Microbial growth curves were obtained by overlapping the time intervals within which the optical density was measured. Optical densities of the suspension were measured spectrophotometrically on an SF-103 spectrophotometer (Akvilon, Russia) every two hours for 48 h at a wavelength of 540 nm and cuvette thickness of 1 cm relative to a cuvette with distilled water. The obtained dependences of optical density on time were used to plot the growth curves for the yeast and bacterial cells.
2.4. Optical microscopy
Pure cultures of the yeasts and bacteria and their co-cultures were investigated by the method of light field microscopy. A Biomed-6 triocular microscope (Biomed, Russia) was used for microscopic analysis; total magnification of the object was ×1600. Before viewing, preparations were fixed and stained. Yeast cells were stained with a fucsin solution; bacterial cells were Gram stained.