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POD > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Peritrichous

A

Many flagella located randomly all around a cell

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2
Q

Endospores

A

Heat-resistant cells rich in calcium dipicolinate that can germinate into growing cells during adverse conditions

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3
Q

Plasma membrane

A

Inner membrane where the respiratory chain is found and phospholipids, LPS, and capsular polysaccharides are formed

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4
Q

Bacterial cell envelope fnxns

A

Provides structure
Energy production thru electron transport chain
Adhesion to host cells via pili and teichoic acids
Escape from immune recognition via capsule
Metabolic uptake of nutrients

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5
Q

Lophotrichous

A

Many flagella located at one end of a bacterium

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6
Q

Peptidoglycan

A

Pentapeptide bridges that are only found in bacteria consisting of an alternating chain of N-acetlymuramic acid and N-acetylglucosamine connected by a B-1,4 linkage

  • Fnxns to interfere w/ phagocytosis, confer shape, and allow uptake of small molecules along with MDP acting as a pyrogen, somnagen, and adjuvant
  • B-1,4 linkage digested by lysozyme
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7
Q

Sacculus

A

Tetrapeptide linkage of LDL connected to N-acetylmuramic acid

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8
Q

Teichoic Acids

A

Found on gram + bacteria and act as an anchor onto host cells

LTA terminates in a FA

LTA is capable of activating the coagulation cascade BUT CANNOT cause fever
-unlike LPS

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9
Q

LPS

A

Found on gram - bacteria and consists of:

  1. Lipid A (endotoxic activity)
  2. Core (structure)
  3. O antigen (serological ID)

*Promotes synthesis of IL-1, TNF-a and other cytokines along w/ activating the complement and coagulation cascade

=> DIC

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10
Q

Braun lipoprotein

A

Found in gram - bacteria and acts to covalently anchor the outer membrane to peptidoglycan

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11
Q

Omp proteins

A

Proteins found on the outer membrane of gram - cells that fnxn to stabilize the outer membrane

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12
Q

Gram - peptidoglycan

A

Is covalently attached to each other (no pentapeptide bridges) and is more porous than G+; floats in periplasmic space

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13
Q

Periplasmic Space

A

Contains hydrolytic enzymes including collagenases, hyaluronidase, and beta-lactamases all of which are virulence factors

*Helps gram - bacteria resist lysozyme action

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14
Q

Two broad classes of virulence factors

A
  1. Promote colonization and survival in host

2. Exhibit toxicity towards host

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15
Q

Biofilms

A

Dense, multiorganism ayers that adhere a bacteria to a surface

  • E.coli cause cystitis in hospitals via catheters
  • Staph. epidermitis can infect artificial hearts
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16
Q

Adhesins

A

Proteins that promote the binding of a bacteria to the host cell

*Teichoic acids in gram + bacteria

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17
Q

Invasins

A

Bacterial surface proteins that cause rearrangements in the host cells actin skeleton and manipulate their way into the cell

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18
Q

Bacterial Iron Acquisition

3 Mechanisms

A
  1. Siderophores chelate iron and bring it inside the cell
  2. Transferrin receptors
  3. Cytotoxins destroy a cell and retrieve the intracellular Fe3+
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19
Q

Bacterial evasion of Destruction

A
  1. Slime layers composed of polysaccharide evades complement
  2. Antigenic switching in Salmonella
  3. Protein A of S. aureus and Protein G of S. pyogenes bind to Fc portion of Abs rendering them useless
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20
Q

AB Toxins

A

Exotoxins with separate subunits

B- promotes entry into cell

A- kills shit

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21
Q

Hemolysins

A

(Pore Formers)

Lyse cell by permitting rapid H2O entry; often uses cholesterol

OR

Remove phospholipid heads

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22
Q

Embden-Meyehof Pathway

A

Glucose + 2 NAD + 2 ADP + 2 Pi => 2 pyruvate + 2 NADH + 1 FADH2 + 2 ATP

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23
Q

TCA

A

Pyruvate+ 3 NAD + FAD + CoA + GDP + Pi => Acetyl-CoA + 2 CO2 + 3 NADH+ 1 FADH2 + 1 GTP

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24
Q

Lactate dehydrogenase action

A

Pyruvate + NADH => Lactate + NAD

-Regenerates NAD

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25
Q

Alcohol Dehydrogenase Action

A

Pyruvate + CO2 => Acetadelhyde + Ethanol

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26
Q

Toxic Byproduct removal (of bacterial metabolism)

