Pathway evolution by horizontal transfer and positive selection is accommodated by relaxed negative selection upon upstream pathway genes in purple bacterial carotenoid biosynthesis.

ABSTRACT: Horizontal gene transfer and selection are major forces driving microbial evolution. However, interactions between them are rarely studied. Phylogenetic analyses of purple bacterial carotenoid biosynthesis genes suggest two lineages: one producing spheroidenone and the other producing spirilloxanthin. Of the latter lineage, Rubrivivax gelatinosus S1 and Hoeflea phototrophica DFL-43 also or instead produce spheroidenone. Evolution of the spheroidenone pathway from that producing spirilloxanthin theoretically requires changes in the substrate specificity of upstream pathway enzymes and acquisition of a terminal ketolase (CrtA). In R. gelatinosus and likely also in H. phototrophica, CrtA was acquired from the Bacteroidetes, in which it functions as a hydroxylase. Estimation of nonsynonymous a

SUBMITTER: Klassen JL 

PROVIDER: S-EPMC2786601 | biostudies-literature | 2009 Dec

REPOSITORIES: biostudies-literature