## 1 Introduction  
More than half of the oxygen in the atmosphere is generated by oxygenic photosynthetic bacteria, known as cyanobacteria [1]. These bacteria, whose biomass exceeds the total mass of zooplankton and fish, play a central role in carbon capture, the release of dissolved organic carbon (DOC), and nutrient cycling (Scheme 1A). It is becoming increasingly apparent that cyanobacterial metabolic pathways, and nutrient cycling itself, are largely governed by the bacteriophages that infect them. With approximately 10 million viruses in every milliliter of seawater [2] and representing more than 94% of nucleic acid entities in the oceans [3], oceanic viruses are \(\sim\)10-fold more abundant than marine bacteria and considerably outnumber other marine organisms, such as phytoplankton, zooplankton, and organisms at higher trophic levels [1, 4]. Based on published data regarding labile DOC release mediated by microbial and zooplankton activities, the partitioning of inputs among these sources suggests (even though much remains to be understood about the exact nature of the chemistry of these short-lived species) that about 20% of labile DOC is released through excretion and death processes of heterotrophic organisms, approximately 40% originates directly from phytoplankton (including cyanobacteria) through extracellular release during photosynthesis, and around 40% is released through phytoplankton death processes, including senescence, sloppy feeding, and viral and fungal lysis [5, 6]. The viral shunt, through the incorporation of carbon in new viruses and the release of carbon during cell lysis, represents a considerable pathway through which DOC is mobilized and redistributed within ecosystems. It is estimated that as much as one-quarter of DOC undergoes the viral shunt process (Scheme 1B) [7]. This highlights the important role that viruses play in the dynamics of carbon cycling, shaping carbon availability and utilization by other organisms in the ecosystem. A greater understanding of the viral shunt process and the chemistries encoded by viruses will provide insights into the intricate connections between viruses, host cells, and the carbon cycle, with implications for ecosystem functioning and biogeochemical processes [7]. Infection of a cyanobacterium by a virus known as a \"cyanophage\" or \"cyanobacterriophage\" can be persistent or lethal, ultimately resulting in host lysis and the release of the progeny phage. In both types of infection, host and phage may exchange genetic material. This results in cyanophage often encoding metabolism-related genes, analogous to cyanobacterial genes. These genes, known as auxiliary metabolic genes (AMGs), play a key role in host metabolism following infection. Here, we analyze AMGs from 153 publicly accessible cyanophage genomes [8; 9; 10; 11] (see Table 1) with the aim of gaining greater insight into the ways in which cyanophages manipulate host metabolism. Cyanophages exhibit a broad distribution across diverse aquatic environments worldwide (Table 1). They are prevalent in both freshwater and marine ecosystems, encompassing lakes, rivers, ponds, oceans, and estuaries. The geographic range of cyanophages can vary, influenced by factors such as local environmental conditions, host cyanobacteria species, and the presence of suitable habitats conducive to their replication and survival. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Phage** & **Taxonomy** & **Host** & \ \begin{tabular}{c} **Geographic** \\ **Distribution** \\ \end{tabular}  & \begin{tabular}{c} **Genome** \\ **Length (Kb)** \\ \end{tabular}