Phages are viruses that infect bacteria. They affect various microbe-mediated processes that drive biogeochemical cycling on a global scale. Their influence depends on whether the infection is lysogenic or lytic. Temperate phages have the potential to execute both infection types and thus frequently switch their infection modes in nature, potentially causing substantial impacts on the host-phage community and relevant biogeochemical cycling. Understanding the regulating factors and outcomes of temperate phage life cycle transition is thus fundamental for evaluating their ecological impacts. This review thus systematically summarizes the effects of various factors affecting temperate phage life cycle decisions in both culturable phage-host systems and natural environments. The review further elucidates the ecological implications of the life cycle transition of temperate phages with an emphasis on phage/host fitness, host-phage dynamics, microbe diversity and evolution, and biogeochemical cycles.

Mangrove is among the most carbon-rich biomes on earth, and the role of viruses in modulating local and global carbon cycling has been extensively implicated. However, few viruses have been isolated from mangrove sediments to date. We reported the isolation of a novel Bacillus phage (named as phage vB_BviS-A10Y) from mangrove sediments. Phage vB_BviS-A10Y had a hexameric head with a diameter of ~79.22 nm and a tail length of ~548.56 nm, which were typical features of Siphoviridae. vB_BviS-A10Y initiated host lysis at 3.5 h post infection with a burst size of 25 PFU/cell. The genome of phage vB_BviS-A10Y was 162,435 bp long with 225 predicted genes, and the GC content was 34.03%. A comparison of the whole genomes of phage vB_BviS-A10Y with known phage genomes in the IMG/VR database showed that phage vB_BviS-A10Y had the highest similarity (73.7%) with Bacillus phage PBC2. Interestingly, abundant auxiliary metabolic genes (AMGs) were identified in vB_BviS-A10Y genome. The presence of β-1,3-glucosyltransferase gene in phage genome supported our previous hypothesis that mangrove viruses may directly manipulate carbon cycling through their encoded carbohydrate-active enzyme (CAZyme) genes. Therefore, our study will contribute to the better understanding of the diversity and potential roles of viruses in mangrove ecosystems. Keywords：Bacillus phage, mangrove, glucosyltransferase, carbon cyclingMangrove forest is a unique community of evergreen shrubs and small trees distributed in intertidal zones and estuarine mudflats in tropical, subtropical, and some temperate bays. Although mangroves cover only 0.1% of the earth's surface, they are among the most carbon-rich biomes on earth due to the complex root structure, high deposition rate, waterlogged, and anoxic sediment [1,2]. Moreover, carbon in mangroves is mostly stored in the soil, dead plants, and animals as complex carbohydrates. Complex carbohydrates or polysaccharides, such as cellulose, pectin, xylan, starch, alginate, mannan, and chitin, are major components of plant cell walls, crustacean shells, and intercellular spaces and are extremely difficult to degrade [3]. Thus, mangroves are an important carbon sink and play an important role in the carbon cycle of the global ecosystem. The contribution