Several new options for possible primers were found
when the nirS sequences were aligned (Table 3; Fig. 1a).
They are all located in the second half of the gene, where
the majority of the sequences have been derived. Unfortunately, there are only nine complete nirS gene sequences in the databases. For several nirS primers, small
modifications were tested, but in Table 1 only the results
from the best primer targeting each primer site is shown.
The best result was obtained with the modified version
of primer cd3F [11] cd3aF in combination with the nirS