Temporal metagenomic characterization of microbial community structure and nitrogen modification genes within an activated sludge bioreactor system

Abstract

Wastewater treatment plays an essential role in minimizing negative impacts on downstream aquatic environments. Microbial communities are known to play a vital role in the wastewater treatment process, particularly in the removal of nitrogen and phosphorus, which can be especially damaging to aquatic ecosystems. There is limited understanding of how these microbial communities may change in response to fluctuating temperatures or how seasonality may impact their ability to participate in the treatment process. The findings of this study indicate that the microbial communities of wastewater are relatively stable both compositionally and functionally across fluctuating temperatures.

Keywords: metagenomics; nitrogen cycle enzymes; wastewater treatment.

Fig 1

A summary of the phyla and genera that were present at ≥1.0% relative abundance. Count data were generated via MetaPhlAn2, and samples from the same date and bioreactor were averaged. Organisms that were <1.0% were summed and reclassified as “Less Abundant.” For the genera data, “Can.” refers to Candidatus, and “Unclassified” represents an unclassified genus belonging to the Dermatophilaceae family.

Fig 2

Heatmap and dendrogram of organisms with relative abundances greater than 1%. The abundance of the bacterial genera across all samples was determined via MetaPhlAn2. Dendrograms were generated using Bray-Curtis as the distance measure.

Fig 3

Abundances of enzymes involved in denitrification and nitrification in the Regina WWTP BNR system. Genes involved in nitrification and denitrification were detected and quantified using the command line tool, HUMAnN2. Each enzyme is present in similar abundances throughout the year with the exception of ammonia monooxygenase.

Fig 4

Redundancy analysis of the microbial communities in the Regina WWTP BNR system. The abundance of the bacterial genera across all samples was determined using the tool, MetaPhlAn2 and used in redundancy analysis using the R package vegan. Select genera are labeled based on their relevance to activated sludge functionality or distance from the origin. Most bacterial genera do not correlate strongly with any month, with notable exceptions such as Cytophaga, Gordonia, and Aeromonas.