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most dominant species in the community. This may suggest that AFP activity did impart
some level of selective advantage to that species within that community at the time of
isolation. Further analysis of all the bacterial strains which demonstrated AFP activity
within their communities would need to be performed, using such techniques as DGGE
and fluorescent in situ hybridisation (FISH), to determine if AFP activity did provide a
selective advantage. The assessment of spatial and temporal variation of the different
communities suggested that between September and November, 2000, the communities
of Ace Lake, Pendant Lake, Triple Lake and Deep Lake generally underwent significant
change in species composition, whereas Club Lake showed no change in its community
profile. During September the communities showed limited variation through the
measured water column. However, the lowest depth recorded for Ace Lake, Pendant
Lake and Triple Lake demonstrated a significant change in community composition
compared with the rest of the measured water column, most likely due to the presence of
different bacterial communities in the sediments, in the case of Pendant and Triple Lakes,
and the chemocline, in the case of Ace Lake. During November each lake showed
significant variation in the communities recorded at each depth, indicating a zonation of
communities, possibly due to the increase in light levels (hence zonation based on light
sensitivity), an overall decrease in the salinity due to ice melt (hence zonation along a
steeper salinity gradient) and increase in temperature (hence zonation along a steeper
temperature gradient).
Denaturing gradient gel electrophoresis (DGGE) is a useful technique for
identifying spatial and temporal dynamics in community structure. However, its
limitations due to bias mean that it requires support from traditional culturing methods
and the determination of 16S rRNA operon heterogeneity (polyphasic taxonomic
approach).
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