Growth Inhibitory Mechanism of Contact-independent Antifungal TM-I-3 Bacillus sporothermodurans Strain against Aspergillus fumigatus and Cladosporium cladosporioides.

We previously identified a new Bacillus sporothermodurans strain, TM-I-3, which produces volatile compounds that show potent inhibitory activity against certain types of fungi, including Aspergillus fumigatus and Cladosporium cladosporioides. Non-contact antifungals derived from this bacterium may provide multidirectional inhibition and may be useful in disease prevention. This study is aimed at identifying the stage of fungal growth that is inhibited by TM-I-3 to elucidate the mechanism of its contact-independent antifungal activity. We evaluated mycelial growth and the gross fungal colony areas after 7 days in each experimental group varying the time in the proximity of TM-I-3 for 24 hours each. The fungal growth inhibition assay showed that TM-I-3 inhibited spore germination: the lag phase in the sigmoid growth curve. The present study demonstrated that TM-I-3 might be an effective fungistatic agent against pathogenic and allergenic fungi.

The Bacteriological Properties of Bacillus Strain TM-I-3 and Analysis of the Volatile Antifungal Compounds Emitted by this Bacteria.

Previously, we isolated and examined a bacterial strain designated as TM-I-3, belonging to the genus Bacillus, from soil in Nagasaki, Japan. This bacterium was able to inhibit the growth of molds, without coming into direct contact with them. Non-contact antifungals are capable of providing multidirectional inhibition and may contribute to disease prevention. In this study, we revealed the bacteriological properties of TM-I-3 and evaluated the antifungal activity of the compounds emitted from this bacterium. In addition, we analyzed the antimicrobial substances released from TM-I-3 using GC/MS to elucidate the mechanism of its action. Antimicrobial compounds from strain TM-I-3 were identified as acetic acid, propanoic acid, isovaleric acid, 2-methylbutanoic acid, and benzaldehyde, which are all reported to have antimicrobial activity. TM-I-3 demonstrated possible efficacy in inhibiting the growth of Aspergillus fumigatus, Cladosporium cladosporioides and Penicillium expansum, which may lead to inhibition of common fungal contaminants of household products and prevention of some pulmonary diseases.