Interruption of Aspergillus niger spore germination by the bacterially produced secondary metabolite collimomycin

Summary Collimonas fungivorans Ter331 ( Cf Ter331) is a soil bacterium that produces collimomycin, a secondary metabolite that inhibits the vegetative growth of fungi. Here we show that Cf Ter331 can also interfere with fungal spore germination and that collimomycin biosynthesis is required for this activity. More specifically, in co‐cultures of Aspergillus niger N402 ( An N402) co‐nidiospores with Cf Ter331, the rate of transition from the isotropic to polarized stage of the germination process was reduced and the relatively few An N402 conidiospores that completed the germination process were less likely to survive than those that were arrested in the isotropic phase. By contrast, a collimomycin‐deficient mutant of Cf Ter331 had no effect on germination: in its presence, as in the absence or delayed presence of Cf Ter331, unhindered germination of conidiospores allowed rapid establishment of An N402 mycelium and the subsequent acidification of the culture medium to the detriment of any bacteria present. However, when challenged early enough with Cf Ter331, the collimomycin‐dependent arrest of the An N402 germination process enabled Cf Ter331 to prevent An N402 from forming mycelia and to gain dominance in the culture. We propose that the collimomycin‐dependent arrest of spore germination represents an early intervention strategy used by Cf Ter331 to mitigate niche construction by fungi in nature.