title: Elucidating the origin of the ExbBD components of the TonB system through Bayesian inference and maximum-likelihood phylogenies.
abstract: Uptake of ferric siderophores, vitamin B12, and other molecules in gram-negative bacteria is mediated by a multi-protein complex known as the TonB system. The ExbB and ExbD protein components of the TonB system play key energizing roles and are homologous with the flagellar motor proteins MotA and MotB. Here, the phylogenetic relationships of ExbBD and MotAB were investigated using Bayesian inference and the maximum-likelihood method. Phylogenetic trees of these proteins suggest that they are separated into distinct monophyletic groups and have originated from a common ancestral system. Several horizontal gene transfer events for ExbB-ExbD are also inferred, and a model for the evolution of the TonB system is proposed.
authors.affiliation: 1326 Mountain Vista Dr SE, Rio Rancho, New Mexico 87124, United States. Electronic address: marmon.livingstone@gmail.com.
authors.forename: Livingstone
authors.initials: L
authors.lastname: Marmon
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D001499:Bayes Theorem; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D016013:Likelihood Functions; D008565:Membrane Proteins / Q000235:genetics*; D010802:Phylogeny
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; C063010:MotA protein, Bacteria; C064779:MotB protein, Bacteria; C057616:tonB protein, Bacteria
keywords: Flagellar motor; Homology; Molecular evolution; Molecular phylogenetics; TonB system