Homemade lao zao (left) produced by starter (right). The strain isolated from the starter, like many domesticated isolates, inconsistently produces sporangia, a characteristic of Amylomyces. Images by T. Y. James.

Amylomyces rouxii NRRL 5866 (type isolate) is a fungus isolated from Look Pang, a sweet glutinous fermented rice dish made in Thailand. The monotypic genus Amylomyces describes Mucoralean fungi characterized by very strong amylolytic activity (starch degradation), abortive, incompletely developed sporangia, and abundant chlamydospores. Additional strains of A. rouxii are known from other Asian food products, including a component of “Chinese yeast” starters. Chinese yeast starters are produced and sold on an industrial scale for the household production of fermented dishes, such as lao zao (醪糟), the sweet, mildly alcoholic dish produced by fermenting sweet glutinous rice. Research has shown that A. rouxii is a polyphyletic assemblage of isolates related to Rhizopus delemar, R. oryzae, and Mucor circinelloides (Kito et al. 2009; Ashu et al. 2015). Presumably the loss of viable sporangiospores in the food-associated isolates is due to artificial selection on strains during their domestication. Having a complete genome sequence will be valuable for identifying which genes have been under selection during the domestication process and the genes involved in sporulation. Because Rhizopus delemar/oryzae are also present in a clinical setting (Chibucos et al. 2016), the genome sequence can be leveraged to investigate differences between domesticated, wild, and clinical strains.

References:

Ashu, E., A. Forsythe, A. A. Vogan, and J. Xu. 2015. Filamentous fungi in fermented foods. Pages 45-75 in D. Montet and R. C. Ray, editors. Fermented Foods, Part I: Biochemistry and Biotechnology. CRC Press, Boca Raton.

Chibucos, M. C., S. Soliman, T. Gebremariam, H. Lee, S. Daugherty, J. Orvis, A. C. Shetty, J. Crabtree, T. H. Hazen, K. A. Etienne, P. Kumari, T. D. O'Connor, D. A. Rasko, S. G. Filler, C. M. Fraser, S. R. Lockhart, C. D. Skory, A. S. Ibrahim, and V. M. Bruno. 2016. An integrated genomic and transcriptomic survey of mucormycosis-causing fungi. Nature Communications 7:11.

Kito, H., A. Abe, I. N. Sujaya, Y. Oda, K. Asano, and T. Sone. 2009. Molecular characterization of the relationships among Amylomyces rouxii, Rhizopus oryzae, and Rhizopus delemar. Bioscience Biotechnology and Biochemistry 73:861-864.