Mutualisms within Hydrothermal Vents

Erica StephensJessica Hanks

Background Definitions

• Mutualism: an interaction between two species when both benefit and increase their fitness. Some benefits would be easy transportation for one organism, and provide chemicals for food supply for another organism.

• Symbiosis: the living together of two dissimilar organisms.• Endosymbiotic: symbiosis in which one symbiont lives within

the body of the other.• TEM: transmission electron microscope, uses electrons instead

of light.• Intracellular: within cells.• Chemoautotrophic: gets energy from inorganic chemical

compounds.• Methanotrophic: use methane to grow and use as their energy

source.• Inorganic: not characterized by vital processes

Questions Addressing?

• What are hydrothermal vents and where are they located?

• What chemicals are released in the vents?

• What types of organisms possess mutualistic relationships in hydrothermal vents?

• How does the bacteria on the organism help them?

What are Hydrothermal Vents?

• Geysers on the seafloor located in the deep ocean.• Are between 1500-4000 meters.• Community includes mussels, crabs, snails, and lobsters. • Formation: the gigantic plates that form the Earth's crust are

moving apart and form cracks in the ocean floor. Seawater goes into these openings and heats up by the molten rock that lies beneath the Earth's crust. As the water is heated, it rises and seeks a path back out into the ocean through an opening in the seafloor, which causes the different types of smokers.

• Temperature: 400 degrees Celsius (doesn’t boil because of the pressure.)

• Pressure: 300 atmospheres of pressure• Contain primary producers who get energy only from inorganic

sources (chemicals).• Continuously gushes out super-hot, mineral rich water.

http://www.ocean.udel.edu/deepsea/level-2/geology/vents.html

Hydrothermal Vent

http://universe-review.ca/I11-02-hydrothermal.jpg

Types of Chimneys

• Black Smokers: superheated water caused by volcano, release sulfur-bearing minerals and iron, which gives the black smoke it’s color.

• http://www.csa.com/discoveryguides/vent/review.pdf

• White smokers: have lower temperatures than the black smokers, contains calcium and silicon. They do not contain metals.

http://www.waterencyclopedia.com/images/wsci_02_img0247.jpg

Mutualism: Bathymodioline mussel and chemoautotrophic and/or

methanotrophic

A new bathymodioline mussel symbiosis at the Juan de Fuca hydrothermal vents: McKiness et.al

This paper explained the new species of mussels found at the Juan de Fuca hydrothermal vents.

Juan de Fuca region was once joined with the East Pacific Rise about 30 MYA

This was a habitat to dense populations of Bathymodioline mussels.

A research cruise on the Endeaver segment of the Ridge in 1999 yielded the first recorded specimens.

Juan De Fuca Ridge was linked to East Pacific Rise approximately 30MYA.

http://www.google.com/imgres?imgurl=http://geomaps.wr.usgs.gov/socal/geology/geologic_history/images/figure1_03.jpg&imgrefurl=http://geomaps.wr.usgs.gov/socal/geology/geologic_history/san_andreas_history.html&h=770&w=572&sz=98&tbnid=cNku-9m1aXnv7M::&tbnh=142&tbnw=105&prev=/images%3Fq%3Deast%2Bpacific%2Brise&hl=en&usg=__w6ZPomQ1JUzYci18DQjQnSeEZMY=&ei=9sTvSffhLJLWlQfRr5k2&sa=X&oi=image_result&resnum=6&ct=image

Mytilid mussels hosting bacterial endosymbionts within their gills are conspicuous members of communities and in the vents located in the Pacific, Atlantic, and Indian oceans.

Bathymodioline mussels are the most common invertebrates that host chemoautotrophic or methanotrophic bacteria.

Types of Oxidizing BacteriaChemoautotroph

synthesize all necessary organic compounds from carbon dioxide

only use inorganic energy sources (chemicals)

Evolutionary scientists believe that the first organisms to inhabit Earth were chemoautotrophs that produced oxygen as a by-product and later evolved into both aerobic, animal-like organisms and photosynthetic, plant-like organisms

Methanotrophable to grow using

methane as their only source of carbon and energy

They can grow aerobically or anaerobically and require single-carbon compounds to survive

Under aerobic conditions, they combine oxygen and methane to form formaldehyde, which is then incorporated into organic compounds.

