RESUMEN
The structure of bacterial suspensions of Escherichia coli M-17 at the counting concentrations of the cells 10(7), 10(8), 10(9) i/ml and in the temperature range of (18-50) degrees C has been investigated by means of orientational conductometric, electron microscopic and UV-spectroscopic methods. On the basis of experimental relationships of the anisotropy of suspensions electric conductivity upon the intensity of a sinusoidal electric field and relaxation of anisotropy after switching off the field the function of the distribution of bacteria with respect to their sizes was evaluated at different temperatures and concentrations. The conductometric function of bacteria distribution is in a good agreement with the analogous function obtained with the help of the electron microscope. In accordance with the functions the suspension of E. coli contained three kinds of cells: high electronic density, low electronic density bacteria and bacteria aggregates. Relative amounts of every kind of bacteria depended on temperature and concentration of cells. The minimum of bacteria aggregates and maximum of low electronic density cells were obtained in the temperature range of (32-42) degrees C. This fact could be explained by the activation of the transport membrane systems in this temperature range. This hypothesis was confirmed by the UV-spectroscopic method.
Asunto(s)
Escherichia coli , Conductometría , Escherichia coli/ultraestructura , Microscopía Electrónica , Espectrofotometría Ultravioleta , TemperaturaRESUMEN
Electro-conductive anisotropy of DNA solution caused by the molecular orientation in the external electric field was investigated. The dependence of a relative change of the conductivity of aqueous-salt DNA solution on the electric field in the amplitude range 0-700 V/cm and in the frequency range 100 Hz-10 kHz was studied. It was pointed out that the field thermal effect is an overcoming factor when the orientation of DNA molecules is investigated by field-free relaxation.
Asunto(s)
ADN , Conductividad EléctricaRESUMEN
The anisotropy of electrical conductivity of suspensions of such bacteria, as E. coli, Serratia marcescens, Pseudomonas fluorescens induced by a sinusoidal external electric field and relaxation of the anisotropy after switching off the field were investigated. On the basis of the experimental relationships the anisotropy of electrical polarizability and coefficient of rotational diffusion of the cells were evaluated. The anisotropy of electrical polarizability and coefficient of the rotational diffusion obtained are in a good agreement with the available data of other methods.