Viral Abundance and a High Proportion of Lysogens Suggest That Viruses Are Important Members of the Microbial Community in the Gulf of Trieste

Biotechnical Faculty, Department of Food Technology, University of Ljubljana, Vecna pot 111, SI-1000 Ljubljana, Slovenia.
Microbial Ecology (Impact Factor: 2.97). 02/2004; 47(1):1-8. DOI: 10.1007/BF03036884
Source: PubMed


Epifluorescence microscopy and transmission electron microscopy were applied to study virioplankton community in the Gulf of Trieste (northern Adriatic Sea). The total viral abundance was in a range between 2.5 x 10(9)/L and 2.9 x 10(10)/L and was positively correlated with trophic status of the environment. Viruslike particles were significantly correlated with bacterial abundance in all samples studied. Correlations with other physicochemical or biological parameters were not significant. The data suggest that, because of the substantial fraction of tailed viruses present (26%), bacteriophages are an important component of the virioplankton community in the Gulf of Trieste. The abundance of viruslike particles in the seawater changed at hour intervals in a range from 1.3 x 10(9)/L to 5.1 x 10(9)/L. A significant fraction (71%) of the bacterial isolates was inducible in vitro by mitomycin C, and a high occurrence (51%) of lysogenic isolates with more than one phage morphotype present in the lysate was detected. The presence of lysogenic bacteria in the seawater was confirmed in situ with a mitomycin C induction experiment on the natural bacterial population. Results suggest that virioplankton is an abundant component of the microbial community in the Gulf of Trieste.

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    • "Prophages are common in cultured bacteria and cyanobacteria, with approximately half of the strains experimentally investigated containing inducible prophages (Padan et al., 1972; Ackermann and DuBow, 1987; Sode et al., 1994; Jiang and Paul, 1996; Ohki and Fujita, 1996; Sode et al., 1997; Jiang et al., 1998). Lysogeny is also prevalent but variable in marine environments , with estimates of the inducible proportion of the natural bacterial assemblages ranging from 0% to 100% (Jiang and Paul, 1996; Cochran et al., 1998; McDaniel et al., 2002; Stopar et al., 2004). Lysogeny has been posited as a mechanism to enhance survival of both the temperate phage (as a prophage) and the host bacterium under adverse conditions (Paul, 2008; Wang et al., 2010). "
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    • "being quantitative in environmental viral morphological studies. Transmission electron 99 microscopy (TEM) sample preparation generally includes one of two approaches: either viruses 100 are concentrated and then adsorbed to TEM grids (e.g., Sommaruga et al., 1995; Stopar et al., 101 2003), or they are directly deposited onto TEM grids using traditional (e.g., Bergh et al., 1989) or 102 air-driven ultracentrifugation (Maranger et al., 1994; Brum and Steward, 2010). Here, we use an 103 air-driven ultracentrifuge with a rotor designed to quantitatively deposit viruses onto TEM grids 104 (Hammond et al., 1981), resulting in high recovery of viruses (Maranger et al., 1994). "
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