Chemotaxis to plant defense compounds in phytopathogens Roberta Genova, Ashleigh Holmes, Mario Cano-Muñoz, Atsushi Ishihara, Naoki Ube, Taiji Nomura, Jose A. Gavira, Miguel A. Matilla, Tino Krell Plos Pathogens, 2026 Plant pathogens possess about twice as many chemoreceptors as the bacterial average, suggesting broad chemotactic capacities. The signals recognized by most phytopathogen chemoreceptors are unknown, and the reasons for this elevated chemoreceptor number is unclear. We identified the signals recognized by three chemoreceptors, PacH, PacI and PacG, in the global phytopathogen Pectobacterium atrosepticum . The ligand-binding domains (LBDs) of these chemoreceptors share modest sequence similarity, but the signals they recognize are structurally similar, and their biosynthetic pathways are interwoven. Whereas PacH and PacI recognized benzoate derivatives, including salicylate, vanillin and p -hydroxybenzoate, PacG bound agmatine, feruloylagmatine and p -coumaroylagmatine. These compounds are known plant defense compounds, their production is induced by pathogen attack, and they typically accumulate at infection sites. All compounds, except agmatine, induced chemoattraction, which was abolished by mutations in the corresponding genes. Agmatine competed with feruloylagmatine and p -coumaroylagmatine for PacG-LBD binding in vitro and antagonized chemotaxis in vivo . A mutant in pacG , but not in other chemoreceptor genes, showed reduced virulence in planta . We report high-resolution structures of PacG-LBD that were used for ligand-docking experiments to identify its binding pocket. PacH, PacI and PacG homologs were identified in other important phytopathogens belonging to the Burkholderia, Erwinia, Ralstonia, Pectobacterium and Dickeya genera. This is the first report of chemotaxis to feruloylagmatine, p -coumaroylagmatine and p -methoxybenzoate, expanding the range of chemoeffectors. Bacteria thus exploit plant defense responses by moving to compounds that are secreted at infection sites in response to pathogen attack. Chemotaxis to plant defense compounds may be a means to access infected plants and infection sites.
Chemoreceptor family in plant-associated bacteria responds preferentially to the plant signal molecule glycerol 3-phosphate Félix Velando, Jiawei Xing, Roberta Genova, Jean Paul Cerna-Vargas, Raquel Vázquez-Santiago, Miguel A. Matilla, Igor B. Zhulin, Tino Krell Genome Biology, 2025 Background Chemotaxis to plant compounds is frequently the initial step for the colonization of plants by bacteria. Plant pathogens and plant-associated bacteria contain approximately twice as many chemoreceptors as the bacterial average does, indicating that chemotaxis is particularly important for bacteria–plant interactions. However, information on the corresponding chemoreceptors and their chemoeffectors is limited. Results We identify the chemoreceptor PacP from the phytopathogen Pectobacterium atrosepticum, which exclusively recognizes phosphorylated C3 compounds at its sCache ligand binding domain, mediating chemoattraction. Using a motif of PacP amino acid residues involved in ligand binding, we identify a chemoreceptor family, termed sCache_PC3, that is specific for phosphorylated C3 compounds. Isothermal titration calorimetry studies reveal that family members preferentially bind glycerol 3-phosphate, a key plant signaling molecule. Family members recognize glycerol 2-phosphate and glycolysis intermediates glyceraldehyde 3-phosphate, dihydroxyacetone phosphate, and 3-phosphoglycerate. This study presents the first evidence of chemoreceptors that bind phosphorylated compounds. We show that the sCache_PC3 family has evolved from an ancestral sCache domain that responds primarily to Krebs cycle intermediates. Members of the sCache_PC3 family are predominantly found in plant-associated bacteria, including many important phytopathogens belonging to the genera Brenneria, Dickeya, Musicola, Pectobacterium, and Herbaspirillum. Consistently, glycerol 3-phosphate is a signal molecule that is excreted by plants in response to stress and infection. Conclusions Chemotaxis toward glycerol 3-phosphate may be a means for bacteria to localize stressed plants and move to infection sites. This study lays the groundwork for investigating the role of chemotaxis to phosphorylated C3 compounds in plant–bacteria interactions and virulence.
