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fundamentals > Microbiology II > Flashcards

Microbiology II Flashcards

1
Q

what do bacteria bind to on phagocytes?

A

TLR-2, TLR-4

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2
Q

what do macrophages secrete when bacterial bind to toll-like receptors?

A

TNFalpha, IL-1beta, and IL-6

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3
Q

how do neutrophils take up bacteria?

A

they are signaled by binding of C3b or antibodies (IgG, IgM) via Fc Receptor

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4
Q

describe Gram negative bacteria in terms of bacteriolysis

A

you CAN for MAC - can have bacteriolysis via alternative and classical complement pathways

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5
Q

describe Gram positive bacteria in terms of bacteriolysis

A

cannot form MAC complex (because don’t have that second plasma membrane) and therefore can only have bacteriolysis via alternative pathway

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6
Q

how do immune cells kill bacteria?

A

NETs, degranulation, ROS

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7
Q

what is in phagocytic granules?

A

lysozyme, serine proteases (elastase, cathepsin G, lactoferrin, anitmicrobial peptides)

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8
Q

what are two enzymes that create ROS?

A

NADPH oxidase, myeloperoxidase

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9
Q

what is Chedial Higashi syndrome?

A

defective phagocytic degranulation

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10
Q

what is part of CGD (chronic granulomatous disease)?

A

you have defective NAPDH oxidase and cannot make ROSs

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11
Q

what type of environment do we get ROS formation?

A

aerobic only, not really in anaerobic or if there is decreased blood flow to the affected area

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12
Q

what are some bacterial defenses to immune cells?

A

capsule blocks C3b deposition
antiphagocytic proteins block C3b deposition
ROS neutralizers - SOD, catalase, peroxidase
LPS blocks antimicrobial peptides (specifically acyl chains on Lipid A)
Efflux pumps pump out antibiotics or antimicrobial peptides
bacterial surface charge and DNAses protect from NETs

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13
Q

NETs?

A

Neutrophil Extracellular Traps

they release granules as well as DNA bound to histones via ETosis pathway

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14
Q

how do antibodies act against bacteria?

A

cause agglutination, block adherence (colonization), neutralize toxins, opsonize, activate classical pathway for complement

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15
Q

how do bacteria evade antibody complement mediated bacteriolysis?

A

molecular mimicry, antigenic variation of target surface during infection, surface molecules bind to C4BP - a negative regulator of classical pathway

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16
Q

what binds to TLR?

A

LPS, techoic acid, peptidoglycan, lipoproteins, flagella

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17
Q

what do encapsulated bacteria cause?

A

miningitis, pneumonia, systemic blood infections via bloodstream or lymphatic dissemination

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18
Q

what do antiphagocytic proteins block?

A

they reduce opsonization by binding soluble negative regulators called factor H and factor HL-1 (i.e. they basically downregulate the complement pathway by stimulating these factors)
it accelerates decay of the alternative pathway C3 convertase
it acts as a cofactor for factor I-mediated degradation of C3b

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19
Q

what about capsules helps protect bacteria?

A

they are negatively charged so they bind positively to antimicrobial peptides, preventing them from contacting the bacterial membrane (LPS does the same because it is negative)

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20
Q

what is Gram Negative toxic shock?

A

caused by LPS (endotoxin) systemic exposure which leads to cardiovascular shutdown
get edema because of all of the TNF excreted which leads to systemic vascular permeability

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21
Q

what is continuous septicemia?

A

primarily in patients with intravascular infection

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22
Q

what is intermittent septicemia?

A

primarily in patients with infections

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23
Q

what is Gram Positive septic shock?

A

host responds to peptidoglycan or teichoic acids that leads to sepsis by binding to TLR-2

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24
Q

what are the three methods of bacterial gene transfer?

A

conjugation, transduction, transformation

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25
Q

what is required for DNA to be stably inherited?

A

ORI needs to be included and if not then homologous recombination needs to occur

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26
Q

what are the three types of recombination?

