Characterization of Natronobacterium magadii phage ΦCh1, a unique archaeal phage containing DNA and RNA

Abstract

SummaryA novel archaeal bacteriophage, ⌽Ch1, was isolated from a haloalkalophilic archaeon Natronobacterium magadii upon spontaneous lysis. The phage-cured strain N. magadii (L13) was used to demonstrate infectivity of phage ⌽Ch1. The turbid-plaque morphology and the fact that N. magadii cells isolated from plaques were able to produce phage indicated that ⌽Ch1 is a temperate phage. The phage morphology resembles other members of Myoviridae-infecting Halobacterium species. In solution below 2 M NaCl, the phage lost its morphological stability and infectivity. One-and two-dimensional SDS-PAGE of phage particles revealed at least four major and five minor proteins with molecular masses ranging from 15 to 80 kDa and acidic isoelectric points. Southern blot analysis of chromosomal DNA of a lysogenic N. magadii strain showed that ⌽Ch1 exists as a chromosomally integrated prophage. The phage particles contain both double-stranded, linear DNA (approx. 55 kbp) as well as several RNA species (80-700 nucleotides). Hybridization of labelled RNA fragments to total DNA from N. magadii and ⌽Ch1 showed that the virion-associated RNA is host encoded. Part of the phage DNA population is modified and restriction analysis revealed evidence for adenine methylation. Phage ⌽Ch1 is the first virus described for the genus Natronobacterium, and the first phage containing DNA and RNA in mature phage particles.

Insights into Head-Tailed Viruses Infecting Extremely Halophilic Archaea

“…1) were typical of virulent head-tailed viruses, and cycles of 6 to 17 h were previously reported for several haloarchaeal head-tailed viruses (9,11,(75)(76)(77)(78). The adsorption efficiency of head-tailed viruses infecting halophilic prokaryotes seems to vary considerably (7,78,79), and it has been observed that viruses with high adsorption rates usually infect a host originating from the same geographical site as the virus (7).…”

Sulfolobus tengchongensis Spindle-Shaped Virus STSV1: Virus-Host Interactions and Genomic Features

“…A fraction of the genomes of ⌽Ch1, a head/tail phage from the haloalkaliphilic archaeon Natrialba magadii, is methylated by virally encoded methylase in a Dam-like fashion (6,29,59). Phage ⌽N of Halobacterium salinarum was also shown to contain a fully cytosine-methylated genome (57).…”

“…DNA modification has been shown to occur in both crenarchaeotal and euryarchaeotal viruses (4,59). A fraction of the genomes of ⌽Ch1, a head/tail phage from the haloalkaliphilic archaeon Natrialba magadii, is methylated by virally encoded methylase in a Dam-like fashion (6,29,59).…”

Structure and assembly mechanism of virus-associated pyramids

“…The major capsid protein can sometimes self-assemble into (a part of) the virion (Vestergaard et al 2008). While many archaeal hosts have evolved a highly robust machinery to thrive under harsh conditions, such as extreme temperature, pH and salinity, their virions have co-evolved to adopt equally stable properties (Witte et al 1997;Porter et al 2005;Prangishvili 2006;Pina et al 2011). These remarkable characteristics make archaeal viruses attractive subjects for structural biology research.…”