OCCURRENCE OF VIRUS-LIKE PARTICLES IN THE DEAD-SEA

Electron-microscopic examination of water samples from the hypersaline Dead Sea showed the presence of high numbers of virus-like particles. Between 0.9 and 7.3 x 10(7) virus-like particles ml(-1) were enumerat ed in October 1994 in the upper 20 m of the water column during the de cline of a bloom of halophilic Archaea. Virus-like particles outnumber ed bacteria by a factor of 0.9-9.5 (average 4.4), A variety of viral m orphologies were detected, the most often encountered being spindle-sh aped, followed by polyhedral and tailed phages. In addition, other typ es of particles were frequently found, such as unidentified algal scal es, and virus-sized star-shaped particles, Water samples collected dur ing 1995 contained low numbers of both bacteria and virus-like particl es (1.9-2.6 x 10(6) and 0.8-4.6 X 10(7) ml(-1) in April 1995), with vi ral numbers sharply declining afterwards (less than 10(4) ml(-1) in No vember 1995-January 1996), It is suggested that viruses may play a maj or role in the decline of halophilic archaeal communities in the Dead Sea, an environment in which protozoa and other predators are absent.