Influence of the nir operon in the adaptation of Staphylococcus aureus to the host environment

• Autor(a) principal: Amorim, André Ricardo Barreiro
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/27763
• topic: Staphylococcus aureus; Physiological conditions; Anaerobic respiration; Siroheme

Staphylococcus aureus is an opportunistic human pathogen, that commensally colonizes the human host and can cause a great number of severe diseases, that can be life-threatening. It is capable of infecting a wide range of tissues, from superficial skin to deeper tissues such as the gastrointestinal track, heart and bones. This variety of tissues show different oxygen concentrations, from highly oxygenated, like blood, to almost anaerobic environments, like the intestines. Little is known of the role played by genes involved in nitrite reduction (NirBD) and siroheme biosynthesis (sirABC) in the adaptation of S. aureus to less oxygenated environments and so it is important to study these genes and the response of this bacteria to the diverse environments found during the host infection. In this work, through qRT-PCR, we observed that oxygen rich environments inhibited the expression of nirR, nirB, sirA and sirC. Hypoxia leads to the onset expression, culminating in higher levels of expression under anaerobic conditions. In anaerobic conditions, nitrates showed to decrease the expression of the nir operon genes and sirC, but their presence also presence improved growth. The mutations ΔnirB, ΔnirD and ΔnirR weaken S. aureus growth, preventing the reduction of nitrites. The deletion of sirC also demonstrated effects, but since the process that is catabolized by this enzyme can occur naturally, but at a lower rate, the effects observed by the deletion of this gene resulted in slightly slower growth and consumption of nitrites, when compared to the wild-type. In summary, S. aureus shows resilience, adapting and surviving, different oxygen environments. It was also showed that the presence of nitrates and oxygen are inhibitors of the expression of the nir and sirC operon genes, in which sirC has been shown to be an enzyme-encoding gene, that when deleted did not impair nitrite reduction by S. aureus.