Effect of CO2 on colony development by Bifidobacterium species.

This report investigates the requirement for CO2 for colony formation by Bifidobacterium species in both anoxic and oxic environments. All tested Bifidobacterium species exhibited difficulty in developing colonies in an atmosphere of 100% N2 but developed well when 1% CO2 was present. In the presence of CO2, the oxygen tolerance of the tested species was not improved. In the absence of CO2, only B. boum, a microaerophilic species, could develop colonies under an N2-based 5% O2 atmosphere, indicating that while CO2 is not an essential factor for colony development, both CO2 and O2 have stimulatory effects on B. boum colony development.