TABLE 3

Percentages of isotopic labeling with 15N or 13Ca derived from SIP gradients

DomainDivision/classSubstrate% incorporationb
ArchaeaCrenarchaeota[15N]urea31
BacteriaActinobacteria[15N]urea17
Bacteroidetes[15N]urea22
Firmicutes[15N]urea31
Planctomycetes[15N]urea22
Verrucomicrobia[15N]urea12
Alphaproteobacteria[15N]urea20
Betaproteobacteria[15N]urea33
Deltaproteobacteria[15N]urea25
Gammaproteobacteria[15N]urea23
ArchaeaCrenarchaeota[13C]bicarbonate22
BacteriaActinobacteria[13C]bicarbonate14
Bacteroidetes[13C]bicarbonate12
Firmicutes[13C]bicarbonate17
Planctomycetes[13C]bicarbonate14
Verrucomicrobia[13C]bicarbonate12
Alphaproteobacteria[13C]bicarbonate18
Betaproteobacteria[13C]bicarbonate15
Deltaproteobacteria[13C]bicarbonate18
Gammaproteobacteria[13C]bicarbonate15
• a Percentages were calculated from 16S rRNA gene frequency data with respect to densities of fractions.

• b Percentages in boldface are at or above the 30% and 15% thresholds used as indicators that uptake of 15N- and 13C-labeled substrates had occurred, respectively.