Environmental Engineering Reference
In-Depth Information
2.3 Molecular Techniques
DNA/RNA based techniques are widely used to identify organisms involved
in anaerobic ammonium oxidation in waste water bioreactors (e.g. [15, 16, 56-
58, 65]). Phylogenetic analyses of the 16S ribosomal RNA sequences indicate
that all known anammox bacteria belong to the order Planctomycetales [58].
There are presently at least three known anammox genera;
Candidatus
'Bro-
cadia',
Candidatus
'Kuenenia' and
Candidatus
'Scalindua'[58]. The average
sequence similarity between members of these genera is generally low, with
less than 85% sequence similarity between members of
Candidatus
'Brocadia'
and
Candidatus
'Scalindua'.
Only a few studies have used molecular ecological techniques to trace anam-
mox bacteria in the marine environment [23, 35, 51]. Anammox derived 16Sr-
RNA sequences have been reported from Black Sea water and from Danish
estuarine sediments [35, 51]. The sequences from these different settings are
nearly identical indicating a low diversity of marine anammox bacteria. The
anammox bacterium from the Black Sea, tentatively named
Candidatus
Scalin-
dua sorokinii is nearly identical (98.1%) to a sequence recently obtained from
a bioreactor shown to have anammox activity [35, 58]. Based on the sequence
obtained from the Black Sea, an oligonucleotide probe has been designed, la-
beled with Cy3 fluorochrome, for fluorescence
in situ
hybridization (FISH).
This probe gave a bright and specific signal with cells from the Black Sea
that have the unusual doughnut shape characteristic for anammox bacteria in
bioreactors. Cells hybridizing with this specific FISH probe were also found in
Randers Fjord sediment [51].
3. DISTRIBUTION OF ANAMMOX IN THE MARINE
ENVIRONMENT
3.1 Sediments
To date, anammox has been detected in practically all the sediments for
which results of anammox assays have been published. These include marine
sites in the Kattegat/Skagerrak area where anammox was first reported [19, 70],
in Long Island Sound [19], and around Greenland [54], as well as locations
in the Thames estuary [73]. Recently, anammox bacteria were also reported
from an African fresh water wetland [32]. Within the small array of marine
sites, anammox rates varied by nearly two orders of magnitude between
5 and
240 µMN
2
d
−
1
, with both extremes represented in the Thames estuary. The
rates decreased towards the mouth of the Thames estuary and towards deeper
water in Kattegat/Skagerrak thus correlating with the metabolic activity of the
sediment. The site with the lowest salinity in the Thames (2‰) was an outlier
in this trend with a relatively low anammox rate.
∼
