Puzzling Plankton Yield Secrets to Role in Evolution/Global Photosynthesis

The analysis of DNA sequences from tiny green algae have provided new insights into the mystery of how new species of plankton evolve—and further highlights their critical role in managing the global cycling of carbon. These findings, by a group led by the DOE Joint Genome Institute (DOE JGI); the Scripps Institution of Oceanography, University of California, San Diego; and the Pierre & Marie Curie University, were published this week in the Proceedings of the National Academy of Sciences.

Ocean-dwelling phytoplankton from the genus Ostreococcus emerge at the primitive root of the green plant lineage, dating back nearly 1.5 billion years. Today, these microscopic, free-living creatures, among the smallest eukaryotes ever characterized, barely a micron in diameter, contribute to a significant share of the world’s total photosynthetic activity. These “picophytoplankton” also exhibit great diversity that contrasts sharply with the dearth of ecological niches available to them in aquatic ecosystems. This observation, known as the “paradox of the plankton,” has long puzzled biologists.

Plumbing the depths of molecular-level information of related species, genomics offers a novel glimpse into this paradox. The researchers compared the genomes of two Ostreococcus species, O. lucimarinus and O. tauri, and saw dramatic changes in genome structure and metabolic capabilities.

“We found several striking features of genome organization,” said DOE JGI’s Igor Grigoriev, the PNAS paper’s senior author. “Overlapping genes conserved across the species may enable them to cross-regulate their expression, while species-specific chromosomes with horizontally transferred genes can account for changes in the cell surface to adapt to different ecological niches.” Grigoriev and his colleagues noted the abundance of selenium-rich proteins that surfaced in their analysis, which he said allows the organisms to horde nutrients and reduced their appetite for iron—an adaptive process in Ostreococcus.

“This work builds on the community’s emerging understanding about how carbon fixation is carried out by picoplankton,” said Brian Palenik, lead author and researcher at the Scripps Institution of Oceanography, University of California, San Diego.

“From an applied perspective, we are learning some of the tricks nature has employed to ‘engineer’ an extremely small eukaryote to thrive in nature—which may well find applications in bioengineering,” said Palenik. “It was particularly interesting to see the predicted use of selenium-containing enzymes as one of the tricks to maintain such tiny cells. There are many mechanisms that can account for species formation in photosynthetic phytoplankton, and this is just one of the major pieces to this long-standing puzzle for biologists.”

“Assimilation of atmospheric CO2 by marine phytoplankton is a global-scale process that is responsible for about half of the biosphere net primary production,” said collaborator and co-author Hervé Moreau of the Pierre & Marie Curie University Oceanic Observatory in Banyuls-sur-mer, France. “This active absorption of hundreds of millions of tons of carbon per day is essential for maintaining the control of the planet’s climate by counteracting greenhouse effects due to human activities. Clearly, this storage capacity is affected by changes in the photosynthetic efficiency of the algae, which in turn is linked to the environmental conditions experienced by these organisms in their environment.”

The ecology of picoeukaryotes, said Moreau, has thus become an intense field of investigation over the last decade as these microalgae, although representing a minor component of the plankton, nevertheless play major roles in oceanic biomass production.

“With even more picoplankton genomes in the sequencing queue at DOE JGI, we’re positioned to secure a better grasp on the mechanisms of species adaptation and the great diversity of biological pathways operating in the oceans,” said Grigoriev. “This will also enable us to predict the roles of these organisms in contributing to primary marine productivity.”

Source: Lawrence Livermore National Laboratory

Related stories:

Water heater choice and maintenance can reduce energy costs
(PhysOrg.com) -- Between 16 and 18 percent of home energy is used to generate hot water, so hot water tank maintenance can pay big dividends on your energy bill.
Proteomics study yields clues as to how tuberculosis might be thwarting the immune system
A link between the immune system and the self-cleaning system by which biological cells rid themselves of obsolete or toxic parts may one day yield new weapons in the fight against tuberculosis and other deadly infectious diseases. Scientists with the U.S. Department of Energy's (DOE) Lawrence Berkeley National Laboratory have discovered proteins residing in both systems that point to "cross-talk" between them.
At 2.8 km down, a 1-of-a-kind microorganism lives all alone
The first ecosystem ever found having only a single biological species has been discovered 2.8 kilometers (1.74 miles) beneath the surface of the earth in the Mponeng gold mine near Johannesburg, South Africa. There the rod-shaped bacterium Desulforudis audaxviator exists in complete isolation, total darkness, a lack of oxygen, and 60-degree-Celsius heat (140 degrees Fahrenheit).
After the first decade of metagenomics -- adolescent growth spurt anticipated
Mostly hidden from the scrutiny of the naked eye, microbes have been said to run the world. The challenge is how best to characterize them given that less than one percent of the estimated hundreds of millions of microbial species can be cultured in the laboratory. The answer is metagenomics—an increasingly popular approach for extracting the genomes of uncultured microorganisms and discerning their specific metabolic capabilities directly from environmental samples. Now, some ten years after the term was coined, metagenomics is going mainstream and already paying provocative dividends according to a "Q&A," News and Views by the U.S. Department of Energy Joint Genome Institute (DOE JGI) microbial ecology program head Philip Hugenholtz and MIT researcher Gene Tyson, published in the 25 September edition of the journal Nature.
Photosynthesizing bacteria with a day-night cycle contain rare chromosome
Researchers sequencing the DNA of blue-green algae found a linear chromosome harboring genes important for producing biofuels. Simultaneously analyzing the complement of proteins revealed more genes on the linear and the typical circular chromosomes then they'd have found with DNA sequencing alone.
Tracking down the menace in Mexico City smog
A new report by scientists who are part of the international MILAGRO Campaign indicates that some of the most harmful air pollution in Mexico City may not come from motor vehicles but instead originates with industrial sources – and that the culprit may be garbage incineration.
Understanding Algae As An Alternative Fuel Source: Will The Real Algae X Please Stand Up
The recent creation of AXI, LLC is an alliance between Allied Minds, Inc. a seed investment company and the University of Washington. The alliance came about because of Professor Rose Ann Cattolico PhD, an algae-to-fuel expert. Professor Cattolico has been on the faculty and conducting algae research since 1975. Her research includes, chloroplast genome architecture and gene function in non-chlorophy b containing algae and functional genetic diversity within stramenopile population. Professor Cattolico has discovered a unique patented technology, she calls Algae X.
Genome of simplest animal reveals ancient lineage, confounding array of complex capabilities
As Aesop said, appearances are deceiving—even in life's tiniest critters. From first detection in the 1880s, clinging to the sides of an aquarium, to its recent characterization by the U.S. Department of Energy Joint Genome Institute (DOE JGI), a simple and primitive animal, Trichoplax adhaerens, appears to harbor a far more complex suite of capabilities than meets the eye. The findings, reported in the August 21 online edition of the journal Nature, establish a group of organisms as a branching point of animal evolution and identify sets of genes, or a "parts list," employed by organisms that have evolved along particular branches.

News discussion:

General Science news