Full text
| |
| Author(s): |
Marina Rocha Borges da Fonseca
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI) |
| Defense date: | 2022-11-01 |
| Examining board members: |
Rodrigo da Silva Galhardo;
Mário Henrique de Barros;
Rogerio Ferreira Lourenço;
José Freire da Silva Neto
|
| Advisor: | Rodrigo da Silva Galhardo |
| Abstract | |
All living organisms must deal with DNA damage coming from various sources, like UV light radiating from the sun, antibiotics, and oxidative stress. DNA damage stimulates various responses, and bacterial cells have evolved to counteract by overexpressing several mechanisms to repair and tolerate these damages. The SOS response is the main common pathway activated during genotoxic stress that can shift the balance between mutagenesis and genome integrity. The formation of single stranded DNA attracts and activates the RecA protein, creating protein-nucleofilaments that promote the autocleavage of the LexA repressor, inducing the expression of all genes that contain the SOS-box promoter sequence. Pseudomonas aeruginosa is an opportunistic pathogen with great phenotypic plasticity, and not surprisingly, the SOS response is not the only pathway activated after DNA damage. By the same stimulus, P. aeruginosa induces the production of pyocins (prt system) and an autolysis pathway (alp system). Pyocins are antimicrobial bacteriocins that usually target different strains of the same species, but its production comes with a cost because the cells that make it lyse and die. The alp system also induces cell death, but it has been linked to virulence in animal models. It is not clear why the three responses are regulated by the same stimulus having conflicting activities like repair and autolysis. Apart from the intricate regulatory activation of responses during genotoxic stress, genes regulated by the SOS response with no unclear functions may offer new insights on the landscape of transcription in these conditions. The PA0922 gene is directly regulated by LexA and is annotated as a probable transcriptional regulator and a repair gene, but no study was focused on its molecular activities. This study aims to characterize the expression of each of the three systems regulated by LexA-like repressors after UV and ciprofloxacin damage and to identify the function of a probable transcription factor regulates by the SOS response, the gene PA0922. We performed total RNA sequencing analysis and qPCR to define the course of expression of each regulon and found that the SOS response is the fastest activated one, only 15 minutes after UV treatment. The prt systems is strongly induced right after, and the alp system being the last one. Additionally, we identified differences in the general profile of expression between UV and ciprofloxacin damages, where the UV damage has an apparent stronger induction of the alp system compared to ciprofloxacin. In the matter of the PA0922 gene, through RNA sequencing analysis we found that the deletion of this gene can interfere with the activation of the genotoxic stress response in treatment with ciprofloxacin and possibly modulate the SOS response. Also, the overexpression of PA0922 is toxic to P. aeruginosa, changes the bacterial shape and represses the expression of a bacterial type 6 secretion system. (AU) | |
| FAPESP's process: | 18/15819-9 - Transcriptomic and functional analisys of the regulation os the SOS response by ciprofloxacin in Pseudomonas aeruginosa |
| Grantee: | Marina Rocha Borges da Fonseca |
| Support Opportunities: | Scholarships in Brazil - Doctorate |