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.