Madrid, 6 November 2009 A team led by researchers from the Scientific Research Council (CSIC) has described for the first time the complex genetic diversity of the community of viruses present in the lakes of Antarctica. The study describes close to 90,000 sequences of viruses from Lake Limnopolar, located on Byers Peninsula, Livingston Island. It is the largest number of viral families found to date in a ‘metagenome’ [full genetic information of a natural community of micro-organisms] in an aquatic environment, according to the study published in this week's issue of the journal Science.
The person in charge of the study, Antonio Alcamo, from the Severo Ochoa Centre for Molecular Biology (a shared centre of the CSIC and the Autonomous University of Madrid), points out that the description of the community of viruses present in this Antarctic lake is the first step towards a better understanding of the role that viruses play in these extreme ecosystems, as well as to determine whether they have evolved independently over millions of years. “The ecosystems of Antarctic lakes are very simple, and are dominated by micro-organisms that have adapted to extreme environmental conditions: low temperatures, almost total darkness for most of the year, and very low levels of nutrients. They are biological systems living at the limit”, explains the CSIC researcher.
In the work area, the lakes remain covered with ice during most part of the year and have very little animal influence. For the article's first signatory Alberto López-Bueno, also a CSIC researcher, ”the results of this study are full of surprises. Although biological diversity in polar environments is expected to be low, we estimate that Limnopolar Lake contains nearly 10,000 different viral species. Moreover, while the aquatic ecosystems described so far are dominated by viruses that infect bacteria (bacteriophages), in Limnopolar Lake the majority of the viruses are those that infect eukaryotic organisms, like algae”.
To obtain these results, the researchers obtained images of the viruses by means of electronic microscopy, and they used a new system of massive sequencing developed by Roche, a pharmaceutical company. In this way they achieved a global vision of the genetic variation of the viruses in these ecosystems, which is known as viral metagenome or viroma.
The team, which included scientists from the Autonomous University of Madrid, the University of Valencia and the Higher Centre for Public Health Research of Valencia, also identified tiny new viruses which form the most abundant population when the lake is frozen over, and which had not been described in other natural environments. These viruses might even belong to previously unknown viral families.
SEASONAL VIRUSES
For the first time, the researchers used a metagenomic approximation to describe how the viral population changes from season to season. The drastic transition from an ice-covered lake in spring to an ice-free lake in summer gives rise to considerable changes in the viral community, which goes from being composed mainly of small stranded DNA viruses to being dominated by large, double stranded DNA viruses, a phenomenon which biologists think is a reaction to a seasonal change in host bodies, which illustrates the importance of the role played by viruses in these ecosystems.
The Byers Peninsula on Livingston Island is one of the few areas in the Antarctic that thaws in summer, and it has been designated as one of the Specially Protected Antarctic Zones due to the important ecological value of its lakes and rivers. This research is part of the LIMNOPOLAR project, which is studying the freshwater systems of the Byers Peninsula. The project co-ordinator, Antonio Quesada, a lecturer at the Autonomous University of Madrid, affirms: “The multidisciplinary research being carried out by Spanish and foreign scientists has made the Byers Peninsula a zone of international reference for environmental studies in Antarctica”.
This project was financed by the Spanish Polar Programme, and the expedition to the Antarctic was possible thanks to the logistical support of the Marine Technology Unit of the CSIC and the Spanish Navy's Oceanographic Research Vessel 'Las Palmas'. Alberto López-Bueno, Javier Tamames, David Velázquez, Andrés Moya, Antonio Quesada and Antonio Alcamí. High diversity of the viral community from an Antarctic lake. Science, 6 Nov 2009. Vol 326: 858-61
Source: CSIC (Spanish Scientific Research Council)
