C-DEBI Newsletter – May 15, 2014

Approaching the high temperature boundary for life in the hydrothermally altered sediments of Guaymas Basin
My research focuses on microbial community structure in the hydrothermally-altered sediments of Guaymas Basin at 2000m water depth in the Sea of Cortez. The thermal range of shallow Guaymas sediments is extreme; on one occasion temperatures increased from 3°C at the sediment-water interface to 200°C in just 45cm. Beyond 80°C and 100°C the isotopic signatures of the anaerobic oxidation of methane (AOM) and organic matter remineralization (OMR) could not be traced and may represent upper thermal constraints for these microbial processes. Temperature logging probes revealed that the shallowest sediments experienced extreme thermal fluctuations, which sometimes varied by 25°C in as little as a day.  Viable microbial life, as indicated by reverse-transcribed 16S rRNA, was detected in sediments with an eight day thermal range of 77°C to 100°C.  454-pyrosequencing recovery of reverse-transcribed 16S rRNA from cool and hot layers of high temperature cores revealed that putative methane cycling archaea and sulfur cycling bacteria were dominant members of the microbial community.  In particular, ANME archaea were very common but distinct cores yielded diverse sequence assemblages, including ANME-1 Guaymas, ANME-2c, and ANME-2d/GoM Arc-1/Methanoperedenaceae. Dominant bacterial groups were Thermodesulfobacteria within the family Thermodesulfobacteriaceae, Epsilonproteobacteria within the family Helicobacteriaceae, and close relatives of the deltaproteobacterium Desulfocapsa exigens. Co-occurrence of OTUs across the four hottest sediment layers suggests that ANME-1 Guaymas and an uncultured representative of a deeply branching MCG subgroup are the most probable archaeal hyperthermophiles, and members of the Thermodesulfobacteriaceae family are likely bacterial hyperthermophiles.

ISSM 2014: Student Volunteers Needed
Students, are you interested in volunteering at the Ninth International Symposium on Subsurface Microbiology (ISSM 2014) in exchange for reducing your conference costs? The conference organizers are seeking student volunteers to assist at the conference. The conference, to be held October 5-10, 2014, at Asilomar State Beach and Conference Grounds in Pacific Grove, California, will showcase the latest developments and research in the expanding field of subsurface microbiology. Volunteer positions may include serving as a room monitor, working at the registration desk, and providing general support throughout the event. Applicants must currently be enrolled full-time as a graduate or undergraduate student. Volunteers would be requested to commit to at least 4 to 8 hours of volunteer assistance each day of the conference. We will work with your schedule so that you can attend the sessions you are most interested in. The volunteer application deadline is May 15, 2014. To learn more about the volunteer details, please download the Student Volunteer Application at www.2014issm.com/students.html.

Ocean Leadership/IODP: Seeking new Members for USAC, JOIDES Resolution Facility Board, Science Evaluation Panel
The Consortium for Ocean Leadership, in association with the International Ocean Discovery Program (IODP), is seeking new U.S.-based members for the U.S. Advisory Committee for Scientific Ocean Drilling (USAC), the JOIDES Resolution Facility Board, and the Science Evaluation Panel. New members will serve three-year terms beginning in October 2014. Scientists interested in volunteering for these opportunities should send a cover letter and a two-page CV to usssp@oceanleadership.org by June 15, 2014. Letters should clearly indicate your primary field of expertise, briefly document any previous committee experience, describe your interests in the scientific ocean drilling programs, and identify your preferred panel or committee assignment. We strongly encourage the involvement of early career scientists, as well as those with more experience. For more information, please visit: http://iodp-usssp.org/committees.

Sulfur Oxidation Genes in Diverse Deep-Sea Viruses
Viruses are the most abundant biological entities in the oceans and a pervasive cause of mortality of microorganisms that drive biogeochemical cycles. Although the ecological and evolutionary effects of viruses on marine phototrophs are well recognized, little is known about their impact on ubiquitous marine lithotrophs. Here, Anantharaman et al. report 18 genome sequences of double-stranded DNA viruses that putatively infect widespread sulfur-oxidizing bacteria. Fifteen of these viral genomes contain auxiliary metabolic genes for the α and γ subunits of reverse dissimilatory sulfite reductase (rdsr). This enzyme oxidizes elemental sulfur, which is abundant in the hydrothermal plumes studied here. Our findings implicate viruses as a key agent in the sulfur cycle and as a reservoir of genetic diversity for bacterial enzymes that underpin chemosynthesis in the deep oceans.

Outreach