Potential Viral Regulation of Sulfur Cycling in Urban Sewer Sediments

Sewer sediments are microbial hotspots for sulfur cycling
and sulfide
generation, which is the leading cause of sewer corrosion and poses
significant economic losses and public safety concerns. However, viruses
in sewer sediments remain inadequately explored regarding their characteristics,
interactions with their hosts, and ecological regulatory potential
for sulfur cycling. In this study, we explored viral characteristics
and virus–host interactions in sewer sediments from three distinct
types of urban functional areas through metagenomics and viromics.
Compared with single-function (commercial and residential) areas,
sewer sediments in multifunctional areas contain higher nutrients
and nutrient-induced acidification, which can promote host density
and drive a shift from lytic to lysogenic infection. This shift may
potentially enhance sulfide formation through the insertion of more
auxiliary metabolic genes related to sulfate reduction into host genomes.
Conversely, a higher viral lytic tendency in single-function area
can lyse sulfate-reducing microorganisms, thereby mitigating sulfide
formation. Phage transplantation experiments and the high prevalence
of key viral hosts across global sewers (76 cities across six countries)
demonstrated the high potential of viruses in alleviating sewer corrosion.
Our findings reveal the dual role of viruses as metabolic “tuners”
in sewer sulfur dynamics, suggesting that comprehensive urban sewer
management requires consideration of exploiting viral lysis.