Phylogenetic Characterization of the Energy-taxis Receptor Aer inPseudomonasand Phenotypic Characterization inP. pseudoalcaligenesKF707

Abstract

15Chemotaxis allows bacteria to sense gradients in their environment and respond by 16 directing their swimming. Aer is a receptor that, instead of responding to a specific 17 chemoattractant, allows bacteria to sense cellular energy levels and move towards favourable 18 environments. In Pseudomonas, the number of apparent Aer homologs differs between the only 19 two species it had been characterized in, P. aeruginosa and P. putida. Here we combined 20 bioinformatic approaches with deletional mutagenesis in P. pseudoalcaligenes KF707 to further 21 characterize Aer. It was determined that the number of Aer homologs varies between 0-4 22 throughout the Pseudomonas genus, and they were phylogenetically classified into 5 subgroups. 23 We also used sequence analysis to show that these homologous receptors differ in their HAMP 24 signal transduction domains. Genetic analysis also indicated that some Aer homologs have likely 25 been subject to horizontal transfer. P. pseudoalcaligenes KF707 was unique among species for 26 having three Aer homologs as well as the receptors CttP and McpB. Phenotypic characterization 27 in this species showed the most prevalent homolog of Aer was key, but not essential for energy-28 taxis. This study demonstrates that energy-taxis in Pseudomonas varies between species and 29 provides a new naming convention and associated phylogenetic details for Aer chemoreceptors. 30 31 73 the Pseudomonas genus with a genetic knockout characterization of three Aer homologs, McpB 74 and CttP in P. pseudoalcaligenes KF707. A phylogeny of Aer was built using sequences 75 obtained from 65 Pseudomonas species providing insight into the distribution throughout the 76 genus and enabling the definition of five 'Aer' groups. Only P. pseudoalcaligenes KF707 had 77 5 the unique feature of possessing three Aer homologs, McpB and CttP making it the ideal 78 candidate to investigate if these receptors had related functions. Using single and combinatory 79 deletion mutants, we found that the most common Pseudomonas Aer homolog had the most 80 influence on energy-taxis. Together these results provide a definition of the Aer energy-taxis 81 receptor as a family with varied distribution in Pseudomonas and implicate the most common 82 Aer homolog as the primary energy-taxis receptor in P. pseudoalcaligenes KF707. 83 84 Results 85To investigate how the number of Aer-like receptors, differences in their amino acid 86 sequences and how they are related phylogenetically, Aer sequences from 65 Pseudomonas 87 species were analyzed. Species with completely sequenced genomes were selected, but for those 88 with many strains only a few representatives that have been highly studied were included (e.g. P. 89 aeruginosa). Species with incomplete (draft) sequences were also included in an attempt to 90 ensure representation from all major Pseudomonas clades [16, 17]. 144 protein sequences were 91 obtained from the NCBI database using the P. aeruginosa PA01 Aer sequence (NP_250252.1) as 92 a BLAST [21] query sequence. All hits ...

Identifying the suite of genes central to swimming in the biocontrol bacteriaPseudomonas protegensPf-5

“…Loss of function of aer_2 , which encodes an aerotaxis receptor, detrimentally affected Pf-5 swimming when disrupted. This gene is homologous to the aer gene in P. aeruginosa PAO1 that encodes the most prevalent aerotaxis receptor in pseudomonads (60). Consistent with our results, loss of the gene encoding the main aerotaxis receptor in the biocontrol bacteria P. chlororaphis PCL1606 detrimentally affected swimming motility (61).…”