Influence of Aerobic Bacteria Concentration on the Process of its Survival in the Presence of Oxygen

Abstract

Purpose of the study is to study the viability of aerobic microorganisms in an oxygen atmosphere with different initial content in the aquatic medium. Compare the effect of gas on different concentrations of bacteria per unit volume of the water. Methods. Aerobic bacteria of the genus Bacillus cereus bacteria type were the studied microorganisms. Model aqueous media were created on the basis of distilled deaerated water with the addition of bacteria of a particular type. Oxygen was bubbled into the microbial water throughout the process at a rate of 0.2 cm3/s. The duration of the study was 2 hours, during which the total gas consumption corresponded to 1.4 dm3. The number of microorganisms (NM) before and after the experiments was determined by counting the colonies that grew on the Petri dishes. Results. A two-stage process of oxygen exposure to aerobic bacteria was detected - accumulation and reduction of its number per unit volume of water during all experiments. At the first stage of the process, there was an increase of NM during 1800-3600 s with its subsequent decrease (II stage). With an increase in the microbial load in the water from 102 to 104 CFU/cm3, the duration of the process of bacterial accumulation was decreased in two times. An active reproduction of bacterial cells was investigated at the low concentration of bacteria in the water, and its active reduction - at the high concentration that is explained by cells destruction under conditions of constant supply of oxygen of the established rate. Conclusions. The oxygen influence on the change of the number of aerobic microorganisms in the aquatic medium is explained. It is investigated that the oxygen action on bacteria in the water divides the process of its viability into two stages: accumulation (I stage) and reduction of its number (II stage). It is shown that the duration of the process of bacteria accumulation in the oxygen atmosphere depends on its initial amount in the water, namely with increasing of the initial NM per unit volume of the water, the duration of the stage of microorganisms accumulation decreases significantly.