Phospho-mimetic CheV interacts with a subset of chemoreceptors Miguel A. Matilla, Mario Cano-Muñoz, Elizabet Monteagudo-Cascales, Tino Krell Mbio, 2025 Chemotaxis pathways are among the most complex signaling systems in bacteria. A central feature of these pathways is the ternary complex formed by chemoreceptors, the autokinase CheA, and the coupling proteins CheW and CheV. Whereas CheW is present in all chemotaxis pathways, CheV is primarily found in bacteria that contain many chemoreceptors. CheV is a fusion of a CheW-like domain to a phosphorylatable receiver domain. The roles of CheV and its phosphorylation are currently uncertain. Pseudomonas aeruginosa contains many chemoreceptors for which the cognate signals have been identified. Quantitative capillary chemotaxis assays of a cheV mutant revealed that responses to certain chemoeffectors, such as nitrate and α-ketoglutarate, were drastically reduced, while responses to others, such as amino acids and inorganic phosphate, were comparable to the wild type, indicating that CheV selectively acts on specific chemoreceptors. To study the mechanism of CheV action, we conducted protein-protein interaction experiments using isothermal titration calorimetry. These studies showed that unphosphorylated CheV fails to bind to cytosolic fragments of the McpN and PctA chemoreceptors, which mediate responses to nitrate and amino acids, respectively. In contrast, the phosphorylation-mimic CheV D238E bound with very high affinity ( K D = 8 nM) to McpN but failed to interact with PctA. Thus, CheV in P. aeruginosa binds to some chemoreceptors but not to others in a phosphorylation-dependent manner. These results suggest that CheV is a regulatory protein that modulates signaling through specific chemoreceptors. CheV may thus facilitate the coordination of chemotaxis responses in complex, multi-chemoreceptor systems. IMPORTANCE CheV is one of the least understood chemosensory signaling proteins. Our demonstration that CheV interacts only with certain chemoreceptors offers fundamental new insights. These findings, combined with the observation that CheV is present in bacteria with numerous chemoreceptors, suggest that CheV plays a role in coordinating chemotactic outputs in complex chemosensory systems. Understanding the mechanisms by which chemotactic responses are defined in bacteria with a high number of chemoreceptors is a major research priority in the field of chemotaxis. While previous studies, including this one, show that the ability to be phosphorylated is crucial for CheV function, the molecular consequences of CheV phosphorylation have remained unclear. Our discovery that phosphorylation is essential for CheV binding to certain chemoreceptors fills in this critical gap in understanding the molecular mechanism of CheV. This study is likely to inspire further research into CheV function in other bacteria using similar approaches.
Pseudomonas aeruginosa Performs Chemotaxis to All Major Human Neurotransmitters Elizabet Monteagudo‐Cascales, Miguel A. Matilla, Zulema Udaondo, José A. Gavira, Tino Krell Microbial Biotechnology, 2025 The ubiquitous pathogen Pseudomonas aeruginosa is attracted to γ‐aminobutyrate (GABA), acetylcholine, histamine, serotonin, epinephrine, norepinephrine, dopamine, tyramine, glycine, and glutamate via chemotaxis. These compounds are all major neurotransmitters in humans. They are also found in various non‐neuronal tissues and are synthesised by different organisms, including bacteria, protozoa, invertebrates, and plants. Many of these neurotransmitters increase the expression of virulence‐related genes in P. aeruginosa, so that chemotaxis to these compounds may constitute an important virulence factor. The chemotactic response is initiated by the direct binding of these compounds to the dCache ligand‐binding domains of the PctC, TlpQ, PctD, PctA, and PctB chemoreceptors. Previous studies have shown that Escherichia coli is attracted to epinephrine, norepinephrine, and dopamine. These responses are mediated by the Tar and Tsr chemoreceptors, which possess four‐helix bundle‐type ligand‐binding domains. The use of structurally dissimilar chemoreceptors to mediate neurotransmitter chemotaxis suggests convergent evolution. This article is intended to stimulate the study of the connection between neurotransmitter chemotaxis and virulence in P. aeruginosa and to expand the search for neurotransmitter chemotaxis in other motile bacteria.
