FeMO2 Dive Cruise 2007
Report Day 12 -- Monday 22 October 2007 -- Some Ongoing FeMO Research Projects
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FeMO2 Dive Cruise 2007 |
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Jason's screens go blank and Dive 314 is ended at 4 AM today. Once aboard, the Jason team confirms that the fiber optics in the tether between Jason and Medea have failed. Fortunately they have another, though shorter tether.
The scientists gather their samples and head to the labs and I begin asking more questions. Rick Davis is working in the radiation lab. He is growing microbes from Lo'ihi in seawater laced with C-14 bicarbonate. Bicarbonate is a carbon atom linked to a hydrogen atom and 3 oxygen atoms: HCO3-. It is the source of carbon from which chemo-synthesizing microbes make organic molecules such as carbohydrates. The process by which organisms make organic molecules from inorganic molecules is called "carbon fixation". Marine organisms fix carbon from HCO3-, plants fix carbon from CO2. Rick is performing carbon fixation experiments to see how much of the HCO3- is converted into organic molecules in the Lo'ihi microbes. In addition to the bicarbonate, Rick is adding things that the microbes need to stay alive - iron and manganese that they can oxidize for energy. When iron is added the microbes that grow using iron will thrive and dominate the enrichment culture. The C-14 will allow the efficiency of carbon fixation to be measured with great sensitivity. If molecules such as lipids are extracted from the enrichment culture, it becomes possible to find out what cellular structures these microbes are putting their energy into.
Suzanna Brauer is doing similar enrichment cultures with Lo'ihi microbes using a stable (non-radioactive) isotope of carbon: C-13. This carbon isotope is not as sensitive a tracer as C-14, but because C-13 is not radioactive, her samples can be analyzed for specific lipids and DNA sequences. Both lipids and DNA can tell researchers which microbes are making the mats. Very probably these microbes and their genetic codes are new to science. Rick and Suzanna are both working in Brad Tebo's lab, and the complementary nature of their experiments can confirm aspects Lo'ihi's microbial community that might otherwise be lost.
Suzanna is also interested in the microbes associated with the manganese oxide crusts, so she is developing a technique that allows her to separate these microbes from Lo'ihi samples using magnetism. The magnetic technique is not new, but Suzanna has developed an organic molecule that binds manganese oxide. She coats magnetic beads with this molecule and then puts the beads into a culture tube with the sample. Those microbes bound to manganese oxide, either because they produce it or because they need it as a resource, stick to the beads along with the manganese oxide. She can then place a magnet next to the culture tube to hold the beads and manganese loving microbes to the side of the tube. She then washes out the remainder of the sample. Those microbes not stuck to the beads are washed away leaving a sample enriched in manganese oxide loving microbes.
Greg Horn is also growing microbes. He's working in the cold van to keep his microbes at deep ocean temperatures. Because microbes are cold blooded, raising the temperature raises their metabolism. Except near volcanoes, deep-sea temperatures are very stable and only a few degrees above freezing. Organisms have adapted accordingly. Warmer temperatures can push some metabolic pathways ahead of others to a threshold where an organism cannot maintain homeostasis - in that case the organism usually dies. The cold van is an attempt to keep the organisms cool, but the van has a failing air conditioner and suspect wiring.
Greg is working with nitrogen metabolic processes that are anaerobic - they don't require oxygen so Greg sets up his incubations in a "glove box" (more like a sand blasting cabinet than the glove box in a car) flooded with a mixture of CO2 and Helium. He is looking at nitrogen metabolism in the deep sea so his incubations are spiked with N-15, a stable isotope of nitrogen. Nitrogen is found in the proteins of every living organism and nitrogen gas makes up 79% of the atmosphere. Microbial metabolic pathways convert nitrogen gas to nitrogen in proteins and back again. There are two principal metabolic processes for generating N2 gas, namely "denitrification" and "anammox" (the first uses nitrate and the second uses ammonia to produce N2 gas). Greg is investigating both of these. He appears to be the first to do so on seafloor basalts. The latest geochemical budgets for nitrogen seem to show that the ocean is producing more N2 gas than it is consuming. The excess leaves the ocean for the atmosphere. Greg's research will measure a rate of N2 production for microbes living on Lo'ihi, and determine the relative contribution of denitrification and anammox to the total.
Other microbial analyses are continuing as well. Dave Emerson has been able to culture a species of microbe from Lo'ihi that extrudes the iron oxide filaments that make up a large portion of the mats (see Dave's story titled "Spinning Rust"). Culturing is a difficult task in the best of circumstances, but probably only about 1 in 1000 microbial species from the deep ocean can be cultured - the rest die. Analysis of the genetics and behavior of this microbe in culture allows researchers to begin to decipher the microbial community building the mats. Craig Moyer's lab has been collecting microbes for genetic analysis. Using a stable region of DNA in the "16S" gene Craig can look at the genetics of mat makers. With careful use of restriction enzymes he can begin to separate individual microbes from the large communities found in the mats and around the vents.
The Jason team replaces the damaged tether with a shorter tether that works in preparation for dive 315. The scientists prep Jason's science basket and load the elevator. The dive plan is a repeat of the original plan for the previous dive. Jason will descend on the old cold vents at Naha on Lo'ihi's south rift. Jason will then proceed up the rift to sample the vents at Pohaku that have not been visited recently then enter Pele's Pit through the spillway and finally climb Pisces Peak and return to the surface. Jason enters the water shortly after 8 PM.
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