Guest lectures

Question 1

Legume Nodule Symbiosis

Answer 1

-legumes and rhizobia live together in symbiosis

Question 2

rhizobia infection of legumes

Answer 2

-infection is not a negative interaction
-it leads to formation of root forming nodule full of rhizobia that fixes nitrogen

Question 3

steps in formation of root nodule

Answer 3

1) recognition-rhizobia attach to plant
2) bacterium secrets nod factors called root hair curling
3) invasion-rhizobia penetrate root hair and multiply within infection thread

Question 4

sanctions hypothesis

Answer 4

legumes cant recognize more parasites or less N fixing rhizobia have to counter parasitism through post infection legume sanction

-reduction of nodule growth
-early nodule death
-decrease carbon supply to nodules
-reduce oxygen supply to nodules

Question 5

Partner choice hypothesis

Answer 5

plants use prenoduleation signals from rhizobia to determine whether to allow noduleation choose non cheating rhizobia

Question 6

crown galls

Answer 6

plant tumors induced by A tumefaciens cells harboring a large plasmid the Ti (tumor induction) plasmid

Question 7

AGROBACTERIUM TUMEFACIENS

Answer 7

forms a parasitic symbiosis w plants causing crown gall disease

Question 8

structure of Ti plasmid

Question 9

initation of tumor formation

Answer 9

-A tumefaciens cells must attach to wound site
-transfers plasmid to plant

Question 10

Primary symbionts for insect

Answer 10

required for host to reproduce
-restricted to bacteriome
–bacterial cells are found in bacteriocytes

Question 11

microbial symbionts can be aquired how

Answer 11

environment (horizontal transmission)
parent (vertical transmission)

Question 12

Heritable symbionts of insects

Answer 12

-obligate
-some exploit metabolic potential of symbiont
-primary symbionts exhibit extreme gene reduction due to it being given to them by host

Question 13

secondary symbionts for insects

Answer 13

not required for reproduction
not always present
can invade different cells and live extracellularly
must provide a benefit- nutritional, environmental, pathogenic

Question 14

Reproductive parasitic symbionts

Answer 14

rickettsia-infected flies reproduce twice as much
wolbachia- infected males sterilize uninfected females

Question 15

defensive symbioses

Answer 15

-defensive strategy used by insects to deter pathogens/predators usually chemicals
-(paederus beetle take cytotoxic chemical from plant to defend it and beetles eggs)