Fig. 1 Bathymodiolus sp. JdF.Transmission electronmicrograph of a transversesection of a gill filament.Bacterial symbionts arelocalized at the apical surface of gill cells (referred to asbacteriocytes as in otherbathymodioline symbioses)along with micelle-like bodies. Due to the poor condition of the fixed gill tissue, the exact location of the symbionts with respect to the host cell membrane is unclear. B bacteriocyte, Bl blood space, S symbiont.Scale bar 1 lm

http://www.springerlink.com/content/m4606t1kt8314548/fulltext.pdf

Stable isotope analysis was performed on the mussels to look for δC13 and δN15.

It was found that for Carbon13=-26.6% and for Nitrogen15=+5.19% in comparison to other Bathymodiodine mussels.

Example of Stable Isotope Analysis

δX- amount of that isotope found compared to the standard

Standard for Carbon 13: 1.11Standard for Nitrogen 15: 0.37

δX= [(Rsample)/(Rstandard)-1] X 10³δX= [(1.08)/(1.11)-1] X 10³δX=-26.6

Table 1 Stable carbon and nitrogen isotope ratios for bathymodioline mussel symbioses

*C chemoautotroph, M methanotroph, NA not available

http://www.springerlink.com/content/m4606t1kt8314548/fulltext.pdf

Habitat/species Symbiont type(s)

d13C (%) d15N (%) Location

Bathymodiolus sp. JdFb

C -26.6 +5.19 Pacific Ocean

B. thermophilusc, d

C -30.5 to -37.1 -8.1 to +9.6 Pacific Ocean

B. breviore C -30.8 to -35.8 NA Pacific Ocean

B. aff. breviof C -20.0 to -30.8 -2.7 to -7.5 Indian Ocean

B. azoricusg C, M -21.3 to -32.6 -10.5 to +0.75

Atlantic Ocean

B. Puteoserpentish

C, M -32.5 to -37.3 -17.2 Atlantic Ocean

On the basis of the 16s rRNA gene sequences, the two different symbiont types group in separate clades on a phylogenetic tree according to their metabolism.

In terms of nutrition:Evidence for translocation via host digestion of

the symbionts.Evidence in terms of TEM observation of

symbionts in “lysosomal bodies” in the gill epithelials.

The cytochrome c oxidase subunit I (COI) gene was used for the host phylogeny (cytochrome c is in the Electron Transport Chain)

A ~1,500 bp portion of the 16S rRNA gene was used for the bacterial symbiont phylogeny.

Fig. 3  Single most parsimonious tree showing phylogenetic relationship of the Bathymodiolus sp. JdF symbiont with symbiotic and free-living γ-Proteobacteria (based on 1,456 bp of 16S rRNA). Bootstrap values >50% indicated on tree. Genbank accession numbers are noted on the tree. Scale bar equals number of changes .

The Juan de Fuca COI sequence is distinct from the other mussel COI sequences concluding that this is probably a new species.

Evolutionary RelationshipsUsing COI sequence analyses, it suggests that

Bathymodiolus sp. JDF is distinct from other species of bathymodioline mussels.

The rarity of this species in the northeast Pacific vents may represent an initial colonization or an occasional settlement from a population that is not well adapted to these particular hydrothermal vent conditions, with potential sources of mussels on the JDFRidge.

This data supports the presence of chemoautotrophic bacterial symbionts in a new species of mussel recently discovered on the Endeaver segment.

Transovarial inheritance of endosymbiotic bacteria in clams inhabiting deep-sea hydrothermal vents and cold seeps: Cary et. al

Vesicomyid clams have specialized gill tissue that habitat endosymbiotic bacteria

Mechanisms of symbiotic inheritance are likely to be dispersal strategies.

