Symbiosis Flashcards
(18 cards)
Types of symbionts
Facultative mutualists
Obligate/depender
Parasitism/exploitation
How do symbionts form
Vertical transmission (maternal)
Horizontal transmission (environment)
Location
Endosymbiont
Gut symbiont
Ectosymbiont
Nutrient services
Photosynthate
Digestion
Anabolism
Micronutrient uptake
Defence/protective symbiosis
Protection against parasites and microbial attack
Eg hamiltonela kills wasp larvae in aphids
Streptomyces bacteria produce antibiotics that stop bee wolf pupa breaking down in the ground
Offence
Bacteria released by nematodes kills host, the parasite benefits
Holobiont
An organism with all its microbes
Why is life symbiotic?
Allows access to a phenotype from another kingdom
Symbionts can be deployed outside the host
Symbionts can be bioreactors
Why do organisms evolve into symbiosis
Byproduct mutualism
Reciprocal altruism
Capture
Filaraisis - nematode worms
Drug design against eukaryotic parasites is constrained
Shared systems mean it’s hard to target pharmacologically without impacting the parallel system in host
Limited drug options which may only kill juvenile worms
Solution is to target a symbiont the worm is dependent on
Filarial worms require Wolbachia bacteria so antibiotic treatment cures worms
Managing methane emissions from ruminants
Rumen is a microbial fermentation chamber
Bacteria break down cellulose to VFAs which give energy to cow
CO2 and H as byproduct
Archaea convert this to methane
To solve this inhibit the final step of methanogenesis by archaea
Activity of methyl coenzyme reductase results in 30% reduction in methane
Boaver metabolised in gut, it’s a feed additive
Agricultural productivity
In crop rotation soil is nitrified via Rhizobia and legume interactions
Rhizobia and mycorhizal fungi are integral to plant health
Stress resistance
Solubilising nutrients
Pathogen resistance
Soil and seed inoculation increases productivity
Microbiome dysbiosis - C difficle case study
Dybiosis - wrong bacteria in wrong abundance
Can occur after infection or antibiotics
C difficle commonly blooms after antibiotic therapy as many spores survive
Dominates microbiota and excludes friendly bacteria
Toxin secreting results in diarrhoe
Antibiotic therapy that does work is a last resort
An alternative is to outcompete with other microbes
Strategy - faecal microbiota transplants
Micronutrient uptake in plants services
Phosphates and nitrates
Fungal hyphae extending from the plant into the soil
Arbuscular mycorrhizae (cellular embedding) and ectomycorrhizae
Can join different trees together nutritionally
Photosynthate services
Acquiring sucrose from algal symbionts
Common in microeukaryotes
Also found in some animals
Digestion services
Digestion of complex polysaccharides - lignin and cellulose to SCFAs
Also detoxification of diet - plants commonly contain secondary toxic compounds
Gut microbes break these down and extend dietary sources
Anabolism services
Essential amino acid synthesis (tryptophan)
Other amino acid synthesis (tyrosine)
They can make B vitamins
Aphids live on a diet without protein, bacteria takes sugar and turns it into tryptophan
Defensive or protective symbiosis services
Avoid predation through countershading or toxicity
Inhibit natural energies
