Modulation of osmotic stress effects on photosynthesis and respiration by temperature in mesophyll protoplast of pea.

Exposure of mesophyll protoplast of pea to osmotic stress decreases the rate of photosynthesis while stimulating marginally the respiratory rate of mesophyll protoplasts. The interaction of osmotic and temperature stress during the modulation of photosynthetic and respiratory rates of pea (Pisum sativum var Azad P1) mesophyll protoplasts was investigated. The protoplasts were exposed to either iso-osmotic (0.4 M) or hyper-osmotic (1.0 M) concentration of sorbitol at 15 degrees and 25 degrees C. The rates of photosynthesis and respiration were studied. At optimum temperature of 25 degrees C, there was a decrease in photosynthesis (< 10%) at hyper-osmoticum (osmotic effect), whereas respiration increased marginally (by about 15%). Low temperature (15 degrees C) aggravated the sensitivity of both respiration and photosynthesis to osmotic stress. At 15 degrees C, the decrease in photosynthesis due to osmotic stress was > 35%, while the respiratory rate was stimulated by 30%. The relative proportion of cytochrome pathway decreased by about 50% at both 15 degrees C and 25 degrees C while that of alternative pathway increased, more so, at 15 degrees C, when the mesophyll protoplasts were subjected to hyper-osmoticum stress. The titration experiments showed that extent of engagement of alternative pathway was higher, the slope value was slightly higher for 15 degrees C compared to 25 degrees C. Low temperature modulates the effect of hyper-osmoticum stress on photosynthesis and respiration, and results in increased participation of alternative pathway.

Studies on isolation and regeneration of protoplast of thermophilic fungus Malbranchea Pulchella VAR. sulfurea

Protoplastos esféricos osmoticamente sensíveis foram isolados de micélio do fungo termofílico Malbranchea pulchella var. sulfurea pela açäo de enzima extracelular (Novozym 234) sobre a parede das células. Estäo descritas as condiçöes para obtençäo de protoplastos estáveis a partir do micélio. O uso de KCL 0,6M como estabilizador osmótico permitiu a liberaçäo do número máximo de protoplastos. A maior parte dos protoplastos foram liberados a partir de micélios cultivados por 96 - 148 h, embora micélios mais jovens liberassem protoplastos mais estáveis e maiores em tamanho. Determinou-se, também, a açäo da enzima sobre a superfície do micélio. O número máximo de protoplastos foi observado em pH 5,5. Estudaram-se também as condiçöes requeridas para a regeneraçäo dos protoplastos

Incremento en la producción de eritromicina por fusión de protoplastos de Streptomyces erythreus / Increasing in the production of erythromycin by fusion of protoplasts of Streptomyces erythreus

El método de fusión de protoplastos fue usado para la obtención de recombinantes con producción antibiótica incrementada en Streptomyces erythreus productora de eritromicina. Se emplearon los mutantes morfológicos 36 UV y P-E obtenidos por luz UV y luz UV-acriflavina respectivamente, los cuales poseían marcadores de resistencia a cloranfenicol y rifampicina. Se establecen las condiciones más apropiadas para la obtención y fusión de protoplastos en estas cepas, llegándose a obtener recombinantes resistentes a ambos antibióticos a frecuencia de 0,57 %, dentro de las cuales fue seleccionado uno con incremento de 4 veces en la producción de eritromicina