Oxygen Profiles in, and in the Agar Beneath, Colonies of Bacillus Cereus, Staphylococcus Albus and Escherichia Coli

Department of Microbiology, University College Cardiff, Newport Road, Cardiff CF2 ITA, UK ABSTRACT SUMMARY: This paper reports the use of microelectrodes to measure O 2 penetration in different aged colonies of Bacillus cereus, Escherichia coli and Staphylococcus albus. In young (18 h) colonies of B. cereus and E. coli O 2 disappeared at depths of 25-30 µm and 35-40 µm respectively. In young S. albus colonies, O 2 reached a minimum but was never completely absent. As colonies aged (24-168 h) the depth to which O 2 penetrated increased. Present address: Ministry of Agriculture Fisheries and Food, Slough Laboratory, London Road, Slough SL3 7HJ, UK.