Membrane entrapped Saccharomyces cerevisiae in a biosensor-like device as a generic rapid method to study cellular metabolism.

We describe a new, faster and convenient method to study some metabolic characteristics - by the successful application of immobilized yeast cells (S. cerevisiae) in a microbial biosensor-like device. Microbial biosensors consist of microorganisms immobilized on the surface of a membrane or in a gel, in close contact with a transducer. Almost all works published to date have used biosensors for analyses in which a concentration-related property of the external medium is measured. A different approach is presented here; we have successfully used S. cerevisiae and a carbon dioxide electrode as the main components of a biosensor-like device, used as a proof of concept, for a system useful to characterize metabolic parameters of the microbial cells immobilized on a carbon dioxide electrode. The biosensor-like device we are presenting allows us to calculate Michaelis-Menten parameters related to the kinetics of transport and degradation of several carbohydrates (i.e., glucose, fructose, galactose, sucrose and xylose, with K(m(app)) of 6.0, 5.8, 0.9, 2.0, and 147 mM, respectively), and the study of the kinetics of expression of non-constitutive proteins related to the transport and degradation of galactose.

Adaptación de Rhodopseudomonas palustris a cambios de condiciones atmosféricas / Adaptation of Rhodopseudomonas palustris to changes in atmospheric conditions

El burbujeo de O2 95%-N2 5% a un cultivo de Rhodopseudomonas palustris crecido en condiciones fotosintéticas provoca un cese inmediato de la síntesis de bacterioclorofila y una disminución de la actividad de la enzima delta-aminolevulinato sintetasa (ALA-S), sin alterar el crecimiento bacteriano. Al cesar el gaseado el nivel enzimático se recupera rápidamente pero el de bacterioclorofila lo hace más lentamente. El agregado de cloramfenicol al cesar el gaseado, no afecta la recuperación de la actividad enzimática. En cambio, si se lo agrega desde el inicio del gaseado, la actividad igual decae pero su recuperación es menor que en ausencia del antibiótico. La enzima de extractos de células gaseadas muestra activación espontánea a 40-C Se postula el efecto de distintos activadores sobre diversas formas de la enzima ALA-S para explicar estos hechos