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Microbes and You > Microbial Symbiosis L11 > Flashcards

Microbial Symbiosis L11 Flashcards

1
Q

what is symbiosis

A

‘living together’

A close, often long term association between organisms

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2
Q

what is symbiosis usually related to

A

Competition
Predation
Defence (avoidance of being eaten)
Co-operation

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3
Q

what are the symbiotic relationships

A

mutualistic
commensalistic
parasitic

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4
Q

what is mutualistic symbiotic relationship

A

two organisms of different species exist in a relationship

in which each individual benefits from the activity of the other

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5
Q

what is commensalistic symbiotic relationship

A

relationships between two organisms where one organism benefits from the other without affecting it

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6
Q

example of mutualistic symbiotic relationship

A

lichens

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7
Q

example of commensalistic symbiotic relationship

A

barnacles on whales

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8
Q

what is parasitic symbiotic relationship

A

non-mutual symbiotic relationship between species,
where one species, the parasite, benefits at the expense
of the other, the host

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9
Q

example of parasitic symbiotic relationship

A

tapeworm - uses nutrients in gut at expense of the host

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10
Q

what are the symbiotic relationships like

A

can be obligate or facultative

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11
Q

why is lichen green

A

algal layer

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12
Q

what happens in algal and fungal layer

A

Critical relationship between algal and fungal – fixing carbon, synthesis
Two layers separated
One gets fixation of carbon other gets nutrients

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13
Q

what are ‘hiding’ places for microbes

A

Skin (Staphylococcus epidermidis)
GI tract (E.coli and the 100 trillion
other bacteria)
Plant roots (Rhizobium ssp.)

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14
Q

what is opportunism example

A

Parasites – Pseudomonas aeruginosa

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15
Q

what is an example of nitrogen fixing bacteria

A

root nodules

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16
Q

what are roots symbiotic association

A

Almost all roots have some form of symbiotic association with soil microorganisms

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17
Q

why are legumes important

A

important “staple” agricultural crops (soy beans provide both human and animal protein) and ‘fix’ atmospheric nitrogen

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18
Q

what is a growth limiting factor of plants

A

usually dont have enough nitrogen

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19
Q

what percentage of legumes are nodulated

A

Approximately 90% of legumes become nodulated, i.e. become associated with rhizobia bacteria

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20
Q

what is exchanged in legume relationship

A

rhizobial species get a nice place to live (plant provides nutrients and energy sources to the bacteria)

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21
Q

what do rhizobia give in return in perfect relationship

A

rhizobia ‘fix’ nitrogen for the ‘lucky’ host plant

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22
Q

what percentage of nitrogen do nitrogen bacteria fix

A

N-Bacteria ‘fix’ 60% of total nitrogen (c.f. artificial and abiotic processes)
requires energy - 16 ATP and enzymes (nitrogenase) to break bonds and fix nitrogen in organic compounds
N2 + 3H2 –> 2NH3

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23
Q

what do legume roots make

A

flavenoids

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24
Q

what do different flavenoids attract

A

different rhizobia spp.

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25
Q

what makes nod factors

A

Rhizobia nodABC genes encode proteins that produce oligosaccharides, called Nod factors

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26
Q

what do bacteria do

A

bacteria colonises plant cells

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27
Q

how are infection threads formed

A

Root hair curls and Rhizobium invades cell wall invaginations, forming infection threads

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28
Q

effect of thread grow through root hair cells

A

infect nearby cells by branching

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29
Q

what do bacteria differentiate into

A

bacteroids

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30
Q

what do bacteroids do

A

perform

nitrogen fixation

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31
Q

in plant what happens in photosynthesis

A

fix carbon and make sugars, broken down in cytoplasm of plant into organic acids
Organic acids assimilated by bacteroids to succinate, malate and fumarate
turn TCA cycle, electrons produced then enter electron transport chain to make ATP
AS WELL AS succinate, malate and fumarate can go through glycolysis
Pyruvate and ATP from electron transport chain drive nitrogenase reaction

