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Proposal defense > Vibrio ecology and virulence > Flashcards

Vibrio ecology and virulence Flashcards

1
Q

Min. temperature for Vp

A

15 deg C

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2
Q

tdh and trh

A

thermostable direct hemolysin and thermostable related hemolysin, considered the major virulent factors for Vp

First used to test for Vp virulence on Wagatsuma agar in the 1970s

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3
Q

tdh and trh virulence (what they do–3 items)

A

lyse RBCs, cause cytotoxicity in cell culture, enterotoxins that cause diarrhea

Both genes exhibit similar biological activity

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4
Q

how similar are the aa sequences for trh and tdh?

A

trh is 67% homologous w/ tdh

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5
Q

have tdh and trh ever been isolated from E-strains?

A

Yes, though both genes are primarily associated with C-strains

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6
Q

Vp chromosome I size

A

3.3 gb (mostly housekeeping genes)

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7
Q

Vp chromosome II size

A

1.8 gb (more variable)

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8
Q

indicators of horizontal gene transfer on Vp chromosome II (4)

A

phage genes, transposons, mobile genetic elements (MGEs), interesting GC regions

all indicative of recent horizontal gene transfer

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9
Q

genes of interest in Vp pathogenicity island on chromosome II

A

TTSS gene sets (2), tdh (2 copies), + homologues to other well studied virulence factors

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10
Q

TTSS (type 3 secretion system) function

A

allows the transport of cytoplasmic proteins across the cell membrane

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11
Q

how many sets of TTSS does Vp have?

A

2 sets– TTSS1 and TTSS2

Each secretory system recognizes distinct proteins and is expressed under different conditions

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12
Q

Which TTSS is found in all Vp strains?

A

TTSS1

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13
Q

Which TTSS is found in only KP-positive strains?

A

TTSS2

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14
Q

Does Vc have a TTSS?

A

no; likely linked to the inflammatory response in Vp infection

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15
Q

YopD and VopD

A

Vp virulence factors

form holes in the host membranes and mediate the injection of effector proteins to disrupt immune defenses, excreted by TTSS1 ((Vop) and TTSS2 (Yop)

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16
Q

how many copies of T6SS (type 6 secretion system) does Vp have?

A

2– T6SS1 and T6SS2

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17
Q

which T6SS is more active under marine conditions for Vp and which chromosome is it located on?

A

T6SS1

chromosome I

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18
Q

which T6SS is more active under lower salinity conditions for Vp and which chromosome is it located on?

A

T6SS2

chromosome 2, only functions in adhesion not cytotoxicity

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19
Q

do non-pandemic strains of Vp have T6SS

A

only partial gene sets

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20
Q

MAM7 (multivalent adehesion molecule 7) function in Vp

A

host adhesion which can then lead to the upregulation of virulence factors, needed for TTSS-mediated cell death

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21
Q

how was toxR first identified?

A

as the regulatory gene for cholera toxin

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22
Q

how much homology is there between Vp and Vc toxR genes

A

Vp toxR aa sequence is 52% similar to Vc toxR

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23
Q

is toxR specific to C-type Vp?

A

No, tox R is also found in E-type Vp and other Vibrio species (though it is thought to be “perfectly” conserved in Vp)

(Kim et al. 1999)

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24
Q

what is the function of toxR?

A

part of the toxRS (toxR +toxS) operon that regulates “virulence-associated genes” including tdh

(Matsumoto et al. 2000)

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25
Q

Which Vp virulence factors are primarily associated w/ KP-pos strains?

A

tdh and trh

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26
Q

how many cases of Vv require hospitalization each year in the US?

A

50, responsible for 95% of seafood-related deaths

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27
Q

what is the fatality rate of Vv infection?

A

50-60%, up to 79% (parker et al. 1991)

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28
Q

how was Vv described prior to 1976?

A

“lactose positive” Vibrio (w/o gas), before being identified as a specis by the CDC in 1976

(15% of Vv are actually lac-; 15% are suc+)

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29
Q

Vv biotype 2

A

associated with infection of eels

all biotype 2 strains have the same LPS (serotype E), different type of LPS than biotype 1

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30
Q

Vv biotype 3

A

associated with Israeli wound infections (Bisharat et al. 1999)

all have vvha (like biotype 1), but vvha are all identical (unlike biotype 1)

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31
Q

what time of year are Vp and Vv infections most common

A

March-October, when waters are warmer

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32
Q

Optimum salinity range for Vv

A

5-10 ppt, up to 25 ppt (Blackwell and Oliver 2008)

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33
Q

Optimum salinity for Vp

A

23 ppt (10-34 ppt salinity range)

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34
Q

How many genomes of Vv +Vp have been completed?

