High Diversity and Functional Potential of Undescribed “Acidobacteriota” in Danish Wastewater Treatment Plants

Abstract

Microbial communities in water resource recovery facilities encompass a large diversity of poorly characterized lineages that could have undescribed process-critical functions. Recently, it was shown that taxa belonging to “Acidobacteriota” are abundant in Danish full-scale activated sludge wastewater treatment plants (WWTP), and here we investigated their diversity, distribution, and functional potential. “Acidobacteriota” taxa were identified using a comprehensive full-length 16S rRNA gene reference dataset and amplicon sequencing surveys across 37 WWTPs. Members of this phylum were diverse, belonging to 14 families, eight of which are completely uncharacterized and lack type strains. Several lineages were abundant, with relative abundances of up to 5% of the microbial community. Genome annotation and metabolic reconstruction of 50 high-quality “Acidobacteriota” metagenome-assembled genomes (MAGs) from 19 WWTPs showed high metabolic diversity and potential involvement in nitrogen and phosphorus removal and iron reduction. Fluorescence in situ hybridization (FISH) using newly-designed probes revealed cells with diverse morphologies, predominantly located inside activated sludge flocs. FISH in combination with Raman microspectroscopy revealed ecophysiological traits in probe-defined cells from the families Holophagaceae, Thermoanaerobaculaceae, and Vicinamibacteraceae, and families with the placeholder name of midas_f_502, midas_f_973, and midas_f_1548. Members of these lineages had the potential to be polyphosphate-accumulating organisms (PAOs) as intracellular storage was observed for the key compounds polyphosphate and glycogen.

The predicted secreted proteome of activated sludge microorganisms indicate distinct nutrient niches

“…Many of these MAGs are from groups known to encode extracellular cytochromes for mediating extracellular electron transfer, such as Anaeromyxobacter (Myxococcota), Geobacterales (Desulfuromonadota) (76) and Geothrix (Acidobacteriota) (77). Multi-heme cytochromes were also previously reported in the same Geothrix -related MAGs (78), although sub-cellular locations were not predicted. Recent experimental work showed increases of Geothrix and Ignavibacteria spp.…”

Development of microbial communities in biofilm and activated sludge in a hybrid reactor

“…Actinobacteriota , as well as Proteobacteria and Bacteroidota , have been reported to be some of the core phyla that are widespread in wastewater treatment systems 18 , 19 . Acidobacteriota are involved in P-removal and have the potential to utilize various organic compounds, including glucose, xylose, acetate, and fatty acids 20 . After Proteobacteria and Bacteroidota , the next most abundant phyla in the activated sludge were Actinobacteriota and Patescibacteria (especially the uncultured Saccharimonadales ).…”

Irrigation water salinity structures the bacterial communities of date palm (Phoenix dactylifera)-associated bulk soil

“…Mycobacterium was also an indicator taxon under saline groundwater irrigation, showing an increase in arabinogalactan-peptidoglycan (cell wall) synthesis that may serve as a potential mechanism for tolerating salinity stress. Subgroup_10 genus (Acidobacteriota) abundance was higher in soil under saline water irrigation, whose members are reported to accumulate starch (Kristensen et al, 2021) and starch accumulation was reported to provide osmoprotectant effect for bacteria against salinity stress (Qiao et al, 2018). The increased Saline groundwater irrigation increased the abundance of Microvirga (Alphaproteobacteria), a free-living, nitrogen-fixing, and nitrate-reducing bacterium isolated from desert soil (Amin et al, 2016), suggesting that it may function as a nitrifier despite salinity-stress.…”