Virus-like particles in bacteria symbiotic in bivalve gills

Abstract

Thyasira gouldi,an arctic bivalve mollusc of the family Thyasiridae, has symbiotic, probably chemoautotrophic, bacteria living in its gills. In specimens collected from Loch Etive in Scotland in 1989, after the local population had undergone an unexplained decline, the gill bacteria contained numerous virus-like particles 60 nm in diameter. The bacteria are not lysed by the virus, and the particles are not present outside the bacteria except in phagocytic vacuoles of the gill cells where the bacteria have been digested, leaving the virus particles unchanged. Similar particles have been discovered in bacterial symbionts ofThyasira flexuosa,but in much smaller numbers.