Beneficial bacteria in the gut of moth larvae produce an antimicrobial agent that kills competing bacteria which otherwise have detrimental effects on insect development. An international team of scientists under the direction of the Max Planck Institute for Chemical Ecology in Jena, Germany, were able to demonstrate for the first time that symbiotic Enterococcus mundtii bacteria secrete the antimicrobial peptide mundticin. It enters harmful germs in the gut of the African cotton leafworm Spodoptera littoralis and kills the unicellular organisms. The symbionts thus ensure a healthy gut flora and reduce the infection risk of the pest insect.
The African cotton leafworm Spodoptera littoralis, a major agricultural pest, is widespread, especially in the Mediterranean. It feeds on a broad range of host plants, such as vegetables, fruit, flowers and crops. According to this new study, the evolutionary success of this insect is partially based on a symbiotic association with microorganisms in its gut.
Larva (above and middle) and pupa (below) of the cotton leafworm Spodoptera littoralis; both have been infected with pathogenic Enterococcus faecalis bacteria.
Yongqi Shao, Zhejiang University, Hangzhou, China
In 2012, researchers from the Department of Bioorganic Chemistry at the Max Planck Institute in Jena showed that the microbiome of Spodoptera littoralis, representing the sum of all microorganisms colonizing this pest insect, changed considerably during larval development.
Whereas first-instar larvae housed a variety of Enterococcus species, late-instar caterpillars were dominated by Enterococcus mundtii bacteria. Related pathogenic Enterococcus species, such as Enterococcus faecalis and Enterococcus casseliflavus, had been completely eradicated from the microbiome of the caterpillars. These observations motivated the scientists to study the factors which influence the composition of the microbiome during insect development in more detail.
Led by Wilhelm Boland, the team of researchers cultivated Enterococcus bacteria for so-called agar diffusion tests. This method is used to show which bacteria spread or are inhibited in their growth when other microorganisms are present in the medium.
They discovered that Enterococcus mundtii bacteria, which are dominant in the gut of the larvae, excrete a chemical substance into the medium. This compound causes the death of other bacterial species. Colleagues from the Leibniz Institute for Natural Product Research and Infection Biology analyzed and identified it as the peptide mundticin KS, a so-called bacteriocin which is produced by several bacteria in order to eliminate competing bacterial strains.
Further investigation revealed that Enterococcus mundtii bacteria produce mundticin as an internal antibiotic in the gut of the caterpillars. The researchers tried to infect insect larvae which were associated with the symbiotic bacteria with pathogenic Enterococcus faecalis bacteria. Thanks to the symbionts, however, the insects were able to successfully clear the pathogens from their guts.
In comparison, larvae which housed an Enterococcus mundtii strain without the gene for the synthesis of mundticin were powerless against pathogen infection. If the infected caterpillars were fed on a diet that contained mundticin many larvae recovered and the pathogen decreased by more than 60% within 24 hours.
“Mundticin is the first microbial compound from the gut of an organism which has been characterized functionally with regard to its effect on the whole gut flora,” states Boland. Which microorganisms in the gut survive and which don’t, however, also depend on the food which contains plant secondary metabolites. “The microbiome is the result of a delicate balance of food-derived, insect-derived and microbial products.” Interactions between those metabolites are currently under investigation.
Many lepidopteran larvae cause major damage in agriculture. In order to control them, farmers have been using bacteria as biological pesticides. “Detailed knowledge of the bacteriocins’ mode of action and the identification of genes that confer resistance against these compounds could significantly contribute to improving pest control with bacteriocin-resistant bacteria,” says first author Yongqi Shao, who performed the studies in Jena.
Shao has been doing research since 2015 at Zhejiang University in Hangzhou, China. The study also provides interesting approaches for medical research. After all, bacteriocins are considered possible alternatives to conventional antibiotics, many of which are facing increasing problems of resistance.
The study was supported in the framework of the Collaborative Research Center 1127 “Chemical Mediators in Complex Biosystems” from the German Research Foundation. [AO/KG]
Shao, Y., Chen, B., Sun, C., Ishida, K., Hertweck, C., Boland, W. (in press). Symbiont-Derived Antimicrobials Contribute to the Control of the Lepidopteran Gut Microbiota. Cell Chemical Biology 24, 1-10. DOI: 10.1016/j.chembiol.2016.11.015
Prof. Dr. Wilhelm Boland, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, 07745 Jena, E-Mail email@example.com, Tel.: +49 3641 57 1201
Contact and Media Requests:
Angela Overmeyer M.A., Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-2110, E-Mail firstname.lastname@example.org
Download high-resolution images via http://www.ice.mpg.de/ext/downloads2017.html
Angela Overmeyer | Max-Planck-Institut für chemische Ökologie
Meadows beat out shrubs when it comes to storing carbon
23.11.2017 | Norwegian University of Science and Technology
Migrating Cells: Folds in the cell membrane supply material for necessary blebs
23.11.2017 | Westfälische Wilhelms-Universität Münster
Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
23.11.2017 | Information Technology
23.11.2017 | Physics and Astronomy
23.11.2017 | Life Sciences