Comparison of culture methods for enumeration of microaerophilic bacteria in marine sediments

Agar-mixed cultures in semi-solid media provide a range of oxygen concentrations which fulfill microaerophilic bacterial requirements. Such conditions are more suitable than those provided by liquid media since, in broth cultures, the oxygen concentration must be determined at a level which might later show a lack of or excess of sensitivity to microaerophilic bacteria, thereby giving an erroneous count. A high content of organic substrates appears to be disadvantageous. It can prevent enumeration of microaerophilic growing rings or even induce false results. Minielectrodes permit the control of the oxygen concentration in each growing ring so as to confirm the efficiency of the culture method used for a selective count of microaerophilic bacteria. Semi-solid seawater culture medium supplemented with calcium succinate at 0.5 gram per litre appears to be an adequate culture medium for counting microaerophilic bacteria in marine sediments.