Fig.1 Chemical structures of a bacterial branched-chain fatty acid (anteiso-C15:0, left) and an unsaturated fatty acid (palmitoleic acid, right).

A collaborative research by Osaka Prefecture University, National Institute for Basic Biology, Shinshu University and Hokkaido University succeeded in cultivating arbuscular mycorrhizal fungi alone that are symbiotic microorganisms associated with plant roots and are expected to be used as a microbial inoculum.

Arbuscular mycorrhizal fungi form symbiotic associations with many crops and play an important role in plant nutrition by providing soil minerals to the hosts. These fungi are obligate symbionts, meaning that they cannot survive without colonization to the host. This feature leads to their uncultivability in the absence of plants. Here, we demonstrated that palmitoleic acid, an unsaturated fatty acid (Fig. 1), promotes the fungal growth and induces next generation spores under symbiotic conditions (Fig. 2).

The newly generated spores were capable of colonizing plant roots. This opens the possibility of pure culture and mass production of arbuscular mycorrhizal fungi. This work was partially supported by JST ACCEL and JSPS KAKENHI.

This research result was published online on the journal "Nature Microbiology" on June 25, 2019

<The paper information>
Title: Stimulation of asymbiotic sporulation in arbuscular mycorrhizal fungi by fatty acids
Authors: Hiromu Kameoka, Ippo Tsutsui, Katsuharu Saito, Yusuke Kikuchi, Yoshihiro Handa, Tatsuhiro Ezawa, Hideo Hayashi, Masayoshi Kawaguchi, Kohki Akiyama
Journal: Nature Microbiology
DOI: 10.1038/s41564-019-0485-7
Katsuharu Saito:http://soar-rd.shinshu-u.ac.jp/profile/en.HCkpPUkh.html

Fig.2: Asymbiotic culture of arbuscular mycorrhizal fungi in a medium containing palmitoleic acid. Arrowheads show secondary spores. Large yellow spores are inoculated parent spores. Extensively branched hyphae are observed.