Sampling Expedition to Vulcano Island
Funded by a Ralph E. Powe Junior Faculty Enhancement Award from Oak Ridge Associated University, and grants from the Department of Energy and the University of Maryland
are from our sampling expeditions to Vulcano Island, in the Aeolian Islands
in Southern Italy, in 2002 and 2003. The expedition members were Jocelyne
DiRuggiero, Tanya Marushak and Ernest Williams, University of Maryland, Karen
Nelson, The Institute for Gemomic Research, and Cecile Labarre, University
of Orsay, France. The Eoliennes form a chain of volcanic islands where two
active volcanoes can be found, Stromboli and Vulcano.
Vulcano is the “birth place” of two high temperature microorganisms Pyrococcus furiosus and Thermotoga maritima. Both grow above 90°C and for this reason are called hyperthermophiles. Chromosome shuffling, lateral gene transfer and mobile genetic elements have been recognized as drivers of genome evolution from microorganisms to higher eukaryotes. Lateral gene transfer plays also a major role in the adaptation of microorganisms to new environment conditions. Using comparative sequence analysis of their complete genome, Karen Nelson showed that 24% of T. maritima open reading frames are most similar to genes found in hyperthermophilic archaea, to which P. furiosus belongs (Nelson et al., 1999). Our group found evidence for a recent lateral transfer of a 16 kb DNA fragment between P. furiosus and another hyperthermophile, Thermococcus litoralis, which was also isolated from Vulcano (DiRuggiero et al., 2000). We intent to pursue our studies of lateral gene transfer using hyperthermophiles as a model microbial community.
The goal of these expeditions was to collect samples from hot springs, underwater and on the beach of Vulcano, to isolate microorganisms growing optimally around 95°C. In order to assess the presence of genes potentially acquired through lateral gene transfer in different populations of Pyrococcus we are using suppressive subtractive hybridization (SSH) and comparative genomic hybridization (CGH) to analyze our Vulcano isolates. We found several target-sequences for lateral gene transfer, with similarity to proteins from archaea, other than Pyrococcus, and from bacteria. Comparative genomic hybridization (DNA/DNA microarray hybridization) between P. furiosus and Volcano isolates further indicated large genomic rearrangements suggesting that genome shuffling, in addition to transposon movements, might represent an adaptive mechanism to the dynamic environment of Volcano.
This project was funded by the Department of Energy.