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32
Q

what happens i the nitrogenase reaction

A

fixing nitrogen to ammonia

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33
Q

what do nitrogen fixing bacteria need to function

A

Nitrogen-fixing bacteria need O2 to generate energy for N2 fixation, but nitrogenases are inactivated by O2

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34
Q

how is oxygen controlled in plant

A

In the nodule, O2 levels are controlled by the O2 - binding protein leghemoglobin

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35
Q

what is AMs

A

Arbuscular mycorrhizas

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36
Q

how is AMs characterised

A

by the formation of unique structures, arbuscules and vesicles by fungi of the division Glomeromycota

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37
Q

what is AMF

A

Arbuscular mycorrhizas fungi

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38
Q

what do AMF do

A

help plants to capture nutrients
such as phosphorus, sulphur, nitrogen and
micronutrients from the soil

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39
Q

what is the most prevalent plant symbiosis

A

Arbuscular mycorrhizas in 80% of vascular plant families in existence today

40
Q

what is the AM lifecycle

A

consists of - host recognition, spore germination, appressorium formation and hyphal growth

41
Q

do all fungi interact with plants

A

Not all fungi will interact will all plants – there is specificity
Specificity associated with chemical contact where they can talk to each other

42
Q

what influences the growth of AM

A

growth of AM hyphae through the soil is influenced by host root hormones known as strigolactones, and soil phosphorus concentration

43
Q

what do is AM fungi growth

A

host-specific chemotaxis

44
Q

what limits fungal attachment to host in AMF lifecycle

A

high phosphate concentrations

45
Q

what is appressorium

A

(an infection structure) is formed on the root epidermis after spore germination

46
Q

what is the appressorium structure

A

appressorium is the structure from which the hyphae can penetrate into the host’s parenchyma cortex

47
Q

what is parenchyma

A

one of three main types of ground tissue, and the most common

48
Q

where is parenchyma

A

in plants

49
Q

how can parenchyma be distinguished

A

distinguished through the thin cell wall compared to other cell types

50
Q

what happens in the AMF lifecycle

A

Spore hits surface of cells
Engage with these structures – can see what plant it is
Fungi that hijack this process
Mutualist relationship

51
Q

what are biotrophs

A

plant-pathogenic fungi which establishes a long-term feeding relationship with the living cells of a host, without killing it as part of the infection process

52
Q

what happens when the fungi inside the parenchyma

A

fungus forms highly branched structures for nutrient exchange with the plant called “arbuscules”

53
Q

what are AM fungi like

A

obligate symbionts – require host plant to grow properly

54
Q

what are AMF limited by

A

limited saprotrophic ability and are dependent on the plant for their carbon nutrition

55
Q

what is the use of AMF

A

ecological restoration projects (phytoremediation) can aid host plant establishment on degraded soil and improve soil quality and health

56
Q

what do AMF facilitate

A

facilitate survival of their host plants growing on metal-contaminated land by enhancing nutrient
acquisition, absorbing heavy metals and
protecting their hosts from metal toxicity

57
Q

what do AMF enhance

A

enhance phytostabilization (immobilization) and phytoextraction (concentration) of heavy metals

58
Q

how is microbial symbionts acquired

A 
Environmental reservoir (horizontal transmission)
Parent (vertical or heritable transmission)
59
Q

example of vertical / heritable transmission

A

Heritable symbionts of insects are obligate (lack a free-living replicative stage, completely dependent on the organism they use)

60
Q

what are primary symbionts needed for

A

host reproduction/survival

61
Q

what are secondary symbionts needed for

A

Not required for reproduction

62
Q

where are the secondary symbionts

A

Not present in every individual

63
Q

where do secondary symbionts invade

A

Can invade different cells and live extracellularly

64
Q

what must primary and symbionts have

A

Must provide a benefit e.g.

