Modelo metabólico em escala genômica integrado com as vias regulatórias associadas ao biofilme de Staphylococcus aureus ST239-SCCmecIII (Bmb9393)

• Autor(a) principal: Costa, Maiana de Oliveira Cerqueira e
• Data de Publicação: 2018
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações do LNCC
• Texto Completo: https://tede.lncc.br/handle/tede/292
• topic: Modelos biológicos; Stafilococos áureos; Modelagem computacional; Rede regulatória transcricional; CNPQ::CIENCIAS BIOLOGICAS::MICROBIOLOGIA

The pathogen S. aureus is one of the Gram-positive bacterias of greater versatility in regards to the diversity of tissues it can infect and the variety of diseases it causes, both in hospitals and community. Apart from the enormous variability of virulence and the great capacity of dispersion on its multiresistant clones such as the BEC (Brazilian Epidemic Clone), the emergence of isolates resistant to different classes of antimicrobials such as the important phenotypes of MRSA (methicillin-resistant Staphylococcus aureus) and VRSA (Staphylococcus aureus resistant to vancomycin) represent a serious problem in public health. Therefore, the present study had as one of the main objectives to reconstruct a transcriptional regulatory network (TRN) for the isolate Bmb9393 of the pathogenic bacterium Staphylococcus aureus. In addition, identifying the regulatory mechanisms that act in the biofilm formation of the bacteria and how the same influences the metabolism through an integrated model. The biofilm is considered an important virulence factor in nosocomial infections, especially those involving adherence to invasive medical devices and host tissues, playing an important role in the persistence of chronic infections. The biofilm can be defined as a sessile microbial community in which cells adhere to a abiotic surface or to other cells and are found surrounded by a protective polymeric extracellular matrix. Growth in biofilm confers innumerable adaptive advantages over planktonic cells species that are dispersed outside this microenvironment, among them it is possible to highlight the decrease in the susceptibility to antibiotics and to the immune system of the host, making it hard to eradicate these infections (1). In this context, having built a TRN as well as a metabolic model on a genomic scale (GEM) for the Brazilian isolate Bmb9393 S. aureus (2). This isolate has an increased ability to produce biofilm and a way to study this phenomenon is through computational modeling with the use of tools that allow the integration of regulatory pathways associated with biofilm production with GEM. The integrative approach is innovative because it is the first that considers the impact of gene regulation in metabolic activity for the pathogen. In addition, it is a pioneer in reconstruction of the TRN for a member belonging to the multiresistant clone BEC responsible for infections in several brazilians hospitals and soon became one of the MRSA clones one of worldwide dispersion. The methodology can be divided into three parts, with the first is the reconstruction of the draft of the TRN of BMB9393 from information obtained on the network published in 2011 for S. aureus N315 (3) enriched with both data from regulons (consisting of a transcription factor - TFs and the set of all genes regulated by them) databases bacterial as RegPrecise and Prodoric, as by manually cured regulatory interactions and prediction of regulatory elements. Still in the first stage, regulons have been identified in which the expression of all target genes was altered in the biofilm condition when compared to the planktonic condition. Regulatory pathways have also been reconstruct for each of these regulons. The second step involved the construction of the metabolic model by applying the (FBA) that utilizes linear optimization to determine the distribution of steady-state reactions in a metabolic network through maximization of a cellular objective, which, in this case, was represented by growth capacity or biomass (4). Finally, the last part includes the integration of the metabolic model with different regulatory pathways of interest, in addition to a pathway associated with the use of lactose by the cell, that was used to validate the methodology employed. Therefore, we obtain a computational model that represents what happens in the organism in a more realistic way, where metabolism and regulation are highly integrated, resulting in more reliable simulations and predictions. It is important emphasize that the integrative approach described in this paper is unpublished for the pathogen S. aures and opens new possibilities in the study of the so complex biofilm phenomenon. The analysis of the regulons associated with the biofilm condition demonstrated a high prevalence of genes related to the central metabolism of the bacteria both on biosynthesis and on compounds degradation. Besides the high use of alternative carbon sources on restrictive conditions that the biofilm growth imposes on cells in the deepest layers, showing the great influence of the central metabolism in virulence and, above all, on the growth of biofilm.