Gumá-Cintrón, Yariela

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    Transcriptomic analysis of cobalt stress in the marine yeast Debaryomyces hansenii
    (2015) Gumá-Cintrón, Yariela; Nadathur, Govind S.; College of Arts and Sciences - Sciences; Schizas, Nikolaos; Sen, Arup; Otero Morales, Ernesto; Department of Marine Sciences; Grove, Kurt A.
    Debaryomyces hansenii is a very versatile marine yeast capable of thriving under extreme conditions. Particularly important studies performed on this yeast include studies on osmotolerance and heavy metal resistance of various strains. With respect to its capability to survive when exposed to high concentrations of the heavy metal cobalt (Co (II)), strain J6 revealed to be highly tolerant. In an attempt to elucidate the mechanisms that activate in order to survive toxic exposure to heavy metals, microarrays of J6 were performed. This revealed that J6 was largely divergent from the type strain’s, 767, genome. Given that the only available genome was that of the type strain, another approach needed to be taken in order to understand how J6 survives exposure to heavy metals. For this reason, a transcriptomic study was needed. By sequencing J6’s RNA after exposure to Co (II) in a time series experiment and comparing it to a control sample, identification of possible products, given that RNA can be used as a proxy for proteins, can thus allow us to identify the function of genes that are turned on and off during exposure. This analysis will provide information on the survival or adaptation mechanisms that J6 has developed. In order to elucidate such mechanisms, various steps need to be followed: (i) identify the concentration of soluble cobalt that reduced the yeast cell density by half (this will give maximum response to stress), (ii) RNA sequencing, (iii) data processing and mapping to other similar yeast genomes, (iv) bioinformatics, in order to allocate biological function to each identified gene and elucidate survival mechanisms, and (v) validation of RNA sequencing data. As a result of this study we were able to identify highly upregulated genes under heavy metal stress conditions to mainly fall into the following categories: (i) DNA damage and repair genes, (ii) oxidative stress response genes, and (iii) genes for cell wall integrity and growth. The main response of D. hansenii when in heavy metal stress is the activation of non-enzymatic oxidative stress response mechanisms and the control of biological production of reactive oxygen species. Our results indicate that although J6 does not seem to be preadapted to survive high heavy metal concentrations, its survival and detoxifying mechanisms are enough for the cells to recover quickly after heavy metal stress conditions.