Lecture 36 Flashcards
What type of bacteria is involved in interactions with marine and deep sea animals? Why?
Chemolithoautotrophs. They can extract energy from chemical compounds and fix CO2, providing animals with an important source of food in an otherwise hostile environment.
Give an example of an animal that associates with chemolithoautotrophic bacteria at shallow, medium, and deep depths in the water column.
Shallow: gutless clam
Medium: mussels (hydrocarbon seeps)
Deep: tube worms
What is the typical habitat of tube worms?
Deep sea hydrothermal vents
Describe the anatomy of the tube worm and how this pertains to their interaction with bacteria.
They lack a mouth and gut. However, they do have tissue called a trophosome which contains sulfide-oxidizing bacterial (SOB) symbionts. They also have a red colour due to hemoglobin in the plume that transports O2 and H2S to the bacteria (similar to leghemoglobin).
Here, the symbionts are feeding the animal instead of the other way around.
Describe the category and functioning of SOB symbionts of the tube worms.
Category: Gammaproteobacteria
They fix CO2 using energy and electrons derived from H2S oxidation. The CO2 is used to make organic matter and nutrients They then pass on these nutrients to the worm.
Describe the habitat of the gutless clam.
They live in estuary habitats rich in organic carbon (river) and sulfate (sea).
Describe the body of the clam and how relates to their relationship to bacteria.
The clam has no mouth, gut, anus, etc. so they can’t digest anything. They can survive because they rely on chemolithoautotrophic sulfide-oxidizing bacteria (SOBs). The bacteria, which live in its gills, provide them with nutrients from both the ocean and river.
Describe the setup of the gutless clam habitat and the bacteria it works with. Include relevant compounds and reactions.
The clam lives in the aerobic zone of the estuary along with its sulfide-oxidizing bacteria (SOBs) in its gills. In the anaerobic zone, there are SRBs.
There is an flux of organic matter from the river and SO42- from the sea. The SRBS will oxidize OM to CO2 and reduce sulfate to H2S. The H2S will then rise through the sediments into the aerobic zone.
The H2S will be oxidized by both the SOBs and the clam’s mitochondria, generating ATP. This energy fuels CO2 fixation by the SOBs. They supply the clam with organic compounds that are its source of carbon and energy.
Describe the typical habitat of C. Mytilidae mussels.
They are found at deep sea cold seeps and hydrothermal vents. Both of these vents release H2S, CH4, and other hydrocarbons.
Describe the symbiotic relationship that mussels participate in.
Mussels from both cold seeps and hydrothermal vents associated with symbiotic bacteria in their gills. The symbionts obtain nutrients, C, and energy from the environment, and hosts obtain nutrients via digestion of the symbiotic bacteria.
What are the two types of symbionts of deep sea mussels? Where are they more common?
- Methanotrophic symbionts (more common in cold seeps)
- Sulfide-oxidizing chemolithoautotrophic symbionts (more common in hydrothermal vent)
Describe how methanotrophic symbionts work with deep sea mussels.
They oxidize CH4 as a carbon, electron, and energy source, and use the enzyme MMO (Methane monooxygenase).
Describe how sulfide-oxidizing chemolithoautotrophic symbionts work with deep sea mussels.
They are similar to those found in the tube worm and clam: they oxidize H2S as an electron and energy source and fix CO2 as a carbon source.
