility plasmid, resistance plasmids, bacterial exotoxins & transposonsPlasmids
Multiple transpositional events can lead to formation of “multi-drug” resistant bacteriumTransposons
The most important way that bacteria acquires multi-drugs resistance is viaConjugation
Nonencapsulated strain of Strep pneumoniae can be transformed into a capsulated strain in this manner Transformation
Phage picks up genes from bacterial DNATransduction
Carry genes for antibiotic resistanceConjugation
Capsulated strain in streptococcus pneumonia arevirulent
Transformation of NON-encapsulated Strep pnuemoniae to CAPSULATED strain (virulent)Transformation
Gene coding for Diptheria toxin is transferred in this mannerTransduction
Transfer of antibiotic resistance genesConjugation
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Extracellular & Intracellular Bacteria

Question Answer
Extracellular bacteriaVibrio Cholerae
Obligate intracellular bacteriaChlamydia
Facultative intracellular bacteriaLegionella & Mycobacterium Tuberculosis
Grows inside macrophages, induces its’ own uptake & blocks lysosomal fusion (Inhibition of phagolysome fusion)Legionella
Grows inside macrophages, destroys phagosome, inhibits lysosomal fusion, escapes and grows in cytoplasm of macrophageMycobacterium Tuberculosis
Facultative Intracellular parasiteListeria monocytogenes
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Bacteriology Lab

Question Answer
Crystal violet, Iodine (mordant), Decolourizer – Acetone / Ethanol, Safranin (counterstain)Gram Stain Procedure (In order)
2 imp bacteria that can grow ONLY on Chocolate AgarHaemophilus influenzae & Neisseria gonorrhoeae
Differentiates bacteria based on utilization of LactoseMacConkey agar (MA)
Mannitol Salt agarDifferentiates S.aureus from S.epidermidis based on fermentation of mannitol
Ping on MacConkey agar (MA) Lactose fermentor
Colorless on MacConkey agar (MA)Non-lactose fermenter
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Bacterial Pathogenesis

Question Answer
Capsulated bacteria can only phagocytes when they areOpsonized
More severe infections with encapsulated bacteria is seen inSplenectomized individuals
Help evade phagocytosisCapsule
Helps Strep pneumonae to degrade IgA proteinIgA proteases
Breakdown IgA immunoglobulin present on mucosal surfacesIgA proteases
3 agents causing meningitis, all are encapsulated and produce IgA proteases Neisseria meningitidis*, Haemophilus influenzae type b*, Streptococcus pneumoniae
Inactivates secretory IgAIgA protease
Slime of Staph epidermidis helps it adhere to prosthetic devises (artificial heart valves, joints)Biofilm production
Why are biofilms a problem in the body?Cells of immune system cannot penetrate biofilm & Antibiotics cannot penetrate
Demonstrates antigenic variationNeisseria gonorrhoeae
Varies the structure of the pili on it’s surface thereby evading the immune systemNeisseria gonorrhoeae
A chemoattractant for neutrophilsC5a
Secreted into the surrounding environmentExotoxins
Is an integral part of the cell wall of only Gram negative bacteriaEndotoxins
An example of exotoxins Secreted into the surrounding environmentDiphtheria Toxin
Toxoids are used in some vaccinesTetanus toxoid, diphtheria vaccine
Loss its toxicity components and retains its antigenicity and cannot causes damage to the bodiesToxoid
Inhibition of protein synthesis by ADP-ribosylation of elongation factor (EF-2), Primary target--> liver Exotoxin A (Pseudomonas aeruginosa)
Inhibition of protein synthesis by ADP-ribosylation of host elongation factor (EF-2), Primary targets--> heart/nerves/epithelium Diphtheria toxin (Corynebacterium diphtheriae)
Inhibits protein synthesis by interfering with 60S ribosomal subunitShiga toxin (Shigella dysenteriae)
Inhibits protein synthesis by interfering with 60S ribosomal unitShiga-like toxin, (verotoxin) & Enterohemorrhagic E.coli
Stimulates adenylate cyclase by ADP-ribosylation of GTP binding protein, Hypersecretion of fluids and electtrolytes from intestinal epitthelium Cholera toxin (Vibrio cholerae)
ADP ribosylation of Gi (inhibitory G protein - negative regulator of adenylate cyclase) causing increased cAMP Pertusssis toxin (Bordetella pertussis)
Decreases phagocytosis; causes edema, kills cellsAnthrax toxin (Bacillus anthracis)
Assembles an injection system in order to affect the effector molecules in the host cell membranesType III secretion system
Mediated septic shock is a leading cause of death, especially in hospitalsEndotoxin
Bind and link MHC-II molecule (of antigen-presenting cell) with T-cell receptor (on T-helper cell) outside of the peptide binding grooveSuperantigens
Blocks release of inhibitory neurotransmitters glycine & gamma-amino butyric acid (GABA), Inhibits neurotransmission in inhibitory synapses, Results in muscle spasms, spastic paralysisTetanus toxin (Clostridium tetani)
Inserts into membrane to form pores, Cell membrane becomes leakyAlpha toxin (Staphylococcus aureus)
Lecithinase: damages cell membranesAlpha toxin* (Clostridium perfringens)
Blocks release of acetylcholine from peripheral cholinergic neurons, Results in flaccid paralysisBotulinum toxin (Clostridium botulinum)
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Bacterial Genetics

