Micro Flashcards
1
Q
What are the human to human routes of transmission?
A
Respiratory
Fecal-oral
Venereal
2
Q
What are the human to vertebrate routes of transmission?
A
Vector (biting arthropod)
Vertebrate reservoir
Vector-vertebrate reservoir
3
Q
What are the benefits of the normal flora?
A
Vitamin K
Occupy niche
Bacteriocidins
Stimulate immune
4
Q
What tissues are sterile?
A
Blood
Alveoli
Muscle
5
Q
What are sources of compromise that lead to an opportunistic infection?
A
Age Cancer Nutritional status Inherited immune deficiencies HIV
6
Q
What are Koch’s postulates?
A
Bacterium in all people who have disease Isolate Inoculate susceptible human Reproduce disease Reisolate and match
7
Q
What are the limitations to Koch’s postulates?
A
Human susceptibility may be inherited Slow viruses Hard to culture Virulence can vary Ethics Diseases caused by multiple pathogens
8
Q
What are two kinds of fungi and how do they differ?
A
Yeasts are unicellular
Molds are multicellular
9
Q
What is the difference between lytic cycle and a latent infection?
A
Lytic-replicate and released by lysing cell
Latent-replication of a small number of viruses
10
Q
What are the characteristics of prokaryotes?
A
No nuclear membrane Binary fission Limited repeat/few introns 70S ribosomes Translation-fmet
11
Q
What are the characteristics of eukaryotes?
A
Membrane bound nucleus mitotic apparatus repeated DNA/introns 80S ribosomes Translation-met
12
Q
What is the difference between prions and viroids?
A
prions-protein only
-Mad Cow, Scrapie, Creutzfeldt-Jakob disease
viroids-RNA only
-mostly plants
13
Q
What are virulence factors?
A
components of a bacterial cell or virus that enhances its ability to cause disease
14
Q
What is a flagella and what is it made from?
A
movement
made from flagellin
15
Q
What are pili and what is it made from?
A
adherence or conjugation
made from pilins
16
Q
What is a capsule and what is unique about anthrax capsules?
A
confers resistance to phagocytosis
made of polysaccharide
anthrax-polypeptide
17
Q
What are cytoplasmic inclusion bodies?
A
sites where nutrient macromolecules are located-energy storage
18
Q
What are endospores?
A
heat resistant can undergo sporulation during nutrient starvation
wall made of calcium dipicolinate
19
Q
What happens during a Gram stain?
A
dye with purple
add mordant (Gram’s iodine)
wash with alcohol
counter stain
20
Q
What is the purpose of the alcohol?
A
dehydrates the peptidoglycan layer-more collapse in Gram positive to trap the stain
21
Q
What is the structure of peptidoglycan?
A
glycan polymers crosslinked by peptide chains
glycan alternates M-G with beta 1,4 linkages
peptide chains coupled to M
pentapeptide bridges (glycine) only present in gram positives
tetrapeptides covalently linked to glycan backbones (AGLA–>3 to 4)
22
Q
What is teichoic acid? What is lipoteichoic acid?
A
anchors polysaccharides
polymers of ribitol phosphate or glycerol phosphate covalently linked to peptidoglycan phosphodiester linkages
surface antigens
23
Q
What is the significance of muramyl dipeptide?
A
produce of peptidoglycan degradation adjuvant mitogen pyrogen somnagen
24
Q
Where is LPS located and what is it?
A
located in outer membrane of gram negative covalent links between three sections -lipid A-endotoxic -core-polysaccharide with KDO -O antigen-serotyping
25
What is the endotoxic portion of LPS and what are the effects?
```
lipid A-->induces IL1 and TNF
sleep
fever
leukopenia
hypoglycemia
hypotension and shock
coagulation
```
26
How can you differentiate between LPS and LTA?
LTA causes coagulation but not fever
27
What are porins?
proteins that allow passive diffusion of small (less than 600 MW) charged molecules
only found in outer membrane of G-
28
What is Braun lipoprotein?
anchors outer membrane to peptidoglycan
| inner leaflet to outer membrane
29
What are Omp proteins?
stabilize the outer membrane and act as receptors
30
How does peptidoglycan differ in a gram negative cell?
only 1-2 layers
no pentapeptide glycine bridge
crosslinked via covalent bond between terminal D-ala to lysine of another tetrapeptide
31
What is located in the periplasmic space?
hydrolytic enzymes including proteases, lipases, nucleases, and components of sugar transport system
32
How can bacteria be classified?
