Abstract
Viruses are the most abundant microorganisms in marine environments and viral infections can be either lytic (virulent) or lysogenic (temperate phage) within the host cell. The aim of this study was to quantify viral dynamics (abundance and infection) in the coastal Red Sea, a narrow oligotrophic basin with high surface water temperatures (22–32 °C degrees), high salinity (37.5–41) and continuous high insolation, thus making it a stable and relatively unexplored environment. We quantified viral and environmental changes in the Red Sea (two years) and the occurrence of lysogenic bacteria (induced by mitomycin C) on the second year. Water temperatures ranged from 24.0 to 32.5 °C, and total viral and bacterial abundances ranged from 1.5 to 8.7 × 106 viruses mL−1 and 1.9 to 3.2 × 105 bacteria mL−1, respectively. On average, 12.24% ± 4.8 (SE) of the prophage bacteria could be induced by mitomycin C, with the highest percentage of 55.8% observed in January 2018 when bacterial abundances were low; whereas no induction was measurable in spring when bacterial abundances were highest. Thus, despite the fact that the Red Sea might be perceived as stable, warm and saline, relatively modest changes in seasonal conditions were associated with large swings in the prevalence of lysogeny.
Highlights
Published: 11 June 2021Viruses are the most abundant microorganisms in oceans [1], varying in number between 105 particles per mL in oligotrophic and deep-sea ecosystems [2,3,4] to 108 particles per mL in productive systems, and comprising an estimated ~1030 double-stranded DNA virus particles in the entire ocean
This study provides seasonal data on viral abundance and inducible lysogens in the surface waters of the Red Sea, an understudied oligotrophic tropical environment characterized by high temperature and salinity
Most notably, ~56% of the HB contained inducible lysogens in January when HB abundance decreased and were at low abundances compared to their highest abundances in spring, where lysogenic heterotrophic bacterial proportion were undetectable, consistent with a switch from lysogeny to lytic viral production when host abundance is highest
Summary
Viruses are the most abundant microorganisms in oceans [1], varying in number between 105 particles per mL in oligotrophic and deep-sea ecosystems [2,3,4] to 108 particles per mL in productive systems, and comprising an estimated ~1030 double-stranded DNA virus particles in the entire ocean Most of these viruses infect bacteria and are estimated to cause 10 to 50% of the total bacterial mortality in surface waters; thereby killing about. The phage DNA integrates into the genome of its host as a prophage and propagates each time the host genome is replicated until an environmental signal triggers the phage to enter the lytic pathway [1,8] Some phages, such as the temperate myovirus P1, which infects strains of gramnegative hosts (i.e., Escherichia coli) may exist as plasmids and do not integrate into the host chromosome. Phage particles are produced resulting in the destruction of the host cell and the release of virions [8,11,12]
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