RESUMO
The laboratory isolation of Legionella pneumophila from seeded donor blood, using the lysis-centrifugation technique, is described. Time to pure culture isolate was 3 to 4 days.
Assuntos
Bactérias/isolamento & purificação , Técnicas Bacteriológicas , Sangue/microbiologia , Doença dos Legionários/microbiologia , HumanosRESUMO
A mating between Escherichia coli 4318 (thi leu Las- Hfr) and E. coli A-1 (Met- Las+ F-) resulted in the formation of prototrophic recombinants having L-asparaginase activities at three distinct levels. The physiology of L-asparaginase synthesis in these recombinants is decribed. One class of recombinants produced significantly more L-asparaginase than E. coli A-1. L-Asparaginase synthesis in the recombinants was inhibited by the presence of dissolved oxygen in the medium and was transiently repressed by the presence of glucose in the same manner as that observed in the parental strains. L-Asparaginase activity was increased by the addition of oxalacetate as well as other members of the tricarboxylic acid cycle.
Assuntos
Asparaginase/biossíntese , Escherichia coli/enzimologia , Recombinação Genética , Asparaginase/metabolismo , Repressão Enzimática , Escherichia coli/genética , Glucose/farmacologia , Glutaminase/metabolismo , Concentração de Íons de Hidrogênio , Oxaloacetatos/farmacologia , Oxigênio/farmacologiaRESUMO
The nutritional requirements and culture conditions affecting biosynthesis of L-asparaginase in a mutant of Escherichia coli HAP designated strain A-1 were studied. Asparaginase activity was increased by the addition of L-glutamic acid, L-glutamine, or commercial-grade monosodium glutamate. The rate of enzyme synthesis was dependent on the interaction between the pH of the culture and the amount of oxygen dissolved in the medium. A critical oxygen transfer rate essential for asparaginase formation was identified, and a fermentation procedure is described in which enzyme synthesis is controlled by aeration rate. Enhancement of L-asparaginase activity by monosodium glutamate was inhibited by the presence of glucose, culture pH, chloramphenicol, and oxygen dissolved in the fermentation medium.