Award Abstract # 1636402
Investigation of viruses and microbes circulating deep in the seafloor

NSF Org: OCE
Division Of Ocean Sciences
Recipient: UNIVERSITY OF HAWAII
Initial Amendment Date: August 11, 2016
Latest Amendment Date: August 29, 2019
Award Number: 1636402
Award Instrument: Standard Grant
Program Manager: Michael Sieracki
OCE
 Division Of Ocean Sciences
GEO
 Directorate For Geosciences
Start Date: October 1, 2016
End Date: September 30, 2020 (Estimated)
Total Intended Award Amount: $285,219.00
Total Awarded Amount to Date: $285,219.00
Funds Obligated to Date: FY 2016 = $285,219.00
History of Investigator:
  • Grieg Steward (Principal Investigator)
    grieg@hawaii.edu
  • Mahdi Belcaid (Co-Principal Investigator)
Recipient Sponsored Research Office: University of Hawaii
2425 CAMPUS RD SINCLAIR RM 1
HONOLULU
HI  US  96822-2247
(808)956-7800
Sponsor Congressional District: 01
Primary Place of Performance: University of Hawaii
1950 East-West Road
Honolulu
HI  US  96822-2319
Primary Place of Performance
Congressional District:
01
Unique Entity Identifier (UEI): NSCKLFSSABF2
Parent UEI:
NSF Program(s): BIOLOGICAL OCEANOGRAPHY
Primary Program Source: 01001617DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s): 1319, 8565, 8811, 9117, 9150
Program Element Code(s): 1650
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.050

ABSTRACT

The ocean does not end at the seafloor. Seawater penetrates deep into the ocean crust forming an enormous subseafloor aquifer. Interactions among seawater, rocks, and microorganisms alter the properties of seawater as it passes through this aquifer. The flux of the altered fluid out of the basaltic rocks and back into the sea is equivalent to the flux of all the rivers on the planet and this exchange of deep-sea fluids influences the chemical balance of the ocean. Obtaining samples of these fluids has been a major obstacle to understanding the biological processes that occur within the ocean basement aquifer, but the development and installation of special wellheads, called CORKs, into boreholes on the seafloor now provides opportunities to probe the biology of the most remote habitat on earth. Recent analyses of fluids sampled from CORKs have shown that the microbial communities in the ocean basement are very different from those of the overlying seawater, but little is known of their ecology. In particular, nothing is known about how viruses interact with the cells in this habitat. When a lytic virus infects a cell, it will lyse and kill the cell, but temperate viruses often establish a stable, symbiotic relationship with the host cell that changes how the cell functions. Because of these important roles, viruses exert a major influence on the size, composition, and activity of microbial communities. Investigating the contributions of lytic and temperate viruses in the ocean basement is therefore central to understanding how activities of microbes in the basement are regulated. For this project, the researchers will sample fluids from the ocean basement in the central Atlantic Ocean to conduct the first investigation of the importance of viruses in a slow spreading crustal system. In addition to publishing the detailed results in scientific journals, the researchers will produce a book (in English and Hawaiian) targeting upper elementary to middle schoolchildren that captures the excitement and challenges of deep-sea exploration and introduces the mysteries of the life forms being discovered deep in the earth?s crust. The book will align with National Ocean Literacy Principles and Common Core Standards. Distribution will be focused on the minority-serving schools in Hawaii with the goal of fostering interest in the ocean, earth, and life sciences in groups traditionally underrepresented in STEM fields.

To collect the viruses and microorganisms in the fluids, the researchers will use both passive and active collection methods with the help of a remotely operated vehicle. For passive collection, micro- and ultrafilters will be connected in series to the wellhead and fluids will be driven through the filters by the pressure differential between aquifer and bottom seawater. For active sampling, mechanical pumps will be used to direct either basement fluids or bottom seawater into sample bags for retrieval and processing aboard ship. Microorganisms and viruses harvested from the fluids will be fractionated to separate populations. The viruses and cells will be examined by electron microscopy to quantify morphological diversity and to determine the proportion of infected cells. Nucleic acids from the cells and viruses will be sequenced to 1) characterize the genetic diversity of the viruses, 2) determine the proportion of cells with integrated viral genomes, 3) identify the functional genes contributed to the cells by the viruses, and 4) link specific viruses to their likely hosts based on analysis of CRISPR elements. The researchers hypothesize that the basement viruses will be distinct from those of bottom seawater and that, compared to surface seawater where cells are more abundant, active lytic infections in the basement will be low, but infections by temperate viruses will be exceptionally common. The data from this project will help to constrain the importance of viruses in recycling of organic carbon in the ocean basement and shed light on how viral genes may be altering the microbial activities that influence ocean chemistry.

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

Intellectual Merit: This project provides a first look at the abundance and genetic diversity of viruses present in the seawater that percolates through the rock deep below the seafloor at a location along the Mid-Atlantic Ridge. The water of the subsurface marine aquifer is referred to as ?basement fluid?. We sampled basement fluid from boreholes drilled through the sediments and into the rock at a sediment-filled basin called North Pond along the mid-ocean ridge in the center of the Atlantic Ocean. The results show that the microbes and viruses in the basement fluids at this location, where the seafloor is spreading slowly and the fluids are cold, are present at lower concentrations and are of very different types from those found along a ridge we sampled previously in the Pacific Ocean, where the seafloor spreads more rapidly and the basement fluids are hot. Changes in the viral composition among multiple samplings from the same boreholes at North Pond suggest that either the viruses in the fluids vary significantly over time and space or that flushing of the sampling lines was not always adequate to ensure collection of a stable, representative sample of fluid. In both the cold basement fluid samples in this project and the hot fluids sampled previously, the viruses and microbes in the basement fluids differ from bottom seawater suggesting that selective pressures in the aquifer lead to shifts in microbial community composition and the accompanying viruses. In both locations, we detected viruses that code for molecular machinery (known as diversity-generating retroelements) that allows them to change one of their proteins very quickly. This is believed to help the viruses rapidly adapt to changes in the cells that they infect. This work provides new insights into life in the marine deep subsurface at a location with cold basement fluid that is expected to be more representative of the global ocean basement biome.

Broader Impacts: This project supported a female post-doctoral researcher who was hired into a tenure-track faculty position in the second year of the project, who mentored graduate and undergraduate students on the project, and who has now competed successfully for her own NSF funding to work in this research area. This project also partially supported a graduate student working on doctoral dissertation in bioinformatics, provided training, data and material for a master?s student of Native Hawaiian ancestry, and provided financial support and laboratory experience for two female undergraduate students. The project also resulted in the development of a bioinformatics tool that is applicable to many types of microbial and viral metagenomic analyses, regardless of habitat from which the sample derive. The tool is thus of general use for scientists engaged metagenomics in disparate areas ranging from the human microbiome to environmental microbiology.


Last Modified: 04/16/2021
Modified by: Grieg F Steward

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