A

Superoxide Dismutase: 2 O2- + 2 H+ => O2 + H2O2

=> Catalase: 2 H2O2 => 2 H2O + O2

OR

Peroxidase: NADH+ H + H2O2 => NAD + 2 H2O

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27
Q

Strict Aerobes

A

Cant make ATP via fermentation

Includes Bacilli, mycobacteria

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28
Q

Strict Anaerobes

A

Lack SOD, Catalase, and Peroxidase

Includes Clostridia

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29
Q

Aerotolerant Anaerobes

A

Lack SOD but use Mn2+ as a radical scavenger

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30
Q

Facultative anaerobes

A

SOD and Catalase produced in presence of O2; can also use fermentation

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31
Q

Microaerophilic Organisms

A

Require low O2 but lack catalase

Includes Camplyobacter

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32
Q

General Secretory System (GSS)

A

Located in cytoplasmic membrane of bacteria and acts to transport materials outside of the cell

*Type III system acts as a molecular syringe and is found in Yersinia and Pseudomonas

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33
Q

Glycerol Transport into bacteria

A

Is transported via facilitated diffusion and then phosphorylated to trap it in the cell

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34
Q

Group Translocation (PTS)

A

Sugar Phosphtransferase System transfer phosphate groups from PEP in the glycolytic cycle to use the energy to bring sugars into the cell

*Also allows the molecule to bypass some steps of glycolysis

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35
Q

Pathogenicity Islands

A

Clusters of genes encoding proteins involved in pathogenesis; same island can be present in different species due to the action of transposons

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36
Q

Quinolones

A

Block the negative supercoiling of bacterial DNA blocking replication and cell growth

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37
Q

Growth Rate Equation

A

b= a X 2^(t/g)

a= # of initial cells; t= total growth time; g= average growth time

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38
Q

DNA-dependent RNA Polymerase

A

Contains:

Sigma subunit- regulates initiation site specificity to holoenzyme @ -10 & -35 positions of the promoter

Rho factor- assists in the termination of genes

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39
Q

Consensus sequence

A

The most frequently found sequence in a bacteria; the more similar the sequence, the better the promoter

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40
Q

Rifampin

A

Binds to the B-subunit of RNAP and inhibits formation of the first phosphodiester bond

*Treats mycobacteria and gram + bacteria

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41
Q

Streptolydigin

A

Binds to the B-subunit of RNAP and blocks elongation

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42
Q

Actinomycin D

A

Binds to double-stranded DNA and blocks movement of RNAP

*Too toxic for clinical use

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43
Q

Translation beginning in bacteria

A

AUG= N-formlymethionine

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44
Q

Shine-Dalgarno Sequence

A

Ribosome binding site that controls the rate of translation initiation

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45
Q

Transpeptidation

A

Transfer of a free amino group to a charged tRNA molecule mediated by peptidyl transferase in the 50s subunit of the ribosome

46
Q

Streptomycin

A

Blocks the assembly of the 70S complex

47
Q

Tetracyclines

A

Blocks binding of charged tRNAs to the A site

48
Q

Chloramphenicol

A

Binds peptidyltransferase and blocks its action

49
Q

Erythromycin

A

Blocks the translocation step of translation

50
Q

Coupling

A

The process of transcription and translation occurring almost simultaneously; can only occur in prokaryotes because???

51
Q

Regulon

A

Structural genes that participate in a single pathway are scattered at different sites in the genome but contain similar controlling elements

52
Q

Polycistronic

A

One continuous mRNA spans over several structural genes and can be translated into several different proteins because ribosomes can bind to internal Shine-Dalgarno sequences

53
Q

lacI

A

repressor protein

54
Q

lacY

A

encodes a permease which permits the uptake of lactose into the cell

55
Q

lacA

A

encodes a transacetylase that will detoxify lactose metabolites

56
Q

P-IIIglc

A

Activates AC under low glucose conditions to create cAMP and induce transcription of lacZYA

57
Q

Two component regulators

A

Used by Bordetella pertussis, BvgS acts as a membrane sensor and phosphorylates BvgA to initiate transcription modifications

58
Q

3 forms of bacterial mutations

A
  1. UV Radiation
  2. Spontaneous mutations
  3. Chemical mutations
59
Q

UV Radiation

A

Causes the formation of 5.6 cyclobutane or 6-4 photoproducts

60
Q

Base analogs

A

A form of chemical mutation where 2-AP is formed instead of A and binds w/ Cytosine OR 5-bromouracil is formed instead of T and binds w/ Guanine

