AME 73:69-80 (2014)  -  DOI: https://doi.org/10.3354/ame01705

ABSTRACT: Diatom viruses likely play an important role in the life cycle of diatoms in marine environments because they kill axenic cultures of their diatom host. Yet, in their natural habitats, diatoms are clearly able to survive viral infections by an unknown mechanism. This study demonstrated that the marine planktonic diatom Chaetoceros tenuissimus Meunier survives complete lysis after infection by an RNA virus (CtenRNAV) in the presence of a bacterial community, but cannot do so in axenic culture. We isolated and maintained the colony-forming survivors as a virus-resistant C. tenuissimus culture, which included both CtenRNAV and the bacterial community. The resistant culture was susceptible to virus infection during the exponential growth phase, but infection was inhibited in the stationary phase. Nautella sp., Sulfitobacter sp., and Polaribacter sp. were isolated from the resistant culture, and all of them contributed to virus resistance. Morphological observations showed that the bacteria seemed to be in close contact with the diatom cells. Taken together, our results indicated that resistance of diatom cells to virus infections may be mediated by coexisting bacteria.

KEY WORDS: Bacteria · Chaetoceros tenuissimus · Diatoms · Virus · Virus resistance