Effects of acidic conditions on the physiology of a green alga (Micractiniumsp.) before and after a 5-year interaction withTetrahymena thermophilain an experimental microcosm
The mechanisms through which algae evolve physiological characteristics related to endosymbiotic associations with heterotrophic organisms remain unclear. We previously showed that a green alga (Micractinium sp.) was able to evolve a host (ciliate)-benefiting phenotype that prolonged the longevity of Tetrahymena thermophila in the absence of bacteria during a 5-year culture period in an experimental microcosm. Comparative experiments between the ancestral alga (i.e. original) and evolved algal clones of the same lineage can be performed to analyse the mechanisms that underlie algal evolution during interactions with ciliates. Here, we investigated the effects of acidic conditions on algal physiology because the acidic conditions within the food vacuoles of Tetrahymena could potentially affect algal evolution during long-term interactions. It might be expected that algal clones isolated from T. thermophila hosts would have developed the ability to resist acidic conditions in order to establish within the h...