Bacterial chemotaxis towards aromatic hydrocarbons in Pseudomonas

Abstract

Bacterial chemotaxis is an adaptive behaviour, which requires sophisticated information-processing capabilities that cause motile bacteria to either move towards or flee from chemicals. Pseudomonas putida DOT-T1E exhibits the capability to move towards different aromatic hydrocarbons present at a wide range of concentrations. The chemotactic response is mediated by the McpT chemoreceptor encoded by the pGRT1 megaplasmid. Two alleles of mcpT are borne on this plasmid and inactivation of either one led to loss of this chemotactic phenotype. Cloning of mcpT into a plasmid complemented not only the mcpT mutants but also its transfer to other Pseudomonas conferred chemotactic response to high concentrations of toluene and other chemicals. Therefore, the phenomenon of chemotaxis towards toxic compounds at high concentrations is gene-dose dependent. In vitro experiments show that McpT is methylated by CheR and McpT net methylation was diminished in the presence of hydrocarbons, what influences chemotactic movement towards these chemicals.

High Specificity in CheR Methyltransferase Function

“…37). We have shown previously that the transfer of the mcpT gene to other species confers chemotaxis toward aromatic compounds, suggesting the establishment of functional signaling complexes between McpT and host proteins (38). The demonstration of efficient methylation of McpT by a foreign CheR methyltransferase is consistent with this suggestion and offers the possibility of "chemotactic engineering" of related strains by the transfer of chemoreceptor genes.…”

“…McpS is encoded by the genome of P. putida KT2440, whereas McpT is a plasmid encoded receptor present in the strain P. putida DOT-T1E (60). The McpT receptor is of biotechnological relevance because it is responsible for the hyperchemotaxis phenotype toward aromatic toxic hydrocarbons such as toluene (38). It has been shown that there is a link between the degradation of aromatic hydrocarbons and FIGURE 12.…”

“…A series of reports shows that chemotaxis toward pollutants increases biodegradation efficiency (for review, see Ref. 37), and a pollutant chemoreceptor, McpT has recently been identified in our laboratory (38). Despite the biotechnological importance of P. putida strains, no information as to the existence of individual chemosensory routes is available.…”

“…putida mediate chemotaxis toward Krebs cycle intermediates (39 -41) and aromatic hydrocarbons (38), respectively. To determine which of the three CheR methylates these chemoreceptors, the coding sequence of both chemoreceptor genes were cloned into an expression vector.…”

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).…”