Direct binding of benzoate derivatives to two chemoreceptors with Cache sensor domains in Halomonas titanicae KHS3

Abstract

Chemotaxis represents a survival strategy that allows microorganisms to perceive changes in the surrounding environment and actively move toward favorable conditions. An amazingly conserved signaling system (Wuichet & Zhulin, 2010) comprises chemoreceptors or MCPs (for Methyl-accepting Chemotaxis Proteins) that control an associated histidine kinase in response to environmental signals. This kinase in turn phosphorylates a response regulator that alters either the swimming behavior through interaction with the flagellar motors (reviewed in Parkinson et al., 2015), or other ways of bacterial movement (Kaimer & Zusman, 2016) to cause net movement toward attractants or away from repellents.Enteric bacteria, the microorganisms where the chemotaxis system has been extensively studied, possess a single set of chemotaxis genes. In general, microorganisms inhabiting stable niches have simple chemotaxis systems with few chemoreceptors, while environmental bacteria that need to cope with varying conditions have more complex chemotaxis systems and a higher number of chemoreceptors (Lacal et al., 2010). Canonical chemoreceptors that sense chemical signals from the medium possess a periplasmic ligand-binding domain (LBD) flanked by two transmembrane segments. The cytoplasmic portion of the receptor comprises, in many cases, a HAMP domain (signal-transducing module that is present in Histidine kinases, Adenylyl cyclases, MCPs,

Chemosensory pathways of Halomonas titanicae KHS3 control chemotaxis behaviour and biofilm formation

“…Thus, the whole length of the membrane-assembled receptor is longer for Htc10 than for all the other chemoreceptors. Presumably, these latter feed information into the chemotaxis pathway, as we have already demonstrated in two specific cases [4]. An alignment of the highly conserved cytoplasmic tip of all the predicted chemoreceptors of H.…”

“…In the same way, the expression of Ht CheR1 gave rise to the high-mobility Tsr band (, fifth lane), whereas Ht CheR2 failed to increase Tsr mobility (, sixth lane). The same happened when a canonical Ht chemoreceptor was expressed: Htc1 [4] changed its electrophoretic mobility upon co-expression with Ec CheR or Ht CheR1, but not with Ht CheR2 (Fig. S1).…”

“… Halomonas titanicae KHS3 is a marine bacterium that was isolated from Mar del Plata harbour, Argentina. It is able to grow on aromatic hydrocarbons, is motile due to peritrichous flagella and shows chemotactic responses to phenanthrene and several other compounds [2–4]. The analysis of its genomic sequence revealed the presence of two chemotaxis-related signal transduction pathways whose characteristics suggest that they might be involved in canonical chemotaxis (chemosensory cluster 1) or in biofilm formation (chemosensory cluster 2) () [3].…”

Multiple detection of both attractants and repellents by the dCache‐chemoreceptor SO_1056 of Shewanella oneidensis

“…Our results reinforce the idea that dCache domains are able to bind a large diversity of ligands. Although many of them have been proved to bind amino acids, some dCache‐containing chemoreceptors have been shown to bind other kinds of molecules, such as lactate, fumarate, malate, polyamines, histamine and benzoate derivatives [29,35,48–50]. Surprisingly, SO_1056 dCache shares similarities with the PctA chemoreceptor described to bind amino acids, while S. oneidensis does not show any chemotactic behaviour towards amino acids [20].…”

“…Strikingly, detection of malate by direct binding to chemoreceptor LBDs has been shown to involve diverse types of domains. Among the chemoreceptors described, PA2652 (P. aeruginosa) and Htc2 (Halomonas titanicae) detect malate via their sCache-containing LBDs with K D of 23 and 30.4 lM, respectively [28,29]. For McpT (Sinorhizobium meliloti) and MCP2201 (Comamonas testosteroni), binding of malate occurs via their 4HB-containing LBDs (K D of 813 and 18.3 lM, respectively) [30,31].…”