Genetic identification of chemotactic transducers for amino acids in Pseudomonas aeruginosa

Abstract

Two chemotactic transducer genes (termed pctB and pctc) and an open reading frame (orfl) were found in the -flanking region which was previously identified as a chemotactic transducer gene in Ps0udomonas eeruginosa. The pctB and pcK: genes encode predicted polypeptides of 629 and 632 amino acids, respectively. Overall, PctB and Pctc had 81 and 75% amino acid identities with PctA, respectively. A null mutant strain PCT2, which contained a deletion in the entire pctC, orfl, pctA and pctB genes, did not show chemotaxis towards all 20 commonly occurring Loamino acids. This mutant strain also failed to respond to amino acid catabolites (cadaverine, baminobutyrate and putrescine) that are strong attractants for the wild-type strain PAOl. To study the role of each gene product in L-amino acid taxis, plasmids harbouring the pctC, orfl, pctA, or pets genes were constructed and introduced into strain PO2 by transformation. The orfl gene did not complement the defect in chemotaxis of strain -2.The pctA gene restored the ability of strain PCT2 to respond to 18 L-amino acids, suggesting that PctA plays a major role in detecting L-amino acids in P. a0ruglnosa. The pctB and pctC genes complemented the defect in chemotaxis to only seven (Ala, Arg, Glu, Lys, Met, Tyr, Gln) and two (His, Pro) Lamino acids, respectively.

Elastin degradation product isodesmosine is a chemoattractant for Pseudomonas aeruginosa

“…A comparison to L-lysine (Fig. 1), confirmed that the response of PAO1 was as expected (Taguchi et al, 1997), albeit at a higher level of chemoattraction than elicited by isodesmosine. Structurally, isodesmosine has the same chiral stereochemistry as L-lysine; however, this amino acid contains three allysyl side chains plus one unaltered lysyl side chain.…”

“…All photographs were taken after 5 min. There are three amino acid receptors in P. aeruginosa strain PAO1: PctA, PctB and PctC (Kuroda et al, 1995;Taguchi et al, 1997). Isodesmosine contains lysine residues and chemotaxis towards lysine is directly linked to PctA and PctB, and therefore we hypothesized that the chemotactic response of P. aeruginosa PAO1 is mediated by some of these receptors.…”

“…Quantitative chemotaxis studies with some of these strains confirmed these results (Table S2). Kuroda et al (1995) and Taguchi et al (1997) identified the chemoreceptors PctA, PtcB and PctC associated with PAO1 chemoattraction towards 20 natural amino acids. Recently, Rico-Jiménez et al (2013) demonstrated that the recombinant ligand-binding region of PctC binds the non-proteinogenic amino acid GABA.…”

“…Ten MCPs have been shown to mediate a flagella-based positive chemotaxis response to malate (PA2652), oxygen (Aer and Aer-2), ethylene (TlpQ), chloroethylenes (McpA), amino acids and gamma aminobutyrate (GABA) (PctABC) and inorganic phosphate (CtpH and CtpL) (Alvarez-Ortega & Harwood, 2007;Hong et al, 2004;Kim et al, 2006Kim et al, , 2007Rico-Jiménez et al, 2013;Shitashiro et al, 2005;Taguchi et al, 1997;Wu et al, 2000). The MCPs responsible for detecting the 20 natural L-amino acids in PAO1 are the paralogous PctA, PctB and PctC receptors (Kuroda et al, 1995;Taguchi et al, 1997). PctA recognizes and mediates the response to most of the natural L-amino acids, while PctB is primarily involved in mediating taxis to glutamine and PctC to histidine and proline.…”

Cytosine chemoreceptor McpC in Pseudomonas putida F1 also detects nicotinic acid

“…Responses to (methyl)phenols and phenylacetic acid are mediated through energy taxis via Aer2 (Luu et al, 2013;Sarand et al, 2008), whilst responses to naphthalene, 2-nitrobenzoate, toluene, 4-chloroaniline, catechol and aromatic amino acids are sensed by chemotaxis via specific MCPs (Grimm & Harwood, 1999;Iwaki et al, 2007;Lacal et al, 2011;Oku et al, 2012;Parales et al, 2000;Taguchi et al, 1997;Vangnai et al, 2013).…”