Biodiscovery and biodiversity of Antarctic bacteria

This PhD dissertation explores aspects of the microbial ecology of Antarctica, focussing on the taxonomy and physiological attributes of Antarctic bacteria, as well as investigating the bacterial diversity of previously uncharacterised Antarctic environments. The University of Tasmania has in its possession a collection of 1600 Actinobacteria strains previously isolated from Antarctic and sub-Antarctic soils. A polyphasic study involving both phylogenetic and phenotypic comparisons was carried out to identify any potentially novel bacterial strains. Five isolates of interest were identified, belonging to the genera Arthrobacter, Promicromonospora, and Rhodococcus. Further studies revealed one Rhodococcus strain exhibited the ability to utilise an unusually wide range of hydrocarbons including both straight chain alkanes and polyaromatic hydrocarbons. During this study it was noted that members of the genus Streptomyces dominated this archive of Actinobacteria, and subsequent antimicrobial screening showed a range of potentially novel antimicrobial compounds effective against the food pathogen Listeria monocytogenes. In addition to the characterisation of soil Actinobacteria, a preliminary look at the bacterial composition of several unique Antarctic environments was undertaken to explore ecological niches that may also play host to novel strains or interesting physiological abilities. Eight epiglacial lakes from the Framnes Mountains were compared using t-RFLP bacterial community profiling. These perennially frozen freshwater lakes possess alkaline waters up to pH 11 and have a similar chemical composition. The community structure differed from one lake to another, but each was dominated by Cyanobacterial with either Bacteriodetes group or Proteobacteria species and eukaryotic algae. To continue the characterisation of unique Antarctic sites, ice was chosen for study as it covers almost the entire continent and its surrounding coastline, with ancient glacial ice providing a snapshot into the past. Initially, marine ice accreted beneath the Amery Ice Shelf was examined for its microbial constituents. The bacteria trapped along this core were found to be heterogeneous, with some of the segments of ice possessing cultureable bacteria, revealing either the cryoprotective nature of some Antarctic bacteria found in low levels throughout the marine ice or that the ice contains liquid brine pockets which act as microhabitats. Following on from this work, ice from the Law Dome glacier dating back 115, 755, and 2467 years was investigated. The bacterial DNA recovered from the ice identifies bacterial members that may be useful in studies in evolution and adaptation. The results from this dissertation highlights the fact there is much still to be learnt about the microbial ecology of Antarctica.