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

11 species) showed AFP activity. This suggests one of two possibilities. Firstly, that the
culture conditions used to isolate the bacteria from these environments were
unintentionally selecting for Proteobacteria, which are considered dominant in cold,
aquatic ecosystems (Lopez-Garcia et al., 2001). Secondly, that all or the majority of
bacteria within the community had an AFP active phenotype, but the cold-shock
conditions used to induce expression of the AFP gene were not sufficient. This second
point is supported by the studies of Duman & Olsen (1993) and Sun et al. (1995), who
both suggested that variation in the length of cold-shock exposure did affect the AFP
activity of the respective bacterial species.
The nineteen bacterial isolates which showed AFP activity were
isolated from
four different lakes. The majority of the isolates came from Ace Lake, the site of previous
isolation of the AFP active bacterium Marinomonas protea (Mills, 1999). This is a
meromictic (permanently stratified) saline lake with low inorganic nitrogen
concentrations (N-NO2, N-NO2 and N-NH4) and high soluble reactive phosphate (SRP)
concentrations, compared with the other lakes from which AFP active bacteria were
isolated (Pendant, Triple and Oval). Pendant Lake, from which five AFP active bacteria
were isolated, had a similar salinity to Ace Lake, but it generally had higher
concentrations of inorganic nitrogen and lower concentrations of SRP. The variation
between the two lakes is attributed to the meromictic status of Ace Lake, which
accumulates nutrients within the anoxic monimolimnion due to downward flux of
particulate and dissolved matter across the chemocline (Laybourn-Parry et al., 2002).
One of the AFP active isolates was isolated from Oval Lake. This isolate has not
been fully characterised; however, in ARDRA analysis it does appear to have a Dice
coefficient of similarity of approximately 75% with the Marinomonas group which could
indicate that it belongs in the Proteobacteria. Oval Lake is also a meromictic
lake (Burke
and Burton, 1988; Gibson, 1999) and although at 8m it is considerably more shallow than
Ace Lake (25m), it was expected to show a similar chemical profile as Ace Lake. The
current study demonstrated that inorganic nutrient concentrations in the surface waters
during the summer were very similar between Oval Lake and Ace Lake. However, Oval
Lake has a considerably higher salinity than Ace Lake, which at 34 ppt is close to marine
salinity.
189