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

contamination was lower as the PCR was prepared from high quality genomic DNA. and
the negative controls on the 16S rRNA PCRs were also negative. Therefore, as this was
the second isolation of S. maltophilia from a related environment in close proximit\ to
the first site of isolation, it was possible to suggest that the isolate is present in that
environment. The AFP activity of isolates 47 and 492 demonstrates a cold adapted
strategy presumably in response to a cold environment. Therefore, it is unlikely that these
two isolates were contaminants, but it would be necessary to determine if non-Antarctic
S. maltophilia strains are AFP active before AFP activity can be used to confirm isolates
47 and 492 as Antarctic strains. Further identification of isolates 492 and 47 is required to
confirm that PCR contamination did not occur. It would be prudent to perform standard
biochemical characterisation of the original isolate to confirm it as S. maltophilia.
Phylogenetic analysis of isolates 47 and 492 was not possible as the 16S rRNA
sequence length was not adequate for inclusion in the phylogenetic alignment. Ho w-ever,
two examples of the Xanthomonas group family were included (Fig 5.4),
Stenotrophomonas maltophilia (AJ293466) and Xanthomonas sp 1018 (AB054969). This
group clusters outside of the main y-Proteobacteria phylogeny, and constitute a partial
outlier to the main grouping, This is also shown by the ARDRA analysis, where isolates
492 and 47 continually show a low level of relatedness with the rest of the patterns (Fig
5.2a & b). This suggests that this phylogeny is robust and that the identification of these
isolates is accurate.
S. maltophilia is a pseudomonad like bacterium that is commonly found as a
commensal organism of birds (as well as aquatic ecosystems), however, there are very
few bird species in Antarctica; only three species were observed around the Ace Lake
sampling site, Adelie penguins (Pygoscelis adeliae. ), South Polar Skuas (Catharacta
maccormicki) and the Snow Petral (Pagodroma nivea). Although it is not currently
known whether Stenotrophomonas maltophilia could have been introduced into Ace Lake
from avian fauna, it is still a possibility.
5.3.2.5 -
The Sphingomonas group, isolate 494.
Isolate 494 was identified as Sphingomonas sp. (Ac No. AF395031) using 16S
rRNA sequencing data. However this identification was based on 153 bp which as with
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