Vesicle-like virion of Haloarcula hispanica pleomorphic virus 3 preserves high infectivity in saturated salt

Abstract

Hypersaline environments that are subject to salinity changes are particularly rich in viruses. Here we report a newly isolated archaeal halovirus, Haloarcula hispanica pleomorphic virus 3 (HHPV3). Its reproduction significantly retards host growth and decreases cell viability without causing lysis. HHPV3 particles require a minimum of 3M NaCl for stability and maintain high infectivity even in saturated salt. Notably, virions are irreversibly inactivated at ~1.5M NaCl in neutral pH, but tolerate this salinity at alkaline pH. The HHPV3 virion is a pleomorphic membrane vesicle containing two major protein species and lipids acquired nonselectively from the host membrane. The circular double-stranded DNA genome contains a conserved gene block characteristic of pleolipoviruses. We propose that HHPV3 is a member of the Betapleolipovirus genus (family Pleolipoviridae). Our findings add insights into the diversity observed among the pleolipoviruses found in hypersaline environments.

Keywords: Archaeal virus; Genome sequence; Halovirus; Hypersalinity; Pleolipoviridae; Pleomorphic virus; Virus life cycle.