61
Q

Base modification

A

Can occur via oxidative deamination which causes C > T mutation

*Important because C is the target in bacterial DNA methylation to distinguish own DNA

62
Q

Alkylation

A

Mutation caused by mustard gas and causes kinks to be formed in the DNA helix

63
Q

Reactive Oxygen

A

Most mutagenic lesion is 8-oxo guanine which pairs w/ A instead of C

Formed due to UV radiation

64
Q

Intercalators

A

Large, flat molecules that slide in b/w base pairs and cause insertions/deletions

*Includes aflatoxin

65
Q

Aflatoxin

A

Popular intercalator that can be modified by cytochrome P450 to form toxic epoxides

66
Q

Photoreactivation

A

Absorbance of UV radiation activates photolyase and repairs cyclobutane dimers

67
Q

Nucleotide Excision

A
  1. UvrA and UvrB binds to DNA and scans for damage
  2. Uvr-complex detects damage and stops
  3. UvrC binds to UvrB and nicks the DNA helix downstream; UvrB nicks it upstream
  4. UvrD separates the damaged DNA and removes it
  5. DNA Polymerase I and DNA ligase replace the removed DNA
68
Q

SOS Inducible Repair System

A
  1. Cells received heavy UV radiation and activate RecA
  2. RecA triggers the cleavage of LexA which is constituently bound to DNA
  3. UmuC and UmuD now free to activate DNA Polymerase III and replicate DNA in a really shitty fashion
69
Q

3 Types of Transposons

A
  1. Insertion sequence elements
  2. Composite Transposons
  3. T2A family
70
Q

Composite Transposons

A

Has a central region flanked by insertion sequence elements on the left and right; central region is gene for antibiotic resistance

71
Q

TnA transposons

A

Contains resolution site and resolvase enzyme that mediate the specific recombination of transposons; also has inverted repeats at the ends and a transposase enzyme

  • utilize Replicative transposition
  • Tn3=ampicillin resistance
72
Q

Replicative Transposition

A

DNA strand is nicked at one strand and the free ends are reconnected to the target DNA; the transposon is then replicated

*This allows a copy of the transposon to remain in the donor DNA

73
Q

Site-specific recombination

A

If repeats are in same direction (tandem), recombination will delete the sequence

If repeats are in opposite direction, recombination will invert the sequence in between

74
Q

Phage DNA Replication

A
  1. ”+” strand is used as a template to create a “-“ strand
    • RF is now created
  2. Phage II Gene product acts as an endonuclease and nicks the “+” strand
  3. Phage begins rolling circle replication and cuts off the product at the end of one rotation
  4. Phage coat proteins bind to the pac site to pack the DNA into a new phage
75
Q

Lamda Phage DNA Replication

A
  1. Lambda phage genome is linear-double stranded DNA but when injected into the bacteria, it becomes circular by joining at “cos” sites
  2. Circular DNA undergoes theta replication in which replication proceeds in two directions
  3. Later switches to rolling circle replication to produce DNA of tandem repeats
    • concatemers*
  4. Concatemers are cut at the cos site to generate single DNA copy for packaging
    • DNA has returned to linear form for packaging
76
Q

T4 Phage DNA Synthesis

A

T4 exists as linear, double-stranded DNA WITHOUT cos sites

=>Replication begins at multiple origins and eventually forms concatemers via homologous recombination

*Utilizes headfull packaging more likely to contain DNA for genetic exchange with bacterial host

77
Q

Lysogen

A

Bacterium that harbors a prophage

*Looks like a fried-egg on a growth plate

78
Q

CII

A

CII is produced until there is an adequate amount when CI and integrase take over; CII promotes the lytic cell cycle

79
Q

CI

A

Produced when adequate CII has been made; contains a dimerization domain to suppress the fnxn of lytic genes and a DNA binding domain

80
Q

Integrase

A

Mediates the recombination of phage DNA w/ the host chromosome by attaching at attP and attB

81
Q

Lysogenic Conversion

A

Bacterium that become superimmune to phage infection due to the prophage genes that have been transmitted to the lysogen

*e.g. cholera toxin

82
Q

Lytic Conversion of prophage

A

RecA binds to CI and triggers autocleavage

-Derepresses the expression of lytic genes

83
Q

Excisase

A

Allows the prophage to be excised from the host chromosome and returns the phage DNA to circular DNA form

*Process also utilizes integrase

84
Q

Generalized Transduction

A

Phages degrade host DNA into small fragments and pack new phage DNA WITH some host DNA; phages then will inject old hosts DNA into new host DNA

85
Q

What makes a phage a transducing phage?

