Cuebas-Irizarry, Mara F.

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    Physiological and transcriptome-based profile of glycosyl hydrolases from the Halophilic archaeon Halogeometricum borinquense
    (2017) Cuebas-Irizarry, Mara F.; Montalvo-Rodríguez, Rafael R.; College of Arts and Sciences - Sciences; Siritunga, Dimuth; Rodríguez-Minguela, Carlos; Department of Biology; Collins, Dana
    Since the discovery of the Archaea domain, a lot of interest has been given to study regulation of gene expression in these microorganisms. However, few reports are available that provides knowledge about how essential pathways can occur in extreme conditions. For halophilic archaea, little is known about genes involved in carbohydrate metabolism and how they are regulated. Therefore, the interest in this research project is to understand the function of glycosyl hydrolases involved in carbohydrate utilization at high salinity. To achieve this goal, the haloarchaeon Halogeometricum borinquense was selected as model since it has shown shorter generation times than other haloarchaea in different media. Also, H. borinquense is able to use glucose, mannose, fructose, xylose, maltose, trehalose, cellobiose, raffinose and glycerol as carbon sources. Cells of H. borinquense were grown in rich media, and minimal media containing three different sugars as its only carbon source: 0.4% (w/v) glucose, 0.4% (w/v) sucrose and 0.6% (w/v) maltose. Enzymatic assays for three different glycosyl hydrolases (α-glucosidase, β-glycosidase and β-galactosidase) were performed under each condition. The results were expressed in fold-difference or how much more or less was the activity in one condition versus another. A decrease in fold-difference in rich media was observed in response to glucose showing that glycosyl hydrolases are less expressed in rich media than glucose. Regarding to maltose and sucrose fold difference for each enzyme respectively was: α-glucosidase’s, 2-, 3- fold; β-glycosidase, 2-, 4- fold; and for β-galactosidase, 6-, 7- fold higher when compared to glucose enzyme levels. Molecular analyses through RNA-seq were performed identifying 39 putative glycosyl hydrolases, and revealed evidence that these enzymes were transcribed differentially as judged by differences across the transcriptome under distinct growth conditions. This investigation remarks the first attempt to address the topic of carbon catabolite repression in hypersaline environments. Specifically, demonstrating that this phenomenon is performed differently than bacterial and eukaryotic organisms, a comparison based on the sugar preference acting as a repressor. Is suggested the yeast extract as a potential repressor in halophilic archaea, such as in thermophilic archaea. In addition to. here is the first transcriptome analysis in H. borinquense which could lead future studies with this organism as model for gene expression and regulation in haloarchaea.