nirS and nirK primers

Here are a few papers I found that have some mixed results using nirS and nirK primers. Most of the primers discussed have varying degrees of success because they were too specific.
Philippot and Hallin 2005 has a good review of molecular methods for detecting denitrifiers, but the first paragraph on p 236 has some good papers on nirS and K primers.
Heylen et al 2006 showed that some of the nirS and nirK primers don't even work well with cultivated microbes, though they found some evidence for HGT which I thought should make the primers a little more general. An interesting paper though.
Henry et al 2004 (and the corrigendum) looked like the most successful paper I've seen so far. They used shorter, less specific primers so they would be more likely to bind and they observed a much broader group of soil denitrifiers.