The phylogenetic distribution of the enzyme rubisco is limited to

The phylogenetic distribution of the enzyme RuBisCo is limited to all photoautotrophs, both bacterial and eukaryotic.

Explanation:

This is because the  RuBisCo mechanism takes place in all photoautotrophs and fixes inorganic CO2 into organic biomass or the biosphere through the Calvin Cycle of photosynthesis. The D-Ribulose-1, 5-Biphosphate Carboxylase-Oxygenase or RuBisCo is a catalytic enzyme that plays a crucial part in photosynthesis through carbon fixation by photoautotrophs including bacteria and eukaryotes. The RuBisCo takes part in photosynthesis especially in Calvin Cycle during fixation of carbon from carbon dioxide to D-Ribulose. Since it is a photosynthetic enzyme, it is present in photoautotrophs .

Ichoose a as my answer