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    Lysogeny and Phage Dynamics in the Red Sea Ecosystem

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    Name:
    Ruba Ashy Dissertation.pdf
    Size:
    3.148Mb
    Format:
    PDF
    Description:
    PhD Dissertation
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    Type
    Dissertation
    Authors
    Ashy, Ruba A. cc
    Advisors
    Agusti, Susana cc
    Committee members
    Duarte, Carlos M. cc
    Daffonchio, Daniele cc
    Moran, Xose Anxelu G. cc
    Vidal, Dolors Vaque
    Program
    Environmental Science and Engineering
    KAUST Department
    Biological and Environmental Sciences and Engineering (BESE) Division
    Date
    2019-11
    Embargo End Date
    2020-12-02
    Permanent link to this record
    http://hdl.handle.net/10754/660363
    
    Metadata
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    Access Restrictions
    At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation will become available to the public after the expiration of the embargo on 2020-12-02.
    Abstract
    Phages are the most abundant components of the marine environments and can control host abundances. The severity of viral infections may depend on whether phages are lytic, lysogenic, or chronic, which can be influenced by host activity and by environmental conditions. Lysogeny remains the least understood process. Knowledge of virioplankton dynamics and their life strategies in the Red Sea remain unexplored. In this Ph.D. research we aimed to quantify virioplankton abundance, the variability on viral and bacterial dynamics, and to investigate the occurrence of lytic and lysogenic phages in the Red Sea. Accordingly, we used the flow cytometric technique to enumerate viral and bacterial abundances in the coastal pelagic area during two years of sampling and in the coastal lagoon waters for one year, together with water column distribution in open Red Sea waters. We conducted incubations of natural microbial communities in the laboratory to induce lysogenic bacteria by using the chemical mutagenic mitomycin C. We also explored the influence of host abundance, temperature, and ultraviolet radiation on viral dynamics and lysogeny. Our results showed that abundances of virses in the Red Sea ranged from 106 to 107 virus-like particles per mL, and bacteria ranged from 104 to 105 cells per mL. We observed a large variability i the values of virus-to-bacterium ratios, and lower values of viral production to those for temperate coastal waters and relatively close to values reported in other oligotrophic areas. Although the lytic phase was prevalent, lysogeny was detected when bacterial abundances decreased. We determined inducible lysogenic bacteria from undetectable to ~56% in the coastal Red Sea, although we found a lower maximum of 29.1% at a eutrophic coastal lagoon. The decay rates of viruses were influenced by UVB exposure, suggesting their susceptibility to solar radiation. Exposure to UVB radiation-induced prophage varied between 4 and 34%. Our findings identified the significant role of viral infections in controlling bacterial abundance and the importance of both lytic and lysogenic phases in the Red Sea waters. This study contributes to the understanding of lysogeny in marine phages.
    DOI
    10.25781/KAUST-087UX
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-087UX
    Scopus Count
    Collections
    Biological and Environmental Sciences and Engineering (BESE) Division; Environmental Science and Engineering Program; Dissertations

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