  • Nutritional
  • Protection from environment
  • Protection from pathogens
65
Q

what do some parasitic symbionts do

A

manipulate their hosts reproduction

66
Q

examples of host reproduction manipulation

A

Embryonic (early) male killing,
Larval (late) male killing
Feminization (turn male into female)
Parthenogenesis induction (virgin birth)

67
Q

where is wolbachia

A

in many arthropod species

68
Q

what is wolbachia

A

usually considered a parasite

69
Q

is wolbachia needed

A

Some host species cannot reproduce, or even survive, without Wolbachia infection

70
Q

does wolbachia have a positive effect

A

may protect some arthropods against viruses, including the dengue fever virus (mosquitoes)

71
Q

what are most wolbachia associated with, and what are they like

A

Drosophila melanogaster are benign to their hosts and provide protection against viruses

72
Q

what is wMelPop

A

virulent wolbachia variant

73
Q

why does wMelPop shorten the hosts lifespan

A

It over-replicates and shortens the lifespan of its host

74
Q

what is octomom

A

Amplification of a Wolbachia genomic region

75
Q

what does wolbachia genomic region contain

A

eight genes

76
Q

what is wolbachia genomic region potentially involved in

A

DNA replication, repair, recombination, transposition or transcription

77
Q

how is wMelPop pathogenic effects

A

by boosting bacterial density inside the host

78
Q

what do termites decompose

A

cellulose

hemicellulose

79
Q

what are termites classified as

A

higher or lower based on phylogeny

80
Q

what does the gut of a termite consist of

A

gut consists of foregut, midgut, and hindgut

81
Q

what happens to the oxygen supplied from blood supply from outside of gut

A

acetate forms H2 forms CH4

82
Q

what does anaerobic cellulose make

A

makes glucose then makes acetate

83
Q

what are termitidae

A

posterior alimentary tract of higher termites

84
Q

what does parasitism include

A

viruses, bacteria, fungi, protozoans, nematodes, insects and arachnids

85
Q

what does parasitism do

A

Primarily injure host in two ways

86
Q

what are the two ways that parasitism injure host

A

consume host tissue

produce toxins

87
Q

what happens in parasitism consuming the host tissue

A

Hookwork (blood and gut mucosa)

Plasmodium (red blood cells)

88
Q

what happens in parasitism producing toxins

A

Tetanus bacilli (Tetanospasmin)
Produce toxins that interferes with synaptic transmission
Diptheria (Diptheria toxin)
Secrets toxin that inhibits protein production

89
Q

what causes cancer in plants

A

Agrobacterium tumefaciens forms a parasitic symbiosis with plants, causing crown gall disease

90
Q

what are crown galls

A

plant tumors

91
Q

what are crown galls induced by

A 
A. tumefaciens cells harboring a large plasmid, 
the Ti (tumor induction) plasmid
92
Q

what happens in Agrobacterium tumefaciens

a parasitic symbiote - form crown galls

A

initiate tumor formation, A. tumefaciens cells must attach to a wound site on the plant
attached cells synthesize cellulose microfibrils and transfer a portion of Ti plasmid to plant cells
DNA transfer is mediated by vir-encoded proteins
Nicking done by specific VirD
Transfer portion into plant via VIrB
tDNA in plant encodes proteins that cause plant to produce crown galls

93
Q

what does cymothoa exigua do

A

parasite enters fish’s mouth through gills attaches to tongue base
extracts blood
less and less blood reaches tongue as parasite grows
parasite replaces fish’s tongue
by attaching its own body to muscles of tongue stub

94
Q

what does an increase in octomom copy number have on drosophila

A

decreased life

increased bacteria present

95
Q

what resistance does wolbachia give to drosophila

A

resistance to RNA viruses

96
Q

what does wolbachia not give protection to - drosophila

A

bacteria

parasitoids

97
Q

what does wolbachia strain wMelPop give to drosophila

A

resistance to

  • bacteria
  • viruses
  • malaria parasites
  • filarial nematodes

Microbes and You (14 decks)

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