Editorial: Chemical Ecology

Chemical Ecology is one of the key factors shaping our environment. Many organisms including humans rely heavily on chemistry for interactions with surrounding life forms. Chemical Ecologists ask fundamental questions: why is a particular compound on Earth and by which mechanisms was it selected from the universal structure space? In other words, Chemical Ecology searches for the ‘raison d'etre’ of molecules produced by living organisms. While for many natural products the original function remains unknown, research performed during recent decades has revealed impressively diverse roles in numerous ecological systems. This issue of Natural Product Reports now aims to summarize current knowledge by providing contributions from leading authors in the field.

First focusing on the smallest of organisms, the article by Traxler and Kolter (DOI: 10.1039/C5NP00013K) literally digs deep to uncover microbial interactions in the soil. Discussing several model organisms, the review investigates from multiple perspectives the impact of microbial natural products on the ecology and physiology of the producers. Furthermore, the authors define terms to clarify interactions and point out that many compounds classified by us as antibiotics could have pleiotropic functions by also acting as pheromones.

Microorganisms are also in the focus of the review by Flores, Biedermann, Engl and Kaltenpoth (DOI: 10.1039/C5NP00010F). Here their symbiotic associations with animals are reviewed, highlighting contributions to host defense, in both terrestrial or aquatic animals. It is likely that the frequency and relevance of such interactions is much higher than considered earlier. Various aspects of defensive symbiosis are discussed, including an evolutionary perspective.

Microorganisms are ubiquitous and it seems likely that all macroorganisms possess a microbiome. The viewpoint by Cantly and Clardy (DOI: 10.1039/C4NP00141A) explores microbial compounds in the context of such associations, drawing attention to the massively increased scale of data provided by new genetic and analytical methods allowing scientists to analyze these phenomena in unprecedented detail.

New metabolomic methods applied to Chemical Ecology are the focus of the review by Kuhlisch and Pohnert (DOI: 10.1039/C5NP00003C). The pros and cons of metabolomics are discussed, and the important link to other omics tools emphasized. Convincing examples show the power of this method.

As Spiteller points out in his review (DOI: 10.1039/C4NP00166D), fungal Chemical Ecology is not well investigated. Nevertheless, evidence for a large variety of interactions between fungi and other organisms by natural products are discussed. These range from chemical communication to chemical defence or chemical attack.

The nematode worm Caenorhabditis elegans is a model species in many respects. Because of its fully sequenced genome and well understood cellular biology, detailed insights into chemistry-related aspects of their physiology and behaviour can be gained. Von Reuss and Schroeder (DOI: 10.1039/C5NP00042D) describe in their article that almost every facet of nematode biology is regulated by a combinatorial toolset of small molecules. The combination of different building blocks gives this and related nematode species access to a large variety of compounds, used at different life stages for different purposes.

Insects comprise the most species-rich group of higher organisms on Earth and have a significant impact on human life. This impact may be the reason for the considerable scientific work devoted to understanding their chemical communication systems and the compounds used, surpassing that of any other taxonomic group.

Ando and Yamakawa (DOI: 10.1039/C4NP00138A) highlight the importance of methyl-branched aliphatic compounds in insect communication. Their thorough review discusses within a broader perspective not only occurrence and analytics, but also various strategic syntheses to generate these compounds.

Another substance class used as pheromones by invertebrates, but also by vertebrates and bacteria, are lactones. As pointed out by Schulz and Hötling (DOI: 10.1039/C5NP00006H), general biosynthetic principles such as storage of polar precursors provide an ideal basis for their use as signaling compounds. The wide variety of associated biological functions, their biosynthesis, as well as their synthesis are discussed in this article.

Scale insects and mealybugs are serious pests to humans, the pheromones of which are structurally unique terpenes and polyketides. The identification of the pheromones synthesized by these tiny insects often proves to be very difficult, yet rewarding. The review by Zou and Millar (DOI: 10.1039/C4NP00143E) summarizes the known occurring structures and discusses different synthetic strategies employed towards accessing these compounds.

Methods are the focus of the highlight by Raguso, Thompson and Campbell (DOI: 10.1039/C4NP00159A). Starting from their own research area on floral chemical ecology they move on to discuss future questions and the relation between biologists and chemists. What is needed to understand each other's work in detail? This question is surely important for many other fields outside Chemical Ecology as well.

As is the case for terrestrial systems, small molecules govern much of the communication in marine habitats. In their minireview, Nunez-Pons and Avila (DOI: 10.1039/C4NP00150H) describe the Chemical Ecology of the benthic Antarctic community. In addition to defence and predation, other aspects such as competition and protection from UV radiation are discussed.

Arguably the most difficult to decipher forms of chemical communication are those among vertebrates because of their complex behavior. Apps, Weldon, and Kramer (DOI: 10.1039/C5NP00029G) discuss various considerations when studying these animals. Often a diverse mixture of compounds is produced varying widely in structure and mass. The review targets the underlying principles.

The twelve articles present in the Themed Issue provide inspiring insights into recent advances in Chemical Ecology. The hope of the editors is that it convinces readers to include aspects of it into their research. Chemical Ecology is an exciting, highly interdisciplinary field at the interface of chemistry and biology that uses methods ranging from genome analysis to chemical synthesis. Knowledge of the mechanisms that regulate natural interactions mediated by chemical compounds may spark new ideas in other areas as well. In the end, we hope that the readers enjoy this issue as much as we did.

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