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AFP active bacterium which was represented by bands of the greatest intensit\ within its
community. This suggests that AFP activity within this bacterium did pros ide it with a
selective advantage within its community. However, as for all the isolates detected ww ithin
the community profiles, the link between band intensity and abundance relies on the
absence of bias which, as described later (section 6.3.2), can significantly affect the
authenticity of such an assumption (Ercolini et al., 2001 b).
As previously stated, the DGGE profiles against which the isolates (except isolate
213) were analysed were not the communities from which they were cultured. Thus it is
possible that the 13 isolates were not present within those communities, as they were not
represented in the community profiles. This would mean that the initial assumption that
those 13 isolates may have been represented in the communities throughout the depth of
their respective lakes is possibly false. The similarity scores for the DGGE community
profile analysis (Fig 6.5a & b, section 6.2.2) show that there is considerable change
within these communities over short periods of time. For example, Isolate 53 was isolated
from Triple Lake at 8m during September. It was analysed against the community profile
for Triple Lake at 8m from November (Fig 6.3a). The community profiles of
Triple Lake
at 8m between September and November had a similarity of 0.61 %, indicating the
community had changed considerably. This change in community is probably due to the
changing environmental conditions during the period September - November; the water
temperature in Triple Lake increased by nearly 7°C from -14°C to -7.5°C.
The ice cover
was halved due to melt and therefore the salinity decreased from 170 ppt to 160 ppt
(Section 3.3.2.3). This probably had a substantial impact on the bacterial community
composition. A similar situation was shown for isolates 154,54,494 and 583 (all isolated
from different depths or times), which suggests why they were not present in the
community profiles selected for analysis.
Isolates 732,302,494
and 583 were represented in the community profiles of
lakes from which they were not isolated (section 6.2.1). It is possible that even though
they were not isolated from those lakes they may have been present within the
community and the culturing conditions used may not have been ideal to isolate them.
This could have been because they may have been competitively excluded from the
initial environmental culture by a species which could utilise the culture medium more
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