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16 Cards in this Set

  • Front
  • Back

What are the three positive symbiosis?




WHat are the four negative symbiosis?




What is Amensalism?

One organism is negatively affected, and the other is not affected.

Describe the symbiosis between hydrogen-sulphide oxidizing bacteria and tube worms.

Tubeworms glum attract CO2, O2 and H2S, which goes down the gut where the bacteria culture is. The bacteria oxidizes H2S with O2 (electron acceptor) and produce energy. The energy is used in the Calvin Cycle to produce glucose.

Describe the symbiosis in a legume plant

nitrogen fixing bacteria and host plant

Describe the integration of the nitrogen-fixing bacterium into the plant.

Bacteria senses flavonoids secreted by plant. Bacteria induce nod genes and produce the nod factor. Bacteria nod attach to root hairs of plant. Induce the formation of infection thread of plant. Bacteria enter infection thread and replication. Infection may branch in further, causing to bacteria to produce more nodes. Plant close membrane and the bacterium becomes a bacteriod. Bacteriod differentiates into a symbiosome.

How are flavonoids specific to a bacterium?

If flavonoids from another plant are detected by a bacterium, the bacterium will turn off the gene expression for nitrogen fixation.

What are the genes for nitrogen fixation of a nitrogen-fixing bacterium? Where are the genes encoded?




Genes are encoded in large plasmids or symbiosis islands.

Give an example of nitrogen-fixing bacteria.



List two advantages to the bacteria in biofilm formation.

1. Protection against stress

e.g. environmental, antibiotics, UV

2. Protection against predators

List one benefit and damage of biofilm formation.

Benefit: maintain and improve ecological health

Damage: costly for the shipping industry, cost dragging & main cause of many post-op infections.

Describe the endosymbiosis relationship between aphids and bacteria (buchnera spp.). Comment on the evolution of the bacteria.

Aphids feed on tree sap, which is not very nutritious, while buchnera spp. in aphids provide them with essential nutrients. Aphids provide home for Buchnera spp. and protect them from environmental stress.

The bacteria has evolved to lose genes that are not associated with the production of nutrients for Aphids, thus it cannot survive without the aphids. It has evolved into sth similar to obligate intracellular pathogen.

Describe the endosymbiosis relationship between squid and aliivibrio fischeri bacteria.

Aliivibrio fischeri bacteria produced AHL (acylated homoserine lactone) that fluorescents in high density. This helps camoflage the squid from predator when in the dark by creating a shadow from the glow. The squid provides home and protection for the bacteria.

What is the advantage of only turning on luminosity when Aliivibrio Fischeri bacteria is in high density in squid?

production of AHL (fluorescent compound) requires energy. Only produce it in high density preserves bacterium energy.

What is meant by a 'coral holobiont' ?

Coral holobiont refers to an entire community of micro-organisms making up a healthy head of coral. Thinking of the coral not just the coral itself, but also the microbial surface and the algae community.

What is the consequent of coral stress?

Coral bleaching.