Glucose 13C-2 and ribose 13C-5 tracer had the highest recovery in most
microorganism groups. There was little to no incorporation of
glucose 13C-4 and ribose 13C-1 in all microorganisms' PLFAs. However,
due to differences in absolute tracer uptake, comparison of
position-specific 13C behavior between the microbial groups is
difficult. Therefore, the relative tracer 13C incorporation (divergence
index (DI)) is better suited for detailed comparison.