A simple and rapid test for differentiation of aerobic from anaerobic bacteria

A rapid qualitative test is proposed for bacterial respiratory type based on 24 h culturing of bacteria in liquid medium supplemented with a redox indicator: methylene blue or resazurin. Five reference bacterial strains with definite respiratory type as well as nine bacterial isolates from a laboratory digester for methane fermentation were used. Results obtained showed that both indicators can be used for distinction of strict aerobes from other bacterial representatives with definite respiration. In addition, the resazurin is able to differentiate strict anaerobes from microaerophiles and other anaerobes. The main advantages of the methylene blue is that it is a cheap, easily accessible dye, wide-used in microbiological practice and the results obtained with it are more stable over time. It was also noticed that the test with both indicators gave reliable results for the bacterial respiration only when an inoculum up to 48 h old was used.