The social microbe II – interactions of microbes and macrobes Flashcards
(70 cards)
1
Q
List some microbial interactions
A
- hosts
- mutualists
- commensals
- symbionts
- pathogens
2
Q
Describe commensal
A
- an animal or plant which lives attached to or as a tenant of another, and shares its food
- distinguished from a parasite, which feeds on the body of its host
- also applied to the host itself
3
Q
Describe symbiosis
A
association of two different organisms which live attached to each other, or one as a tenant of the other, and contribute to each other’s support.
4
Q
Define infection
A
colonisation of the host from an infection source
5
Q
Define transmissibility
A
ability to spread from host to host
6
Q
Define carriage
A
establishment of a long-term harmless relationship
7
Q
Define disease
A
infections that damage the host (pathology)
8
Q
Define pathogenicity
A
ability to cause disease
9
Q
Define virulence
A
severity of disease caused
10
Q
Describe soil amoeba
A
- exhibit all types of interactions with bacteria
- prey on bacteria as a food source
- bacteria can parasitise them,
- pre-adapted to parasitise phagocytes
- have endosymbiotic mutualists
11
Q
List some intracellular lifestyle
A
- predator-prey
- parasitism
- mutualism
12
Q
What are the implications of the intracellular predator-prey lifestyle?
A
- food web and nutrient cycling
- selective force for bacterial community
- mechanisms of intracellular killing
13
Q
What are the implications of the intracellular parasitic lifestyle?
A
- discovery of new pathogens
- identification of new virulence factors
- drinking water safety
- human health
14
Q
What are the implications of the intracellular mutualistic lifestyle?
A
- mechanisms of genome reduction and gene transfers
- coadaptation in endosymbiosis
- origin of organelles
15
Q
Explain diverging host associations
A
- very large ancient population of free living bacteria undergoes recombinational change
- infection causes host association
- diverges into mutualism and pathogenesis
- forms commensal and pathogen respectively
- forms symbiont and obligate respectively
- forms smaller, younger populations
- limits recombinational exchange
16
Q
Describe the stages of host adaptation
A
- free living and extracellular microbe acquires genes by HGT, causes changes within the genome
- forms early stage facultative intracellular microbes; gene loss
- forms advanced stage obligate intracellular microbe
- forms extreme stage obligate intracellular mutualist
- forms organelle
17
Q
What are the roles of the mycobiont in lichens
A
- protection of the photobiont
- absorb mineral nutrients.
18
Q
What are the roles of the prokaryotic photobiont in lichens
A
- synthesis of organic nutrients
- nitrogen fixation
19
Q
Describe Rhizobium and Fabaceae
A
- major source of fixed nitrogen for plants
- species-specific for bacteria and plants
– co-evolution of host and symbiont
20
Q
Describe the role of the plant in the legume/rhizobium symbiosis
A
- nutrition
- low oxygen tension (leghaemoglobin)
- protection
21
Q
Describe the role of the bacterium in the legume/rhizobium association
A
nitrogen fixation
22
Q
Describe the formation of Rhizobium root nodules
A
- recognition and attachment
- invasion
- travel through infection thread
- bacteroid formation
- bacterial and plant growth to form the nodules
23
Q
Describe the Verminephrobacter symbiosis in earthworms
A
- almost all earth worms harbour species-specific
endosymbionts - Verminephrobacter
- vertically transmitted
- evolutionary ancient association.
- bacteria live on host waste products.
- beneficial for host reproduction (nutritional advantage)
- reductive evolution of the bacterial genome results in streamlining
24
Q
Describe the nephridia of an earthworm
A
- clitellum
- intestine
- septum
- pore to exterior
- nephrostome (intake)
- 1st loop
- 2nd loop
- ampulla
- 3rd loop bladder
25
Describe the genome evolution of vertically transmitted extracellular symbionts
26
Describe Verminephrobacter symbionts
- high host fidelity
- vertical transmission
- extracellular lifestyle
- scope for HGT
- different pattern of genome evolution from intracellular symbionts
- two different environments: nephridia and cocoon
27
Describe free-living microbes
- recombination within and between populations
- few pseudogenes
- few mobile elements
28
Describe the genetics of Verminephrobacter
- genetic mixing, fluctuating environment
- ongoing uptake and loss of genes
- many mobile elements and genome rearrangements
- accelerated evolutionary rates
- few pseudogenes
- no genome reduction
- continuous genome rearrangements
29
Describe the genetics of insect endosymbioses
- no genetic mixing, stable environment
- host restriction
- accumulation of pseudogenes
- expansion of mobile elements
- chromosomal rearrangements
- accelerated evolutionary rates and gene loss
- loss of mobile elements
- few pseudogenes
- small and stable genome; AT-bias
30
Describe aphid symbionts
- Buchnera genus
- e.g. Acyrthosiphon pisum (pea aphid)
- e.g. Schizaphis graminum (wheat aphid)
31
List some ant symbionts
- Blochmannia floridanus
- Blochmannia pennsylvanicus
32
List a Tsetse fly symbiont
Wigglesworthia glossinidia brevipalpis
33
Describe bligate mutualistic insect endosymbionts
- P-symbionts
- restricted to bacteriome
- domesticated by the host
- cannot invade naïve hosts
- dependent on host-based mechanisms for transmission
34
P-symbionts
primary symbionts
35
bacteriome
consists of specialised host cells (bacteriocytes)
36
Describe facultative insect endosymbionts
- S-symbionts
- erratically distributed
- not required for host reproduction
- resemble pathogens
- can colonize uninfected hosts & establish stable, maternally inherited infection
- can confer benefits, including protection against natural enemies
37
S-symbionts
secondary symbionts
38
Describe facultative insect endosymbiont pathogen resemblance
invade cells, including reproductive organs
39
Describe insect endosymbiotic reproductive manipulators
- parasites that spread by increasing host reproduction through females offspring;
- through reproductive incompatibility between infected and uninfected insects
- infected males sterilise uninfected females
- e.g. Wolbachia spp.
