Paris Lavin

Short timescale dynamics of phytoplankton in Fildes Bay, Antarctica

Abstract Phytoplankton is responsible for most primary production in Antarctica, but the short timescale dynamics of its size structure and composition are poorly described and understood. The abundance and composition of phytoplankton in Fildes Bay, western Antarctic Peninsula, was followed for 12 days during the summer using a range of methods, including size fractionation of chlorophyll, microscopy, flow cytometry and terminal-restriction fragment length polymorphism (T-RFLP) of the plastid 16S rRNA gene. A rapid increase in biomass and cell abundance occurred in response to a vertical mixing event. This increase also resulted in a shift in composition from diatoms to Prymnesiophyceae, and then back to diatoms as the water column re-stratified. Our results show a strong dominance of nanophytoplankton represented by Thalassiosira and Phaeocystis. The rapid response of the phytoplankton suggests that it is well adapted to short-term environmental changes.

Biological Interactions and Simulated Climate Change Modulates the Ecophysiological Performance of Colobanthus quitensis in the Antarctic Ecosystem.

Most climate and environmental change models predict significant increases in temperature and precipitation by the end of the 21st Century, for which the current functional output of certain symbioses may also be altered. In this context we address the following questions: 1) How the expected changes in abiotic factors (temperature, and water) differentially affect the ecophysiological performance of the plant Colobanthus quitensis? and 2) Will this environmental change indirectly affect C. quitensis photochemical performance and biomass accumulation by modifying its association with fungal endophytes? Plants of C. quitensis from King George Island in the South Shetland archipelago (62°09′ S), and Lagotellerie Island in the Antarctic Peninsula (65°53′ S) were put under simulated abiotic conditions in growth chambers following predictive models of global climate change (GCC). The indirect effect of GCC on the interaction between C. quitensis and fungal endophytes was assessed in a field experiment carried out in the Antarctica, in which we eliminated endophytes under contemporary conditions and applied experimental watering to simulate increased precipitation input. We measured four proxies of plant performance. First, we found that warming (+W) significantly increased plant performance, however its effect tended to be less than watering (+W) and combined warming and watering (+T°+W). Second, the presence of fungal endophytes improved plant performance, and its effect was significantly decreased under experimental watering. Our results indicate that both biotic and abiotic factors affect ecophysiological performance, and the directions of these influences will change with climate change. Our findings provide valuable information that will help to predict future population spread and evolution through using ecological niche models under different climatic scenarios.

Isolation and molecular characterization of Thraustochytrium strain isolated from Antarctic Peninsula and its biotechnological potential in the production of fatty acids

Thraustochytrids are unicellular protists belonging to the Labyrinthulomycetes class, which are characterized by the presence of a high lipid content that could replace conventional fatty acids. They show a wide geographic distribution, however their diversity in the Antarctic Region is rather scarce. The analysis based on the complete sequence of 18S rRNA gene showed that strain 34-2 belongs to the species Thraustochytrium kinnei, with 99% identity. The total lipid profile shows a wide range of saturated fatty acids with abundance of palmitic acid (16:0), showing a range of 16.1–19.7%. On the other hand, long-chain polyunsaturated fatty acids, mainly docosahexaenoic acid and eicosapentaenoic acid are present in a range of 24–48% and 6.1–9.3%, respectively. All factors analyzed in cells (biomass, carbon consumption and lipid content) changed with variations of culture temperature (10 °C and 25 °C). The growth in glucose at a temperature of 10 °C presented the most favorable conditions to produce omega-3fatty acid. This research provides the identification and characterization of a Thraustochytrids strain, with a total lipid content that presents potential applications in the production of nutritional supplements and as well biofuels.

Cepa antártica de Bacillus sp., con actividad extracelular de tipo agarolítica y alginatoliasa

Diversas bacterias asociadas a macroalgas pueden usar ficocoloides como fuente de carbono. Las bacterias de la Antartica, poseen caracteristicas fisiologicas adaptativas que habrian evolucionado para permitir su supervivencia y funcionamiento dentro de las condiciones adversas de ese ecosistema. Por lo tanto, bacterias aisladas desde algas antarticas podrian tener la capacidad de degradar enzimaticamente azucares complejos a temperaturas inferiores que aquellas aisladas desde zonas mas calidas, lo que potencialmente podria tener aplicaciones en la mejora en procesos industriales que utilizan enzimas. El analisis del gen ribosomal 16S indica que la cepa bacteriana aislada desde algas varadas en la Isla Rey Jorge (Antartica), pertenece al genero Bacillus. El sobrenadante libre de celulas presento actividad agarasa y alginatoliasa. Se encontraron diferencias significativas en la temperatura optima para hidrolizar agarosa y alginato, evaluada dentro de un rango de 4 a 30 °C. La actividad agarolitica fue mayor a 4 °C, mientras que la actividad alginatoliasa fue mayor a 30 °C. Estos resultados poseen un alto valor biotecnologico y podria ser utilizada con fines industriales.

First characterization of gastrointestinal culturable bacteria of Patagonian toothfish Dissostichus eleginoides (Nototheniidae)

The Patagonian toothfish Dissostichus eleginoides is one of the most important fisheries from the Southern Ocean. The biology of this species is relatively well studied and some nutritionals issues have also been reported; however there is no information about the composition of the bacterial community of the gastrointestinal tract, which is essential to characterize the microbiota of this fish. The bacterial flora of D. eleginoides is here described for the first time using culturable methods. By applying traditional culture-based techniques and 16S rDNA sequencing methods it was possible to characterize the families Vibronaceae and Moraxellaceae, which were mainly represented by Vibrio and Psychrobacter, respectively. This Patagonian fish shows a microbiota very similar to other cold waters fishes.

The trade-off between antimicrobial production and growth of an Antarctic psychrotroph Streptomyces sp. strain INACH3013

The trade-off between antimicrobial production and growth of an Antarctic psychrotroph Streptomyces sp. strain INACH3013 PARIS LEONARDO LAVIN, SHEAU TING YONG, CLEMENTE MICHAEL V.L. WONG, ALEX RICARDO GONZALEZ PEREZ and CRISTINA DORADOR Laboratorio de Complejidad Microbiana y Ecología Funcional, Instituto Antofagasta, Universidad de Antofagasta, Chile Biotechnology Research Institute, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, Malaysia National Antarctic Research Centre, University of Malaya, 50603 Kuala Lumpur, Malaysia Universidad de los Lagos, Region de los Lagos, Chile palavin@gmail.com