Banca de QUALIFICAÇÃO: ANDREZA GENY DE ARAUJO ANDRADE

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : ANDREZA GENY DE ARAUJO ANDRADE
DATE: 28/06/2024
TIME: 09:00
LOCAL: Sala de Videoconferência da Faculdade de Medicina - UFCA (campus Barbalha)
TITLE:

OXIDATIVE STRESS AND GROWTH IMPAIRMENT INDUCED BY IRON AND MANGANESE IN PPGPP0 MUTANT BACILLUS SUBTILIS

KEY WORDS:

Keywords: Bacillus subtilis, ppGpp0, Oxidative 

PAGES: 41
BIG AREA: Ciências da Saúde
AREA: Medicina
SUMMARY:

The bacterium Bacillus subtilis is a Gram-positive, non-pathogenic, endospore-producing organism, forms biofilm, produces lipopeptide antibiotics and is characterized as a viable microorganism for carrying out antimicrobial screening due to its evolutionary proximity to pathogenic Gram-positives. In these bacteria, the guanosine penta/tetraphosphate nucleotide (p)ppGpp is produced, which participates in several cellular processes, but in situations of nutritional deficiency, these bacteria begin to undergo changes that activate the production of (p)ppGpp in greater quantities for metabolic regulation. The objective of this study was to understand the impact of the absence of guanosine tetraphosphate (ppGpp0) synthesis on cell growth and iron/manganese toxicity under oxidative stress in Bacillus subtilis. Bacillus subtilis PY79 and ppGpp0 strains were cultivated in 20 mL of liquid LB medium with shaking or in solid LB medium, both at 37°C for 15 hours. Bacterial growth was measured in the absence or presence of FeSO4 and MnSO4 at different concentrations, every hour, for 10 hours. Hydrogen peroxide (H2O2) levels were detected using AmplexRed/Horseradish Peroxidase, and the activities of antioxidant enzymes (catalase and superoxide dismutase) were assessed. Cellular respiration was measured using a Clark electrode. Tests demonstrated that ppGpp0 mutants showed a delay in growth compared to the PY79 control, and none of the cells grew in Fe2+ at a concentration of 4mM. At concentrations equal to or lower than 1mM FeSO4, Bacillus subtilis tolerated it well. However, compared to the wild type (PY79), the ppGpp0 mutant strain exhibited a significantly increased sensitivity to Fe2+, showing a delay in entering the exponential phase of growth. The ppGpp0 mutant produced higher levels of H2O2 (in the stationary phase) when stimulated by Fe2+ (2mM). Mn2+ induced stress caused a marked increase in the latency phase of cell growth in Bacillus subtilis mutants for ppGpp0. The presence of these metals induced an increase in oxygen consumption compared to strains without Fe2+ and Mn2+. Antioxidant enzymes did not show significant differences in activities. Our findings indicate that ppGpp is essential for iron and manganese homeostasis in Bacillus subtilis. Furthermore, the data suggest that iron toxicity impedes growth through a redox-mediated mechanism.

COMMITTEE MEMBERS:
Interno - FRANCISCO NASCIMENTO PEREIRA JUNIOR
Presidente - HEBERTY DI TARSO FERNANDES FACUNDO
Externa à Instituição - JANAÍNA ESMERALDO ROCHA
Interna - MARIA ELIZABETH PEREIRA NOBRE