40
Describe Buchnera
- obligate intracellular
endosymbionts of aphids.
- without the bacteria the aphids die of starvation
- bacteria are maternally transmitted
– and therefore co-evolve with the aphid
41
Describe Buchnera phylogeny
- most Buchnera genes have close homologues in the Enteric bacteria
- the distant ancestor of Buchnera was probably somewhat like present day Escherichia coli, that has undergone extensive reductive evolution
42
Describe the metabolic interdependence of Aphids and Buchnera
- bacteria located in
‘bacteriocytes’
- surrounded by an aphid-derived membrane;
- unculturable
- vertically transmitted via the ovary
43
bacteriocytes
- specialised insect cells
- aka mycetocytes
44
Describe the host role in the Aphid-Buchnera symbiosis
supplies energy, carbon, and nitrogen, in the form of glutamine from phloem
45
Describe the symbiont role in the Aphid-Buchnera symbiosis
production of amino acids, especially tryptophan (12
to 16 copies of trpEG genes).
46
Describe the long-term co-evolution of Aphid-Buchnera
- mutualistic symbiosis
- probably established 150 to 250Mya
47
Describe Wolbachia
- large group of intracellular alphaproteobacteria
endosymbionts
- restricted to Ecdysozoan species
- essential for survival and reproduction of nematodes: mutualists
- present in ~66% of insects
- infect the germ line
- often manipulate host sex ratios for their own benefit: pathogenic capacity
48
Who is Wolbachia related to?
- Anaplasma
- Ehrlichia
- Rickettsia
49
Who does Wolbachia infect?
- terrestrial arthropods
- filarial nematodes
50
Describe the four reproductive phenotypes of Wolbachia
- feminisation of genetic males
- parthenogenic elimination of males from reproduction
- male killing of infected males
- cytoplasmic incompatibility
51
Whose genetic males do Wolbachia feminise?
- Hemiptera
- Isopoda
- Lepidoptera
52
For which groups does Wolbachia do parthenogenic elimination of males from reproduction?
- Acari
- Hymenoptera
- Thysanoptera
53
For which groups does Wolbachia do male killing of infected males?
- Coleoptera
- Diptera
- Lepidoptera
- Pseudoscorpiones
54
Describe cytoplasmic incompatibility in Wolbachia
prevents infected males mating with females without the
same Wolbachia
55
For which groups does Wolbachia do cytoplasmic incompatibility?
- Acari
- Coleoptera
- Diptera
- Hemiptera
- Hymenoptera
- Isopoda
- Lepidoptera
- Orthoptera
56
Describe the use of Wolbachia for disease vector control
- release of Wolbachia-infected males into wild populations where Wolbachia is absent
- release of females harbouring Wolbachia
- release of Wolbachia wMelPop via females
57
Describe the release of Wolbachia-infected males into wild populations where Wolbachia is absent
reproductive incompatibility with wild females results
in embryonic death of offspring.
58
Describe the release of females harbouring Wolbachia
- offspring with Wolbachia have reduced competence as pathogens vectors
- as only females transmit disease, males not used
- Wolbachia spreads via cytoplasmic incompatibility
59
Describe the release of Wolbachia wMelPop via females
- pathogen blocking and spread via cytoplasmic incompatibility
- reduces insect lifespan, further decreasing pathogen transmission
60
Describe termite symbioses
- symbiotic associations with hindgut microbiota are essential to utilise complex biopolymers
- flagellates and bacteria occur in the gut of lower termites
- higher termites possess only bacteria
- e.g. spirochetes
61
complex biopolymer
wood
62
Describe cellulose and symbioses
- metabolic pathways to utilise cellulose has evolved in many bacterial groups
- form the bases of many symbioses
63
Describe carbohydrate polymers
- abundant biological molecules
- used for storage or as structural components
64
Describe cellulose
- linear polymer of glucose
- most common carbohydrate synthesised by plants
- key part in the carbon cycle.
- insoluble crystalline microfibrils: highly resistant to enzymic hydrolysis.
65
Describe ruminants
- digest cellulose for 9-12 hours
- variety of bacteria convert polymers such as cellulose to glucose and then to fatty acids
66
Describe the rumen
large (100-150l) fermenter kept at constant temperature
67
Describe the Hawaiian bobtail squid (Euprymna scolopes)- Vibrio fischeri Symbiosis
- light generated by Vibrio fischeri bacterial symbionts camouflage Hawaiian bobtail squid
- prey animals cannot see the squid’s shadow from below.
- squid mucus attracts many bacterial species of into the light
organ
– ciliated cells create a current that expels most bacteria, and hydrogen peroxide creates an environment that only Vibrio fischeri survive
- inside the light organ, Vibrio fischeri is provided with sugars and amino acids
- daily rhythm of alternating symbiont metabolism between glycerol phosphate respiration and chitin fermentation facilitates luminescence
- light organ becomes acidic at night, increasing oxygen availability
- female squid have a second symbiotic organ containing a simple symbiotic community
68
Describe the holobiont
organisms are an expression of a combination of their genome and their microbiota.
69
Describe the human microbiota
- dynamic
- major role in health and disease: dysbiosis
70
Describe the functions of the indigenous microbiota
- catabolism and bioconversion of dietary or host derived compounds can make nutrients more available to the host.
- synthesise important cofactors or bioactive signaling molecules (e.g. amines)
- signaling between the microbiota and the host can trigger alterations in host function (e.g. altered expression of mucus or alteration of the immune response)
