A Genomic View of Secondary Metabolite Production in Cyanobacteria - Advances in Botanical Research - page 224

Homologous genes coding for these two enzymes have been identified
in Pseudanabaena and Planktothricoides strains, and they form an operon.
However, neither inactivation nor in vitro studies were reported on this
biosynthetic pathway, in cyanobacteria.
5. CONCLUSION
In the past decade, an impressive number of biosynthesis of cyanobac-
terial secondary metabolites has been unravelled. This is of course directly
related to the number of genome sequences recently obtained for this
group of bacteria. The biosynthetic pathways that have been elucidated are
very diverse reflecting the chemical diversity of the secondary metabolites,
and some very interesting enzymatic reactions have been discovered. In the
near future, more cyanobacterial genomes will be released and it is expected
that new clusters coding for biosynthetic enzymes involved in secondary
metabolism will be discovered. However, there is a real need for more
predictive bioinformatics to aid the annotation of these genes involved in
secondary metabolism. In particular, it would be very useful to be able to
predict the structure of the metabolite from the cluster sequence, although
this might not be possible for complex metabolites. Better genetic tools for
manipulating cyanobacteria will also be needed for studying the functions
of the identified clusters of genes. Another interesting possibility is the het-
erologous expression of entire clusters to facilitate the chemical identifica-
tion of the metabolite, but again this is not yet possible for large clusters
of genes. The other main difficulty, in this field, resides in the isolation
and structural identification of the metabolites, even using the up-to-date
chemical tools. This is probably why there are still orphan clusters in cya-
nobacterial genomes, that is, clusters of genes coding for the biosynthesis of
unknown secondary metabolites.
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