C-DEBI Newsletter – January 16, 2014

Cruise Report from AT26-09: Discovery, sampling, and quantification of flows from cool yet massive ridge flank hydrothermal springs on Dorado Outcrop, eastern Pacific Ocean
There were many successes in the expedition to Dorado Outcrop and to the CORKs at ODP Holes 1253A and 1255A despite losing a week of scheduled ship, Jason, and Sentry time to accommodate HOV Alvin certification. Major accomplishments at Dorado Outcrop include: (1) proving correct the hypothesis that Dorado outcrop is a regional focus of massive, low-temperature, hydrothermal discharge, (2) locating, sampling, and deploying experiments in numerous springs of low-temperature hydrothermal fluid emanating from the outcrop; (3) completion of 72 measurements of heat flow on and around Dorado outcrop, most co-located on chirp or seismic lines; and (4) conducting extensive surveys from which we produced bathymetric, sediment thickness, and water column temperature anomaly maps. Major accomplishment at the ODP Hole 1253A and 1255A CORKs include: (1) downloading long-term pressure data from both holes; and (2) recovering the downhole instrument string from ODP Hole 1253A. The weather and crews of the Atlantis, Jason and Sentry made it possible for us to utilize all assets to collect the most complete data set possible in the given time frame. NSF OCE 1130146 “Collaborative Research: Discovery, sampling, and quantification of flows from cool yet massive ridge flank hydrothermal springs on Dorado Outcrop, eastern Pacific Ocean” was awarded to C-DEBI Co-I Wheat, Co-I Fisher and Hulme. Additional support was provided by C-DEBI through Research Grants (Orcutt, McManus, Vidoudez) and Postdoctoral Fellowships (Bertics, Briggs, and Inderbitzen).

Hot Off the Press: Carbon adsorption onto Fe oxyhydroxide stalks produced by a lithotrophic iron-oxidizing bacteria (C-DEBI Contribution 201) in Geobiology
Iron (Fe)-oxidizing bacteria have the potential to produce morphologically unique structures that may be used as biosignatures in geological deposits. One particular example is Mariprofundus ferrooxydans, which produces extracellular twisted ribbon-like stalks consisting of ferrihydrite, co-located with organic and inorganic elements. It is currently thought that M. ferrooxydans excrete and co-precipitate polysaccharides and Fe simultaneously; however, the cellular production of these polysaccharides has yet to be confirmed. Here, Bennett et al. report on a time-series study that used scanning transmission X-ray microscopy and C 1s and Ca 2p near-edge X-ray adsorption fine structure spectroscopy to investigate production of polysaccharides over the growth cycle of M. ferrooxydans. The production and morphology of twisted iron stalks were consistent with previous observations, but unexpectedly, in the log phase, the carbon content of the stalks was extremely low. It was not until stationary growth phase that a significant component of carbon was detected on the stalks. During the log phase, low levels of carbon, only detectable when the stalks were thin, suggested that M. ferrooxydans produce an extracellular polysaccharide template onto which the Fe precipitates. By stationary phase, the increased carbon association with the stalks was a result of adsorption of organic compounds that were released during osmotic shock post-stalk production. In the environment, elevated concentrations of DOC could adsorb onto the Fe stalks as well as a number of other elements, for example, Si, P, Ca, which, by preventing chemical interactions between the Fe nanoparticles, will prevent structural deformation during recrystallization and preserve the structure of these filaments in the rock record.

Methanotrophic archaea possessing diverging methane-oxidizing and electron-transporting pathways in ISME Journal
Anaerobic oxidation of methane (AOM) is a crucial process limiting the flux of methane from marine environments to the atmosphere. The process is thought to be mediated by three groups of uncultivated methane-oxidizing archaea (ANME-1, 2 and 3). Although the responsible microbes have been intensively studied for more than a decade, central mechanistic details remain unresolved. On the basis of an integrated analysis of both environmental metatranscriptome and single-aggregate genome of a highly active AOM enrichment dominated by ANME-2a, Wang et al. provide evidence for a complete and functioning AOM pathway in ANME-2a. All genes required for performing the seven steps of methanogenesis from CO₂ were found present and actively expressed. Meanwhile, genes for energy conservation and electron transportation including those encoding F₄₂₀H₂ dehydrogenase (Fpo), the cytoplasmic and membrane-associated Coenzyme B–Coenzyme M heterodisulfide (CoB-S-SCoM) reductase (HdrABC, HdrDE), cytochrome C and the Rhodobacter nitrogen fixation (Rnf) complex were identified and expressed, whereas genes encoding for hydrogenases were absent. Thus, ANME-2a is likely performing AOM through a complete reversal of methanogenesis from CO₂ reduction without involvement of canonical hydrogenase. ANME-2a is demonstrated to possess versatile electron transfer pathways that would provide the organism with more flexibility in substrate utilization and capacity for rapid adjustment to fluctuating environments. This work lays the foundation for understanding the environmental niche differentiation, physiology and evolution of different ANME subgroups.
 

C-DEBI seeks nominations for the next three speakers for this program. Potential speakers can be nominated by colleagues, mentors, or those mentored by C-DEBI participants; they can also self nominate. Selected C-DEBI Networked Speakers will make a presentation online, using video conferencing tools, with assistance from the C-DEBI main office at USC. Presentations are to be about 30 minutes in length, with time allocated for questions and discussion. For more information about the Speaker Series and nomination request, please see: https://www.darkenergybiosphere.org/outputs-resources/networked-speaker-series/.
 

The 3rd International Conference of Geobiology, June 16-18, 2014, Wuhan, China
Registration deadline is Feb 28, 2014.