L10- Microbial associations with animals Flashcards
What problem do herbivores have?
Animals can’t digest cellulose. Herbivores depend on cellulytic/fermenlative microbes.
What specialised modifications do organisms have for digestive tracts?
Hind gut fermentors- modified extension of small intestine-> after stomach. (poor efficiency- 1st herbivores)
Rumen fermentors- Rumen= main fermentation centre. Comes beffore main absorption chamber “stomach”. 4 chambered- stomach. Evolved and took over as main herbivore.
What do ruminants absorb from food? Use as energy source?
Fatty acids. (not sugar). CO2 and methane are made in the fermentation and released by belching (eructation)
What is grass often infected with?
A range of fungi (called endophytes because they live within plant tissues). Some of these produce toxic chemicals to insects, some of these can affect the animals that eat the grass. Tremorgens inhibit and excite smooth muscle and affects skeletal smooth muscle.
What do termites eat?
They eat wood and then deposit their faeces in a fungal garden. Then eat the fungus.
What do termites need?
They need fungus, and N-fixing spirochetes.
WHat do leaf-cutting ants do?
Chew up the leaves, then poke it into the fungal-garden. Then they eat the fungus. Hyphae swell at tips on the surface of mycelium-> which the ants eat.
Streptomycetes on insect cuticle produce antibiotics.
Do ambrosia beetles harm trees?
No, they insert ambrosia fungus into the tree but just a thin layer which doesn’t harm it. However Dutch elm disease was caused by a parasytic fungus- Ophiostoma ulmi which gets carried in by the beetle. Oh dear.
What’s the tree’s defence to dutch elm disease?
The plant produces intrusions (tyloses) which block water flow through the xylem. This blocks the yeast form of the parasytic fungus which travels through the xylem. However if too many xylems are completely blocked- the tree dies.
How do marine animals e.g. anglerfish use bacteria?
They use bioluminescent bacteria to attract prey or mates. Or to disguise against predators eg the Hawaiian squid. We still don;t know how they flash on and off.
