Molecular and Chemical Ecology

The Experimental Biology Research Group is devoted to understanding the genes and metabolites that regulate ecological interactions. Our experimental system includes plants, herbivore insects, and herbivore natural enemies such as predators and entomopathogenic nematodes. Our research has lately focused on Photorhabdus bacteria, the symbionts of Heterorhabditis entomopathogenic nematodes. In particular, we have investigated their phylogenetic relationships, implemented methods to identify them rapidly, and improved their biological control potential.

More recently, we have started to unravel the adaptive value of one of its most prominent traits: Bioluminescence. Photorhabdus bacteria produce light when they multiply inside their host insects. Therefore, the organisms that are infected by Photorhabdus bacteria are bioluminescent. What are the benefits that could explain the occurrence and prevalence of this trait? This is one of the questions that we are currently tackling by studying the regulatory potential of Photorhabdus bioluminescence in belowground multi-trophic interactions.

• Plant-associated CO2 mediates long-distance host location and foraging behaviour of a root herbivore
  Arce, Carla C. M.; Theepan, Vanitha; Schimmel, Bernardus C. J.; Jaffuel, Geoffrey; Erb, Matthias; Machado, Ricardo A. R.
  Elife  10.7554/eLife.65575 Published: APR 20 2021
• Photorhabdus heterorhabditis subsp. aluminescens subsp. nov., Photorhabdus heterorhabditis subsp. heterorhabditis subsp. nov., Photorhabdus australis subsp. thailandensis subsp. nov., Photorhabdus australis subsp. australis subsp. nov., and Photorhabdus aegyptia sp. nov. isolated from Heterorhabditis entomopathogenic nematodes
  Machado, Ricardo A. R.; Muller, Arthur; Ghazal, Shimaa M.; Thanwisai, Aunchalee; Pages, Sylvie; et al.
  International Journal Of Systematic And Evolutionary Microbiology  10.1099/ijsem.0.004610 2021
• Herbivore-induced plant volatiles mediate defense regulation in maize leaves but not in maize roots
  van Doan, Cong; Zust, Tobias; Maurer, Corina; Zhang, Xi; Machado, Ricardo A. R.; et al.
  Plant Cell And Environment 10.1111/pce.14052  Early Access: APR 2021
• Morphological, morphometrical, and molecular characterization of Metarhabditis amsactae (Ali, Pervez, Andrabi, Sharma and Verma, 2011) Sudhaus, 2011 (Rhabditida, Rhabditidae) from India and proposal of Metarhabditis longicaudata as a junior synonym of M. amsactae
  Bhat, Aashaq Hussain; Srivastava, Shreyansh; Rana, Aasha; Chaubey, Ashok Kumar; Machado, Ricardo A. R.; et al.
  Journal Of Nematology e2020-116 10.21307/jofnem-2020-116  2020
• The plant metabolome guides fitness-relevant foraging decisions of a specialist herbivore
  Machado, Ricardo A. R.; Theepan, Vanitha; Robert, Christelle A. M.; Zust, Tobias; Hu, Lingfei; Su, Qi; Schimmel, Bernardus C. J.; Erb, Matthias
  PLOS BIOLOGY 19(2) Article Number: e3001114, DOI: 10.1371/journal.pbio.3001114   FEB 2021
• Morphological and molecular characterization of Heterorhabditis bacteriophora isolated from Indian soils and their biocontrol potential
  Rana, Aasha; Bhat, Aashaq Hussain; Chaubey, Ashok Kumar; Shokoohi, Ebrahim; Machado, Ricardo A. R.
  Zootaxa  DOI: 10.11646/zootaxa.4878.1.3  NOV 12 2020
• Volatile-mediated defence regulation occurs in maize leaves but not in maize root
  van Doan, Cong; Zust, Tobias; Maurer, Corina; Zhang, Xi; Machado, Ricardo A. R.; et al.
  Plant Cell And Environment  DOI: 10.1111/pce.13919  OCT 2020
• Molecular and Phenotypic Characterization of Heterorhabditis indica (Nematoda: Rhabditida) Nematodes Isolated During a Survey of Agricultural Soils in Western Uttar Pradesh, India
  Bhat, Aashaq Hussain; Chaubey, Ashok Kumar; Shokoohi, Ebrahim; Machado, Ricardo A. R.
  Acta Parasitologica  DOI: 10.1007/s11686-020-00279-y  SEP 2020
