Isolated from a hypersaline lake in Australia, the spherical
haloarchaeal virus SH1 also has a nonenveloped
icosahedral virion with an inner lipid layer. It carries several lipid moieties, which have been
selectively acquired from the host during virion assembly,
and 11 structural proteins. The subnanometre resolution structure revealed a
complex capsid formed from a single b-barrel capsid
protein, with claw-like spikes at the vertices of the virion. Transcriptional studies have
shown that the SH1 genes are organized into a relatively
small number of operons transcribed in three temporal
stages; antisense RNA may be involved in transcription
regulation.