Table 2.

Correlations of predicted second-tier functional abundances between metagenomic and PICRUSt annotations.

Function		Metagenome (%)*	PICRUSt (%)†	Spearman r	P-value
1st tier	2nd tier
Metabolism	Amino acid metabolism	21.46 ± 0.28	11.15 ± 0.15	0.825	0.032
	Biosynthesis of other secondary metabolites	0.83 ± 0.03	0.96 ± 0.10	0.111	0.746
	Carbohydrate metabolism	11.24 ± 0.13	10.36 ± 0.34	−0.330	0.321
	Energy metabolism	6.08 ± 0.13	5.50 ± 0.15	0.696	0.017
	Enzyme families	ND	1.79 ± 0.04	NA	NA
	Glycan biosynthesis and metabolism	1.90 ± 0.28	1.63 ± 0.08	0.797	0.003
	Lipid metabolism	1.79 ± 0.15	4.28 ± 0.07	−0.023	0.947
	Metabolism of cofactors and vitamins	5.29 ± 0.26	4.12 ± 0.15	−0.513	0.107
	Metabolism of other amino acids	1.04 ± 0.05	2.07 ± 0.05	0.388	0.238
	Metabolism of terpenoids and polyketides	1.53 ± 0.05	2.57 ± 0.08	0.065	0.851
	Nucleotide metabolism	5.00 ± 0.09	3.01 ± 0.10	0.155	0.650
	Xenobiotics biodegradation and metabolism	0.63 ± 0.11	4.66 ± 0.23	0.425	0.193
Genetic Information Processing	Folding, sorting, and degradation	3.96 ± 0.15	2.23 ± 0.04	−0.220	0.516
	Genetic information processing	ND	2.06 ± 0.07	NA	NA
	Replication and repair	5.51 ± 0.08	6.76 ± 0.23	0.410	0.210
	Transcription	2.79 ± 0.09	2.32 ± 0.06	0.741	0.009
	Translation	10.64 ± 0.26	4.01 ± 0.11	0.256	0.447
Environmental Information Processing	Membrane transport	7.01 ± 0.46	12.40 ± 0.35	0.064	0.853
	Signaling molecules and interaction	ND	0.18 ± 0.01	NA	NA
	Signal transduction	3.88 ± 0.23	2.21 ± 0.16	0.811	0.002
Cellular Processes	Cell communication	0.01 ± 0.00	ND	NA	NA
	Cell growth and death	2.01 ± 0.04	0.44 ± 0.01	−0.081	0.813
	Cell motility	0.29 ± 0.06	2.49 ± 0.38	0.804	0.003
	Cellular processes and signaling	ND	3.27 ± 0.33	NA	NA
	Transport and catabolism	0.95 ± 0.05	0.37 ± 0.01	0.533	0.092

^*Mean percent abundance of the functional trait among all samples by metagenomic analysis.

^†Mean percent abundance of the functional trait among all samples by PICRUSt inference.