CHARACTERIZATION OF A LYTIC VIRUS INFECTIOUS TO THE BLOOM-FORMING MICROALGA AUREOCOCCUS ANOPHAGEFFERENS (PELAGOPHYCEAE)

Aureococcus anophagefferens Hargraves and Sieburth has caused recurrin g monospecific blooms in Long Island embayments since it was first des cribed in 1985. It was termed the ''brown tide,'' due to the resulting water color, and has had a devastating effect on Long Island's (New Y ork) marine ecosystem. In 1992, a virus that was capable of causing ly sis of A. anophagefferens was isolated and maintained in culture. We r eport on the further characterization of this virus, Aureococcus anoph agefferens virus-1 (AaV-1), indicated by a buoyant density of 1.2776 g .mL(-1) in a CsCl equilibrium gradient. Electron microscopy revealed a phage with a hexagonal head and tail similar to previously described phages. By using adenovirus for calibration, the virus was found to ha ve a head 50-55 nm wide and a tail 70-75 nm long. The viral band was i nfectious to A. anophagefferens after dialysis. The virus was composed of at bast 16 distinct polypeptides ranging in molecular weight from 20 to 230 kDa. The adsorption coefficient for the virus was 7.2 x 10(- 9) mL.min(-1), and the burst size was calculated to be 9.4 viruses per A. anophagefferens cell at 20 degrees C. Complete lysis of A. anophag efferens occurred with a titer as low as 893 viruses.mL(-1), and the l ower limit of infectivity was 93 viruses.mL(-1). The virus lost its in fectivity between 30 degrees and 40 degrees C. These results suggest t hat AaV-1 is highly infectious and that the role of the virus in preve nting or ending A. anophagefferens blooms needs further investigation.