Can P. bursaria live in association with any and all strains/species of Chlorella? In an experiment to help answer
this question, Chlorella was collected, and cultured separately, from three different sources: (1) P. bursaria
cytoplasm, (2) free-living Chlorella, and (3) from cytoplasm of other protist species. A population of P. bursaria
was treated with the herbicide, paraquat, which killed all of its zoochlorellae, but otherwise left P. bursaria
unharmed. The zoochlorella-free paramecia were then introduced to a 1:1:1 mixture of Chlorella from the three
cultures listed above, and subsequently reestablished a contingent of zooclorellae. Two weeks later,
zoochlorellae were collected from the P. bursaria cells and tested to determine which Chlorella strain(s) had been
maintained within P. bursaria.
The different strains of Chlorella are morphologically indistinguishable. Consequently, which of these would be
the best test to perform on Chlorella, both before and after re-establishment of zoochlorellae, to determine
which Chlorella strains had been maintained within P. bursaria?
A) Determine the chemical composition of its cell wall.
B) Determine the absorption spectrum of its photosynthetic pigments.
C) Determine the sequence of a portion of its mitochondrial DNA.
D) Determine the sequence of an exon of a ribosomal RNA gene.
E) Determine the endosymbiontʹs diameter.