Cottrell, M.T. and C.A Suttle. 1994. Comparison of viruses that lyse the marine photosynthetic flagellate Micromonas pusilla using quantitative DNA-DNA hybridization. Abstracts American Society Limnology and Oceanography, and Phycological Society American, Miami, FL, June 1994.

Total genomic DNA from each of eight clonal isolates of Micromonas-virus were labeled with 35S-dATP by nick translation. Each probe was hybridized against DNA from each of the eight Micromonas-viruses, Chlorella-virus (PBCV-1), lambda phage and M. pusilla, as well as, an area of filter containing no DNA. After hybridization and washing the radioactivity bound to each target was quantified by liquid scintillation counting. Our objective was to compare the similarity among viruses isolated from a single water sample to the similarity among viruses isolated from geographically distant locations. The highest and lowest similarities we observed were 94.6 + 27.5 % (mean + s, n = 6) for virus strains SP1 and SP2 isolated from a California coastal water sample and 18.6 + 2.4% for strains SP2 and PB8; the latter isolated from New York estuarine water. However, the similarity between viruses isolated from a single water sample was not always greater than the similarity between viruses isolated from different locations. Viruses PB7 and PB8 were isolated from a single New York estuarine sample but were only 26.6 + 9.5% similar; whereas, PB7 was quite similar (46.6 + 5.5%) to PL1, a virus from Texas coastal water. The similarity between the Micromonas-viruses and the Chlorella-virus was not significantly different from zero (P > 0.9, Student's t). Based on our findings we conclude that the genetic variation among Micromonas-viruses isolated from a single water sample can be as large as the variation between viruses isolated from different oceans.