• Identification of Photorhabdus symbionts by MALDI-TOF MS
  Hill, Virginia; Kuhnert, Peter; Erb, Matthias; Machado, Ricardo A. R.
  Microbiology-sgm 166(6): 522-530 DOI: 10.1099/mic.0.000905  JUN 2020
• Entomopathogenic nematodes from Mexico that can overcome the resistance mechanisms of the western corn rootworm
  Bruno, Pamela; Machado, Ricardo A. R.; Glauser, Gaetan; Kohler, Angela; Campos-Herrera, Raquel; et al.
  Scientific Reports 10(1), 10.1038/s41598-020-64945-x May 2020
• Engineering bacterial symbionts of nematodes improves biocontrol potential of the western corn rootworm (Feb, 10.1038/s41587-020-0419-1, 2020)
  Machado, RAR; Thonen, L; Arce, CCM; Theepan, V; Prada, F; Wuthrich, D; Robert, CAM; Vogiatzaki, E; Shi, YM; Schaeren, OP; Notter, M; Bruggmann, R; Hapfelmeier, S; Bode, HB; Erb, M
  NATURE BIOTECHNOLOGY,  DOI: 10.1038/s41587-020-0478-3, MAR 2020
• Engineering bacterial symbionts of nematodes improves biocontrol potential of the western corn rootworm
  Machado, RAR; Thonen, L; Arce, CCM; Theepan, V; Prada, F; Wuthrich, D; Robert, CAM; Vogiatzaki, E; Shi, YM; Schaeren, OP; Notter, M; Bruggmann, R; Hapfelmeier, S; Bode, HB; Erb, M
  NATURE BIOTECHNOLOGY, DOI: 10.1038/s41587-020-0419-1, FEB 2020
• Plant defense resistance in natural enemies of a specialist insect herbivore
  Zhang, Xi; van Doan, Cong; Arce, Carla C. M.; et al.
  PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA  DOI: 10.1073/pnas.1912599116,  NOV 12 2019
• The Desaturase Gene Family is Crucially Required for Fatty Acid Metabolism and Survival of the Brown Planthopper, Nilaparvata lugens
  Zeng, Jia-mei; Ye, Wen-feng; Noman, Ali; et al.
  INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES doi: 10.3390/ijms20061369, MAR 19 2019
• Photorhabdus khanii subsp. guanajuatensis subsp. nov., isolated from Heterorhabditis atacamensis, and Photorhabdus luminescens subsp. mexicana subsp. nov., isolated from Heterorhabditis mexicana entomopathogenic nematodes
  Machado, RAR; Bruno, P; Arce, CCM; Liechti, N; Kohler, A; Bernal, J; Bruggmann, R; Turlings, TCJ
  INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 69 (3):652-661; 10.1099/ijsem.0.003154 MAR 2019
• Convergent evolution of a metabolic switch between aphid and caterpillar resistance in cereals
  Li, B; Forster, C; Robert, CAM; Zust, T; Hu, L; Machado, RAR; Berset, JD; Handrick, V; Knauer, T; Hensel, G; Chen, W; Kumlehn, J; Yang, P; Keller, B; Gershenzon, J; Jander, G; Kollner, TG; Erb, M
  SCIENCE ADVANCES, 4 (12):10.1126/sciadv.aat6797 DEC 2018
• Whole-genome-based revisit of Photorhabdus phylogeny: proposal for the elevation of most Photorhabdus subspecies to the species level and description of one novel species Photorhabdus bodei sp nov., and one novel subspecies Photorhabdus laumondii subsp clarkei subsp nov.
  Machado, RAR; Wuthrich, D; Kuhnert, P; Arce, CCM; Thonen, L; Ruiz, C; Zhang, X; Robert, CAM; Karimi, J; Kamali, S; Ma, J; Bruggmann, R; Erb, M
  INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 68 (8):2664-2681; 10.1099/ijsem.0.002820 AUG 2018
• Aboveground herbivory induced jasmonates disproportionately reduce plant reproductive potential by facilitating root nematode infestation
  By: Machado, Ricardo A. R.; Arce, Carla C. M.; McClure, Michael A.; et al.
  PLANT CELL AND ENVIRONMENT  doi: 10.1111/pce.13143, APR 2018
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• Chemical and molecular aspects of plant-herbivore-natural enemy interactions
• Ecology of Photorhabdus entomopathogenic bacteria (EPB)
• Ecology of Heterorhabditis entomopathogenic nematodes (EPN)
• Foraging behaviour of Diabroticine larvae
• Insect resistance to EPB and EPN
• Plant responses to herbivory

• Ecology
• Microbiology
• Molecular Biology
• Plant-Animal Interactions
• Plant-Microbe Interactions