The second exception is the lytic virus His1, which possesses a linear double-stranded DNA of 14.9 kb and infects the extreme halophile Haloarcula hispanica ( 4). voltae strain A3 containing a circular double-stranded DNA of 23 kb, of which an integrated copy was found in the host chromosome ( 30). The first one was described as a virus-like particle (VLP) isolated from M. There are two known exceptions, both showing a lemon-shaped morphology resembling SSV1, the type member of the Fuselloviridae. In contrast, all but two of the as-yet-described viruses of extreme halophiles and methanogens have the classical head-and-tail morphology typical of many bacterial phages and have therefore been assigned to the virus families Myoviridae or Siphoviridae ( 1). Its complete nucleotide sequence has been determined ( 19). SSV1 is temperate and forms stable lysogens by site specifically inserting its 15.5-kb circular genome into the host chromosome ( 31). The best studied virus is the lemon-shaped SSV1, whose original host is the hyperthermophile Sulfolobus shibatae. The droplet-shaped Guttaviridae ( 3) have not yet been established as an acknowledged virus family. Our knowledge about archaeal viruses is still rather limited, and among known archaeal viruses that have been reported, only few have been studied in detail at the molecular level.Īll known crenarchaeotal viruses display unusual morphotypes and compose three novel families which were created to account for their unique features, namely, the filamentous Lipothrixviridae ( 2, 13, 32), the lemon-shaped Fuselloviridae ( 18, 25), and the rod-shaped Rudiviridae ( 20). The Archaea domain comprises two major phyla, namely, the Crenarchaeota, including the extremely thermophilic sulfur-metabolizing Archaea of the orders Sulfolobales and Thermoproteales, and the Euryarchaeota, containing mainly the methanogens, the extreme halophiles, and the hyperthermophilic order Thermococcales ( 29). These results suggest that PAV1 persists in the host strain in a stable carrier state rather than a prophage. Screening of a large number of Thermococcales isolates did not permit to find a sensitive host. UV, gamma irradiation, treatment with mitomycin C, and various physiological stresses had no effect on PAV1 production. Under standard growth conditions, the host cells continuously release PAV1 particles into the culture supernatant without spontaneous lysis, with a maximum reached in the late stationary phase. No integrated form of the PAV1 genome could be detected in the host chromosome. It contains a double-stranded circular DNA of 18 kb which is also present in high copy number in a free form in the host cytoplasm. Sensitivity of the virus-like particle to organic solvents and detergents suggested that the envelope of PAV1 may contain lipids in addition to proteins. This particle, named PAV1, is lemon-shaped (120 nm × 80 nm), with a short tail terminated by fibers, and resembles the virus SSV1, the type member of the Fuselloviridae, isolated from Sulfolobus shibatae. These standards can be detected by fluorescence when excited at appropriate wavelengths.We describe the first virus-like particle of a hyperthermophilic euryarchaeote which was discovered in a strain of “ Pyrococcus abyssi” previously characterized in our laboratory. Precision Plus Protein Kaleidoscope Standards are a mixture of ten multicolored recombinant proteins (10–250 kD). Place this handy selection guide magnet on your refrigerator or lab bench to eliminate the guesswork and make protein standard selection simple.
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