Based on the functional characteristics of the Cyanobacteria and Proteobacteria phyla, which phylum do you think is more deeply rooted in the tree of life (i. e., which phylum branches off closer to the last universal common ancestor).

Proteobacteria

Explanation:

The cyanobacteria are the bacteria which once evolved the mechanism used carbon dioxide and water to produce oxygen but the proteobacteria evolved during the time when Earth had no oxygen as a result of which the metabolism was evolved which were independent of oxygen thus are sulfur oxidising bacteria, iron-oxidizing bacteria and other anoxygenic metabolisms.

This shows that the proteobacteria were more evolved and are highly adaptive to the condition on Earth and shows greater diversity therefore this phylum is deeply rooted in the tree of life.

Thus, proteobacteria phylum is correct.

answer; the correct answer is (beta)