Features of growth of microorganisms on a nutrient medium and their microscopic researches were studied. Cavitation treatment (22 kHz, 91 W, 1.65 W/сm3) of water with simultaneous action of bubbled inert gases (argon and helium) on the viability of microbial cells (Diplococcus and Sarcina) are presented. The highest water disinfection was obtained for water samples with Sarcina lutea cells for both used gases under cavitation conditions. Both investigated types of the cocci bacteria were destroyed faster under Ar/US-action after comparison of the effectiveness of the gas nature action on the water disinfection.