Microbiology Flashcards
(110 cards)
1
Q
Peritrichous
A
Many flagella located randomly all around a cell
2
Q
Endospores
A
Heat-resistant cells rich in calcium dipicolinate that can germinate into growing cells during adverse conditions
3
Q
Plasma membrane
A
Inner membrane where the respiratory chain is found and phospholipids, LPS, and capsular polysaccharides are formed
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
5
Q
Lophotrichous
A
Many flagella located at one end of a bacterium
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
7
Q
Sacculus
A
Tetrapeptide linkage of LDL connected to N-acetylmuramic acid
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
9
Q
LPS
A
Found on gram - bacteria and consists of:
- Lipid A (endotoxic activity)
- Core (structure)
- O antigen (serological ID)
*Promotes synthesis of IL-1, TNF-a and other cytokines along w/ activating the complement and coagulation cascade
=> DIC
10
Q
Braun lipoprotein
A
Found in gram - bacteria and acts to covalently anchor the outer membrane to peptidoglycan
11
Q
Omp proteins
A
Proteins found on the outer membrane of gram - cells that fnxn to stabilize the outer membrane
12
Q
Gram - peptidoglycan
A
Is covalently attached to each other (no pentapeptide bridges) and is more porous than G+; floats in periplasmic space
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
14
Q
Two broad classes of virulence factors
A
- Promote colonization and survival in host
2. Exhibit toxicity towards host
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
16
Q
Adhesins
A
Proteins that promote the binding of a bacteria to the host cell
*Teichoic acids in gram + bacteria
17
Q
Invasins
A
Bacterial surface proteins that cause rearrangements in the host cells actin skeleton and manipulate their way into the cell
18
Q
Bacterial Iron Acquisition
3 Mechanisms
A
- Siderophores chelate iron and bring it inside the cell
- Transferrin receptors
- Cytotoxins destroy a cell and retrieve the intracellular Fe3+
19
Q
Bacterial evasion of Destruction
A
- Slime layers composed of polysaccharide evades complement
- Antigenic switching in Salmonella
- Protein A of S. aureus and Protein G of S. pyogenes bind to Fc portion of Abs rendering them useless
20
Q
AB Toxins
A
Exotoxins with separate subunits
B- promotes entry into cell
A- kills shit
21
Q
Hemolysins
A
(Pore Formers)
Lyse cell by permitting rapid H2O entry; often uses cholesterol
OR
Remove phospholipid heads
22
Q
Embden-Meyehof Pathway
A
Glucose + 2 NAD + 2 ADP + 2 Pi => 2 pyruvate + 2 NADH + 1 FADH2 + 2 ATP
23
Q
TCA
A
Pyruvate+ 3 NAD + FAD + CoA + GDP + Pi => Acetyl-CoA + 2 CO2 + 3 NADH+ 1 FADH2 + 1 GTP
24
Q
Lactate dehydrogenase action
A
Pyruvate + NADH => Lactate + NAD
-Regenerates NAD
25
Alcohol Dehydrogenase Action
Pyruvate + CO2 => Acetadelhyde + Ethanol
26
Toxic Byproduct removal (of bacterial metabolism)
Superoxide Dismutase: 2 O2- + 2 H+ => O2 + H2O2
=> Catalase: 2 H2O2 => 2 H2O + O2
OR
Peroxidase: NADH+ H + H2O2 => NAD + 2 H2O
27
Strict Aerobes
Cant make ATP via fermentation
Includes Bacilli, mycobacteria
28
Strict Anaerobes
Lack SOD, Catalase, and Peroxidase
Includes Clostridia
29
Aerotolerant Anaerobes
Lack SOD but use Mn2+ as a radical scavenger
30
Facultative anaerobes
SOD and Catalase produced in presence of O2; can also use fermentation
31
Microaerophilic Organisms
Require low O2 but lack catalase
Includes Camplyobacter
32
General Secretory System (GSS)
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
33
Glycerol Transport into bacteria
Is transported via facilitated diffusion and then phosphorylated to trap it in the cell
34
Group Translocation (PTS)
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
35
Pathogenicity Islands
Clusters of genes encoding proteins involved in pathogenesis; same island can be present in different species due to the action of transposons
36
Quinolones
Block the negative supercoiling of bacterial DNA blocking replication and cell growth
37
Growth Rate Equation
b= a X 2^(t/g)
a= # of initial cells; t= total growth time; g= average growth time
38
DNA-dependent RNA Polymerase
Contains:
Sigma subunit- regulates initiation site specificity to holoenzyme @ -10 & -35 positions of the promoter
Rho factor- assists in the termination of genes
39
Consensus sequence
The most frequently found sequence in a bacteria; the more similar the sequence, the better the promoter
40
Rifampin
Binds to the B-subunit of RNAP and inhibits formation of the first phosphodiester bond
*Treats mycobacteria and gram + bacteria
41
Streptolydigin
Binds to the B-subunit of RNAP and blocks elongation
42
Actinomycin D
Binds to double-stranded DNA and blocks movement of RNAP
*Too toxic for clinical use
43
Translation beginning in bacteria
AUG= N-formlymethionine
44
Shine-Dalgarno Sequence
Ribosome binding site that controls the rate of translation initiation
45
Transpeptidation
Transfer of a free amino group to a charged tRNA molecule mediated by peptidyl transferase in the 50s subunit of the ribosome
46
Streptomycin
Blocks the assembly of the 70S complex
47
Tetracyclines
Blocks binding of charged tRNAs to the A site
48
Chloramphenicol
Binds peptidyltransferase and blocks its action
49
Erythromycin
Blocks the translocation step of translation
50
Coupling
The process of transcription and translation occurring almost simultaneously; can only occur in prokaryotes because???