Question Answer
Spread of genes for antibiotic resistanceTransposons
Genes for antibiotic resistance (Genes for most bacterial exotoxins)Resistance Plasmids
Genes directing transfer of plasmid to other cellsFertility Plasmid
Plasmid that carry genes for antibiotic resistance *=> MULTIPLE DRUG RESISTANCEConjugative Plasmids
Nonencapsulated strain of Strep pneumoniae can be transformed into a capsulated strain in this mannerTransformation
Process by which bacteria take up fragments of naked DNA and incorporate them into their genomesTransformation
Transfer of genetic material that requires a bacteriophageTransduction
The process by which bacteria transfer genes from one cell to another by cell-to-cell contact via a Fertility factor (F plasmid)Conjugation
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Bacterial Pathogenesis

Question Answer
Two bacteria that produce pili that allows them adhere to mucous membranesNeisseria Gonorrhoeae and E.coli
A bacteria that produces copious capsular material of some bacteria allows it to attach to prosthetic devices and form a biofilmStaph. Epidermidis
Some bacteria produce an extracellular material that surrounds the cell wall and helps them evade phagocytosis (Antiphagocytic), which causes them to be more virulenCapsules
Some bacteria secrete enzymes that cleave secretory IgA present on mucosal surfacesIgA Proteases
Prevents bacteria from being carried away by mucus or washed swept away by fluidsAdherence to host surfaces
Three agents causing meningitis, all are encapsulated and produce IgA proteasesNeisseria meningitidis, Haemophilus influenzae type b, & Streptococcus pneumoniae
A bacteria that uses Antigenic variation to escape host defensesNeisseria gonorrhoeae
Subjecting exotoxins to low heat and chemicals (eg. Formaldehyde) in the laboratory environment inactivates them. They Lose toxicity (cannot cause host tissue damage), but retain antigenicity and can be used in ~some vaccinesToxoids
A-B subunit toxin that inactivates elongation factor-2 therefore inhibits protein synthesis by ribosomeDiphtheria Toxin
A-B subunit toxin that increases cyclic AMP (cAMP) which leads to hypersecretion, loss of water and ions and diarrheaCholera Toxin
Toxins that are inhibitors of eukaryotic protein synthesisPseudomonas, Shiga, Shiga-like, Corynebacterium diphtheriae (Inhibit Protein Synthesis = Cell Death)
Toxins that increase cAMPcAMP….cAεP = Cholera, Anthrax, E.coli, Pertussis
Alpha Toxins that are CytolysinsClostridium perfringens & Staphylococcus aureus
NeurotoxinsClostridium tetani & Clostridium botulinum
Toxins that are SuperantigensTSST-1 (toxic shock syndrome toxin) from Staph aureus, Streptococcus pyogenes, Staph aureus Enterotoxin
Cause non-specific activation of T-helper lymphocytes. Bind and link MHC-II molecule (of antigen-presenting cell) with T-cell receptor (on T-helper cell) outside of the peptide binding grooveSuperantigens
Some bacteria are able to “inject” the exotoxins they produce directly into host target cells using this system. Because the toxin directly enter a host cell they evade the antibodies (antitoxin) present in extracellular fluidType III secretion system
Structural part of cell wall (outer membrane). Found ONLY in Gram negative bacteria. Released into host circulation following bacterial cell lysis. Composed of Lipopolysaccharide (LPS) and Lipid A (toxic moiety)Endotoxins
High concentrations of endotoxins in blood leads toSeptic shock (gram negative bacterial sepsis)
Endotoxin-mediated septic shock is a leading cause of death, especially inHospitals
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