Volatiles produced by the mycophagous soil bacterium Collimonas.

It is increasingly recognized that volatile organic compounds play an import role during interactions between soil microorganisms. Here, we examined the possible involvement of volatiles in the interaction of Collimonas bacteria with soil fungi. The genus Collimonas is known for its ability to grow at the expense of living fungi (mycophagy), and antifungal volatiles may contribute to the attack of fungi by these bacteria. We analyzed the composition of volatiles produced by Collimonas on agar under different nutrient conditions and studied the effect on fungal growth. The volatiles had a negative effect on the growth of a broad spectrum of fungal species. Collimonas bacteria did also produce volatiles in sand microcosms supplied with artificial root exudates. The production of volatiles in sand microcosms was enhanced by the presence of fungi. The overall picture that we get from our study is that antifungal volatiles produced by Collimonas could play an important role in realizing its mycophagous lifestyle. The current work is also interesting for understanding the ecological relevance of volatile production by soil bacteria in general as we found strong influences of root exudates composition and incubation conditions on the spectrum of volatiles produced.