Adsorption of Tolaasins, the Toxins Behind Mushroom Bacterial Blotch, by Microbacterium spp. is Insufficient for Its Detoxification

Tolaasins are lipodepsipeptides secreted by Pseudomonas tolaasii , the causal agent of bacterial blotch on several kinds of cultivated mushrooms. Our previous study reported on tolaasin detoxification by Microbacterium sp. K3-5 as a potential biocontrol of the disease. In this study, the tolaasin-detoxifying activities of various type strains of Microbacterium spp. were evaluated through chemical and biological assays. The bacterial cells of all tested strains of Microbacterium spp. showed tolaasin I-elimination from liquid phase. However, the toxin activities of tolaasins were still retained on the tolaasin-treated bacterial cells of all Microbacterium strains except M. foliorum NBRC 103072 T . Furthermore, intact tolaasin I was recovered from the tolaasin-treated bacterial cells of all tested strains except M. foliorum NBRC 103072 T . Our data reveal that Microbacterium spp. can be characterized as effective tolaasin I-eliminating bacteria through cell adsorption, but that this adsorption alone is insufficient for actual tolaasin detoxification. The biological degradation process must be needed to carry out the detoxification.