Symbiosis In The Deep: Tubeworms & Bacteria Lecture (2021) PDF

Symbiosis in the Deep – Tubeworms and Bacteria Prof Simon Andrews [email protected] BI2MBC MARINE BIOLOGY &...

Symbiosis in the Deep – Tubeworms and Bacteria Prof Simon Andrews [email protected] BI2MBC MARINE BIOLOGY & CONSERVATION Part 2 (of 3 parts): Discovery of Novel HTV Life!  Animals living around hydrothermal vents Giant Tube Worms Invertebrate communities Giant Tube worms (up to 2.4 m length) – Riftia pachyptila Giant clams Large mussels Crabs, gastropods, polychaete worms, ‘spaghetti’ worms, new fish species, shrimps Alvin’s meter-long temperature probe extends toward a community of galatheid crabs perched atop pillow lava and a dense field of mussels. John B. Corliss cradles a (Photo by Robert Hessler. specimen of a giant clam retrieved on 1977 Galápagos Rift expedition. (Photo by Emory Kristof © National Geographic Society.) Anatomy of a giant tube worm No mouth, gills, digestive system or anus Modified gut – spongy tissue ‘trophosome’ half of body mass rich in S granules High density of S-oxidising bacteria Mainly Epsilonproteobacteria (chemolithotroph/autotroph) H2S + 2O2  SO4 + H+ + energy Calvin cycle (CO2  CHO) ‘Chemosynthetic’ Symbiotic relationship Bacterium and an Animal!  The two steps of sulphur oxidation: Thioautotop Step 1: HS- oxidation to sulphur or sulphite – released e- enters ETC yielding a H+ gradient hic bacteria allowing ATP production (oxidative phosphorylation) – energy generation Step 2: ‘APS pathway’ – sulphite oxidation. APS reductase AMP + SO32-  APS (adenosine 5'- phosphosulfate) ATP sulfurylase APS + PPi  ATP + SO42- Giant Tube Worms - unusual blood! Haemoglobins that carry H2S (as well as O2) Helps prevent toxicity to tube worm tissue CO2 levels are v high in GTW blood (20-30 mM) S isotope ratio analysis shows that the symbiont S is same as that of vent, not sea water – proof that geothermal HS- is utilised by the worm GTW haemoglobin – is a giant hexameric form, and binds H2S using Zn, O2 using haem It is also extracellular! https:// divediscover.whoi. edu/hydrothermal- Bacteri a Hydrothermal vent prokaryotes include chemosynthetic bacteria and archaea at the base of the food chain. They grow in the water and on almost every surface at the vents, and in tiny spaces below the seafloor. Some bacteria form symbiotic relationships with tubeworms, clams, mussels and shrimp. Shrimps 15 species of shrimp live at vent sites globally. ~Half live in the Atlantic and half in the Pacific. In the Pacific, but each vent site supports only one species. They typically live around clumps of tube worms and mussels. In the Atlantic, shrimp often gather in huge swarms along the sides of active black smokers. Some kinds of shrimp are host to different kinds of bacteria that may help them gain nourishment from the hydrothermal fluids Mussels Mussels are very late to colonize hydrothermal vent sites. They clump together in cracks in the seafloor. Symbiotic bacteria live in the mussels’ gills. Like the microbes living inside tubeworms, these bacteria use energy from chemicals in the vent fluids to produce sugars. The sugars provide nourishment for both the mussels and the bacteria. Mussels can also filter food from the water, so if hydrothermal fluid stops flowing out of the vent, mussels can survive for a short period of time.  Clams colonize hydrothermal vents later than mussels. Each clam has a big muscular foot that it wedges into cracks in the ocean floor. A clam also uses its foot to move around. Just like the mussels, clams depend on symbiotic bacteria that live in their gills. These bacteria use the chemicals in the hydrothermal fluid to produce sugars. The clams use some of these sugars for food. Despite their thick shells, clams are eaten by crabs and octopi. Clams Zoarcid fish These two-foot long white fish are top predators around vents. They eat everything from tubeworms to shrimp. Despite their huge appetites, these fish are slow and lethargic. They spend a lot of time floating around clumps of tube worms and mussels  There are several species of crabs that live around hydrothermal Crabs vents. One type is the Galatheid crab, or squat lobster. These white crabs live throughout the ocean, but their numbers increase around hydrothermal vents where food is plentiful. These crabs are scavengers. They hang out in mussel beds where they eat bacteria and dead animals. Octopus There are several species of octopus that only live around hydrothermal vents. Some species have only been seen a few times. They are typically one meter long, and their heads are about the size of an orange. Octopi are top predators. They live among or even under clumps of mussels. They eat crabs, clams, and mussels. Dandelions Fuzzy-looking balls -a colony of many individual animals related to the Portuguese-Man- O-War and other jellyfish. They use long whisker-like tentacles to anchor on rocks and to move around. The dandelions are scavengers. They are some of the last animals to colonize vent sites and high numbers usually means that the vents are no longer active and most of the other organisms are dying. Food-web of hydrothermal vent communities Most vent species are non-symbiotic Most feed by grazing or filtering bacteria Food web of vents – four layers, and two types of primary producers H2S (and methane) at the base of the web Hydrothermal vent bacteria Thiobacillus Thiomicrospira H S-oxidising bacteria Thiothrix 2 Beggiatoa Pyrolobus And methylotrophic bacteria (growth on methane) fumarii Archaea at +100 ˚C! Pyrolobus and Pyrodictium – in smoker chimney walls The most thermophilic of all! Use H2 as energy source End of part 2 – please now view part 3 of this lecture