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MCDB 131 > Lecture 13 - bacterial interactions with eukaryotes > Flashcards

Lecture 13 - bacterial interactions with eukaryotes Flashcards

1
Q

Symbiosis

A

Intimate association between organisms of different species

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2
Q

Syntrophy

A

Association requiring two or more partners to complete a metabolic pathway

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3
Q

Synergism

A

Optional cooperation where both species benefit but are able to grow independently from one another

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4
Q

Commensalism

A

One partner benefits, while the other is unaffected

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5
Q

Amensalism

A

One species harms another but is neither affected nor benefited by the action

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6
Q

Mutualism

A

Each partner benefits from the other

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7
Q

Can mutualistic species grow independent of one another

A

Sometimes

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8
Q

Example of mutualism

A

Lichens: composite organism formed by the mutualistic relationship between fungi and cyanobacteria/algae
- fungus is dependent on cyanobacteria/algae for carbohydrate
- fungus provides minerals for cyanobacteria/algae, but is not necessary for their growth

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9
Q

Parasitism

A

Intimate association where one partner benefit by harming a specific host

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10
Q

Wolbachia

A

Bacteria that commonly infects insects and nematodes as intracellular symbionts

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11
Q

What kind of relationship does wolbachia have with its hosts?

A

Mutualistic or parasitic depending on the host

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12
Q

Can wolbachia survive independently?

A

No. Must reside in the cytoplasm of a host because its genome has been pared down. Unable to live without materials from the host

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13
Q

Relationship between Wolbachia and Brugia malayi

A

Mutualistic
- wolbachia is required for the growth of brugia (nematode)

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14
Q

How was the relationship between Wolbachia and Brugia confirmed?

A

Antibacterial therapy that kills Wolbachia was more effective at clearing a Brugia infection than antihelminthic therapy that kills Brugia

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15
Q

What is the result of the relationship between Wolbachia and Brugia?

A

Brugia blocks lymphatic system in humans –> swelling of extremities

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16
Q

What aspect of Wolbachia is important in its relationship with Brugia?

A

Wolbachia can make FAD (essential e- carrier) and provide it to brugia

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17
Q

How is Wolbachia passed to new insect hosts?

A

Inherited through egg cytoplasm (only passed down through females)

18
Q

How does Wolbachia influence sexual differentiation in insects?

A
  • male killing
  • feminization
  • parthenogeneis
  • cytoplasmic incompatibility
19
Q

Male killing

A

Infected males die during larval development

20
Q

Feminization

A

Infected males develop into females or infertile pseudo-females

21
Q

Parthenogenesis

A

Reproduction of infected females without males

22
Q

Cytoplasmic infertility

A

Infected males can’t produce progeny with uninfected females or with females that carry another Wolbachia strain

23
Q

Outcome of cytoplasmic infertility

A

Increased proportion of infected progeny in the population

24
Q

Example of syntrophy

A

Mixotricha paradoxa
- protozoan that has at least four bacterial symbionts that provide useful materials for it
- lives in the hindgut of termites and provides essential materials for wood breakdown and consumption

25
Q

What do bacterial symbionts do in Mixotricha paradoxia

A
  • Spirochetes and “anchor bacteria” on the outer surface provide locomotion for Mixotricha
  • cytoplasmic symbionts perform mitochondrial functions to provide energy for Mixotricha
26
Q

What does Mixotricha do to help termites?

A

Converts wood polysaccharides to acetic acid which is taken up by the termite

27
Q

Endophytes

A

Bacteria or fungi that colonize the transport vessels of plants

28
Q

What do endophytes to to their hosts?

A

Produce alkaloids and enzymes that deter plant pathogens and root feeding nematodes –> promotes plant growth

29
Q

What is the problem with endophytic pathogens for us?

A

Endophytic pathogens live in the vessels of plants and therefore can’t be washed off of raw produce

30
Q

Rhizoplane

A

Plant root surface

31
Q

Rhizosphere

A

Region of soil outside the rhizoplane that receives substances from the root

32
Q

Rhizobium

A

Bacteria that enter cortical cells of legume roots and provide fixed nitrogen to the plant

33
Q

How do rhizobium enter plant roots?

A
  • attracted to the legume by chemotaxis towards exuded flavonoids
  • bacterial Nod factor induces root hair to curl around it and take it up into the infection thread
  • rhizobia enter cortical cells and differentiate into bacteroids
34
Q

What do rhizobia and legumes provide one another?

A
  • rhizobia provides fixed nitrogen
  • legumes provide malate and minerals
  • legumes also provide leghemoglobin which sequesters O2 and precisely delivers it to electron transfer system of bacteria
35
Q

Why is leghemoglobin necessary for rhizobia/legume interactions?

A

Rhizobia use nitrogenase to fix nitrogen. Nitrogenase can’t function in the presence of oxygen, so it must be kept separate

36
Q

Why is malate important for rhizobia/legume interactions?

A

Malate is used in the TCA cycle for energy production. Lots of energy is needed for nitrogen fixation.

37
Q

Why is the rumen important in bovine systems?

A

Largest digestive chamber that contains a diverse microbial community that aids in breakdown of plant fibers

38
Q

End product of cellulose breakdown in cows

A

Bacteria ferment glucose and create short chain fatty acids that can be taken up by the animal

39
Q

Byproducts of cellulose breakdown in cows

A

Methane

40
Q

Influence of starch and sugars on bovine microbiome

A

Starch and sugars are broken down by gram - bacteria like E. coli. Increased starch/sugar intake promotes their growth and causes dysbiosis

41
Q

One way to treat gut dysbiosis in cattle

A

Add fistula to cows to allow transplantation of rumen material between cows

42
Q

In a healthy population, what aspects of the microbiome are variable and which are constant?

A
  • carriage of microbial taxa is variable (not every individual will have the same amount of each type of bacteria)
  • metabolic pathways remain stable

MCDB 131 (15 decks)

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