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MicroEco > Lecture 15 - Microbial Communication > Flashcards

Lecture 15 - Microbial Communication Flashcards

1
Q

What must bacteria be able to do in order to survive due to the fact that the environments they inhabit are complex and subject to rapid change?

A

must adapt by being able to sense and respond to the rapid changes

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2
Q

What are the 6 functions of bacterial communication?

A

coordination of gene expression within a single or unrelated population(s) | evade host immune response | coordinate virulence gene expression | inhibit a competitor | inhibit/stimulate host colonization

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3
Q

What are the 3 different kinds of bacterial communication?

A

intraspecies, interspecies, and inter-kingdom

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4
Q

What is intraspecies signaling?

A

communication within a population of same species

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5
Q

What is interspecies signaling?

A

communication between populations of different species

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6
Q

What is inter-kingdom signaling?

A

abusing signal pathways by signaling molecules of one organism (bacteria) to change behavior of another organism (animal) from a different kingdom

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7
Q

What are bacterial pheromones?

A

signals that alter bacterial behavior

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8
Q

What are the characteristics of communication signals that bacteria use to communicate?

A

small molecules released from cell (active transport or passive diffusion)

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9
Q

What must cells – that a bacteria is attempting to communicate with – must possess?

A

the ability to recognize the signaling molecules = receptors = can be within cells or on surface of cell

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10
Q

What is quorum sensing?

A

type of bacterial communication that regulates gene expression due to signaling molecules

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11
Q

What is quorum sensing dependent on?

A

population dependent <> population density increases = quantity of signaling molecules increases

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12
Q

Which type of bacteria uses quorum sensing?

A

both gram+ and gram– but use different signal molecules

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13
Q

What are the 4 ecological roles of quorum sensing?

A

coordinate gene expression (within one species or between different species), evade host immune responses, direct signaling between bacterium and host

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14
Q

What is AHL?

A

N-acyl homoserine lactone = best studied diffusible signal, many bacterial species can produce this

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15
Q

What are the structural components of AHL? Which part stays consistent?

A

homoserine lactone ring and fatty-acyl side chain | the homoserine lactone ring stays consistent

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16
Q

Which bacterium uses AHL? Which one can’t and why?

A

gram– | gram+ can’t use AHL because they lack a porous outer membrane (like seen in gram– cells) instead they have a thick peptidoglycan cell wall

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17
Q

What is specificity determined by within the AHL molecule?

A

length and modifications of side chain

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18
Q

What is vibrio fischeri? Where are they found on?

A

marine bacteria capable of bioluminescence found free-living within the ocean OR attached on the light organ of an animal

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19
Q

What is the population density of Vibrio fischeri when it is in the open ocean? What is the consequence of this in terms of cell signaling? What operon transcription depends on this signaling pathway?

A

low density = low chemical signaling activity | the Lux operon = won’t be transcribed

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20
Q

What is the population density of Vibrio fischeri when it is on the light organ of a marine animal? What is the consequence of this in terms of cell signaling?

A

high population density because they are more concentrated within one area = high chemical signaling activity &raquo_space;> signals diffuse into cells and bind to transcription factor for Lux-operon = luminescence

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21
Q

What is the Lux operon expression dependent on?

A

amount of AHL molecules

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22
Q

What do the signal molecules function closely as?

A

transcription factors that can inhibit or enhance gene expression

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23
Q

Where are the genes, that these signaling molecules control, usually located at?

A

on an operon

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24
Q

What is another name for interspecies signaling?

A

“cross-talk”

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25
Q

What was the example discussed in class to explain how interspecies signaling works?

A

Pseudomonas species produce phenazines

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26
Q

What are phenazines?

A

three-pigmented antibiotics

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27
Q

What is positive cross-talk?

A

species A restores the ability of an activity in species B | beneficial type of communication

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28
Q

What is negative cross-talk?

A

species A inhibits the ability of an activity in species B | detrimental type of communication

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29
Q

What causes Crown galls disease in plants?

A

A. tumefaciens

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30
Q

What are the symptoms of Crown galls disease?

A

development of “galls” at the soil surface or “crown” of the plant

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31
Q

What are galls?

A

tumor-like structures as a result of a lot of cell-division triggered by A. tumefaciens

32
Q

Where are the genes necessary for the bacteria to cause Crown galls disease found at?

A

on a plasmid in which region will be transferred to the plant genome

33
Q

How does A. tumefaciens engineer the plant?

A

inserts genes from plasmid into plant genome in order for it to produce food source that bacterium needs

34
Q

What is the sensor protein? What does it act as? Where is it located?

A

senses environmental signal | acts as a kinase = phosphorylates response regulator | found on plasma membrane

35
Q

What is the response-regulator? What does it act as? Where is it located?

A

acts on whatever the cell needs to do to respond appropriately according to the signal received | acts as a transcription factor (activator/repressor) | found in cytoplasm

36
Q

What initiates the bacterial infection of A. tumefaciens to the plant to cause Crown galls disease?

A

plant gets damaged and releases many compounds

37
Q

When the plant is damaged, what are the compounds it releases? What do these compounds act as? How does A. tumefaciens interact with these compounds?

A

phenolic compounds act as signaling molecules &raquo_space;> interacts with sensor protein on A. tumefaciens

38
Q

What are the sequence of events following the sensor protein on A. tumefaciens interacting with phenolics?

