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"Cell size and morphology are two extremely important characteristics in the adaptation of bacteria to the external environment and are often associated to bacterial survival and growth. In Staphylococcus aureus, a common colonizer of human skin and mucus membranes, the small spherical shape of cells may be an advantage during colonization, helping this pathogen to evade host immune system. The fact that cell shape is maintained over consecutive generations evidences the existence of tightly regulated underlying mechanisms. Bacterial shape is maintained by the existence of an external cell wall mainly composed of peptidoglycan (PGN), a mesh-like molecule made by glycan chains cross-linked by short peptide bridges. Localization of PGN synthesis is dependent on the action of cytoskeletal proteins, which direct the activity of proteins involved in this synthesis, including Penicillin-Binding Proteins (PBPs) and proteins from the shape, elongation, division and sporulation (SEDS) family, to specific regions of the cells. T(...)"

"The emergence and spread of antibiotic resistance in bacteria constitutes one of the major challenges to global public health and is predicted to further escalate during the 21st century. One of the most frequent multi-drug resistant pathogens is methicillin-resistant Staphylococcus aureus (MRSA), a gram-positive coccoid bacterium that causes difficult to treat infections with severe morbidity and mortality rates. Many of the commonly used antibiotics target steps in the biosynthesis of peptidoglycan (PG), a robust but flexible meshlike macromolecule that withstands the intense internal turgor in the cell, among other functions. The integrity of the PG layer is of the utmost importance to bacteria, which must ensure that incorporation of new PG strands and remodelling of the existing ones is timely coordinated with the progression of the cell cycle. Despite its clinical relevance, many fundamental biological processes in S. aureus remain to be elucidated.(...)".

Tese de mestrado em Microbiologia Aplicada, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, em 2018 Submitted by Cristina Manessiez (camanessiez@fc.ul.pt) on 2018-12-21T16:26:21Z No. of bitstreams: 1 ulfc121928_tm_Andreia_Duarte.pdf: 2979967 bytes, checksum: be85b8cb563fd01ef18f95600a6382c9 (MD5) Made available in DSpace on 2018-12-21T16:26:32Z (GMT). No. of bitstreams: 1 ulfc121928_tm_Andreia_Duarte.pdf: 2979967 bytes, checksum: be85b8cb563fd01ef18f95600a6382c9 (MD5) Previous issue date: 2018

Dissertation presented to obtain the Ph.D degree in Biology The bacterial cell wall (CW) is of critical importance to cell viability. Impairment of CW synthesis or integrity rapidly leads to cell lysis and death. As there is no equivalent structure to the bacterial CW in mammalian cells, many important antibiotics target the enzymes responsible for its synthesis. The scaffold of the CW consists of the polymer peptidoglycan (PGN), a meshlike structure composed of glycan strands cross‐linked by short peptides. The final steps of PGN synthesis are catalysed by the penicillin‐binding proteins (PBPs), which assemble lipid‐linked disaccharide peptide precursors of PGN into high molecular weight oligomers via transglycosylation and transpeptidation reactions. These proteins have been proposed to work in multi‐enzyme complexes that would also include CW hydrolases.(...)

Tese de mestrado. Biologia (Microbiologia Aplicada). Universidade de Lisboa, Faculdade de Ciências, 2013 Submitted by Lurdes Saramago (lurdes.saramago@fc.ul.pt) on 2014-01-17T14:59:52Z No. of bitstreams: 1 ulfc103229_tm_pedro_fernandes.pdf: 3086841 bytes, checksum: 9fcb94aeaffcb283a16bc851f57640af (MD5) Made available in DSpace on 2014-01-17T15:00:58Z (GMT). No. of bitstreams: 1 ulfc103229_tm_pedro_fernandes.pdf: 3086841 bytes, checksum: 9fcb94aeaffcb283a16bc851f57640af (MD5) Previous issue date: 2013