| Title | Alcohol dehydrogenase 1 participates in the Crabtree effect and connects fermentative and oxidative metabolism in the Zygomycete Mucor circinelloides |
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| Author | Rosa Angélica Rangel-Porras1, Sharel P. Díaz-Pérez2, Juan Manuel Mendoza-Hernández1, Pamela Romo-Rodríguez1, Viridiana Alejandre-Castañeda2, Marco I Valle-Maldonado2,3, Juan Carlos Torres-Guzmán1, Gloria Angélica González-Hernández1, Jesús Campos-Garcia2, José Arnau4, Víctor Meza-Carmen2, and J. Félix Gutiérrez-Corona1* |
| Address | 1Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, 36050, Guanajuato, Gto., Mexico, 2Institute of Chemical-Biological Research, Universitary City, Michoacán University, 58030, Morelia, Mich., Mexico, 3Michoacán State Public Health Laboratory, 58279 Morelia, Mich., Mexico, 4Department of Fungal Strain Technology, Novozymes A/S Krogshoevej 36, Bagsvaerd, Denmark |
| Bibliography | Journal of Microbiology, 57(7),606–617, 2019, |
| DOI | 10.1007/s12275-019-8680-z |
| Key Words | Mucor circinelloides, ADH1 enzyme, Crabtree effect, fermentative and oxidative metabolism |
| Abstract | Mucor circinelloides is a dimorphic Zygomycete fungus that produces ethanol under aerobic conditions in the presence of glucose, which indicates that it is a Crabtree-positive fungus. To determine the physiological role of the alcohol dehydrogenase (ADH) activity elicited under these conditions, we obtained and characterized an allyl alcohol-resistant mutant that was defective in ADH activity, and examined the effect of adh mutation on physiological parameters related to carbon and energy metabolism. Compared to the Adh+ strain R7B, the ADH-defective (Adh-) strain M5 was unable to grow under anaerobic conditions, exhibited a considerable reduction in ethanol production in aerobic cultures when incubated with glucose, had markedly reduced growth capacity in the presence of oxygen when ethanol was the sole carbon source, and exhibited very low levels of NAD+-dependent alcohol dehydrogenase activity in the cytosolic fraction. Further characterization of the M5 strain showed that it contains a 10-bp deletion that interrupts the coding region of the adh1 gene. Complementation with the wild-type allele adh1+ by transformation of M5 remedied all the defects caused by the adh1 mutation. These findings indicate that in M. circinelloides, the product of the adh1 gene mediates the Crabtree effect, and can act as either a fermentative or an oxidative enzyme, depending on the nutritional conditions, thereby participating in the association between fermentative and oxidative metabolism. It was found that the spores of M. circinelloides possess low mRNA levels of the ethanol assimilation genes (adl2 and acs2), which could explain their inability to grow in the alcohol. |