. 24/7 Space News .
Scientists Sequence Genome Of Organism Central To Biosphere's Carbon Cycle

The diatom species Thalassiosira pseudonana, with a hard outer shell of silica shaped like a hatbox and delicately marked with pores, is between 3 and 4 microns in size. Photo credit: Nils Kroger, Universitat Regensburg/Science
Berkeley CA (SPX) Oct 04, 2004
The first ever genomic map of a diatom, part of a family of microscopic ocean algae that are among the Earth's most important inhabitants, has yielded surprising insights about the way they may be using nitrogen, fats and silica in order to thrive.

Diatoms, most of which are far too tiny to see without magnification, are nevertheless thought to absorb carbon dioxide, a major greenhouse gas, in amounts comparable to all the world's tropical rain forests combined.

"These organisms are incredibly important in the global carbon cycle," says Virginia Armbrust, a University of Washington associate professor of oceanography and lead author of a research article in the Oct. 1 issue of Science.

Together, these single-celled organisms generate as much as 40 percent of the 50 billion to 55 billion tons of organic carbon produced each year in the sea, and in the process use carbon dioxide and produce oxygen.

And they are an important food source for many other marine organisms.

The genome work, funded by the Department of Energy and conducted at its Joint Genome Institute in California, gives insight into how the diatom species Thalassiosira pseudonana prospers in the marine environment, Armbrust says.

It's important to understand because diatoms like Thalassiosira pseudonana and other phytoplankton are vital components of the biosphere's role in mediating global warming.

"Now that we have a glimpse at the inner workings of diatoms, we're better positioned to understand how changes in the environment will translate into increases or decreases in diatom abundance," says Dan Rokhsar, who heads computational genomics at the Joint Genome Institute and one of the co-authors on the article.

Scientists would like to better understand how these organisms react to changes in sea temperatures, the amount of light penetrating the oceans and nutrients.

"Oceanographers thought we understood how diatoms use nitrogen, but we discovered they have a urea cycle, something no one ever suspected," Armbrust says.

A urea cycle is a nitrogen waste pathway found in animals and has never before been seen in a photosynthetic eukaryote like a diatom, she says.

Nitrogen is crucial for diatom growth and is often in short supply in sea water, depending on ocean conditions.

The genome work revealed that diatom Thalassiosira pseudonana has the genes to produce urea-cycle enzymes that may help to reduce its dependence on nitrogen from the surrounding waters.

The genome work also shed additional light on how this diatom species uses fats, or lipids, that it is known to store in huge amounts.

"Learning the actual pathways they use to metabolize their fats helps explain the ability of diatoms to withstand long periods with little sunlight � even to overwinter � and then start growing really rapidly once they return to sunlight," she says.

Three or four microns in width � as many as 70 could fit in the width of a human hair � Thalassiosira pseudonana is among the smallest diatoms.

Like its brethren, it is encased by a frustule, a rigid cell wall delicately marked with pores in patterns distinctive enough for scientists to tell the species apart.

Another new finding reported in Science concerns the unusual way the diatom metabolizes silicon to form its characteristically ornate silica frustule.

"Diatoms can manipulate silica in ways that nanotechnologists can only dream about. If we understood how they can design and build their patterned frustule as part of their biology, perhaps this could be adapted by humans," Rokhsar says.

Scientists on the project, which includes 46 researchers from 26 institutions, also considered the evolutionary implications revealed by the genomic work.

The research provided direct genetic confirmation of a hypothesis that diatoms evolved when a heterotroph, a single-cell microbe, engulfed what scientists say was likely a kind of red alga.

The two became one organism, an arrangement called endosymbiosis, and swapped some genetic material to create a new hybrid genome.

"This project helps illustrate the amazing diversity of life on our planet," Armbrust says.

"Diatoms display features traditionally thought to be restricted to animals and other features thought to be restricted to plants. Diatoms, with complete disregard for these presumed boundaries, have mixed and matched different attributes to create an incredibly successful microorganism. It's exciting to imagine the novelty in the oceans that still await our discovery."

Related Links
Joint Genome Institute
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express

New Hydrothermal Vents Discovered As "South Pacific Odyssey" Research Begins
University Park PA (SPX) Sep 24, 2004
A team of 27 U.S. marine scientists beginning an intensive program of exploration at the Lau Basin, in the South Pacific, has discovered a new cluster of hydrothermal vents along a volcanically active crack in the seafloor.



Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only














The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.