In my function  as a scientist at RWTH Aachen University, I participated in the second Bio Natural Conference, which dealt with diverse topics related to natural products. At the conference I gave a presentation on the work of Dr. Jana Foerster (neé Reiter), who did her PhD at RWTH Aachen, dealing with the topic of allicin from garlic as a natural antibiotic 1. There will be a separate article on this topic, which will take a deeper look at the antibiotic properties of allicin from garlic. It might be of interest for a lot of people, since allicin is responsible for the typical odor of freshly cut garlic! 

Due to the current covid pandemic, the meeting itself was not held in Portugal as originally planned, but digitally on November 18th and 19th via Zoom. A wide variety of topics were covered, such as natural products as drugs, natural product chemistry, bioactivity, natural products in food and cosmetics, and natural products from marine organisms. For interested readers, an abstract book is available, which gives an overview of the different topics and speakers.  

At this point I would like to take the opportunity to present a personal highlight, which seemed simple but ingenious to me at the same time. Ms. Deniz Tasdemir from GEOMAR Center for Ocean Research in Kiel addressed the topic of „microbial dark matter“ and inactive gene clusters in her talk. In a nutshell, microbial dark matter is related to the concept of dark matter in astrophysics. In astrophysics, it is a hypothetical form of matter that is as yet intangible and thus not directly investigable. The analogy in the microbial context here is that we can only cultivate 1-2% of all bacteria in the laboratory, which means that we cannot enrich and study natural products from these bacteria by cultivation yet. But even if we can cultivate bacteria or fungi in the laboratory, this does not mean that they also produce all the natural products they would theoretically be capable of, since corresponding genetic synthesis clusters are not per se permanently active. Synthesic processes always cause an investment of fitness, which means that resources that could normally be invested in growth and reproduction would be diverted to such syntheses. Since growth and reproduction can determine the race to the Top of the microbial food chain, certain synthesis processes are thus activated only when needed. Such a need exists, for example, when microorganisms need to suppress the defenses of a host or fight against other microorganisms for survival. The idea was therefore not to cultivate microorganisms in pure culture as usual, but together with another organism. As soon as the two organisms would meet, the researchers expected that new substances would be synthesized by the organisms to fight the other competitor, respectively. These „gladiatorial games“ were indeed successful, allowing new substances to be synthesized and characterized that had not be seen in pure culture.  

For example, in one of the works presented by Ms. Tasdemir, a marine fungus was pitted against terrestrial plant pathogens, namely against the bacteria Pseudomonas syringae and Ralstonia solanacearum, as well as against the fungi Magnaporthe oryzae and Botrytis cinerea 2. The idea was that these pathogens which are aggressive against plant hosts due to their lifestyle, could behave similarly aggressive in a different competitive situation, thereby provoking a response in the marine fungi. Finally, this competitive situation led to the discovery of new substances produced by the marine fungi that were not produced in pure culture, i.e. without competitors. 

References 

1 Reiter, J., Hübbers, A.M., Albrecht, F., Leichert, L.I.O., and Slusarenko, A.J. (2020). Allicin, a natural antimicrobial defense substance from garlic, inhibits DNA gyrase activity in bacteria. Int. J. Med. Microbiol. 310, 151359. 

2 Oppong-Danquah, E., Parrot, D., Blümel, M., Labes, A., and Tasdemir, D. (2018). Molecular Networking-Based Metabolome and Bioactivity Analyses of Marine-Adapted Fungi Co-cultivated With Phytopathogens. Front. Microbiol. 9. 

Microbial coliseum and new natural products 

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