16S rRNA-directed oligodeoxynucleotide (CG1255R) for the bacteria was used to detect and localize in host germ tissues. These genes were amplified from the ovarial tissue of three

species of clams: Calyptogena magnifica Calyptogena phaseoliformis Calyptogena pacifica

1. Horizontally

• spread of symbionts between contemporary hosts

2. Vertically

• transfer from parent to offspring

3. Environmentally

• reinfection of the new host generation from an environmental shock of microorganisms

The researchers collected 3 clam species from the deep-sea research vessel Alvin from 3 Eastern Pacific sites:East Pacific Rise

C. magnificaMonterey Canyon

C. phaseoliformisAxial site on the Juan De Fuca Ridge

C. pacifica

Monterey Canyon

Juan de Fuca Ridge

East Pacific Rise

Fig 2. Restriction analysis of ovarial amplification products. Agarose gel showing amplified ovarial and gill eubacterial 16S rDNA (lanes A) and the same product cut with the restriction endonuclease Hae III (Promega) (lanes B). Two independent primer sets were used in the amplifications: a eubacterial set and a symbiont-specific set for the vesicomyid clams (Calyptogena spp.). All amplifications of ovarial rDNA had restriction fragments identical to the symbiont amplification products out of the gills from respective hosts.

Chemoautotrophic symbiosis: Mariana Gastropods

Snails in the western Pacific oceans contains endosymbiotic bacteria within specialized gill cells.

The gills of these snails contain sulfur.

Measurements show that the snails are exposed to vent water with temperature of 25 degrees Celsius and concentrations of hydrogen sulifde.

http://www.biolbull.org/cgi/reprint/174/3/373

Mariana Gastropods Continued…They have chemoautotrophic symbiosis.The bacterial endosymbionts are responsible for

sulfur oxidation and generating ATP. This was found out by looking at a frozen tissue sample at room temperature by TEM

By using the TEM, is was found that the bacteria was packed densely within microvilli-fringed cells.

The presence of bacteria within the gill cells coupled with the activities of enzymes that were responsible for fixing carbon dioxide and taking out energy from sulfide.

The snails rely on their symbionts for detoxifying the sulfide.

Refer to Mariana Gastropod overhead

Mutualism: Giant Tube Worms (riftia pachyptila).

The tube worms are one the most abundant species located in the hydrothermal vents.

They can grow up to 2 meters long.The tube worms have no mouth, gut, anus, or

digestive system.They house chemoautotrophic bacteria.Tubeworms get their energy by/from:

Symbiotic bacteria that live their body cavity called the trophosome.

Take in chemicals from the ventsChemicals get in their blood stream to the bacteriaThe bacteria breaks the chemicals down

Tube Worms Cont…The process of breaking down the chemicals take

place in the tube worm called the trophosome.The trophosome is packed with blood vessels and

chemosynthetic microbes. Scientists believe that the hemoglobin that fills the tube worm’s cardiovascular system gives the tube worms its color and is important to transport sulfur and oxygen.

The tube worms must be close enough to the vents to pick up hydrogen sulfide and be within close proximity of cool seawater, which contains oxygen

Anatomy of a Tube Worm

http://www.chemosynthesis.co.uk/study/studythirdpic.JPG

Future Research• Find a better way to collect more information about other

organisms besides the ones mentioned. • Try to locate more hydrothermal vents.

• Try to see if there are similarities or differences between vents in similar geographic locations.

References

• http://universe-review.ca/I11-02-hydrothermal.jpg• http://www.csa.com/discoveryguides/vent/review.pdf• http://www.springerlink.com/content/m4606t1kt8314548/fulltext.pdf• http://www.ocean.udel.edu/deepsea/level-2/geology/vents.html• http://www.waterencyclopedia.com/images/wsci_02_img0247.jpg• http://www.bionewsonline.com/o/p/shana_k_goffredi_2004_3082.htm• http://www.uga.edu/~sisbl/stable.html• http://www.biolbull.org/cgi/reprint/174/3/373