Efeito de Factores Ambientais na Via Biossintetica do Alginato em Pseudomonas aeruginosa dependencia da transcricao de genes do alinato e da ectividade de enzimas biossinteticas da fase do crescimento e das concentracoes de O_2 e Cu"2"+

Abstract

Among 33 Pseudomonas aeruginosa isolates from patients with nosocomial infections or cystic fibrosis (CF) or from water springs, 11 ribotypes were identified. Only 3 CF isolates produced the exopolysaccharide (EPS) alginate. The profiles of restriction fragments length polymorphism were identical for the mucoid and the respective non-mucoid spontaneous variant. The maximal alginate specific production was observed in the deceleration phase of growth of the high-producing strain P. aeruginosa 8821M, being the higher molecular mass EPS produced at the stationary phase. The activities of alginate biosynthetic enzymes phosphomannose isomerase (PMI), phosphomannomutase (PMM), GDP-mannose pyrophosphorylase (GMP) and GDP-mannose dehydrogenase (GMD) peaked earlier at the late exponential phase. Growth-phase-dependent activity of alginate enzymes correlates with the level of transcription of the encoding alginate genes algA (PMI-GMP), algC(PMM) and algD (GMD) during growth, concurring with the transcription of the regulatory gene AlgRl. Although the increase of dissolved oxygen tension (0-70% of air saturation) led to increased algA, algC and algD transcription, alginate production peaked at 5% or air saturation. This was attributed to oxidative inactivation of alginate enzymes, particularly of the most sensitive, PMI and PMM. Supplementation of growth medium with CuCl_2 (0 to 5 mM) stimulated, at intermediate concentrations, the transcription of alginate genes. However, alginate production was inhibited by Cu"2"+, as the result of oxidative inactivation, despite the induction by Cu"2"+ of the antioxidative response. This response involved the increase of the specific activity of catalase, superoxide dismutase (with the induction of the manganese-dependent activity) and glucose 6-phosphate dehydrogenaseAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga