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.