```
structure
biochemical typing
serotyping
phage typing
genotyping
```
33
What is the most important method for phylogenetic analysis?
16S rRNA how closely related organisms are
34
How do pili contribute to adherence?
binding to receptor-either glycoprotein or glycolipid
35
How do adhesins contribute to adherence?
teichoic acids in gram positive
| f protein binding to fibronectin
36
What are biofilms?
dense, multiorganism layers on surface
37
How can bacteria invade?
invasins-rearrange actin cytoskeleton
38
What are siderophores?
chelate iron effectively
receptors for transferrin
cytotoxins-damage/kill host cells
39
How can bacteria evade the immune system?
capsules
complement
antigenic switching-H1/H2
40
What are exotoxins?
secreted, located in periplasm of gram negative
41
How does the diptheria toxin work?
ADP-ribosylates host EF-2 protein and shuts down protein synthesis
42
What are cytolysins?
allow water to enter and lyse cell
43
What are phospholipases?
destabilize by cleaving charged heads
44
What are the components of the cell envelope?
plasma membrane+cell wall+intervening material
45
Where is the tetrapeptide linked?
carboxyl group of M of glycan
46
What is the sacculus?
covalent linkage between tetrapeptides allows glycan backbones to be linked together
47
What does lysozyme cleave?
Beta 1,4 linkages
48
How do bacteria replicate?
binary fission
49
What are the basic nutrient requirements?
```
glucose
NH4
Mg
Mn
SO4
PO4
```
50
What are chemoorganotrophs?
all human pathogens are chemoorganotrophs
| use glucose, other sugars, aromatics, and organic polymers for carbon and energy
51
What is fermentation?
glycolytic pathway and NAD regeneration (through either lactate or ethanol)
substrate level phosphorylation occurs here
provides intermediates for amino acid, nucleotide
52
Why is the TCA important?
generates 4 and 5 carbon intermediates for biosynthetic reactions and reduced NAD/FAD
provides intermediates for amino acid, nucleotide
53
What is important about the electron transport chain?
more efficient ATP generation
54
What are prototrophs?
no requirements beyond simple carbon, nitrogen and sulfure
55
What are auxotrophs?
organisms that require molecules to be added for growth
56
How can oxygen be toxic?
final acceptor of electrons in oxidative phosphorylation
can produce superoxide, hydroxyl radical, hydrogen peroxide, hydroxide ion
byproducts can kill cells
57
How can cells remove toxic oxygen?
catalase (H2O2-->H2O+O2)
superoxide dismutase (forms H2O2)
peroxidase requires organic electron receptor
58
What are strict aerobes?
require oxygen
| have SOD and catalase
59
What are strict anaerobes?
fermentative
| lack SOD and catalase
60
What are aerotolerant anaerobes?
fermentative
| can scavenge radicals with Mn
61
What are facultative anaerobes?
can produce ATP via oxidative phosphorylation or fermentation
can induce SOD and catalase
62
What are mcroaerophilic organisms?
require low O2 and generate via oxidative phosphorylation but lack catalase
63
What is the general secretory system?
transports proteins to gram positive extracellular or periplasm of gram negative
64
What are sec independent pathways?
multiprotein complexes that span the inner and outer membrane (type III acts like a syringe)
65
What are exozymes?
virulence factors that help an organism invade, colonize, multiply, or cause disease
66
What is facilitated diffusion and what is an example?
mediated by protein, energy independent
| glycerol-ATP phosphorylates to help efficiently trap it in the cell
67
What is proton gradient active transport?
energy from pumping of protons
| uses more energy than group translocation
68
What is ATP dependent active transport?
galactose-shock sensitive because protein is in periplasm
| more energy than group translocation
69
What is group translocation?
complex of phosphotransferase proteins that transfer phosphate group from PEP to sugar
functions as regulator of glucose effect
70
What are examples of siderophores?
enterobactin and hydroxamate-bind iron and transport into cell
serve as a virulence factor
71
How doe supercoiling impact replication?
negative superhelicity means bacteria DNA can convert to a molecule with unwound helical regions
72
How are replication and cell division coordinated?
initiation of chromosome replication coincides with septum formation
73
What are the sigma factor and rho proteins?
sigma-initiation site specificity (-10 and -35)
| rho-termination
74
What is the consensus sequence?
sequence found most frequently
| weak promoters may require activator proteins
75
How does Rifampin work?
binds to RNAP and inhibits the formation of the first phosphodiester bond-treat mycobacteria and gram positive
76
How does Streptolydigin work?
blocks elongation
77
How does Actinomycin D work?
blocks movement of RNAP, used in cancer therapy
78
What is the function of the 50S subunit?
peptide bond formation
79
What does 23S do?
ribozyme-peptidyltransferase
| responsible for transpeptidation
80
What does 30S do?
initiation and site for tRNA binding
81
What do all proteins start with?
f-met
82
What are the stop codons?