A

~10

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35
Q

How many genes make up a TTSS?

A

20-30

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36
Q

How long does it take for a Vv infection to advance to primary septicemia?

A

Hours to days, 36h on average

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37
Q

What is the incubation period for a Vv wound infection?

A

3h to 8d

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38
Q

Vv capsule (CPS) function

A

anti-phagocytic

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39
Q

Is CPS importance for Vv virulence?

A

YES, it is essential.

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40
Q

What is th difference between transluscent and opaque strains of Vv?

A

Transluscent– no CPS, LD50>10^6-10^8 CFUs

Opaque– much more virulent; have CPS, LD50

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41
Q

How is CPS related to biofilm formation in Vv?

A

CPS+ strains are not as good at forming biofilms; possible reason E-strains (CPS-) do better in the environment than C-strains.

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42
Q

Function of LPS in Vv

A

lipid polysaccharide

causes symptoms related to endotoxic shock

43
Q

What happens when mice are treated w/ Vv LPS (no live cells)

A

they die in 30-60 mins; Vv LPS is very very virulent!

44
Q

vvha

A

Vv hemolysin

linked to virulence but no change in mutant strains

45
Q

vvpE

A

Vv metalloprotease

linked to virulence but no change in mutant strains

46
Q

flgC &flgE

A

Vv flagellar proteins

mutants have reduced cell adherence

47
Q

RTX toxin

A

Vv toxin involved in cytoskeletal rearrangements in host cells, more toxin is produced when Vv is in contact with host cell

48
Q

luxR (smcE)

A

Vv quorum sensing genes

Mutants have increased virulence

49
Q

RpoS

A

Vv stress response factor

Has effects on adherence and cytotoxicity

50
Q

hlyU

A

Vv transcriptional activator associated with virulence

51
Q

What is the problem with mouse models of Vv infection?

A

lab experiments indicate that ALL strains of Vv are virulent based on animal lethality, but there are

52
Q

how many oysters are consumed in the US each year?

A

75-80 million

53
Q

How are C v. E-types of Vv differentiated?

A

using the virulence correlated gene

C strains have vcgC allele
E strains have the vcgE allele

Not a virulence genes, just correlated with virulence

54
Q

What percent of C-type Vv strains are isolated from clinical samples?

A

90% (Rosche et al. 2005)

55
Q

What percent of E-type Vv strains are isolated from environmental samples?

A

93% (Rosche et al. 2005)

56
Q

What is the concentration of Vv in seawater?

A

Average of 1-50 CFUs/mL, up to 10^4 CFUs/mL

57
Q

What percent of natural flora is Vv in SE esuarine populations?

A

0.15% (Pfefferel et al. 2003)

58
Q

What is the concentraion of Vv in shellfish?

A

up to 10^6 CFUs/mL, varies dramatically and has a strong correlation with temperature

59
Q

What are other reservoirs for Vibrio?

A

sediments, plankton, non-molluscan shellfish, fish

Large range of concentrations

60
Q

What percent of attached bacteria found on plankton/sediment is Vv?

A

up to 57%, higher than Vv found in surrounding water (Heidelberg et al. 2002)

61
Q

what salinities have the greatest concentration of Vv?

A

5-10 ppt, result independent of temperature (Randa et al. 2004)

62
Q

At 20-25 deg C, temperature must be greater than _____ for Vv to grow.

A

20deg C

63
Q

True or false: Vv responds to environmental parameters similarly to other Vibrios

A

True: Vv numbers correlate well with total Vibrios

64
Q

True or false: environmental strains decline in human serum

A

True (Williams et al. 2014, Vv metatranscriptomics paper)

65
Q

pilF

A

used to detect pathogenic Vv strains through a polymorphism in the pilF (pilin) gene

This gene ahs been implicated in human pathogenicity and is useful for distinguishing pathogens in all three Vv biotypes.

66
Q

Min temp for Vv

A

20 deg C

67
Q

Why is urease activity important for Vp?

A

Breaks down urea, an important nitrogen source

68
Q

What percent salt is required by Vv/Vp?

