In my function as a scientist at RWTH Aachen University, I participated in the second Bio Natural Conference (https://bionaturalconference.com/), 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 Ph.D. at RWTH Aachen University on allicin from garlic as a natural antibiotic 1. There is a separate article on her research, which takes a deeper look at the antibiotic properties of allicin from garlic.

Due to the current Covid pandemic, the meeting itself was not held in Portugal as originally planned, but was held digitally on November 18th and 19th 2021. A wide variety of topics were covered, such as Natural Products (NPs) as drugs, NP chemistry, bioactivity, NPs in food and cosmetics, and NPs from marine organisms. For interested readers, an abstract book is available online and gives an overview of the different topics and speakers (https://bionaturalconference.com/pdfs/BioNaturals-2021_AbstractBook.pdf).

At this point I would like to take the opportunity to relate 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 (https://www.geomar.de/) 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 the majority of 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 in cultivation that they would theoretically be capable of, since corresponding genetic synthesis clusters are not per se permanently active and may only be expressed under conducive conditions. Synthetic processes need energy and resource investment on the part of the cell and that can have fitness costs unless there are associated benefits. Since growth and reproduction can determine the race to the Top of the microbial food chain, certain synthetic processes are thus activated only when needed. Such a need exists, for example, when microorganisms need to suppress the defenses of a host they are trying to infect, or in the struggle against other microorganisms for survival.  

The idea was therefore not to cultivate microorganisms in axenic ‘pure’ culture, 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 each other. The strategy behind these ’gladiatorial games‘ was indeed successful, allowing new substances to be synthesized and characterized that had not before been recorded in pure culture.

For example, in one of Ms. Tasdemir’s presentations, a marine fungus was pitted against various terrestrial plant pathogens, namely against the bacteria Pseudomonas syringae, Ralstonia solanacearum, and 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 aggressively 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., in the absence of competitors.

There were many other interesting contributions and the symposium was a great success, allowing discussion between participants in on-line forums.

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. 

Jan Borlinghaus, 06.12.2021

Inter-Microbial Competition: Microbes in the Colosseum and New Natural Products

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