Examinando por Autor "Fuentes, Danitza N."

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    Motility modulation by the small non-coding RNA SroC in Salmonella Typhimurium
    (Oxford University Press, 2015-08) Fuentes, Danitza N.; Calderón, Paulina F.; Acuña, Lillian G.; Rodas, Paula I.; Paredes-Sabja, Daniel; Fuentes, Juan A.; Gil, Fernando; Calderón, Iván L.
    Bacterial regulatory networks of gene expression include the interaction of diverse types of molecules such as the small non-coding RNAs (sRNAs) and their cognate messenger RNAs (mRNAs). In this study, we demonstrated that the Salmonella Typhimurium sRNA SroC is significantly expressed between the late-exponential and stationary phase of growth in an rpoS-dependent manner. The expression of flagellar genes predicted as targets of this sRNA was quantitatively analyzed in both a ΔsroC mutant and a SroC-overexpressing (pSroC) strain. Deletion of sroC increased flagellar gene expression (i.e. flhBAE and fliE). Conversely, overexpression of SroC reduced flhBAE and fliE expression. These observations correlated with phenotypic evaluation of motility, where sroC deletion slightly increased motility, which in turn, was drastically reduced upon overexpression of SroC. The effects of deletion and overexpression of sroC in biofilm formation were also examined, where the ΔsroC and pSroC strains exhibited a reduced and increased ability to form biofilm, respectively. Furthermore, electron microscopy revealed that the wild-type strain overexpressing SroC had a non-flagellated phenotype. Taken together, our results showed that S. Typhimurium sRNA SroC modulates the flagellar synthesis by down-regulating the expression of flhBAE and fliE genes. © FEMS 2015. All rights reserved.
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    Ítem
    The small RNA RyhB homologs from Salmonella typhimurium participate in the response to S-nitrosoglutathione-induced stress
    (Academic Press Inc., 2014-07) Calderón, Paulina F.; Morales, Eduardo H.; Acuña, Lillian G.; Fuentes, Danitza N.; Gil, Fernando; Porwollik, S.; McClelland, Michael; Saavedra, Claudia P.; Calderón, Iván L.
    Typically, the expression of sRNAs is activated in response to environmental stimuli in order to regulate gene expression through post-transcriptional mechanisms. In the present work we show that the Salmo nella typhimurium paralogous sRNAs RyhB-1 and RyhB-2 are induced in response to the nitrosating agent S-nitrosoglutathione (GSNO). Inactivation of these sRNAs decreased S. typhimurium resistance to GSNO and increased the levels of nitrosylated proteins. These results prompted us to evaluate a possible role of these sRNAs in nitrosative stress resistance. RNA profiling was used as a screen to identify novel RyhB-1 and RyhB-2 regulated targets. A subset of genes was filtered based on their potential role in the response to nitrosative stress and their expression was analyzed by quantitative RT-PCR in wild type, single and double mutant strains (DryhB1, DryhB2 and DryhB1 DryhB2) treated with GSNO. In response to GSNO RyhB-1 and RyhB-2 negatively regulate the expression of the genes cyoABC (cytochrome bo oxi dase), cydB (cytochrome bd oxidase), cybC (cytochrome b-562), and positively regulate the nirBCD operon (nitrite reductase system). Together, these results suggest that RyhB-1 and RyhB-2 finely tune the expres sion of genes coding for cytochrome oxidases and the nitrate reductase system, allowing the cell to cope with GSNO-induced stress. 2014 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).