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

Chapter 7: GENERAL DISCUSSION
7.1 -
Discussion
The strategies adopted by micro-organisms in adapting to survive and, in some
cases thrive, in cold environments is of great interest to biologists, not only from an
academic perspective, but also for the novel compounds and biological pathways of
biotechnological interest, which can be gained from the study of such adaptations
(Herbert, 1986; McMeekin & Franzmann, 1988; Nichols et al., 1993; Feller & Gerdav.
1997; Russell & Hamamoto, 1998; Naganuma, 2000; Asgeirsson & Andresson, 2001:
Demirjian et al., 2001; Duman & Serianni, 2002). Prokaryotes have colonised Antarctica
through birds and air-borne transportation (Abyzov, 1993; Marshall, 1996) as well as
transportation through the marine ecosystem. It is likely that the majority of bacterial
isolates from the current study are marine derived, as the lacustrine systems under study
were formed from isolated pockets of seawater (Laybourn-Parry & Marchant. 1992b). In
Antarctica, the continuous exposure to extreme cold moulds not only the environment but
also the microbial communities therein. The ubiquitous nature of bacteria within the
Antarctic microbial community is well demonstrated by the characterisation of bacterial
species from this extreme environment (Wright & Burton, 1981; Franzmann, 1991,
Franzmann et al., 1990; Franzmann & Dobson, 1992; Dobson et al., 1993; Franzmann &
Dobson, 1993; Franzmann, 1996; Bowman et al., 1997; Franzmann et al.,
1997; Labrenz
et al., 1998; McCammon et al., 1998; Labrenz et al., 1999; Bowman et al., 2000b;
Labrenz et al., 2000; Lawson et al., 2000; McCammon & Bowman, 2000; Pearce &
Butler, 2002; ). The methods which these bacteria employ for cold adaptation are largely
unidentified. The current study demonstrated the occurrence of antifreeze proteins
(AFPs) as a cold adaptive mechanism in the bacterial populations from the lakes of the
Vestfold Hills, Eastern Antarctica (68°S 78°E).
Nineteen bacterial isolates, comprising eleven characterised taxa. were identified
as being positive for AFP activity during the current study. Previously, only four other
bacterial species have been identified as AFP active, Psychrobacter uratilvorans,
Rhodococcus erythropolis (Duman & Olsen, 1993), Pseudomonas putida (Sun er al.,
1995) and A farinomonas protea (Mills, 1999). One of the eleven species from the current
186