SUMMARYThe photosynthetic marine flagellate Micromonas pusilla (Butch.) Manton et Parke (Prasinophyceae) and its cytoplasmic virus, M. pusilla virus (MPV), were cloned. Host cells were maintained in liquid culture. Infectivity titration was by endpoint dilution, using loss of host chlorophyll as an indicator of the presence of infective virus. The virus growth cycle was characterized by an eclipse period of 3 h, a latent period of 7 h and a total lytic cycle of 14 h. The average burst size was 72 infective particles per cell. Inhibition of CO2 photoassimilation began 2 h after inoculation with virus. An almost immediate decrease in in vivo chlorophyll a fluorescence in infected cells was lightdependent. M. pusilla cells can mutate to virus resistance at the cell surface. Host range mutants of MPV exhibited variable infectivity in different strains of M. pusilla.
A new artificial seawater medium has been tested with 83 strains of coastal and open ocean phytoplankton from 11 different algal classes. The cultures were carried through four transfers, representing a period of eight weeks for most species. Only three species could not be maintained in the enriched artificial seawater, and 16 species, mainly from the Prymnesiophyceae and Dinophyceae, had reduced final cell yields compared to those grown in enriched natural seawater. Since 77% of the species tested grew equally well in enriched artificial or natural seawater and more than 95% could be maintained in the artificial medium, this recipe is useful over a broad spectrum of species. The artificial seawater base was enriched with a modified ES enrichment solution; the primary modifications were the omission of Tris and the addition of Si. Enriched medium was autoclaved without precipitation by lowering the pH before autoclaving. This was accomplished by adding equimolar amounts of Na‐HCO3 and HCl which produced NaCl and CO2 during the heating process. When no pH buffer was used, precipitation could only be avoided by autoclaving the artificial seawater base as two separate salt solutions (with Ca and Sr separated from CO3−2 and SO4−2), cooling, mixing and aseptically adding the sterilized enrichment solution.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.