Isolation and Genetic Analysis of Haloalkaliphilic Bacteriophages in a North American Soda Lake

Abstract

Mono Lake is a meromictic, hypersaline, soda lake that harbors a diverse and abundant microbial community. A previous report documented the high viral abundance in Mono Lake, and pulsed-field gel electrophoresis analysis of viral DNA from lake water samples showed a diverse population based on a broad range of viral genome sizes. To better understand the ecology of bacteriophages and their hosts in this unique environment, water samples were collected between February 2001 and July 2004 for isolation of bacteriophages by using four indigenous bacterial hosts. Plaque assay results showed a differential seasonal expression of cultured bacteriophages. To reveal the diversity of uncultured bacteriophages, viral DNA from lake water samples was used to construct clone libraries. Sequence analysis of viral clones revealed homology to viral as well as bacterial proteins. Furthermore, dot blot DNA hybridization analyses showed that the uncultured viruses are more prevalent during most seasons, whereas the viral isolates (Aphi and phi2) were less prevalent, confirming the belief that uncultured viruses represent the dominant members of the community, whereas cultured isolates represent the minority species.

Trade-Offs between Competition and Defense Specialists among Unicellular Planktonic Organisms: the “Killing the Winner” Hypothesis Revisited

“…In accordance with KtW, a number of studies in marine and freshwater environments found that virus and host communities of either specific populations or entire assemblages are linked (26,37,33,51,69,96,98,107,108,112), and there is evidence suggesting similarly coupled prokaryotic and viral communities in a soda lake (80). The details vary, however.…”

Culture-Independent Approaches for Studying Viruses from Hypersaline Environments

“…To the best of our knowledge, the first report of a metagenomic approach to describe the viral assemblage in hypersaline environments is that of Sabet et al (51) in their study of Mono Lake (a "moderately hypersaline" system). Viral DNA was prepared for PFGE, and the 35-to 55-kb band was cloned into bacterial artificial chromosomes.…”

“…This work constitutes the first example of how to reconstruct an (almost) complete genome from an uncultured halovirus. The reason for reconstructing only one genome was the low efficiency of the fosmid library, a problem previously encountered (51). The analysis of this genome (named environmental halophage-1 [EHP-1], although if this virus is infecting an archaeon this name may not be appropriate according to reference 45) revealed a GC content of 51%, lower than those of previously isolated halophages.…”

Virioplankton Community Structure in Tunisian Solar Salterns

“…Haloviral genomic diversity, in terms of genome size distribution, has also been analyzed by pulsed-field gel electrophoresis (PFGE) (25,31,47,48,50,51). In some cases, while several morphotypes can be observed by TEM in a given sample, only a single DNA band is observed in PFGE gels, indicating that viral "species" present in the sample harbor a very similar genome size (28,50,51).…”

“…In some cases, while several morphotypes can be observed by TEM in a given sample, only a single DNA band is observed in PFGE gels, indicating that viral "species" present in the sample harbor a very similar genome size (28,50,51). Sequence data from hypersaline systems (viral metagenomes from the Mono and Reba lakes and Bras del Port and San Diego solar salterns) have also shown that the uncultured halovirus community is highly diverse and not related to the culturable fraction (28,45,47,51,53). We used culture-independent approaches to analyze the viral assemblage of selected ponds from Sfax multipond solar salterns in southeast Tunisia.…”