Large double-stranded DNA viruses which cause the lysis of a marine heterotrophic nanoflagellate (Bodo sp.) occur in natural marine viral communities

A virus (BV-PLV1) w h ~c h causes lysis of 2 stralns of a marlne heterotiophic nanoflagellate belonging to the genus Bodo (strains E l and E4) was isolated from the coastal waters of Texas USA Transmission electron microscopy of ultrath~n sectlons of ~nfected nanoflagellates revealed the presence of int!acellular virus-hke particles 48 h f o l l o \ ~~n g ~n f e c t ~o n , concomitant with a d e c l ~n e In flagellate numbers The vilus contalns double-stranded DNA, 1s hexagonal In cross section, ca 230 to 300 nm in diameter and contains an electron dense core It is morphologically slmilar to virus-l~ke particles w h ~c h have been obselved In other heterotrophic nanoflagellates, and to viruses which have been ISOlated which ~n f e c t eukaryot~c phytoplankton Addition of the vlrus to cultures of Pseudobodo parvulus (ATCC 50091, formerly Bodo parvulus) or Paraphysomonas imperforata (straln VS1) did not ~e s u l t in lysis To our knowledge t h ~s is the first virus infecting heterotrophic nanoflagellates which has been isolated and inaintained in culture The presence of viruses in seawater which cause lysis of phagotrophlc nanotlayellates implies that viruses Infect microzooplankton populat~ons In the sea and suggests another ~~n p o r t a n t role for viruses in aquatic n~icrobial communities KEY WORDS.Protozoa Flagellates .Viruses .