Investigation of genome diversity in Antarctic Dry Valley soils

• Main Author: Whiting, Samantha J.
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: UCL (University College London) 2005
• Subjects: Antarctic; McMurdo Dry Valleys; Victoria Land; Antarc*; Antarctica
• Online Access: https://discovery.ucl.ac.uk/id/eprint/1446727/1/Whiting.SamanthaJ_thesis.pdf; https://discovery.ucl.ac.uk/id/eprint/1446727/

The McMurdo Dry Valleys of South Victoria Land, Antarctica contain some of the most extreme biotopes on earth; extreme to the extent they have long been considered valid Martian analogues. Life within Dry Valley mineral soils, where water contents range from 0.2-5.0% w/w and mean annual temperatures fall below -20 C, must further contend with desiccating winds, diurnal freeze-thaw cycles, and high seasonal UV radiation. Our knowledge to date of the microbiology of this biotope has been restricted to cultivation studies. This study sought to investigate microbial diversity in Antarctic Dry Valley soils using both cultivation and cultivation-independent techniques. Phylogenetically-informative ribosomal RNA gene libraries were generated from Archaea-, Bacteria- and Eukarya- specific PCR products amplified directly fro m DNA extracted from Dry Valley soils. This approach permits a more representative assessment of microbial diversity, as it circumvents the need for cultivation; it is estimated that only 0.1-10% of microorganisms in soil can be cultivated in vitro. Dry Valley soils were found to support a high diversity of bacterial species based upon the analysis of 16S rRNA gene clone sequences, the majority of which showed little similarity to previously cultivated bacteria. The diversity of Archaea and eukaryotes was reduced in comparison, and included members of the non- thermophilic Crenarchaeota and species of fungi respectively. To complement these molecular analyses, bacteria were also cultivated in vitro from Dry Valley soils. Additionally, functional gene diversity was investigated in these soils focusing on integrons and their associated gene cassettes. Using a PCR-based strategy, evidence was obtained for the presence of class 1 integrons in Antarctic soils. Furthermore, a unique aadA gene cassette encoding a streptomycin/spectinomycin adenyltransferase was recovered in this study. These data reveal Dry Valley soils to support a microbial community of considerable genetic diversity, and provide fresh ...