Lecture 13: Animal-Microbes Flashcards
(22 cards)
What is the difference between commensalism and mutualism?
- Commensalism: 0/+
- Mutualism: +/+
What are some examples of positive microbe-animal positive interactions?
- Stinkbug and Pantoea
- Protozoa and termites (+/+)
- Marine worms and bacteria (+/+)
- Herbivore rumen and microbe (+/+)
Explain the protozoan-termite relationship.
(+/+)
1. Protozoa live in the gut of termites and wood roaches
- Digest the cellulose ingested by their host
- Produces acetate
2. Termites
- Oxidize the acetate
- Don’t produce cellulase
What type of positive interaction do marine worms and bacteria have? Give specific examples.
Both species benefit (+/+)
- Ectosymbiont example: roundworms with Candidatus Thiosymbion ectosymbionts
- Endosymbiont example: segmented worms with Candidatus Thiosymbion endosymbionts
What are ruminants?
Herbivorous cud-chewing mammals (ex. goats, deer, cows) with high cellulose diet (indigestible)
What is the rumen?
Organ that lacks cellulases, is anaerobic, near neutral pH
Describe the rumen microbiota.
- Complex, dense microbial community
- Bacteria: cellulose fermenters, starch fermenters
- Archaea, protozoa, fungi
Explain rumen metabolism.
- Large production of gas removed via eructation
- VFAs produced and cross into bloodstream
- Ruminant gains further nutrition (amino acids and vitamins)
What do the tube worm and bacteria each provide for the other in their mutualistic relationship?
- Bacteria provide sugars for worm
- Worm provides shelter and carbon dioxide
What are some bioluminescent organisms?
- Photobacterium
- Vibrio species
What are the likely functions of bioluminescent symbioses?
- Species recognition (mating)
- Feeding lures (deep sea fish)
- Counterillumination (predation, camouflage)
What do the bobtail squid and Vibrio each provide for the other in their mutualistic relationship?
- Squid provides shelter and nutrients for Vibrio
- Vibrio provides camouflage
Describe the mutualistic relationship between mollusca and bacteria.
Snails, clams, and mussels gill tissue have chemosynthetic symbionts
What do the aphids and Buchanera aphidicola each provide for the other in their mutualistic relationship?
- Aphids
- Feed on phloem sap, which is rich in carbs but poor in most amino acids except glutamine
- Drop sugar water feces -
Buchanera aphidicola
- Intracellular endosymbionts (reside in bacteriocytes)
- Can make all amino acids for host aphid
- Use the glutamine from aphid to make arginine
What are some examples of phototrophic associations?
Host/Symbiont
- Cnidarians –> zooxanthellae
- Sponges –> cyanellae
- Molluscs –> zoonxanthellae
Explain the mutualistic relationship between coral polyps and zooxanthellae.
- Zooxanthellae live in the tentacle epidermal tissue
- Zooxanthellae fix carbon –> facilitate the calcification of the reef structure
What is coral bleaching? What are the possible causes?
- Death of zooxanthellae –> corals lose pigment
- Temperature and disease
What are some examples of commensalism involving humans?
-
Lactobacillus in human intestines
- They get our extra food but we are not hurt by it -
Corynebacterium in human eyes
- Eat our dead skin cells but we are not hurt by it -
Staphylococcus epidermidis
- Use the dead skin cells of the human skin for nutrients
Define microbiome.
The collection of microorganisms living in and on the body, along with their genetic material
What are the effects of the human gut microbiome on human nutrition?
- Metabolically most active human organ
- Microbes makeup ~30% of fecal matter
- Microbes help digest food
- Fermentation produces VFAs
- Microbes supply vitamin B12 & K
- Modified bile acids - steroid metabolism
- Gases - CO2, CH4 and H2S
Explain oral biofilm succession.
- Acidic glycoprotein film from saliva
- Initially Colonized by Streptococcus spp.
- Later colonized by others (Fusobacterium, Spirochetes,
Actinomycetes) - Anaerobiosis is maintained by poor oxygen diffusion through plaque biofilm
- Dental caries/periodontal disease can result
What are some examples of negative animal-microbe interactions? (i.e. predation and parasitism)
- Ants eating fungi
- Fungi eating nematodes
