Lecture 14 - Microbe-Animal Interactions

Question 1

What is the first prediction to explain the origin of the eukaryotic cell?

Answer 1

in iron-sulfur world = bacteria and archaea have syntropic interaction &raquo_space;> DNA moves into centralized structure (nuceloid) &raquo_space;> chimera of bacteria and archaea = eukarya

Question 2

What is the thiodendron stage?

Answer 2

bacteria and archaea cells didn’t fuse together but have a very veryyyyyy close interaction (as if they were boutta fuse)

Question 3

What kind of interaction did bacteria and archaea have?

Answer 3

syntropic interaction - exchange of nutrients

Question 4

What are the 2 different classes of symbionts between animal and microbe interactions?

Answer 4

primary and secondary symbionts

Question 5

What are the characteristics of primary symbionts?

Answer 5

transmitted maternally, super small genomes, live in a bacteriome; have a long evolutionary mutualistic relationship with host

Question 6

What are the characteristics of secondary symbionts?

Answer 6

transmitted maternally and horizontally, negatively/positively affect host, facultative (transient), intermediate genome size, can be ecto- or endo-

Question 7

What is a bacteriome?

Answer 7

specialized organelle structure where all the symbionts live

Question 8

What is a Buchnera?

Answer 8

primary symbiont of an Aphid

Question 9

what are the three types of interactions between animals and microbes?

Answer 9

symbiosis, commensalism, and parasitism

Question 10

How is Buchnera passed onto the next generation of Aphids?

Answer 10

Buchnera within mother Aphid infects developing embryos during development

Question 11

What method do primary symbionts commonly used to be transmitted maternally?

Answer 11

during embryo development within the mother

Question 12

How do genome sequence comparison between symbionts indicate a long symbiosis?

Answer 12

no overlap but will not find some biosynthesis genes in host DNA but are found in their symbiont’s DNA and genes are not lost that fast = time needed for that to happen

Question 13

What are the characteristics of parasites for animals?

Answer 13

generally unicellular colonizes host, evades host immune responses, transmits to new host

Question 14

What is responsible for the parasitic activity of a nematode onto an insect?

Answer 14

nematode’s bacterial endosymbiont

Question 15

What is the life cycle/pathogenesis of a parasitic nematode? (sequence of events)

Answer 15

infective juvenile exits insect cadaver = free living &raquo_space;> infects and goes inside another insect &raquo_space;> vomits intestinal contents into insect hemolymph &raquo_space;> bacterial endosymbiont kills insect &raquo_space;> nematode grows, eats up vomit with bacteria, and reproduces

Question 16

What does the nematode’s bacterial endosymbiont release/secrete that causes the death of an insect?

Answer 16

toxins, antibiotics and virulence factors

Question 17

What is Wolbachia?

Answer 17

gram– the bacterium that infects insects

Question 18

What type of relationship does Wolbachia have with arthropods?

Answer 18

reproductive parasite

Question 19

What type of relationship does Wolbachia have with nematodes? What does the Wolbachia do for the nematode?

Answer 19

mutualistic symbiont that provides nutrients and aids in reproduction

Question 20

What are the characteristics of Wolbachia?

Answer 20

not easily transmitted, mother can only transmit bacterium to offspring via infected eggs, males are dead-end hosts because they don’t transmit

Question 21

What are the 4 different strategies of how Wolbachia gets rid of the males?

Answer 21

feminization, parthenogenesis, male-killing, cytoplasmic incompatibility

Question 22

What dictates which strategy will Wolbachia use?

Answer 22

depends on host

Question 23

What is the Wolbachia strategy of feminization?

Answer 23

converting infected males into females = 2x transmission rate | most beneficial strategy, least common

Question 24

What is the Wolbachia strategy of parthenogenesis?

Answer 24

infected female reproduces without males and ends up with infected females = 2x transmission rate | NO males involved, NO fertilization

Question 25

What is the Wolbachia strategy of male-killing?

Answer 25

killing male offspring, occurs only in hosts with high sibling competition = kill brothers if it benefits the sistas (ex: 1 sister vs 2 brothers = obvi the bros will die)

Question 26

What is the Wolbachia strategy of cytoplasmic incompatibility?

Answer 26

modification of male gametes so that incompatibility exists = zygote lethality | most common and phylogenetically diverse

Question 27

When would Wolbachia use the cytoplasmic incompatibility strategy?

Answer 27

when an Infected Male mates with Uninfected Female | Infected Males are incompatible with Uninfected Females

Question 28

How is cytoplasmic incompatibility strategy theoretically explained?

Answer 28

in a mixed population = infected males increase the fitness of infected females by decreasing the fitness of non-infected females

Question 29

What is the selective advantage for insects to keep the Wolbachia infection?

Answer 29

have a higher resistance to RNA viruses and to insecticides

Question 30

What are the 5 symbionts that live within the termite's gut?

Answer 30

protozoan, methanogenic archaeon, acetogenic-CO2-reducing bacteria, fermenting bacteria, and N2-fixing bacteria

Question 31

What does the protozoan do in the termite's gut?

Answer 31

takes up cellulose molecule to convert it into acetate, CO2, and H2

Question 32

What do methanogenic archaeons do in the termite's gut?

Answer 32

takes up H2 and CO2 to make methane

Question 33

What do acetogenic-CO2-reducing bacteria do in the termite's gut?

Answer 33

takes up H2 and CO2 to make acetate

Question 34

What do fermenting bacteria do in the termite's gut?

Answer 34

uptakes uric acid and converts it into acetate and nitrogenic compounds

Question 35

What do N2-fixing bacteria do in the termite's gut?

Answer 35

converts N2 into NH3 = amino acids

Question 36

Which symbiont is the primary symbiont in the termite's gut?

Answer 36

protozoans

Question 37

What is the key molecule the termites need that its symbionts help create? What does the termite need this molecule for?

Answer 37

acetate to use a carbon/energy source

Question 38

What converts the wood particle into cellulose for the termite?

Answer 38

salivary gland releases cellulase that breaks down wood particles

Question 39

What is the molecule that precedes CO2, H2, and acetate and is converted by the protozoans in the termite's gut?

Answer 39

pyruvate

Question 40

What type of symbiotic relationship do the symbionts within a termite's gut have?

Answer 40

symbioses within a symbioses

Question 41

What other animal's gut is similar to that of the termite?

Answer 41

Ruminant gut of a cow

Question 42

What is the trophosome structure of a tube worm?

Answer 42

where all of the bacteria are and where the uptaken molecules are taken through the Calvin cycle and sulfur oxidation

Question 43

What do the gills of a tube worm function as?

Answer 43

takes up the molecules from the environment

Question 44

Where, in the ocean, do tube worms live?

Answer 44

in deep sea vents

Question 45

What symbionts do Mealy bugs have?

Answer 45

many species have one primary symbiont but have different secondary symbionts = symbiont within a within a symbiont within a Mealy bug

Question 46

What is a unique characteristic about the symbiotic relationships of the symbionts within a Mealy bug (including the bug itself)?

Answer 46

amino acid biosynthesis pathways spans across all symbionts/insect

Question 47

In animal-microbe interactions, what does the animal host usually provide for the microbe?

Answer 47

habitat and nutrients

Question 48

In animal-microbe interactions, what does the microbe usually provide for the animal host?

Answer 48

maturity of immune system (MI), helps with digestion (D), developmental inducer (DI), microbial homeostasis (MH) = MI-D-DI-MH