Nav: Home

The secret language of microbes

April 14, 2016

Social microbes often interact with each other preferentially, favoring those that share certain genes in common. However, the basis for this behavior, known as "kind discrimination," is often unclear. A new study reveals a so-called "green beard" system used by a fungus to decide whether or not it should approach a new individual in the neighborhood and fuse with it.

The new study, performed at the University of California (Berkeley) and publishing in the Open Access journal PLOS Biology on 14th April, shows that the filamentous fungus Neurospora crassa uses a set of highly divergent genes to discriminate "self" from "non-self" cells over a distance and to actively seek out those favored cells (those of the same "kind").

This mechanism of discrimination fits a hypothesis called the "green beard effect," a name coined by Richard Dawkins to describe a model for the evolution of kind discrimination. According to this system, organisms must acquire three things - an arbitrary peculiarity (the "green beard"), the ability to detect the green beard on others, and the tendency to treat such green-bearded individuals preferentially.

When genetically identical asexual spores of Neurospora crassa germinate (termed germlings), they undergo chemotropic interactions and eventual cell fusion. "These genetically identical cells undergo a dialog, alternately 'listening' and 'speaking', which is essential for chemotropic interactions," says lead author Professor N. Louise Glass. In this study, the researchers examined how genetically different germlings communicated, discovering to their surprise that N. crassa populations fall into discrete communication groups.

"It seems like all strains speak the same basic fungal language, but due to different dialects, some strains cannot understand each other, and therefore are unable to establish communication necessary for cell fusion," says Dr Jens Heller, first author of the study.

Germlings from the same communication group are chemically attracted to each other, but germlings from different communication groups grew past each other to find a germling of their own communication type. The authors subsequently identified a specific set of highly variable genes (called "determinant of communication" or doc genes) within N. crassa populations that mediate the communication group affiliation.

By analyzing communication frequency of strains lacking the doc genes or where versions of the doc genes associated with a different communication group were "swapped", the authors show that genetic differences at the doc genes are necessary and sufficient to determine "self" identity. While genetically different strains with identical doc genes show up to 95% communication frequency, strains that are otherwise genetically identical but differ only in their version of the doc genes communicate with less than 10% frequency. "It was fascinating and surprising for us to see how well this kind discrimination system actually works," says Dr. Jens Heller. These data indicate that the doc genes function as "green beard" genes, involved in mediating long distance kind recognition by actively searching for one's own type, which results in cooperation between non-genealogical relatives.

Fusion between germlings brings fitness advantages to N. crassa, such as more rapid colony establishment. Dr Heller says, "Since we know that programmed cell death can result from fusion of incompatible partners in N. crassa, choosing the right partner at a distance can be important". Prof. Glass, principal investigator of the study, summarizes, "Our findings reveal a heretofore under-appreciated complexity in fungal communication. We have only scratched the surface on communication and interactions of these enigmatic organisms."
In your coverage please use this URL to provide access to the freely available article in PLOS Biology:

Contact: Louise Glass (

Citation: Heller J, Zhao J, Rosenfield G, Kowbel DJ, Gladieux P, Glass NL (2016) Characterization of Greenbeard Genes Involved in Long-Distance Kind Discrimination in a Microbial Eukaryote. PLoS Biol 14(4): e1002431. doi:10.1371/journal.pbio.1002431

Funding: This work was funded by a National Institute of General Medical Sciences grant (R01 GM060468) and a National Science Foundation grant (MCB 1412411) to NLG. JH was supported by a research fellowship from the Deutsche Forschungsgemeinschaft (HE 7254/1-1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

About Biology

PLOS Biology is an open-access, peer-reviewed journal published by PLOS, featuring research articles of exceptional significance, originality, and relevance in all areas of biology. For more information visit, or follow @PLOSBiology on Twitter.

Media and Copyright Information

For information about PLOS Biology relevant to journalists, bloggers and press officers, including details of our press release process and embargo policy, visit

PLOS Journals publish under a Creative Commons Attribution License, which permits free reuse of all materials published with the article, so long as the work is cited.

About the Public Library of Science

The Public Library of Science (PLOS) PLOS is a nonprofit publisher and advocacy organization founded to accelerate progress in science and medicine by leading a transformation in research communication. For more information, visit


This press release refers to upcoming articles in PLOS Biology. The releases have been provided by the article authors and/or journal staff. Any opinions expressed in these are the personal views of the contributors, and do not necessarily represent the views or policies of PLOS. PLOS expressly disclaims any and all warranties and liability in connection with the information found in the release and article and your use of such information.


Related Fungus Articles:

Single fungus amplifies Crohn's disease symptoms
A microscopic fungus called Candida tropicalis triggered gut inflammation and exacerbated symptoms of Crohn's disease, in a recent study conducted at Case Western Reserve University School of Medicine.
A novel anticandidal compound containing sulfur from endophytic fungus
There is a continuous search for new, safe and relatively cheaper drugs with the advent of new diseases and increasing antibiotic resistance.
Plants cheat too: A new species of fungus-parasitizing orchid
Plants usually produce their own nutrients by using sun energy, but not all of them.
How a fungus inhibits the immune system of plants
A newly discovered protein from a fungus is able to suppress the innate immune system of plants.
What happens to a pathogenic fungus grown in space?
A new study, published this week in mSphere, provides evidence that Aspergillus fumigatus, a significant opportunistic fungal threat to human health, grows and behaves similarly on the International Space Station compared with earth.
Fungus a possible precursor of severe respiratory diseases in pigs
Pneumocystis carinii causes mild forms of pneumonia in pigs and was considered of low diagnostic relevance.
Rare fungus product reduces resistance to antibiotics
Microorganisms, among them fungi, are a natural and rich source of antibiotic compounds.
How to organize a cell: Novel insight from a fungus
University of Exeter researchers have found novel insight into the ways cells organise themselves.
Deadly fungus threatens African frogs
Misty mountains, glistening forests and blue-green lakes make Cameroon, the wettest part of Africa, a tropical wonderland for amphibians.
Invasive amphibian fungus could threaten US salamander populations
A deadly fungus causing population crashes in wild European salamanders could emerge in the United States and threaten already declining amphibians here, according to a report released today by the US Geological Survey.

Related Fungus Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Moving Forward
When the life you've built slips out of your grasp, you're often told it's best to move on. But is that true? Instead of forgetting the past, TED speakers describe how we can move forward with it. Guests include writers Nora McInerny and Suleika Jaouad, and human rights advocate Lindy Lou Isonhood.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...