Energy-taxis by Pseudomonas species allows swimming towards optimal environments for generating cellular energy, precluding the need to sense carbon sources and oxygen. Aerotaxis, which has been taken to mean swimming towards oxygen or a source of metabolizable carbon has been attributed to the methyl-accepting chemotaxis protein Aer. In P. aeruginosa McpB (Aer-2) also contributes and may directly sense oxygen whereas in P. putida the second of three Aer energy-taxis sensor homologs, 'Aer2' is the key receptor. Here we sought to disentangle the ambiguity between aerotaxis and energy-taxis and between McpB (Aer-2) and Aer2. Phylogenetic characterization of sequences from a wide range of Pseudomonas species revealed that Aer homologs have been duplicated and horizontally transferred within the genus but can be divided into 5 groups. Phenotypic characterization in P. pseudoalcaligenes KF707, which has 3 Aer homologs and McpB showed that all homologs as well as McpA (CttP) and McpB (Aer-2) contribute to energy-taxis, though the most ancestral Aer homolog is key but not essential to this behaviour. As McpB (Aer-2) is rare in the genus, these results indicate that energy-taxis and aerotaxis are linked but distinct behaviours and that energy-taxis in Pseudomonas involves more genes than previously thought.