Orientational Spectra Research Articles

Effect of Sulfonamides on the Electrophysical Properties of Bacterial Cells

Abstract: The effect of sulfonamide drugs on the electrophysical properties of Escherichia coli strains B-878 and K-12 was investigated by the example of sulfacetamide sodium (sulfacyl sodium). Substantial changes in the orientational spec-tra of cell suspensions incubated with various concentrations of sulfacetamide sodium occurred only at the first five fr e-quencies of the orienting electric field (740–2800 kHz). Sulfacetamide sodium at 0.08 µg/ml changed the magnitude of the electro-optical signal of the suspensions. A study of the time course of sulfacetamide sodium effect on the cells showed that the signal magnitude decreased by 57% of the no-drug control after 5 min of exposure to the drug and that on subsequent exposure, the signal magnitude remained almost unchanged (changes no greater than 5% of the no-drug con-trol). The spectral changes differed significantly for the sensitive and resistant strains. The orientational spectral changes induced by sulfonamides may be useful for testing the resistance of bacteria to this family of drugs.

Action of ampicillin and kanamicin on the electrophysical characteristics of Escherichia coli cells

We examined the effect of ampicillin and kanamycin on the electrophysical characteristics of ampicillin- and kanamycin-sensitive and ampicillin- and kanamycin-resistant Escherichia coli cells. Substantial changes in the orientational spectra (OS) of suspensions of cells incubated with various ampicillin and kanamycin concentrations took place only at the first five frequencies of the orienting electric field (10–1000 kHz). The maximal change in the magnitude of the electro-optical signal occurred at 50 µg mL−1 of ampicillin and 10 µg mL−1 of kanamycin. The suspension-OS changes did not depend on the antibiotic-action period. Under the action of ampicillin and kanamycin, sensitive and resistant E. coli strains gave different electro-optical (EO) effects. It follows that the sensitive and resistant E. coli strains exhibit different of the EO effect on the action of ampicillin and kanamycin. Thus, the suspension-OS changes occurring under the effect of ampicillin and kanamycin may be used as a test for resistance to this antibiotic in the cells studied.

The effect of ampicillin on the electrophysical properties of Escherichia coli cells

The study of the effect of ampicillin on the electrophysical properties of Escherichia coli cells showed that this antibiotic influences the orientational spectra (OS) of the ampicillin-susceptible E. coli strains K-12 and XL-1 within the frequency range 10-1000 kHz of the orienting electric field and does not affect the OS of the ampicillin-resistant strains K-12(pUC-18) and XL-1(pHEN1). The change in the electrooptical signal of the ampicillin-susceptible cells was maximum at an ampicillin concentration of 50 microg/ml and did not depend on the exposure time. The conclusion is drawn that changes in the OS of cells can be used to evaluate their resistance to ampicillin.

Determination of organophosphorus aromatic nitro insecticides by using electric-field cell orientation in microbial suspensions

We examined the effect of the cellular metabolism of the organophosphorus aromatic nitro insecticides metaphos and sumithion on the electro-physical properties (EPPs) of Pseudomonas putida C-11, P. putida BA-11, and Acinetobacter calcoaceticum A-122 suspensions. We used the dependences of cell-suspension absorbance changes induced by electric-field orientation on the orienting-field frequency in the range 10–10,000 kHz. Substantial orientational-spectrum changes, caused by insecticide action, occurred at frequencies of 10–1000 kHz. The plots of electro-optical effect versus insecticide-concentration were linear over the following concentration ranges: 0.5–3.0 mM metaphos and 0.5–3.5 mM sumithion for P. putida C-11 and BA-11; and 0.5–2.0 mM metaphos and 0.5–2.5 mM sumithion for A. calcoaceticum A-122. We discuss the possibility of developing a biosensor-method based on the measurement of cell-suspension orientational spectra (OS).

Electro-optical properties of microbial cells as affected by acrylamide metabolism

The electro-optical (EO) properties of a microbial cell suspension of a Brevibacterium strain were studied during the process of metabolism of acrylamide and certain other amides. Upon optimisation of cell growth conditions, followed by EO measurements, we found that acrylamide produced a specific effect on the cell orientational spectra (OS) over the frequency range 10 to 502 kHz. The other amides used also affected the EO properties of the cells.