Fig. 5: Global distribution and functional potentials of Myxococcota and Bdellovibrionota in activated sludge.
The analysis was performed based on microbiota datasets of 1 186 activated sludge samples from 269 WWTPs globally published by the Global Water Microbiome Consortium [2]. Stacked bars (A) showed the average relative sequence abundance of Myxococcota and Bdellovibrionota across the samples collected from each country. The potential impact of predatory bacteria on sludge performance was assessed by testing the correlation (B) between their abundance and the removal of BOD (biochemical oxygen demand), COD (chemical oxygen demand), ammonia nitrogen (NH4-N), total nitrogen (TN), and total phosphorus (TP). The color and size of the circles indicate Spearman’s rank correlation coefficients, and circles were displayed only for significant correlation (p < 0.05, n = 529, 281, 423, 268, and 364, for BOD, COD, NH4-N, TN, and TP removal, respectively, corrected with the Benjamini–Hochberg method for multiple testing). Only the genus-level taxa with average relative sequence abundance >0.1% across all the 1 186 samples are shown, with the putative predators identified by SIP in the microcosm experiment marked with a yellow background. Genera of Myxococcota and Bdellovibrionota are indicated with purple and yellow bars, respectively. Examples showed how the sludge properties potentially influence Myxococcota, including that conductivity was negatively correlated with the relative sequence abundance of Haliangium (C) and mle1-27 (D), whereas aeration tank hydraulic retention time showed positive correlation with Haliangium (E).
