Virus-Like Particles in an Ultra-Oligotrophic Lake on Vancouver Island, British Columbia

Abstract

Transmission electron microscopy (TEM) seasonal studies of concentrated water samples from Sproat Lake, Vancouver Island, British Columbia, revealed numerous polygonal virus-like particles of variable size (60–200 nm). These particles (ca. 107/mL) were either free-living or associated with host picoplankters. Negative staining of living samples provides clear evidence of early stages of phage–picoplankton interactions. These phages display a six-sided head (ca. 90 nm dia.) with a distinct appendage (ca. 200 nm) or striated tail (ca. 130 nm). Viruses with dense matrices, deprived of envelopes or occurring as empty shells were found in the marginal area of invaded cells. Morphological changes such as invagination of the photosynthetic lamellae with the appearance of 'virogenic stroma' or with disruption of the cell membrane and the cell wall are described. Comments on the possible functional significance of viral agents in the biology and ecology of host cells are presented.