Banca de DEFESA: ANDREZA GENY DE ARAUJO ANDRADE

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : ANDREZA GENY DE ARAUJO ANDRADE
DATE: 30/07/2024
TIME: 14:00
LOCAL: Sala de Videoconferência - Faculdade de Medicina - UFCA
TITLE:

ANALYSIS OF OXIDATIVE STRESS AND GROWTH IMPAIRMENT INDUCED BY IRON AND MANGANESE IN PPGPP0 MUTANT Bacillus subtilis

KEY WORDS:

Keywords: Bacillus subtilis, (p)ppGpp, Stringent response, Nutritional deficiency

PAGES: 62
BIG AREA: Ciências da Saúde
AREA: Medicina
SUMMARY:

Bacillus subtilis is a Gram-positive bacterium that produces lipopeptide antibiotics with antibacterial and antifungal functions. It is a non-pathogenic rod-shaped bacterium that forms biofilm and endospores and is used as a model microorganism for studies related to infectious diseases. This bacterium produces the nucleotide guanosine penta/tetraphosphate (p)ppGpp, which participates in several cellular processes. However, in situations of nutritional deficiency, these bacteria begin to undergo changes that activate the production of (p)ppGpp in larger 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 grown in 20 mL of liquid LB Broth (Lennox) medium with shaking or in solid LB Broth (Lennox) medium, both at 37 °C for 15 h. Bacterial growth was measured in the absence or presence of iron sulfate (FeSO4) and manganese sulfate (MnSO4) at different concentrations, every hour, for 10 h. Hydrogen peroxide (H2O2) levels were detected using AmplexRed/Horseradish peroxidase, and the activities of antioxidant enzymes (catalase and superoxide dismutase) were evaluated. Cellular respiration was measured using a Clark-type electrode. The tests demonstrated that the ppGpp0 mutants presented a growth delay compared to the PY79 control, and none of the cells grew in FeSO4 at a concentration of 4 mM. At concentrations equal to or lower than 1 mM of FeSO4, Bacillus subtilis tolerated well. However, compared to the wild type (PY79), the ppGpp0 mutant strain exhibited significantly increased sensitivity to FeSO4, showing delayed entry into the exponential phase of growth. The ppGpp0 mutant produced higher levels of H2O2 (in the stationary phase) when stimulated by FeSO4 (2 mM). MnSO4-induced stress caused a marked increase in the lag 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 FeSO4 and MnSO4. Antioxidant enzymes did not show significant differences in activities. It is concluded that the comparative studies between Bacillus subtilis PY79 and ppGpp0 strains were fundamental to confirm that the absence of the ppGpp nucleotide significantly compromises bacterial growth, resulting in a notable delay throughout the exponential phase in the presence of high concentrations of Fe2+ and Mn2+.Furthermore, the limitation of cell growth by Fe2+ is through a mechanism related to the redox state.

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