Lytic to temperate switching of viral communities

To understand the activity of marine viruses, experiments on viral production, viral decay and the percentage of lytic and lysogenic bacterial cells among the total number of bacterial cells were carried out seasonally at two stations in the Adriatic Sea with different trophic conditions. Additionally, we are providing an insight on the enrichment with dissolved and particulate organic matter by viral lysis in the studied area. Viral production was higher at the coastal station than at the open-sea station. Viral decay rates were also higher at the coastal sea station than at the open-sea station, and accounted for approximately 40% of viral production at both investigated stations. The percentage of lysogenic infection was lower than that of lytical infection, which indicates the prevalence of the lytic cycle at both stations. Viruses had a significant influence on bacterial mortality through high daily removal of the bacterial standing stock at the coastal and open-sea station. The viruses contributed to the restoration of dissolved organic carbon, nitrogen and phosphorus in the microbial loop by lysing the bacterial cells at the studied stations. All the above suggest that viruses are important in the microbial food web and an important factor in the control of bacterial populations within the study area.

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“…However, new findings suggest that lysogeny could also be favoured in environments with increased host density [18,19].…”

Section: Open Accessmentioning

confidence: 99%

Viral dynamics in two trophically different areas in the Central Adriatic Sea

et al. 2017

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“…The ecological incidence of chronic infections, by which viruses disseminate by budding or diffusion through host membranes, has been much less documented in marine ecosystems (Thomas et al, 2011(Thomas et al, , 2012. Despite the global impact of viral infection in the ocean, the regulation of infection dynamics and the relative share among the different infection strategies remain far from understood (Knowles et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Temperature is a key factor in Micromonas–virus interactions

et al. 2017

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The genus Micromonas comprises phytoplankton that show among the widest latitudinal distributions on Earth, and members of this genus are recurrently infected by prasinoviruses in contrasted thermal ecosystems. In this study, we assessed how temperature influences the interplay between the main genetic clades of this prominent microalga and their viruses. The growth of three Micromonas strains (Mic-A, Mic-B, Mic-C) and the stability of their respective lytic viruses (MicV-A, MicV-B, MicV-C) were measured over a thermal range of 4-32.5°C. Similar growth temperature optima (T opt ) were predicted for all three hosts but Mic-B exhibited a broader thermal tolerance than Mic-A and Mic-C, suggesting distinct thermoacclimation strategies. Similarly, the MicV-C virus displayed a remarkable thermal stability compared with MicV-A and MicV-B. Despite these divergences, infection dynamics showed that temperatures below T opt lengthened lytic cycle kinetics and reduced viral yield and, notably, that infection at temperatures above T opt did not usually result in cell lysis. Two mechanisms operated depending on the temperature and the biological system. Hosts either prevented the production of viral progeny or maintained their ability to produce virions with no apparent cell lysis, pointing to a possible switch in the viral life strategy. Hence, temperature changes critically affect the outcome of Micromonas infection and have implications for ocean biogeochemistry and evolution.

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“…CRISPR-cas is repressed by glucose and activated by cAMP receptor protein-cAMP in Pectobacterium atrosepticum (17). In addition to these mechanisms, theory and data suggest phage proliferation-and therefore risk of infectionincreases with increasing bacterial cell density (18,19). Bacteria monitor cell density using a cell-cell communication mechanism known as quorum sensing (QS).…”

mentioning

confidence: 99%

Quorum sensing controls the Pseudomonas aeruginosa CRISPR-Cas adaptive immune system

Høyland‐Kroghsbo

Paczkowski

Mukherjee

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

238

223

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CRISPR-Cas are prokaryotic adaptive immune systems that provide protection against bacteriophage (phage) and other parasites. Little is known about how CRISPR-Cas systems are regulated, preventing prediction of phage dynamics in nature and manipulation of phage resistance in clinical settings. Here, we show that the bacterium Pseudomonas aeruginosa PA14 uses the cell-cell communication process, called quorum sensing, to activate cas gene expression, to increase CRISPR-Cas targeting of foreign DNA, and to promote CRISPR adaptation, all at high cell density. This regulatory mechanism ensures maximum CRISPR-Cas function when bacterial populations are at highest risk for phage infection. We demonstrate that CRISPR-Cas activity and acquisition of resistance can be modulated by administration of proand antiquorum-sensing compounds. We propose that quorum-sensing inhibitors could be used to suppress the CRISPR-Cas adaptive immune system to enhance medical applications, including phage therapies.quorum sensing | CRISPR | immunity | phage | phage defense

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Lytic to temperate switching of viral communities

Cited by 454 publications

References 77 publications

Viral dynamics in two trophically different areas in the Central Adriatic Sea

Viral dynamics in two trophically different areas in the Central Adriatic Sea

Temperature is a key factor in Micromonas–virus interactions

Quorum sensing controls the Pseudomonas aeruginosa CRISPR-Cas adaptive immune system

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