A

sensor kinase = phosphorylates response-regulator(RR) &raquo_space;> RR induce gene expression from plasmid &raquo_space;> gene transcription product = excised as T-DNA &raquo_space;> T-DNA transferred into wounded cell and localizes to nucleus &raquo_space;> T-DNA inserts into plant chromosome

39
Q

What is T-DNA?

A

the region of the plasmid that is transferred into the plant in response to plant signals following wounding

40
Q

What is the food source of A. tumefaciens that plants are engineered to produce?

A

opines

41
Q

What are opines?

A

nitrogen and carbon-containing compounds

42
Q

What does transcription of T-DNA lead to? (2things)

A

opines and plant hormones

43
Q

What is the function of opines? (A. tumefaciens)

A

binds to the repressor = cause conformational change = repressor falls off = transcription of genes

44
Q

What happens if there are no opines available?

A

the repressor is bound to genes that activate conjugation

45
Q

What is conjugation?

A

a way to share DNA/transfer plasmids between cells

46
Q

What effect does the T-DNA have on the plant that causes Crown gall’s disease?

A

produces plant growth hormones = plant will grow & constant cell division = galls

47
Q

How does A. tumefaciens maintain the plasmid within the population?

A

quorum sensing mechanism is needed to activate the conjugation genes so it can go and share its plasmid to other bacteria

48
Q

What is the signaling molecule needed for quorum sensing mechanism with A. tumefaciens?

A

opines

49
Q

How can we use quorum sensing as a type of biocontrol?

A

develop engineered microbes that can easily bread down quorum sensing signals such as opines and AHLs

50
Q

What signaling molecule do gram+ bacteria use?

A

small peptides which are different in structure compared to AHLs

51
Q

What does S. aureus use as a signaling molecule?

A

auto-inducing peptide (AIP)

52
Q

What is S. aureus?

A

human pathogen uses quorum sensing as part of its pathogenesis

53
Q

What is a “pro-peptide”?

A

peptide + some sequence that will be processed with a protease to create AIP

54
Q

What is the function of AIP? (3 functions)

A

upregulates transcription of: pro-peptide = AIP and RNA III and downregulates transcription of cell surface proteins

55
Q

Why would S. aureus want to downregulate expression of cell surface proteins?

A

less cell surface proteins = hide from host immune system

56
Q

What is significant about RNA III?

A

results in the production of virulence factors

57
Q

What type of system does S. aureus use?

A

The three-component system

58
Q

What is the “three-component system”?

A

the 2-component system + quorum sensing

59
Q

What is lactobacillus?

A

found in our gut and is one of our probiotics

60
Q

In what ways can lactobacillus help protect us against pathogens like S. aureus?

A

colonizing our gut can help prevent colonization of S. aureus | its inducing peptides (IPs) bind to surface protein on membrane &raquo_space;> 2-component regulatory system produces: bacteriocin and pre-IP

61
Q

What is bacteriocin?

A

targets pathogens

62
Q

What is the function of the small non-coding mRNA used in the quorum sensing system?

A

binds to Lux-operon mRNA = leads to degradation of Lux-operon mRNA = no bioluminescence

63
Q

When would the small non-coding mRNA, used in the quorum sensing system, not be produced?

A

when there is a high concentration of signaling molecules = last Lux-operon mRNA will not be phosphorylated = bioluminescence

64
Q

What is a neuropeptide?

A

fragment of peptidoglycan

65
Q

What is a neuropeptide indicative of?

A

bacterial cell was lysed or cell-wall-degrading antibiotic is present

66
Q

What do spore-forming bacteria use neuropeptides as?

A

as germinants to trigger vegetative growth

67
Q

What can eukaryotes use neuropeptides as?

A

as a signal that a bacterium is present within host tissues

68
Q

What is quorum quenching?

A

the idea of preventing quorum sensing mechanisms

69
Q

What are the 3 ways that quorum quenching can block the quorum sensing mechanisms?

A

prevents synthesis of signaling molecules (small peptides and AHLs) | interfere with signal receptor | directly inactivate signaling molecules

70
Q

What is the sequence of events when lactobacillus binds to S. aureus’ AIP? (relating to quorum quenching)

A

recognition of AIP triggers lactobacillus to produce and release RNA-III-inhibiting protein (RIP) &raquo_space;> S. aureus uptakes RIP = causes degradation of RNA III within S. aureus = prevents toxin production

71
Q

What are the 3 consequences of interkingdom signaling?

A

bacteria can eavesdrop on host by responding to host signals | host-interfering signals can interfere with bacterial signaling | host can undergo altered host gene expression when it recognizes bacterial signals

72
Q

What are the 2 quorum sensing systems that Pseudomonas uses?

A

uses virulence factors and some AHLs

73
Q

In what ways do the AHLs produced by pseudomonas influence host defensive responses? (the Pseudomonas that colonize the lung tissues of ICPs (immunocompromised patients/people))

A

downregulates lymphocyte proliferation; downregulates production of immune cells, and reduces apoptosis (when cell knows its infected)

74
Q

What is a regulon?

A

a higher order operon-type structure where a lot of genes/operons are regulated and triggered by 1 signaling molecule

75
Q

What can easily overwhelm the immune system?

A

quorum sensing mechanisms and regulon

MicroEco (10 decks)

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