51
Regulon
Structural genes that participate in a single pathway are scattered at different sites in the genome but contain similar controlling elements
52
Polycistronic
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
lacI
repressor protein
54
lacY
encodes a permease which permits the uptake of lactose into the cell
55
lacA
encodes a transacetylase that will detoxify lactose metabolites
56
P-IIIglc
Activates AC under low glucose conditions to create cAMP and induce transcription of lacZYA
57
Two component regulators
Used by Bordetella pertussis, BvgS acts as a membrane sensor and phosphorylates BvgA to initiate transcription modifications
58
3 forms of bacterial mutations
1. UV Radiation
2. Spontaneous mutations
3. Chemical mutations
59
UV Radiation
Causes the formation of 5.6 cyclobutane or 6-4 photoproducts
60
Base analogs
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
Base modification
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
Alkylation
Mutation caused by mustard gas and causes kinks to be formed in the DNA helix
63
Reactive Oxygen
Most mutagenic lesion is 8-oxo guanine which pairs w/ A instead of C
Formed due to UV radiation
64
Intercalators
Large, flat molecules that slide in b/w base pairs and cause insertions/deletions
*Includes aflatoxin
65
Aflatoxin
Popular intercalator that can be modified by cytochrome P450 to form toxic epoxides
66
Photoreactivation
Absorbance of UV radiation activates photolyase and repairs cyclobutane dimers
67
Nucleotide Excision
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
SOS Inducible Repair System
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
3 Types of Transposons
1. Insertion sequence elements
2. Composite Transposons
3. T2A family
70
Composite Transposons
Has a central region flanked by insertion sequence elements on the left and right; central region is gene for antibiotic resistance
71
TnA transposons
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
Replicative Transposition
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
Site-specific recombination
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
Phage DNA Replication
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
Lamda Phage DNA Replication
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
T4 Phage DNA Synthesis
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
Lysogen
Bacterium that harbors a prophage
*Looks like a fried-egg on a growth plate
78
CII
CII is produced until there is an adequate amount when CI and integrase take over; CII promotes the lytic cell cycle
79
CI
Produced when adequate CII has been made; contains a dimerization domain to suppress the fnxn of lytic genes and a DNA binding domain
80
Integrase
Mediates the recombination of phage DNA w/ the host chromosome by attaching at attP and attB
81
Lysogenic Conversion
Bacterium that become superimmune to phage infection due to the prophage genes that have been transmitted to the lysogen
*e.g. cholera toxin
82
Lytic Conversion of prophage
RecA binds to CI and triggers autocleavage
-Derepresses the expression of lytic genes
83
Excisase
Allows the prophage to be excised from the host chromosome and returns the phage DNA to circular DNA form
*Process also utilizes integrase
84
Generalized Transduction
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
What makes a phage a transducing phage?
1. Cannot cause complete degradation of host DNA
| 2. Must have low sequence specificity for packing DNA into its head
86
Specialized Transduction
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
Conjugation
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
F plasmid
Self-transmissable that includes genes for pilus, helicase, and primase
*Must help mobilizable plasmids when necessary
89
F plasmid transfer
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
Transconjugant
Cell that receives an F plasmid after conjugation
91
Hfr
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
F' plasmid
"Prime Factor"
Give rise to recombinant strains when homologous recombination b/w IS1 and F plasmid occurs; bacterial DNA is then transferred later
93
R plasmid
Large plasmid associated with multiple antibiotic resistance genes; exists due to transposon-mediated recombination
94
Transformation
Uptake of naked DNA by a bacterial cell; does not require a phage or plasmid
95
Transfection
Process of eukaryotic cells uptaking naked DNA
96
Competence
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
Limitations to Koch's postulates
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
Viroids
Organisms that consist of RNA only; delta Hepatitis
99
Metro diploid
Partial diploid state in a bacterium resulting from transfer of some bacterial material
100
Homologous Replication
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
Insertion Sequence Elements
Transposons containing only the genes necessary for transposition
Bracketed by repeat sequences of the host DNA
102
Resolvase
Enzyme required for the Replicative transposition of TnA transposons
103
Antigenic expression in Salmonella
Hin invertase moves the promoter away from the H2 gene and activates expression of its repressor
=>Expression of H1 Gene
104
What Phages have no Lytic cycle?
Filamentous Phages
105
Cro
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
Lipofuscin
"Brown Atrophy"
Undigested lipid molecules that appear in dying cells
107
Cardinal sign of coagulation necrosis
Eosinophilic cytoplasm
*Fibrinoid necrosis can also appear this way but more smudgy
108
Shock-sensitive Activve transport mechanism
Sensitive to osmotic shock; cannot transport galactose across with carrier protein in the periplasm
109
Cardiac Hypertrophy
Shows increased ANP; myosin heavy chain is replaced with B-chain which produces slower, more favorable contractions
110
Mitochondrial apoptosis pathway
Inhibited by Bcl; triggered by the loss of survival signals
