Environmental Engineering Reference
In-Depth Information
3 General Conclusions
The many roles of DMS and DMSO in microbial metabolism and physiology
outlined above are reflected in the diversity of enzymes that are involved in the
transformation of these organic sulfur compounds and the wide phylogenetic
distribution of the ability to metabolize DMS within the bacterial and archaeal
phyla.
There is still a huge discrepancy in the level of insight and understanding of the
biochemistry, genetics, and structure-function relationships of DMS transforming
enzymes, where DMSO reductases have been investigated in considerable detail,
while there is still a lot to be learnt about the biochemistry of both DMS dehydro-
genases and DMS monooxygenase enzymes, their structure-function relationships
and, for the latter, the role of metals in catalysis. There is also a clear discrepancy in
the distribution of DMS-converting enzymes and their relative abundance in the
currently available genome sequences. While genes encoding DMSO reductase of
either the Dor- or Dms-type are present in a large number of bacterial genomes,
DMS dehydrogenases and DMS monooxygenases appear to have a much more
limited distribution, and reasons for this apparent specialization are currently
unknown, but the skewed distribution of these enzymes might at least partly be
due to the relative overrepresentation of, e.g., Proteobacterial genomes in current
databases, while DMS dehydrogenase and DMS monooxygenase genes are found in
bacterial groups for which fewer genome sequences are available.
There is also clear potential for discovery of additional enzymes involved in
DMS biotransformations, such as the methyltransferases in aerobic
DMS-degrading methylotrophs and the NAD(P)H-dependent DMSO-converting
enzymes reported to exist in DMSO 2 and DMSO-degrading Hyphomicrobium and
Arthrobacter strains which are known to be expressed during aerobic heterotrophic
growth of these bacteria.
DMS and related methylated sulfur compounds play important roles in the
global biogeochemical cycle of sulfur and have relevance in many different areas
due to their effect on atmospheric chemistry, atmospheric sulfur transport as well as
being signalling compounds affecting the behavior of animals. They are important
flavor compounds in foods and beverages, but may be produced in the human body
due to disease or metabolic disorders. As industrially relevant chemicals as well as
byproducts of sewage treatment processes, they can cause nuisance odors which
need to be deodorized using biotechnological applications.
Considering these varied roles of DMS and related compounds it is clear that
further insights into the molecular processes underlying DMS transformations will
be required to advance our understanding of the interplay of DMS biotransforma-
tions and the global sulfur cycle.
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