A

Vv: 0.5%
Vp: 2-3%

69
Q

What is the thermolabile hemolysin (tlh) gene used for?

A

Detection of Vp (present in Vp but not other vibrio species)

70
Q

Are Vv/Vp oxidase positive?

A

Yes

71
Q

What sugars can Vv/Vp both utilize?

A

mannitol, mannose

72
Q

Are Vv urease positive?

A

Variable (Vp is usually urease+)

73
Q

Which organisms (Vv or Vp) is lac+?

A

Vv

74
Q

Which organisms (Vv or Vp ) is ara+?

A

Vp

75
Q

What is the primary role of heterotrophs in the N cycle?

A

Remineralization and decomposition of dissolved and particulate N (may also be consumers of both inorganic and organic N)

76
Q

Can Vibrio fix Nitrogen?

A

4 species in the Vibrionaceae can and may be associated with plants and urchins

77
Q

What N cycle-related functions can Vibrio carry out? (3)

A

nitrogen fixation, reduction (assimilatory and dissimilatory), ammonification

No known role in nitrification

78
Q

What is the half-saturation constant for Vp? What does this mean?

A

500 uM, very high

Is the concentration supporting 1/2 maximum glucose uptake, indicates rapid growth/turnover potential

79
Q

During aerobic respiration, what percent of C is used for biomass?

A

30-50%

80
Q

During fermentative metabolism, what percent of C is used for biomass?

A

10%; most products are excreted (C leaking)

Likely an important contributor to DOC

81
Q

What important enzymes do Vibrio have for the breakdown/remineralization of phosphorus? (2)

A

5’ nucleotidases (cleave 5’ nucleotides)

alkaline phosphatase (cleaves inorganic phosphate)

82
Q

List the three “core” genome features of Vibrios?

A
  1. motility
  2. morphological plasticity
  3. organic matter cycling
83
Q

What is the primary bottom up control on Vibrio?

A

Substrate availability

84
Q

What is the primary top down control on Vibrio?

A

Predation (viral lysis, selective grazing)

85
Q

How do Vibrio help to stimulate the anaerobic foodchain?

A

Via substances (like H2) that are released during anaerobic respiration

86
Q

What is the incubation period for a Vibrio infection?

A

3h-8d (average 24h)

87
Q

What secretory system excretes the RTX toxin?

A

Type I

88
Q

What Vv virulence factor do female hormones protect against?

A

LPS

89
Q

What is the percentage of Vv in coastal estuaries?

A

~0.15% (total Vibrio usually

90
Q

What percent of total Vv has been shown to be attached ?

A

57%

91
Q

What does the pilF gene assay detect?

A

a polymorphism in the pilF gene associated with virulence

92
Q

What does the pilF do?

A

Codes for a pilin protein, important for horizontal gene transfer via conjugation

93
Q

What amount of rainfall constitutes a “storm event”

A

> 1.27 cm

94
Q

Is the VNBC state unique to Vibrio?

A

No, has been documented in other taxa; possibly up to 30 species

95
Q

How many Vp O serotypes are there? K?

A

O: 13
K: 71

96
Q

When did Vp O3:K6 emerge?

A

mid-1990s in Japan and India

97
Q

What are the biochemical characteristics of O3:K6?

A

tdh+, trh-, urease-

98
Q

Does Vv have a TTSS?

A

Yes, but has only recently been studied and has not yet been implicated in virulence

99
Q

Why is tdh problematic as a marker for virulence?

A

Present in some benign environmental strains, some tdh+ strains are negative for hemolysis activity, and tdh mutants still caused disease in the mouse model

100
Q

Virulence of O4 serovar Vp can usually be predicted by ________ _________.

A

urease activity; O4 strains tend to be urease +

101
Q

What are siderophores?

A

Iron storage proteins which are produced under iron-limiting conditions; important in both clinical and environmental strains

Higher concentration may give a competitive advangtage

102
Q

What is the GC content of Vp’s pathogenicity island on Chromosome II? What is the GC content of the rest of the genome?

A

~40% – PI
~45% – rest of genome
This is indicative of horizontal gene transfer

103
Q

When is the TTSS triggered in Vp?

A

When the organism comes into contact with other cells

104
Q

What two antibiotics are all Vibrio resistant to?

A

colistin and polymixin B

Proposal defense (9 decks)

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