Notes on: Behavior of a virus in a symbiotic system, Paramecium bursaria-Zoochlorella. 1978

Endosymbiotic Chlorella do not appear to be infected because:

“In contrast to the ingested cells, the zoochlorellae growing symbiotically within the cytoplasm of the ciliate were free of detectable particles”

Apparently Chlorella “free and in the wild” wasn’t obviously infected either:

“Signs of infection with ZCV were not observed in any of the free-living strains of Chlorella and the zoochlorella in axenic culture under the present experiment conditions”

But then there were some infected isolated endosymbionts (which appears to contradict their last statement):

“In the control experiment, in which no ZCV particles were added to the isolated symbiotic zoochlorellae, only a few infected cells were found.  This level of infection seemed to be ascribable to ZCV particles which could not be removed after 3 rinses in the course of  the isolation of the symbiotic zoochlorella”

What is the source of the virus they are purifying?

Their source of virus is an axenic culture of Paramecium derived from a single cell (from a pond) that was allowed to grow into stationary phase (1 month old) –> low speed spin (1,600xg, 10 minutes) –> filter supernatant through 0.4um filter —> concentrate filtrate by high speed spin (23,000-45,000xg, 30-60 minutes)… store at 5C…. note no details on re-suspension of the pellet.

They note that the started these cultures with a “single cell of P. bursaria, free of all extracellular zoocholrella”.  I see three possibilities:

(1) virus comes from food vacuoles of that Paramecium

(2) virus reactivates from one of the symbiotic zoochlorella in that Paramecium

(3) virus was a contaminant that came along with that single cell perhaps attached to the portozoan

They called this an axenic culture, so, if the endosymbiotic Chlorella are not competent hosts for the virus, where is this virus amplifying if they didn’t transfer any extracellular Chlorella?  Does Paramecium release endosymbionts to live free and in the wild??  Can endosymbiotic Chlorella survive lysis of its host cell?

The bottom line appears to be that they only get high levels of virus when Chlorella is cultured with Paramecium.  I know Van Etten’s group worked this out in the 80s-90s but I am not sure anyone has gone back “to the wild” with this virus.


Kawakami & Kawakami 1978 J. Protozoology 25(2)


About SubOptimist

I am an Associate Professor in the Science Department at Georgia Perimeter College, Clarkston. I teach introductory biology courses at both the majors and non-majors level in addition to microbiology. Previous to that I spent 7 years as a postdoctoral researcher on different viruses. While I don't miss being on the "grant treadmill", I think better when I write and miss writing up data for papers and grants; this blog helps me with that a little. And sometimes my kids' insanely funny and cute antics need to be shared with the world. Any view expressed in this blog is that of me personally and not Georgia Perimeter College or the GPC Clarkston Science Department.
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