March 8, 2013
Extreme Algae Steals Genes For Survival From Bacteria Prey
Brett Smith for redOrbit.com - Your Universe Online
Some microorganisms have developed the ability to thrive in the most hostile environments on Earth, from the superheated geothermal vents to pools of toxic drainage deep underground.
While the ability to pilfer genes from another microorganism has been seen before, scientists have never observed this ability in a eukaryote — an organism with a nucleus.
In the study, a team of German and American scientists found this adoptive capacity in the red algae Galdieria sulphuraria. These algae live in the heavy metal-filled drainage found on the floor of old mineshafts. Thriving in water as caustic as battery acid, they rely on a diet of bacteria instead of using photosynthesis as most algae do.
To understand how the algae are able to withstand such an extreme environment, the international team performed a comparative genetic analysis. The analysis revealed something quite unexpected: the algae were committing genetic larceny on their neighbors. In depth genetic analysis showed much of the DNA responsible for G. sulphuraria´s extreme adaptations did not originate in the evolutionary history of red algae but rather was stolen from its bacterial prey.
"The age of comparative genome sequencing began only slightly more than a decade ago, and revealed a new mechanism of evolution — horizontal gene transfer — that would not have been discovered any other way," said Dr. Matt Kane, program director of the National Science Foundation's (NSF) Division of Environmental Biology. "This finding extends our understanding of the role that this mechanism plays in evolution to eukaryotic microorganisms."
Horizontal gene transfer has been seen in different kinds of bacteria, but this is the first time it has been seen in an algae. These eukaryotic single-cell organisms are able to survive in their toxic, mercury-filled environment due to transport proteins and enzymes produced by genes it stole from bacteria.
G. sulphuraria has also been found in the scalding hot springs of Yellowstone Park, and a genetic analysis of these algae showed their specific capacity for heat tolerance comes from a single gene that was adopted from a bacterium millions of years ago.
"The results give us new insights into evolution," said co-author Gerald Schoenknecht of Oklahoma State University´s Department of Botany. "Before this, there was not much indication that eukaryotes acquire genes from bacteria."
The analysis also showed Galdieria's stolen genes give it tolerance to high salt concentrations and an ability to tap into wide variety of unlikely food sources.
"It's usually assumed that organisms with a nucleus cannot copy genes from different species — that's why eukaryotes depend on sex to recombine their genomes,” said Martin Lercher of Heinrich-Heine-University in Dusseldorf, Germany. "How has“¯Galdieria managed to overcome this limitation? It's an exciting question."
According to Lercher´s colleague Andreas Weber, the team´s findings are “¯"a dream come true for biotechnology.”
"Galdieria has acquired genes with interesting properties from different organisms, integrated them into a functional network and developed unique properties and adaptations,” added Weber, who also co-authored the study.
The team noted these findings could have implications for the future production of biofuels.