M. Isabel Reis dos Santos

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Sinorhizobium meliloti is capable of establishing a symbiotic nitrogen fixation relationship with Medicago sativa. During this process, it must cope with diverse environments and has evolved different types of transport systems that help its propagation in the plant roots. TolC protein family members are the outer-membrane components of several transport(More)
Burkholderia multivorans is an opportunistic pathogen capable of causing severe disease in patients with cystic fibrosis (CF). Patients may be chronically infected for years, during which the bacterial population evolves in response to unknown forces. Here we analyze the genomic and functional evolution of a B. multivorans infection that was sequentially(More)
Linear regression metamodels have been widely used to explain the behavior of computer simulation models, although they do not always provide a good global fit to smooth response functions of arbitrary shape. In the case study discussed in this paper, the use of several linear regression polynomial results in a poor fit. The use of a non-linear regression(More)
In this paper, we investigate and discuss some of the main issues concerning the estimation of nonlinear simulation metamodels. We propose a methodology for identifying a tentative functional relationship, estimating the metamodel coefficients and validating the simulation metamodel. This approach is illustrated with a simple queueing system. Finally, we(More)
The TolC protein from Sinorhizobium meliloti has previously been demonstrated to be required for establishing successful biological nitrogen fixation symbiosis with Medicago sativa. It is also needed in protein and exopolysaccharide secretion and for protection against osmotic and oxidative stresses. Here, the transcriptional profile of free-living S.(More)
This article explores the use of metamodels as simulation building blocks. The metamodel replaces a part of the simulation model with a mathematical function that mimics the input–output behavior of that part, with respect to some measure of interest to the designer. The integration of metamodels as components of the simulation model simplifies the model(More)
Frequently, the main objective of statistically designed simulation experiments is to estimate and validate regression metamodels, where the regressors are functions of the design variables and the dependent variable is the system response. In this article, a weighted least squares procedure for estimating the unknown parameters of a nonlinear regression(More)
The nitrogen-fixing bacterium Sinorhizobium meliloti must adapt to diverse conditions encountered during its symbiosis with leguminous plants. We characterized a new symbiotically relevant gene, emrR (SMc03169), whose product belongs to the TetR family of repressors and is divergently transcribed from emrAB genes encoding a putative major facilitator(More)