Abstract
Marine viruses are major drivers of global biogeochemical cycles and energy fluxes, yet the importance of viral impacts on the succession and diversity of the bacterial community remains largely unexplored. Here, we explored viral life strategy and its potential effect on the bacterial community by experimental incubations of eutrophic coastal waters under lysogen-induced and non-induced treatments. The lysogen-induced treatment showed relatively constant viral and bacterial abundances, lytic and lysogenic viral production throughout the experimental period, together with the progressive declines in not only the relative abundances for SAR11, Rhodobacteraceae, Alteromonadaceae, and SAR86 but the bacterial community diversity. Conversely, the non-induced treatment observed the marked variation in the abundances of viruses, bacteria and cells with high nucleic acid content over the time course of incubation, which was congruent with the drastic shift in lytic and lysogenic viral production as well as the succession of bacterial community. Our results supported the hypotheses that a high level of lysogeny would occur with the increasing density of bacteria with rapid growth rate, which may contribute to a relatively lower host community diversity, whereas the lysogeny to lysis switching would fuel growth opportunities for less-active or initially rare bacterial taxa and generate a more diverse bacterial community. Altogether, the present study underscored the crucial regulatory role of the viral lysis-lysogeny pattern in bacterial community dynamics, composition and diversity, highlighting the viral impact on the microbial food web and biogeochemical processes.
Highlights
Microbes are the keystone in marine ecosystem functions and play a central role in the microbial food web and elemental cycling in the ocean (Falkowski et al, 2008)
In the non-induced treatment, the bacterial abundance after 24 h of incubation showed a sudden bloom that was mostly contributed by the high nucleic acid (HNA) cells with a high proportion of HNA cells reaching 70.75% (Figure 1)
SAR11 clade confirmed that the HNA cells were more active members and suggested that this subgroup was the winner in competing for resources (Figures 1, 3; Eilers et al, 2000; Suttle, 2007; Xu et al, 2013; Kirchman, 2016)
Summary
Microbes are the keystone in marine ecosystem functions and play a central role in the microbial food web and elemental cycling in the ocean (Falkowski et al, 2008). A higher level of lysogenic viral production (lysogenic VP) usually appears with a lower bacterial abundance or activity in marine ecosystems, and lysogeny has been previously hypothesized to be a preferable survival strategy for both the virus and the host in harsh environments (Paul, 2008; Payet and Suttle, 2013; Brum et al, 2016; Chen et al, 2019). A newly proposed “Piggyback-the-Winner” model suggested that lysogeny would be increasingly favored with a higher microbial density or activity (Knowles et al, 2016; Coutinho et al, 2017) This new insight into marine lysogeny contrasted with the traditional understanding of viral dynamics and their interactions with host microbes (Weinbauer, 2004; Paul, 2008; Winter et al, 2010), and revealed the intricate nature of marine lytic and lysogenic virus-host interactions. More research works is needed to unveil the roles of the viral lysis-lysogeny pattern in regulating the bacterial community
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