ý.,,: V. ý ýý . - Nottingham eTheses - University of Nottingham

The remaining five AFP active isolates were cultured from the extremely
hypersaline Triple Lake. All five isolates were characterised as belonging to genera
which have shown an association with extreme environments, i. e. Halomonas,
Psychrobacter, Idiomarina and Pseudomonas (James et al., 1994; Meyer et al., 1998;
Obata et al., 1998; Ivanova et al., 2000; Kaye & Baross, 2000; Maruyama et al., 2000;
Teske et al., 2000; Brown & Bowman, 2001; Duilio et al., 2001; Mergaert et al., 2001;
Panicker et al., 2002; Camardella et al., 2002) . The hypersalinity of Triple Lake causes
severe temperature fluctuation throughout the year; during the summer the water
temperature can reach 3 to 4°C and during the winter it can fall to -14°C.
It has been
suggested that the AFP activity of the characterised isolates should be considered one
adaptation to survival of the bacterial cell in the extreme cold (Sun et al., 1995).
However, due to the extreme hypersalinity of the environment the chances of freezing are
low, unless the isolate exists in the surface water, where a 30cm thick ice cover forms
during the winter. The possibility of the bacteria freezing is low, because adaptations to
extreme salinity generally involve an increase in intracellular solute potential to allow
biochemical functioning within the high osmotic stress environment (Kushner, 1978,
Wright and Burton, 1981). Thus, AFP activity is possibly redundant in their current
environment, but it is suggested that the bacteria evolved AFP activity during a time
when they were exposed to freezing stresses. The salinities within Ace Lake, Pendant
Lake and Oval Lake are low enough to allow substantial freezing of the surface waters
during the winter and so AFP activity could have evolved in such an environment. To
date there have been no recorded isolations of Pseudomonas, Halomonas, Psychrobacter
or Idiomarina from either Ace Lake, Pendant Lake or Oval Lake. This could imply that,
while the species from the hypersaline lakes have evolved AFP activity, they did not
originate within the saline lakes. This in turn could suggest that the saline lakes - Ace
Lake, Pendant Lake and Oval Lake - are not the only locations in which AFP activity has
evolved. This is substantiated by Psychrobacter urativorans, which was isolated from
ornithogenic soils in an Adelie penguin colony in the Vestfold Hills (Cavanagh et a!.,
1996), and as such would have been exposed to freezing stresses. The close association of
the predatory South Polar Skua (Catharacta maccormicki) with the penguin colony.
means that it could have acted as a vector for the bacteria to Triple Lake. This suggests
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