A

homologous recombination, site specific, and transposition

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27
Q

what is homologous recombination?

A

when a free homologous sequence is recombined to its homologue in the bacterial genome

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28
Q

what enzyme is needed for homologous recombination?

A

RecA

*remember holliday junctions

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29
Q

what is site specific recombination?

A

specific sites in the chromosome accept new DNA - these are break points

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30
Q

what enzyme is required for site specific recombination?

A

integrases

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31
Q

what is transposition?

A

you move transposable elements into non-specific sites

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32
Q

what enzyme deals with transposition?

A

transposases

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33
Q

what is transformation?

A

picking up naked DNA

requirements: dsDNA, have competence, recombinaiton must occur

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34
Q

how do you get competence to be transformed?

A

you experience evironmental stress

35
Q

describe the mechanism for taking DNA into the bacterial cell?

A

DNA binds to an extracellular receptor and is threaded through complex where it loses one strand
the remaining strand is bound by ssb’s and then RecA mediates the movement of DNA to the chromosome (does homologous recombination)

36
Q

what is transduction?

A

it is mediated by a bacteriophage that accidentally puts bacterial DNA into its capsid and then infects other bacterial cells with it

generalized: takes up loose bacterial genes
specialized: improper excision of viral DNA taking some

37
Q

what are lytic early genes?

A

make enzymes for DNA synthesis and then replicate their own genome

38
Q

what are lytic late genes?

A

make heads, tails so DNA can be packaged up and eventually cause cell lysis

39
Q

what does it mean when a bacteria is resistant to phage?

A

it doesnt have the right phage receptor proteins

40
Q

what are the enzymes produced by viruses that cause lysis?

A

lysozyme, lysin

41
Q

what method of recombination do phages use to integrate into genome?

A

site specific recombination

42
Q

what genes are expressed during viral lysogeny?

A

only phage repressor gene is transcribed
phage replication genes are turned off
the repressor gene is a cytoplasmic protein and prevents other phages from infecting the cell and represses the transcription of own gene
(this is the product of the C1 gene)

43
Q

how does the lysogenic virus get induced again?

A

RecA detects DNA damage and binds to ssDNA which then cleaves the repressor proteins, the genes that were previously repressed not are expressed and cause lytic cycle to commence; get reversal of site specific recombination

44
Q

what is conjugation?

A

when cell-to-cell contact and formation of pili leads to movement of DNA into one bacterial cell from another
requires the F plasmid gene that allows for creating of pilus

45
Q

what does conjugated DNA need to have?

A

F pilu gene, origin of transfer gene, origin of replication gene, IS elements (insertion sequence)

46
Q

what is it called when you have integration of new DNA into host chromosome via conjugation?

A

Hfr (high frequency recombination)

47
Q

describe the sequence of conjugation.

A

form pilus, retract pilus to bring close, cytoplasms fuse, relaxase generates a ss nick at origin of transfer, the single strand is transferred into the other cell, recombination occurs, and the single strand comes back into first cell

48
Q

what are R factors?

A

they confer resistance to antibiotics and contain an ORI, a resistance transfer factor, and have HIGH genetic plasticity

49
Q

what are the two types of transposition mechanisms?

A

non-replicative (cut and paste)

replicative - both donor and target maintain sequences

50
Q

what are IS elements?

A

insertion sequences - small DNA sequences that contain direct or inverted terminal repeats and ecnode transposase that mediate transposition of IS elements (contain no known related genes unrelated to transposition)

51
Q

what are transposons?

A

larger than IS elements, though they also contain direct or inverted terminal repeats and some have same sequence of IS elements
they also encode transposase
also have genes unrelated to transposition

52
Q

what do all viruses have?

A

protein capsids, enzymes, and nucleic acids

53
Q

what do only some viruses have?

A

lipid envelopes

54
Q

what are the possible shapes of a viral capsid?

A

icosahedral, helical

55
Q

what are the monomers of protein capsids?

