Significant differences between the metagenome taxa were also deduced at the class level to specifically examine differences within the Proteobacteria phylum (Figure 4). EGT matches to Alphaproteobacteria and Deltaproteobacteria were proportionally

higher in the +NO3- metagenome, while matches to Gammaproteobacteria were relatively higher in the –N metagenome (Figure Salubrinal mw 4). Figure 3 Significant phylum differences between the +NO 3 – and –N metagenomes. Results of a Fisher exact test (conducted with the Statistical Analysis of Metagenomic Profiles program) showing the significant differences of environmental gene tag (EGT) matches to phyla between treatments. Higher EGT relative abundance in the +NO3- metagenome have a positive difference between proportions (closed circles), while higher EGT relative abundance in the –N metagenome have a negative difference between proportions (open circles). Figure 4 Significant class differences in the domain bacteria between the +NO 3 – and –N metagenomes. Results of a Fisher

exact test (conducted with the Statistical Analysis of Metagenomic Profiles program) showing the significant differences of environmental gene tag (EGT) matches to class between treatments. Higher EGT relative abundance in the +NO3- metagenome have a positive difference selleck chemical between proportions (closed circles), while higher EGT relative abundance in the –N metagenome have a negative difference between proportions (open circles). Discussion Metagenomic analysis revealed treatment differences

both for functional and taxanomic EGTs between Morin Hydrate our +NO3- and –N metagenomes. These differences were apparent even though the metagenome sequencing conducted here returned a lower number of sequences than are typically reported for shotgun metagenome studies [20–22]. However, a shotgun metagenomic sequencing effort conducted by Fierer et al. [23], where comparable sequence numbers to ours are reported, was able to elucidate increases in functional genes with increased N fertilization, suggesting that our sequence numbers are adequate for determining relative metabolic and taxonomic changes. A somewhat surprising result was no proportional abundance change in any of the N metabolism EGTs between our treatments with the BLASTX comparison to the SEED database. Particularly surprising was no change in the denitrification EGTs (determined with the BLASTX) between treatments and no detection of denitrification genes with the BLASTN, other than two sequence matches to nitrate reductase in the +NO3- treatment. The two sequence matches with the BLASTN in the +NO3- metagenome were to the nitrate reductase genes napA and napB. Because the periplasmic nitrate reductases, which are the products of napA and napB, are used in both denitrification and DNRA [12], no conclusions can be drawn on which of these microbial groups grew to a level where they could be detected in the +NO3- microcosms.