An acoustic method for the analysis of bacterial cells

The application of a biological electroacoustic sensor based on a lateral electric-field-excited piezoelectric resonator for the study of bacterial cells that interact with specific bacteriophages, mini-antibodies, and polyclonal antibodies was successfully demonstrated. The determined lower limit of microbialcell detection was approximately of 10³ to 10⁴ cells/mL for the duration of the assay of 10 min. The possibility of bacterial-cell detection via interaction with specific agents in the presence of extraneous microbiota was shown. The method allowed us to determine the spectrum of lytic activity of bacteriophages and the sensitivity of microbial cells to bacteriophages. The results of the study showed that application of a sensor piezoelectric lateral-field resonator is a promising technique for the detection and identification of microbial cells and determination of their phage resistance in microbiology, medicine, and veterinary medicine. Furthermore, the results of the experiments made it possible to understand the mechanisms of the processes that occur in a suspension of bacterial cells in the presence of various biological agents. The method also may provide useful information regarding biophysical mechanisms of interactions that occur in microbial populations.     

Application of the method of electro-acoustical analysis for the detection of bacteriophages in a liquid phase

The possibility of the application of electro-acoustic analysis for the detection of bacteriophages was demonstrated for the first time based on the example of the interaction of the FA1-Sp59b bacteriophage with bacterial cells of the strain Azospirillum lipoferum Sp59b. Piezoelectric cross-field resonators with a 1-mL chamber for analyzed liquid were used as the biological sensor. It was revealed that the dependences of the real and imaginary parts of the electrical impedance of the resonator loaded with a suspension of viruses and microbial cells on the frequency was significantly different from those dependences of the resonator that contained a control cell suspension without the virus. It was shown that detection of the FA1-Sp59b bacteriophage using microbial cells was possible with both extraneous viral particles and extraneous microbial cells. The proposed method allows one to accurately determine the type of identified virus after a 5-minute interaction with indicating bacterial culture. As well, the minimum concentration of viruses is five virus particles per cell. These results as a whole demonstrate the possibility of detecting specific interactions of bacteriophages with microbial cells and provide a basis for the development of a biological sensor for the quantitative detection of viruses directly in the liquid phase.     

Analysis of interaction of bacterial cells and bacteriophages in conducting suspensions with an acoustic sensor

The possibility of analyzing bacterial cells infected by a specific bacteriophage, using Escherichia coli as an example, with an acoustic sensor directly in suspensions with different initial electrical conductivities was studied. The analysis was based on measurement of the time dependence of phase and the complete loss of output sensor signals of fixed frequency before and after biological interaction of microbial cells and bacteriophages. The aforementioned sensor makes it possible to detect bacterial cells and assess their viability in conducting suspensions. It was shown that the conductivity of the buffer solution should not exceed 10 μS/cm and the minimum detectable concentration of microbial cells was ~10⁴ cells/mL.     

A Study of the Effect of Terahertz Electromagnetic Radiation on Microbial Cell Viability

Biophysics - Abstract—The effect of pulsed terahertz radiation at a wavelength of 66 μm, a pulse duration of 100 ns, and a pulse energy of 200 mJ on a suspension of microbial cells was...     

Immunodetection of bacteriophages by a piezoelectric resonator with lateral electric field

It has been demonstrated that electroacoustic analysis with polyclonal antibodies can be used for bacteriophage detection. The frequency dependences of the real and imaginary parts of electrical impedance of a resonator with a viral suspension with antibodies were shown to be essentially different from the dependences of a resonator with control viral suspension without antibodies. It was shown that ΦAl-Sp59b bacteriophages were detected with the use of antibodies in the presence of foreign virus particles. The ΦAl-Sp59b bacteriophage content in the analyzed suspension was ~10¹⁰–10⁶ phages/mL; the time of analysis was no more than 5 min. The optimally informative parameter for obtaining reliable information was the change in the real or imaginary part of electrical impedance at a fixed frequency near the resonance upon the addition of specific antibodies to the analyzed suspension. It was demonstrated that the interaction between bacteriophages and antibodies can be recorded, offering good prospects for the development of a biological sensor for liquid-phase identification and virus detection.     

A method of acoustic analysis for detection of bacteriophage-infected microbial cells

The dependence of the changes of physical parameters of the suspension of Azospirillum brasilense Sp7 cells infected by FAb-Sp7 bacteriophage on their number and exposure time was studied using a biological sensor based on a piezoelectric resonator with a lateral electric field. The change in the value of the analytical signal was recorded at 1 minute from the beginning of the infection of the cells by bacteriophage. The selectivity of the action of the FAb-Sp7 bacteriophage was studied for Azospirillum brasilense (strains Cd, Sp107, Sp245, Jm6B2, Br14, KR77, S17, S27, SR55, and SR75), A. lipoferum (strains Sp59b, SR65, and RG20a), A. halopraeferans Au4, Nitrospirillum amazonense Am14, Niveispirillum irakense (strains KBC1 and KA3) bacteria, as well as for heterologous bacteria of the genera Escherichia coli (strains XL-1 and B-878), Pseudomonas putida (strains C-11 and BA-11), and Acinetobacter calcoaceticum A-122. The limit of the reliable determination of the concentration of microbial cells during bacteriophage infection process was found: ~10⁴ cells/mL. At the same time, the presence of heterologous cell cultures (E. coli XL-1 cells) did not complicate the detection. It was shown that the method of electroacoustical analysis of cell suspensions can be used for the detection of microbial cells of Azospirillum infected by the FAb-Sp7 bacteriophage. The results are promising for the development of methods for determining and controlling the number of soil microorganisms.