Fig. 6

The gene frequency of key metabolic genes in the metagenomes of shallow-sea, deep-sea, and terrestrial geothermal systems. More detail on datasets is shown in Table S3. The average gene frequencies are presented as mean values ± standard error of mean. Differences were considered significant if the p-value of an ANOVA was less than 0.05 (*, p < 0.05; ***, p < 0.001; ****, p < 0.0001). Green, shallow-sea hydrothermal systems; red, deep-sea hydrothermal systems; purple, thermal spring