This work investigated the microbial content of decaying nodules from alders. The 16S rDNA composition of the microbiome of six senescent alder nodules was investigated by 454 sequencing. All nodules still had some Frankia sequences present, but in each case it was only detected at minor levels, with other organisms predominating. Although organisms from three different phyla (Bacteroidetes, Proteobacteria and Actinobacteria) constituted almost all (98% or more) of all sequences, Bacteroidetes were most abundant in four nodules with Proteobacteria being most abundant in the other two. In addition a few families were represented at a level of 10% or more of the total sequences: Sphingobacteriaceae (all 6 nodules); Chitinophagaceae (5 of 6); non-Frankia Actinomycetales (2 of 6); Caulobacteraceae (2 of 6); Flavobacteriaceae (2 of 6); Oxalobacteraceae (1 of 6); and Xanthomoadaceae (1 of 6). Analysis at the genus level showed a diverse range of organisms, with members of the genus Pedobacter being found at an abundant level within most nodules.