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Thèse de Doctorat
DOI
10.11606/T.42.2014.tde-24092014-161707
Document
Auteur
Nom complet
Fernanda Nogales da Costa Vasconcelos
Unité de l'USP
Domain de Connaissance
Date de Soutenance
Editeur
São Paulo, 2014
Directeur
Jury
Spira, Beny (Président)
Baldini, Regina Lúcia
Fernandes, Andrea Balan
Galhardo, Rodrigo da Silva
Maldonado, Gabriel Padilla
Titre en portugais
Caracterização dos genes phoA1phoA2, phoB, phoU e PstS, membros do regulon PHO de Chromobacterium violaceum.
Mots-clés en portugais
Chromobacterium violaceum
Regulon PHO
Resumé en portugais
Chromobacterium violaceum é uma bactéria de vida livre, móvel, que habita fontes de água e solos pobres de regiões tropicais e subtropicais. Nestes habitats, em que a concentração de fosfato é baixa, o regulon PHO encontra-se ativado. No laboratório, esta bactéria é capaz de crescer razoavelmente bem, apesar da limitação de fosfato, atingindo um rendimento celular similar ao observado na abundância deste nutriente. Mutações nos genes pstS, phoU, phoA1 e phoA2 foram construídas. As mutações pstS e phoU não causaram qualquer alteração no padrão de expressão da fosfatase alcalina, sugerindo que estes genes não participam da repressão dos genes de PHO. Porém, o mutante pstS mostrou-se deficiente na captação de Pi. Os mutantes phoA1 e phoA2 apresentaram, cada um, severa redução na atividade da fosfatase alcalina. Foi investigada a possibilidade de PhoA1 e PhoA2 formarem uma proteína heterodimérica. Fusões transcricionais entre phoU e phoB ao gene lacZ, revelaram que estes genes respondem à carência de Pi. Surpreendentemente, C. violaceum se mostrou pouco resistente a estresses ambientais.
Titre en anglais
Characterization of phoA1, phoA2, phoB, phoU, e pstS genes, members of the PHO regulon from Chromobacterium violaceum.
Mots-clés en anglais
Chromobacterium violaceum
PHO regulon
Resumé en anglais
Chromobacterium violaceum is a free-living, mobile bacterium that inhabits water sources and soils of tropical and subtropical regions, where the phosphate concentration is low. The PHO regulon is activated in response to low phosphate concentration in the environment. Surprisingly, the growth yield of C. violaceum under phosphate excess or under phosphate limitation is very similar. Mutations in pstS, phoU, phoA1 and phoA2 genes were constructed. The expression of alklaine phosphatase was not affected by the phoU and pstS mutations, suggesting that these genes do not participate in the repression of the PHO regulon. However, the pstS mutant was deficient in the uptake of Pi. The phoA1 and phoA2 mutants presented each one a severe reduction in alkaline phosphatase activity. The hypothesis that PhoA1 and PhoA2 form a heterodimeric protein was investigated. Transcriptional fusions between the promoters of phoB and phoU to lacZ showed that these genes respond to Pi starvation. Stress resistance assays showed that C. violaceum is generally sensitive to environmental stresses.
 
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Date de Publication
2014-10-07
 
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