Pseudomonas aeruginosa Performs Chemotaxis to the Neurotransmitters Serotonin, Dopamine, Epinephrine and Norepinephrine Elizabet Monteagudo‐Cascales, Andrea Lozano‐Montoya, Tino Krell Microbial Biotechnology, 2025 Bacteria use chemotaxis to move to favourable ecological niches. For many pathogenic bacteria, chemotaxis is required for full virulence, particularly for the initiation of host colonisation. There do not appear to be limits to the type of compounds that attract bacteria, and we are just beginning to understand how chemotaxis adapts them to their lifestyles. Quantitative capillary assays for chemotaxis show that P. aeruginosa is strongly attracted to serotonin, dopamine, epinephrine and norepinephrine. Chemotaxis to these compounds is greatly decreased in a mutant lacking the TlpQ chemoreceptor, and complementation of this mutant with a plasmid harbouring the tlpQ gene restores wild‐type‐like chemotaxis. Microcalorimetric titrations of the TlpQ sensor domain with these four compounds indicate that they bind directly to TlpQ. All four compounds are hormones and neurotransmitters that control a variety of processes and are also important signal molecules involved in the virulence of P. aeruginosa. They modulate motility, biofilm formation, the production of virulence factors and serve as siderophores that chelate iron. Additionally, this is the first report of bacterial chemotaxis to serotonin. This study provides an incentive for research to define the contribution of chemotaxis to these host signalling molecules to the virulence of P. aeruginosa.
Bacterial sensor evolved by decreasing complexity Elizabet Monteagudo-Cascales, José A. Gavira, Jiawei Xing, Félix Velando, Miguel A. Matilla, Igor B. Zhulin, Tino Krell Proceedings of the National Academy of Sciences of the United States of America, 2025 Bacterial receptors feed into multiple signal transduction pathways that regulate a variety of cellular processes including gene expression, second messenger levels, and motility. Receptors are typically activated by signal binding to ligand-binding domains (LBDs). Cache domains are omnipresent LBDs found in bacteria, archaea, and eukaryotes, including humans. They form the predominant family of extracytosolic bacterial LBDs and were identified in all major receptor types. Cache domains are composed of either a single (sCache) or a double (dCache) structural module. The functional relevance of bimodular LBDs remains poorly understood. Here, we identify the PacF chemoreceptor in the phytopathogen Pectobacterium atrosepticum that recognizes formate at the membrane-distal module of its dCache domain, triggering chemoattraction. We further demonstrate that a family of formate-specific sCache domains has evolved from a dCache domain, exemplified by PacF, by losing the membrane-proximal module. By solving high-resolution structures of two family members in complex with formate, we show that the molecular basis for formate binding at sCache and dCache domains is highly similar, despite their low sequence identity. The apparent loss of the membrane-proximal module may be related to the observation that dCache domains bind ligands typically at the membrane-distal module, whereas studies have failed to find ligands bound in the membrane-proximal module. This work advances our understanding of signal sensing in bacterial receptors and suggests that evolution by reducing complexity may be a route for shaping diversity.
Thermal shift assay to identify ligands for bacterial sensor proteins Elizabet Monteagudo-Cascales, Mario Cano-Muñoz, Roberta Genova, Juan J Cabrera, Miguel A Matilla, Tino Krell FEMS Microbiology Reviews, 2025 Bacteria sense and respond to changing environmental conditions using a diverse range of receptors. Currently, the signals recognized by most receptors remain unknown, thereby limiting our understanding of their function. Since its introduction a decade ago, ligand screening by the thermal-shift assay has identified the signal molecules recognized by numerous receptors, solute-binding proteins, and transcriptional regulators. This progress is summarized in this review. Signal identification is facilitated by the fact that ligand-binding domains can be generated as individual soluble proteins that retain the signal-binding capabilities of the full-length proteins. Various issues relevant to the reliability of the thermal shift assay are discussed, including false-positive and false-negative results, the value of a protein pH screen prior to ligand screening, and the need to verify results with methods for the direct study of ligand binding, such as isothermal titration calorimetry. This review was inspired by the XVIII conference on Bacterial Locomotion and Signal Transduction (Cancun, January 2025), where several notable advances were reported based on the application of the thermal shift assay.
