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The LuxR Homolog ExpR, in Combination with the Sin Quorum Sensing System, Plays a Central Role in Sinorhizobium meliloti Gene Expression. Hanh H. Hoang, 2004.Quorum sensing, a population density-dependent mechanism for bacterial communication and gene regulation, plays a crucial role in the symbiosis between alfalfa and its symbiont Sinorhizobium meliloti . The Sin system, one of three quorum sensing systems present in S . meliloti, controls the production of the symbiotically active exopolysaccharide EPS II . Based on DNA microarray data, the Sin system also seems to regulate a multitude of S . meliloti genes, including genes that participate in low-molecular-weight succinoglycan production, motility, and chemotaxis, as well as other cellular processes . Most of the regulation by the Sin system is dependent on the presence of the ExpR regulator, a LuxR homolog . Gene expression profiling data indicate that ExpR participates in additional cellular processes that include nitrogen fixation, metabolism, and metal transport . Based on our microarray analysis we propose a model for the regulation of gene expression by the Sin/ExpR quorum sensing system and another possible quorum sensing system(s) in S . meliloti . Pharmacokinetics of Indinavir Combined with Low-Dose Ritonavir in Human Immunodeficiency Virus Type 1-Infected Children. A. S. Bergshoeff, 2004.So far, no pediatric doses for indinavir combined with ritonavir have been defined . This study evaluated the pharmacokinetics of 400 mg of indinavir/m2 combined with 125 mg of ritonavir/m2 every 12 h (q12h) in 14 human immunodeficiency virus type 1-infected children . The area under the concentration-time curve from 0 to 24 h and the minimum concentration of drug in serum for indinavir were similar to those for 800 mg of indinavir-100 mg of ritonavir q12h in adults, while the maximum concentration of drug in serum was slightly decreased, with geometric mean ratios (90% confidence intervals in parentheses) of 1.1 (0.87 to 1.3), 0.96 (0.60 to 1.5), and 0.80 (0.68 to 0.94), respectively . Identification of Two-Component Regulatory Systems in Bifidobacterium infantis by Functional Complementation and Degenerate PCR Approaches. Laura E. MacConaill, 2003.Two-component signal transduction systems (2CSs) are widely used by bacteria to sense and adapt to changing environmental conditions . With two separate approaches, three different 2CSs were identified on the chromosome of the probiotic bacterium Bifidobacterium infantis UCC 35624 . One locus was identified by means of functional complementation of an Escherichia coli mutant . Another two were identified by PCR with degenerate primers corresponding to conserved regions of one protein component of the 2CS . The complete coding regions for each gene cluster were obtained, which showed that each 2CS-encoding locus specified a histidine protein kinase and an assumed cognate response regulator . Transcriptional analysis of the 2CSs by Northern blotting and primer extension identified a number of putative promoter sequences for this organism while revealing that the expression of each 2CS was growth phase dependent . Analysis of the genetic elements involved revealed significant homology with several distinct regulatory families from other high-G+C-content bacteria . The conservation of the genetic organization of these three 2CSs in other bacteria, including a number of recently published Bifidobacterium genomes, was investigated .
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