Presence and role of viruses in anaerobic digestion of food waste under environmental variability.

Background: The interaction among microorganisms in the anaerobic digestion of food waste (ADFW) reactors lead to the degradation of organics and the recycling of energy. Viruses are an important component of the microorganisms involved in ADFW, but are rarely investigated. Furthermore, little is known about how viruses affect methanogenesis.

Results: Thousands of viral sequences were recovered from five full-scale ADFW reactors. Gene-sharing networks indicated that the ADFW samples contained substantial numbers of unexplored anaerobic-specific viruses. Moreover, the viral communities in five full-scale reactors exhibited both commonalities and heterogeneities. The lab-scale dynamic analysis of typical ADFW scenarios suggested that the viruses had similar kinetic characteristics to their prokaryotic hosts. By associating with putative hosts, a majority of the bacteria and archaea phyla were found to be infected by viruses. Viruses may influence prokaryotic ecological niches, and thus methanogenesis, by infecting key functional microorganisms, such as sulfate-reducing bacteria (SRB), syntrophic acetate-oxidizing bacteria (SAOB), and methanogens. Metabolic predictions for the viruses suggested that they may collaborate with hosts at key steps of sulfur and long-chain fatty acid (LCFA) metabolism and could be involved in typical methanogenesis pathways to participate in methane production.

Conclusions: Our results expanded the diversity of viruses in ADFW systems and suggested two ways that viral manipulated ADFW biochemical processes. Video Abstract.