The unexpected habitat in sewer pipes for the propagation of microbial communities and their imprint on urban waters

Abstract

Modern urban sewer pipe infrastructure is a unique niche where microbes can thrive. Arcobacter, Acinetobacter, Aeromonas, and Trichococcus are among the organisms that dominate the microbial community of sewage influent, but are not major members of human fecal microbiome, drinking water, or groundwater. Pipe resident communities in untreated sewage are distinct from sewer biofilm communities. Because of their high biomass, these organisms likely have a role in biotransformation of waste during conveyance and could represent an important inoculum for treatment plants. Studies demonstrate stormwater systems act as direct conduits for sewage to surface waters, releasing organisms propagated in sewer pipes. Frequent occurrence of these pipe residents, in particular Arcobacter, demonstrates the extent that urban infrastructure impacts rivers, lakes, and urban coasts worldwide.

Figure 1

Dominant bacterial families in fecal human microbiome, untreated sewage and sewer biofilm based on 16S rRNA gene amplicon data. Only the top 10 dominant families among at least one of the three environments are displayed. Fecal-derived taxa are represented using red/orange hue colors, while non-fecal-derived taxa are colored in blue/green hue. List of the publications: a [26], b [66], c [67], d [6], e [3], f [19], g [68], h [69]. *: data reprocessed from the SRA files using the 454 Mothur SOP and Silva132 database. **: sewer pilot.

Figure 2

Box plot depicting the relative abundance of the bacterial groups Arcobacter, Acinetobacter, Aeromonas and Trichococcus within sewage influent from 71 U.S. cities [6]. A total of 31 cold cities (blue dots, average air temperature over the campaigns ≤ 10°C), and 40 warm cities (red dots, average air temperature over the campaigns > 10°C) were sampled in January, May and August between 2012 and 2013. *Six outliers were removed from the plot for Arcobacter (88.9, 85.5, 84.4, 73.1, 58.9, and 44.6%) and one for Trichococcus (1.5%).

Figure 3

Log2 fold change comparison between the relative abundance of bacterial families in untreated sewage and biofilm. Families more abundant in sewage are represented using green bars, while families more abundant in biofilm are in orange. Relative abundance of the families per compartment are listed on the left of the plot. The relative abundance per family was computed by averaging the abundances pondered with the number of sample from the publications described in the Figure 1. Relative abundance higher than 10% are in bold. Only the families with a relative abundance higher than 1% in at least one of the two compartments were considered.

Box 1 Figure.

Illustration of the dynamic between urban sanitary sewers and stormwater systems with changing groundwater levels.