Bacterial explorer cells growing up a rock embedded in agar. Image supplied by Jones et al. (CC BY 4.0)

Exploring the earth

A “stationary” species of soil bacteria moves around widely when grown in the presence of fungi.

Soil is home to many bacteria. In fact, soil gets it characteristic ‘earthy’ smell from a common type of soil bacteria known as Streptomyces. Remarkably, Streptomyces are also the original sources of most of the antibiotics that are prescribed by doctors to treat bacterial infections. Scientists have been studying Streptomyces for over 70 years, and in all this time, there has been unanimous agreement on how these bacteria grow. That is to say that, unlike most other bacteria, Streptomyces grow like plants: they don’t move, and instead produce spores that are dispersed like seeds. This stationary lifestyle makes these bacteria somewhat vulnerable to predators, and so it is thought that Streptomyces make antibiotics to help protect themselves from other bacteria that are able to move around in the soil.

However, this established view of Streptomyces growth has now been turned on its head because Stephanie Jones and co-workers have discovered that Streptomyces bacteria can indeed move when grown in the presence of fungi. Specifically, when a species of Streptomyces is grown with yeast, some of the bacteria start to explore their environment, move over the top of other bacteria and up hard surfaces to heights that would be the equivalent of humans scaling Mount Everest.

Unexpectedly, Jones and co-workers also found that these “explorer” Steptomyces can communicate with nearby Streptomyces bacteria with a perfume-like airborne signal and convince their relatives to begin exploring too. Furthermore, while this volatile signal promotes the growth of Streptomyces, it adversely affects other bacteria and makes them sicker such that they are less able to grow and survive.

Together these findings reveal new ways that bacteria and other microbes can interact and communicate with each other. They also emphasise that researchers will need to consider such long-range communication strategies if they hope to better understand microbial communities.

To find out more

Read the eLife research paper on which this eLife digest is based: Streptomyces exploration is triggered by fungal interactions and volatile signals” (January 3, 2017).
Read a commentary on this research paper by Vineetha Zacharia and Matthew Traxler: “Bacteria: Exploring new horizons”
eLife is an open-access journal that publishes outstanding research in the life sciences and biomedicine.
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