| dc.description.abstract | In a previous study, metagenomic DNA extracted from Antarctic Dry Valley soils was used
to construct a large contig bacterial shotgun fosmid library (Anderson, 2008). In the current
study, clones were selected based on a functional screen for putative lipolytic enzymes,
which incorporated tributyrin in agar screening plates. Clones were subsequently subjected to
next-generation sequencing and bioinformatic analysis, which allowed for further
investigation of a portion of the Antarctic metagenome. Assembly and annotation of the
genetic data encoded on three fosmid clones allowed for the identification of the genes
responsible for tributyrin hydrolysis. Furthermore, hypotheses relating to survival and
adaptation to abiotic conditions prevalent in the extreme Antarctic environment were
developed (Chapter 3). A cold adapted esterase was subsequently characterised and showed
substrate preference for para-nitrophenyl propionate. The optimum temperature and pH for
the enzyme, DEaseI was 25 ° C and 8.5, respectively. In addition, results indicated that
DEaseI was sensitive to thermal inactivation (Chapter 4). Furthermore, in fosmid clone
LD13, one particular ORF annotated as a Water HYpersensitity response protein, became the
focus of further study. When sub-cloned into a heterologous host, both ionic and osmotic
stress tolerance was observed in vivo. The protein also exhibited a cryoprotective function in
vitro, preventing cold denaturation of malate dehydrogenase during cycles of freeze-thaw
(Chapter 5). This study demonstrates the value of combinatorial in silico and ‘-omic’ based
techniques for the discovery and functional characterisation of potentially novel genes from
bacteria which inhabit Antarctic Dry Valley soils. | en_US |