A
  1. Cannot cause complete degradation of host DNA

2. Must have low sequence specificity for packing DNA into its head

86
Q

Specialized Transduction

A

When the prophase is excised from the host, chromosome recombination may take place b/w phage and bacterial DNA instead of at hybrid attachment sites; host DNA with sequences close to the attachment sites are more likely to be transferred

87
Q

Conjugation

A

Transfer of DNA to a recipient cell via a plasmid trasmitted by a sex/F pilus

Endonuclease cuts at the Ori-T site and the DNA is rolled into the donor cell

  • Meanwhile, both sides of the nick are being replicated
  • Strand is cut in the middle of the DNA being transfered
88
Q

F plasmid

A

Self-transmissable that includes genes for pilus, helicase, and primase

*Must help mobilizable plasmids when necessary

89
Q

F plasmid transfer

A
  1. Endonuclease cuts at oriT sige
  2. Helicase unwinds the plasmid DNA
  3. Strand w/ nick is transferred via the sex pilus; complementary strands for both the donor and recipient DNA begin to be synthesized
90
Q

Transconjugant

A

Cell that receives an F plasmid after conjugation

91
Q

Hfr

A

Bacterial strain containing an integrated F plasmid in the bacterial chromosome (usually exists as an episome)

*Genes closer to the oriT site are more likely to be transferred

92
Q

F’ plasmid

A

“Prime Factor”

Give rise to recombinant strains when homologous recombination b/w IS1 and F plasmid occurs; bacterial DNA is then transferred later

93
Q

R plasmid

A

Large plasmid associated with multiple antibiotic resistance genes; exists due to transposon-mediated recombination

94
Q

Transformation

A

Uptake of naked DNA by a bacterial cell; does not require a phage or plasmid

95
Q

Transfection

A

Process of eukaryotic cells uptaking naked DNA

96
Q

Competence

A

The ability of a bacteria to uptake naked DNA; appears late in the growth cycle

Can be induced in two ways:

  1. Calcium phosphate treatment
  2. Electroporation
97
Q

Limitations to Koch’s postulates

A
  1. Human susceptibility to disease varies
  2. Some bacteria are not as easily cultured as others
  3. Late onset of growth
  4. Virulence can vary within some species
  5. Ethical considerations of postulate 3
  6. Polymicrobial diseases
98
Q

Viroids

A

Organisms that consist of RNA only; delta Hepatitis

99
Q

Metro diploid

A

Partial diploid state in a bacterium resulting from transfer of some bacterial material

100
Q

Homologous Replication

A

A single-stranded DNA is generated which invades a DNA duplex and forms a Holiday Junction

=>Homologous recombination b/w genetic material then occurs

101
Q

Insertion Sequence Elements

A

Transposons containing only the genes necessary for transposition

Bracketed by repeat sequences of the host DNA

102
Q

Resolvase

A

Enzyme required for the Replicative transposition of TnA transposons

103
Q

Antigenic expression in Salmonella

A

Hin invertase moves the promoter away from the H2 gene and activates expression of its repressor

=>Expression of H1 Gene

104
Q

What Phages have no Lytic cycle?

A

Filamentous Phages

105
Q

Cro

A

A gene whose expression is induced after RecA cleaves CI during radiation damage in a lysogen

=>Inhibits expression of CI causing the lytic cycle to occur

*Excisase and Integrase also now expressed to excise phage DNA from the lysogen

106
Q

Lipofuscin

A

“Brown Atrophy”

Undigested lipid molecules that appear in dying cells

107
Q

Cardinal sign of coagulation necrosis

A

Eosinophilic cytoplasm

*Fibrinoid necrosis can also appear this way but more smudgy

108
Q

Shock-sensitive Activve transport mechanism

A

Sensitive to osmotic shock; cannot transport galactose across with carrier protein in the periplasm

109
Q

Cardiac Hypertrophy

A

Shows increased ANP; myosin heavy chain is replaced with B-chain which produces slower, more favorable contractions

110
Q

Mitochondrial apoptosis pathway

A

Inhibited by Bcl; triggered by the loss of survival signals

POD (4 decks)

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