Figure 4
Microbial abundance and the correlation between different physicochemical parameters and microbial relative abundance. (A) The species-level taxonomic abundance of microbiome. Stacked bar plots showing the relative abundance and distribution of the dominant abundant species (43 taxa), with ranks ordered from bottom to top by their increasing proportion among the four metagenomics groups. Each stacked bar plot represents the abundance of each strain in each sample of the corresponding category. The relative abundances of archaeal species (red color legends) steadily improved as energy demand increased (lowest relative abundance in Group-I and highest relative abundance in Group-IV). In contrast, the relative abundances of most of the known bacterial species gradually decreased with the passage of time (increased energy production), and mostly remained higher in Group-I and lower in Group-IV. (B) Spearman’s correlation analysis between different physicochemical parameters [pH, CH4 (%), CO2 (%), O2 (%), Others (%), H2S (ppm), Env_Temp (°C) (Environmental_Temperature), Dig_Temp (°C) (Digester_Temperature), Dig_pre (mb) (Digester_pressure), Humidity (%)] and dominant microbial relative abundance at species level. The numbers display the Spearman’s correlation coefficient (r). Blue and red colors indicate positive and negative correlation, respectively. The color density, circle size, and numbers reflect the scale of correlation. *Significant level (*p < 0.05; **p < 0.01; ***p < 0.001). The R packages, Hmisc (https://cran.r-project.org/web/packages/Hmisc/index.html) and corrplot (https://cran.r-project.org/web/packages/corrplot/vignettes/corrplot-intro.html) were used respectively to analyze and visualize the data.
