Symbiosis Flashcards
What is being conferred in a biofilm, and how in an action to prevent being susceptible to antibiotics?
Tolerance, biofilm is breeding ground for antibiotic resistance - horizontal gene transfer.
What are the 3 types of symbiosis, describe them:
Commensal (one benefits more than the other without causing harm/benefit)
Parasitic (one benefits off the other, other suffers a detriment)
Mutualistic (both benefit)
What can bacteria do that plants cannot do, which is the prime reason why rhizobium is associated with legumes?
Plants cannot convert nitrogen to ammonia, bacteria can - mutualistic.
Describe the mechanism of rhizobium in legumes:
Plants produce flavonoids, bacteria produce nod factors in response.
Plants get that rhizobacteria are here and can now recruit them into the root to access nitrogen.
What do bacteria produce in response to flavonoids in the rhizosphere?
Bacteria produce nodulation factors (nod factors) - recognised by the plant to activate the symbiosis signalling pathways.
Where do rhizobia gain entry into the plant root?
Through the root hairs that grow around the bacteria attached at the root surface.
Where are the rhizobia?
They are trapped inside the root hair curl, the infection threads are initiated at the site of the root hair curls. the nodules initiate the site of bacterial infection.
How do rhizobia differentiate into a nitrogen fixing state?
The rhizobia are released into membrane bound compartments inside the cells of the nodule - here they differentiate into an N2 fixing state.
Nitrogenase is ____ to oxygen?
It is sensitive to oxygen
Describe the central nitrogen fixating zone.
This is the main route of O2 diffusion through the nodule apex, this generates a longitudinal O2 gradient.
The free oxygen concentration drops to less than 50nm in the central nitrogen-fixing zone containing Rhizobium Bacteroids.
Where do rhizobium fix nitrogen ?
In a microaerobic, nitrogen rich environment.
What is an example of an aerobic turned anaerobic environment in the body?
Cancer cells which turn hypoxic as they grow away from the blood vessels.
Why do nod +++ nodules not grow as much as the Soybean WT?
As the soybean plant spends too much time investing energy into forming nodule structure leading the nod+++ to be stunted and pale in comparison to the wild type.
What do Frankia (GP) species form associations with?
Alder, birch, beech, walnut, buckthorn and roses.
What are many of the plants types that are colonised by Frankia?
Actinorhizal; these are pioneers of disturbed sites and early successional. Have important impacts on late successions.
How does Frankia nitrogen fixate in the root hairs?
By deformation in root hairs of alder (alnus).
What is the mechanism between the establishment of symbiosis between arbuscular mycorrhizal fungus and plants?
Strigolactone (signal) by the plant root signals to arbuscular mycorrhizal fungi (AMF) in the rhizosphere.
Fungi in response produce mycorrhizal factors (MYC factors) - activate symbiosis pathway.
What does the AMF invasion involve?
The infection peg from the hyphopodium that allows fungal hyphal growth into the root epidermal cell.
Fungus colonises plant root cortex through intracellular hyphal growth.
Arbuscules are formed in inner root cortical cells from the intercellular hyphae.
Name the parts of the mechanism of arbuscular mycorrhizal fungus symbiosis and its invasion:
Strigolactone (signal)
Rhizosphere
MYC factors
Infection peg from hyphopodium - hyphal growth in root cell
Root cortex (intracellular growth)
Arbuscules in inner root cortical cells from the intercellular hyphae.
Describe endomycorrhizal fungus interactions with plants?
- distributive hyphae
- absorptive hyphae
- spores
Describe ectomycorrhizal fungus interactions with roots of pine?
- mantle hyphae cover the roots of pine
- Dichotomously (in two) branched mycorrhizal short roots.
What are some of the mutualistic associations between mycorrhizal fungi and plants?
- provides fungus access to nutrients (glucose and sucrose) translocated from leaves to root on fungus partners
- fungus mycelium has higher absorptive capacity for water and minerals - large S.A - plant benefits
- mycorrhizal network underground carbon and water plant to plant transport.
What is a particularly important role of mycorrhizal fungi?
Phosphate uptake and translocation.
What are marine microbial symbiosis enclosed by?
Mesophyll matrix (sponges) ex: spongiobacteria
What are some of the benefits of mutualists bacteria in microbial ecology?
- nitrogen fixation
- denitrification
- provide a chemical defence mechanism
What does alvibrio fischeri provide to the bobtail squid?
This is a luminescent bacteria which can produce light at night to offset the squids shadow and hide it from predators.