Ubiquitous purine sensor modulates diverse signal transduction pathways in bacteria Elizabet Monteagudo-Cascales, Vadim M. Gumerov, Matilde Fernández, Miguel A. Matilla, José A. Gavira, Igor B. Zhulin, Tino Krell Nature Communications, 2024 Purines and their derivatives control intracellular energy homeostasis and nucleotide synthesis, and act as signaling molecules. Here, we combine structural and sequence information to define a purine-binding motif that is present in sensor domains of thousands of bacterial receptors that modulate motility, gene expression, metabolism, and second-messenger turnover. Microcalorimetric titrations of selected sensor domains validate their ability to specifically bind purine derivatives, and evolutionary analyses indicate that purine sensors share a common ancestor with amino-acid receptors. Furthermore, we provide experimental evidence of physiological relevance of purine sensing in a second-messenger signaling system that modulates c-di-GMP levels.
Bacterial amino acid chemotaxis: a widespread strategy with multiple physiological and ecological roles Miguel A. Matilla, Tino Krell Journal of Bacteriology, 2024 Chemotaxis is the directed, flagellum-based movement of bacteria in chemoeffector gradients. Bacteria respond chemotactically to a wide range of chemoeffectors, including amino, organic, and fatty acids, sugars, polyamines, quaternary amines, purines, pyrimidines, aromatic hydrocarbons, oxygen, inorganic ions, or polysaccharides. Most frequent are chemotactic responses to amino acids (AAs), which were observed in numerous bacteria regardless of their phylogeny and lifestyle. Mostly chemoattraction responses are observed, although a number of bacteria are repelled from certain AAs. Chemoattraction is associated with the important metabolic value of AAs as growth substrates or building blocks of proteins. However, additional studies revealed that AAs are also sensed as environmental cues. Many chemoreceptors are specific for AAs, and signaling is typically initiated by direct ligand binding to their four-helix bundle or dCache ligand-binding domains. Frequently, bacteria possess multiple AA-responsive chemoreceptors that at times possess complementary AA ligand spectra. The identification of sequence motifs in the binding sites at dCache_1 domains has permitted to define an AA-specific family of dCache_1AA chemoreceptors. In addition, AAs are among the ligands recognized by broad ligand range chemoreceptors, and evidence was obtained for chemoreceptor activation by the binding of AA-loaded solute-binding proteins. The biological significance of AA chemotaxis is very ample including in biofilm formation, root and seed colonization by beneficial bacteria, plant entry of phytopathogens, colonization of the intestine, or different virulence-related features in human/animal pathogens. This review provides insights that may be helpful for the study of AA chemotaxis in other uncharacterized bacteria.
