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Research conducted by C. Solano and co-researchers has updated our knowledge about salmonellosis
2009 JUL 20 - (NewsRx.com) -- "Bacteria have developed an exclusive signal transduction system involving multiple diguanylate cyclase and phosphodiesterase domain-containing proteins (GGDEF and EAL/HD-GYP, respectively) that modulate the levels of the same diffusible molecule, 3'-5'-cyclic diguanylic acid (c-di-GMP), to transmit signals and obtain specific cellular responses. Current knowledge about c-di-GMP signaling has been inferred mainly from the analysis of recombinant bacteria that either lack or overproduce individual members of the pathway, without addressing potential compensatory effects or interferences between them," scientists in Spain report. "Here, we dissected c-di-GMP signaling by constructing a Salmonella strain lacking all GGDEF-domain proteins and then producing derivatives, each restoring 1 protein. Our analysis showed that most GGDEF proteins are constitutively expressed and that their expression levels are not interdependent. Complete deletion of genes encoding GGDEF-domain proteins abrogated virulence, motility, long-term survival, and cellulose and fimbriae synthesis. Separate restoration revealed that 4 proteins from Salmonella and 1 from Yersinia pestis exclusively restored cellulose synthesis in a c-di-GMP-dependent manner, indicating that c-di-GMP produced by different GGDEF proteins can activate the same target. However, the restored strain containing the STM4551-encoding gene recovered all other phenotypes by means of gene expression modulation independently of c-di-GMP. Specifically, fimbriae synthesis and virulence were recovered through regulation of csgD and the plasmid-encoded spvAB mRNA levels, respectively," wrote C. Solano and colleagues. The researchers concluded: "This study provides evidence that the regulation of the GGDEF-domain proteins network occurs at 2 levels: a level that strictly requires c-di-GMP to control enzymatic activities directly, restricted to cellulose synthesis in our experimental conditions, and another that involves gene regulation for which c-di-GMP synthesis can be dispensable.." Solano and colleagues published their study in Proceedings of the National Academy of Sciences of the United States of America (Genetic reductionist approach for dissecting individual roles of GGDEF proteins within the c-di-GMP signaling network in Salmonella. Proceedings of the National Academy of Sciences of the United States of America, 2009;106(19):7997-8002). For more information, contact I. Lasa, University of Public Navarra, CSIC Gobierno Navarra, Institute Agrobiotecnol, Navarra 31006, Spain. Publisher contact information for the journal Proceedings of the National Academy of Sciences of the United States of America is: National Acad Sciences, 2101 Constitution Avenue NW, Washington, DC 20418, USA. Keywords: Spain, Salmonellosis, Cyclase, Enzyme Research, Enzymology, Phosphodiesterases, Salmonella. This article was prepared by Proteomics Weekly editors from staff and other reports. Copyright 2009, Proteomics Weekly via NewsRx.com.
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