Chapter 23 Flashcards
(41 cards)
What are Lichens?
- Leafy, encrusting microbial symbioses
- mutualistic relationship (fungus and green alga(or cyanobacteria)
Relationship of Lichens
Phototroph produces organic matter, fungus protects phototroph from dying out
What are consortia?
freshwater microbial mutualisms
Relationship of consortia
Green sulfur bacteria (epibionts) phototrophy
flagellated rod shaped bacterium (movement)
What is the “genus species” name of consortia?
Chlorochromatium aggregatum
What is the The Legume-Root Nodule Symbiosis?
Infection of legume roots by N-fixing bacteria, leads to formation of root nodules
Importance of LRNS?
Increases the fixed nitrogen content of the soil, can grow well under poor soil vs plants that don’t have it
What is O2 levels controlled by in the root nodule
leghemoglobin (O2 binding protein)
Process of Root Nodule Formation
- Recognition and attachment
- Bacterium secretes Nod factors causing root hair curling
- Invasion. Rhizobia penetrate root hair and multiply within an infection thread.
- Bacteria in infection thread grow toward root cell.
- Formation of bacteroid state within plant root cells. Continued plant and bacterial cell division leads to nodules.
What genes encode proteins in LRNS
NodABC (Nod factors)
Major reactions and nutrients exchanges in bacteroid
Photosynthesis-> sugars -> organic acids –> (in bacteria) **succinate, malate, fumarate -> citric acid cycle -> ETC -> proton motive force -> ATP then **-> pyruvate -> nitrogenase AND FINALLY ATP goes into nitrogenase to make N2 -> NH3 -> glutamine asparagine
In the ETC, what reactions are made?
O2 + Lb -> O2 - Lb (O2 joins H2O in cell again and Lb goes out)
Nonlegume nitrogen fixing symbioses?
Water fern Azolla -> contains N-fixing cyanobacteria
Alder tree Alnus -> contains N-fixing Frankia (vesicles)
What is beneficial about Mycorrhizae?
Mutualism between plant roots and fungi in which nutrients are transferred in both directions (phosphorus, nitrogen, water from soil to plant, carbohydrates (photosynthates to the fungus>)
What are the two classes of Mycorrhizae?
Ectomycorrhizae
Endomycorrhizae
What are ectomycorrhizaes?
Fungal cells that form sheath outside of root, found primarily in forest trees
(there is little penetration into root tissue)
What are endomycorrhizaes?
Fungal cells that penetrate deeply into root forming fungal mycelium (which is embedded within root tissues)
more common than ectomycorrhize
found in >80% of terrestrial plant species
How are microbial symbionts acquired for insects?
Horizontal transmission (environment) Vertical or heritable transmission (parent)
Which symbionts of insects lack a free-living replicative stage
Hertiable (vertical) symbionts
Differences between primary, secondary, and parasitic symbionts?
Primary: required for host reproduction restricted to bacteriome Secondary: not required for reproduction not always present in every individual, can invade different cells and/or live extracellularly **MUST PROVIDE A BENEFIT** (nutritional, protection from environment, pathogens etc) Parasitic: manipulate host's reproductive tissue
What do primary symbionts show extreme results of?
Extreme gene reduction
(~160 to 800 kbp vs 2 to 8 MBP of freeliving bacteria)
ONLY KEEPS GENES FOR HOST FITNESS
(loses catabolic genes, loses anabolic genes)
Key points of termites
- Decompose cellulose and hemicellulose
- classified as higher or lower
Relationship of Hawaiian Bobtail Squid & Vibrio Fischeri
Bioluminescent V. fischeri in light organ emit light that resembles moonlight and camouflages squid from predators (whiel v.f. supplied with nutrients)
Transmission of V. Fischeri is
Horizontal