UAG, UAA, UGA
83
What controls the rate of translation initiation?
sequence in 5' UTR called the Shine-Dalgarno sequence
| complementary between 16S rRNA sequence
84
How does streptomycin work?
block assembly of 70S initiation complex and cause misreading
85
How does tetracycline work?
blocks binding of charged tRNAs to acceptor site
86
How does chloramphenicol work?
binds peptidyltransferase and blocks reaction
87
How does erythromycin work?
blocks translocation step
88
How can gene expression be controlled?
```
gene copy number
transcription initiation
mRNA stability
translation initiation
protein stability
```
89
What is an operator?
location where regulatory proteins like repressors bind
90
What is diauxic growth?
sequential growth
| bacteria preferentially use glucose and then will adjust to lactose when glucose has been depleted
91
What is negative inducible control?
inactivation of repressor
92
What is negative repressible control?
activates repressor
93
What is positive inducible control?
activates activator
94
What is positive repressible control?
inactivates activator
95
What happens to the lac operon in the presence of glucose?
no transcription
repressor bound
low cAMP
IIIGlc stops transport of sugars
96
What happens to the lac operon in the presence of lactose?
allolactose changes repressor (unbound)
high PIIIGlc leads to high cAMP (transport of sugars not inhibited)
cAMP activates the activator (CAP)
97
What happens to the lac operon in the presence of lactose and glucose?
allolactose changes repressor so it is unbound
| IIIGlc stops transport of sugar (activator is not activated-low cAMP)
98
How do two component regulators work?
first component senses environment-can be a protein kinase
| second component-transcriptional activator
99
What is quorum sensing?
genes activated when concentration of bacteria reaches a threshold
100
What is global regulation?
regulation of multiple metabolic pathways by single regulator
101
What is a bacteriophage? What are the components?
virus that infects bacteria
nucleic acid-ss or ds, RNA or DNA
capsid of proteins
102
What does phage lambda infect?
E. coli
103
What does P22 infect?
Salmonella
104
How does T1 infect?
tonB receptor (enterochelin receptor)
105
How does lambda infect?
maltose binding protein
106
How does MS2 infect?
sides of flagella
107
How does F1 infect?
tip of the flagella
108
How does the chromosome circularize?
binding at the cohesive ends (cos sites)
109
How does a lytic virus replicate? What is formed?
rolling circle mechanism
| forms concatamers
110
How does a lysogenic virus integrate?
reciprocal recombination at attachment sites (att)
111
How can a lysogenic virus switch to lytic?
mutation leads to activation of recA to cleave the repressor
112
How does cholera become virulent?
presence of CTX phage
113
How does diptheria become virulent?
prophage B toxin
114
What is a meroploid?
partially diploid organism
115
What is complementation analysis?
mutation in two genes
if mutation phenotype persists-same gene
if normal phenotype-different genes (intergenic complementation occurred)
116
What is transformation?
uptake of naked DNA into a cell followed by recombination or replication
117
What determines whether the DNA will recombine or replicate?
homology to genome
118
What is transduction?
transferring of host DNA to recipient by bacteriophage
119
What is generalized transduction?
mistakenly packages host DNA
120
What is specialized transduction?
leaves some of its DNA and takes some host DNA because adjacent region was excised imprecisely
121
What is conjugation?
transfer of DNA from one bacterial cell of one mating type to another
122
What is the F+ plasmid?
self replicating plasmid
123
What is the Hfr chromosome?
integrate, mediated by IS regions (homology)
| genes near integration are transferred at a high frequency
124
What is a F' plasmid?
excise imprecisely from Hfr chromosome and take bacteria with it
125
What is type I excision?
portion of F left behind and portion of bacteria taken instead
126
What is type II excision?
portion of bacteria taken in addition to the full F plasmid
127
What is the R plasmid? What is an example of acquiring antibiotic resistance?
R plasmid confers resistance to antibiotics
| MRSA gaining vancomycin resistance associated with enterococcus faecalis
