[2S02a] 04. Brewing, Fermentation and Food Technology - Part 2

3:30 PM - 3:45 PM JST(6:30 AM - 6:45 AM UTC)

[2Brew-12] Mechanisms of colony-colony growth inhibition in a single strain of the industrial filamentous fungus Aspergillus oryzae

○Yuya Hamanaka¹, Takuya Katayama², Jun-ichi Maruyama¹ (1. The Univ. of Tokyo (Japan), 2. Nat. Inst. Infect. Dis. (Japan))

Keywords:

Aspergillus oryzae,filamentous fungi,microbial interaction

Fungal-fungal interactions arise between neighboring species as they compete for territory and nutrients. In filamentous fungi, growth inhibition between colonies of different species or strains, referred to as the “antagonistic effect”, has been studied for over a century, particularly in the context of biological control. In contrast, we found that growth inhibition also occurs between colonies of a single strain in the filamentous fungus Aspergillus oryzae, which is widely used for Japanese traditional fermentation processes such as sake, soy sauce, and miso production. Various A. oryzae strains exist depending on their industrial applications, and many of these strains exhibit the growth inhibition. Although this phenomenon has long been recognized empirically by fermentation practitioners, its molecular mechanism remains largely unknown. Through screening of a transcription regulatory gene deletion library, we demonstrated that this inhibition involves the RGS (Regulator of G protein signaling) protein FlbA, which accelerates the GTPase activity of the G protein α subunit FadA. A GTPase-deficient, constitutively active mutant of fadA phenocopied the ΔflbA strain, supporting the involvement of G protein signaling in the growth inhibition. Furthermore, screening for mutants that escape colony-colony growth inhibition, combined with whole-genome sequencing, suggested the involvement of epigenetic modifications. Collectively, our findings provide novel mechanistic insights into colony-colony growth inhibition and may inform strategies for optimizing fungal growth and enzyme production during koji making.