A

capsomeres

56
Q

what are M proteins?

A

they are enzymes in viruses that fill the inside of the capsid

57
Q

what is the viral envelope?

A

it is made from lipids derived from host cell membrane and it makes it VERY sensitive to detergents
(non-enveloped viruses are hardier and survive as fomites)

58
Q

what do DNA+/- viruses do?

A

they directly transcribe once they get into cell (+mRNA)

59
Q

what do ssDNA viruses do?

A

they make complementary DNA strand and then transcribe mRNA

60
Q

what do RNA +/- viruses do?

A

they are directly translated - the + strand

61
Q

what do RNA + viruses do?

A

they are directly translated

62
Q

what do RNA - viruses do?

A

they make +RNA and are translated, must remake -RNA in order to be incorp into genome

63
Q

what do reverse transcriptase RNA+ viruses do?

A

they use reverse transcriptase to make dsDNA and then get mRNA from that

64
Q

what do reverse transcriptase DNA +/- viruses do?

A

DNA, transcribed to mRNA and then reverse transcribed to make a DNA genome (i.e. to put into new capsids)

65
Q

where do RNA and DNA viruses replicate in human cells?

A

RNA viruses replicate in the cytoplasm, DNA viruses replicate in the nucleus

66
Q

what does RNA dependent RNA polymerase do?

A

replicates RNA from RNA template

67
Q

what does RNA dependent DNA polymerase do?

A

this is the reverse transcriptase - it makes DNA from RNA

68
Q

what does DNA-dependent RNA polymerase do?

A

it makes RNA from DNA - sourced from host

69
Q

what does DNA polymerase do?

A

replicates DNA (can be from host or virus)

70
Q

what are the three ways that a virus can enter a host cell?

A
  1. direct penetration (inject genetic material without capsid coming in)
  2. membrane fusion (viral envelope merges with cell membrane and lets virus in)
  3. endocytosis
71
Q

cytopathic effect (CPE)

A

this is the morphologic changes that happen in cells upon viral infection; includes ballooning, rounding, lysis, or giant cell formation (syncytium) (NOT ALL VIRUSES do this)

72
Q

viral tropism

A

this is the localization of virus to particular cells based on the cell’s expression of receptors

73
Q

relationship between +RNA viruses and RdRP?

A

+RNa viruses have genes for RdRP in their RNA and it is produced after entry

74
Q

relationship between -RNA viruses and RdRP?

A

-RNA viruses have previously packaged the RdRP in their capsids

75
Q

where is the reverse transcriptase in retroviruses?

A

it is in their viral particles

76
Q

what PAMPs that the innate immune system recognizes?

and what PRRs actually recognize them?

A

dsDNA recognized by TLR-3, 7, 8 and RIG-I
uncapped RNA recognized by RIG-I
unmethylated CpG residues recognized by TLR-9
cytosolic DNA is recognized by AIM2 and cGAS

77
Q

what is re-assortment of viral genes?

A

when you mix around large segments of your genome

78
Q

what is antigenic shift?

A

occurs from the re-assortment of viral genomes in the large animal reservoirs of the virus (happens in viruses with segmented genomes)

79
Q

what is antigenic drift?

A

occurs as a consequence of mutations introduced by the viral RNA dependent RNA polymerase lack of proofreading activity during replication

80
Q

what is viremia?

A

the spread of the free virus or through infected macrophages, lymphocytes, dendritic cells, endothelial cells or through neurons

81
Q

stages of viral disease (acute)?

A

entry - primary replication site - dissemination - secondary replication site - spread to other hosts

82
Q

what are zoonoses?

A

animals or insects that can pass along viruses

83
Q

what kills noncytolytic (enveloped) viruses?

A

CTL or NK cells that kill virus-infected cells

84
Q

what kills cytolytic (non-enveloped) viruses?

A

antibody mediated - the antibodies inactivate extracellular viruses and control their cell-free spread - they target viral entry

fundamentals (11 decks)

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