The pH Robustness of Bacterial Sensing Elizabet Monteagudo-Cascales, David Martín-Mora, Wenhao Xu, Victor Sourjik, Miguel A. Matilla, Álvaro Ortega, Tino Krell Mbio, 2022
Amino acid sensor conserved from bacteria to humans Vadim M. Gumerov, Ekaterina P. Andrianova, Miguel A. Matilla, Karen M. Page, Elizabet Monteagudo-Cascales, Annette C. Dolphin, Tino Krell, Igor B. Zhulin Proceedings of the National Academy of Sciences of the United States of America, 2022
Flagella, Chemotaxis and Surface Sensing Miguel A. Matilla, Félix Velando, Elizabet Monteagudo-Cascales, Tino Krell Advances in Experimental Medicine and Biology, 2022
Histamine: A bacterial signal molecule Tino Krell, José A. Gavira, Félix Velando, Matilde Fernández, Amalia Roca, Elizabet Monteagudo-Cascales, Miguel A. Matilla International Journal of Molecular Sciences, 2021
Identification of ligands for bacterial sensor proteins Matilde Fernández, Bertrand Morel, Andrés Corral-Lugo, Miriam Rico-Jiménez, David Martín-Mora, Diana López-Farfán, José Antonio Reyes-Darias, Miguel A. Matilla, Álvaro Ortega, Tino Krell Current Genetics, 2016
Specific gamma-aminobutyrate chemotaxis in pseudomonads with different lifestyle Jose Antonio Reyes‐Darias, Vanina García, Miriam Rico‐Jiménez, Andrés Corral‐Lugo, Olivier Lesouhaitier, Dalia Juárez‐Hernández, Yiling Yang, Shuangyu Bi, Marc Feuilloley, Jesús Muñoz‐Rojas, Victor Sourjik, Tino Krell Molecular Microbiology, 2015
Bioavailability of pollutants and chemotaxis Tino Krell, Jesús Lacal, Jose Antonio Reyes-Darias, Celia Jimenez-Sanchez, Rungroch Sungthong, Jose Julio Ortega-Calvo Current Opinion in Biotechnology, 2013
Responses of Pseudomonas putida to toxic aromatic carbon sources Tino Krell, Jesús Lacal, M. Eugenia Guazzaroni, Andreas Busch, Hortencia Silva-Jiménez, Sandy Fillet, José A. Reyes-Darías, Francisco Muñoz-Martínez, Miriam Rico-Jiménez, Cristina García-Fontana, Estrella Duque, Ana Segura, Juan-Luis Ramos Journal of Biotechnology, 2012
Laboratory research aimed at closing the gaps in microbial bioremediation Juan-Luis Ramos, Silvia Marqués, Pieter van Dillewijn, Manuel Espinosa-Urgel, Ana Segura, Estrella Duque, Tino Krell, María-Isabel Ramos-González, Sergey Bursakov, Amalia Roca, Jennifer Solano, Matilde Fernádez, José Luís Niqui, Paloma Pizarro-Tobias, Regina-Michaela Wittich Trends in Biotechnology, 2011
Bacterial chemotaxis towards aromatic hydrocarbons in Pseudomonas Jesús Lacal, Francisco Muñoz‐Martínez, José‐Antonio Reyes‐Darías, Estrella Duque, Miguel Matilla, Ana Segura, José‐J. Ortega Calvo, Celía Jímenez‐Sánchez, Tino Krell, Juan L. Ramos Environmental Microbiology, 2011
Diversity at its best: Bacterial taxis Tino Krell, Jesús Lacal, Francisco Muñoz‐Martínez, José Antonio Reyes‐Darias, Bilge Hilal Cadirci, Cristina García‐Fontana, Juan Luis Ramos Environmental Microbiology, 2011
The shikimate pathway and its branches in apicomplexan parasites Craig W. Roberts, Fiona Roberts, Russell E. Lyons, Michael J. Kirisits, Ernest J Mui, John Finnerty, Jennifer J. Johnson, David J. P. Ferguson, John R. Coggins, Tino Krell, Graham H. Coombs, Wilbur K. Milhous, Dennis E. Kyle, Saul Tzipori, John Barnwell, John B. Dame, Jane Carlton, Rima McLeod Journal of Infectious Diseases, 2002
Reply: Shikimate pathway in apicomplexan parasites Craig W. Roberts, John Finnerty, Jennifer J. Johnson, Fiona Roberts, Dennis E. Kyle, Tino Krell, John R Coggins, Graham H. Coombs, Wilbur K. Milhous, Saul Tzipori, David J. P. Ferguson, Debopam Chakrabarti, Rima McLeod Nature, 1999
Evidence for the shikimate pathway in apicomplexan parasites Fiona Roberts, Craig W. Roberts, Jennifer J. Johnson, Dennis E. Kyle, Tino Krell, John R. Coggins, Graham H. Coombs, Wilbur K. Milhous, Saul Tzipori, David J. P. Ferguson, Debopam Chakrabarti, Rima McLeod Nature, 1998
Correction: Evidence that the active site in type II dehydroquinase from Streptomyces coelicolor is near the single tryptophan (Biochemical Society Transactions (1997) 25 (93S)) Biochemical Society Transactions, 1997
