Conditions influencing the growth-promoting/sustaining effects of carbon material in agar plates

Mixing powdered graphite or activated charcoal into nutrient-rich agar plat es under ordinarily non-permissive stress conditions caused promotion and s ustenance of the growth of Bacillus carboniphilus. The growth of the cells was approximately proportional to the amount of carbon material in the agar plate, and was markedly, although not completely, inhibited by shielding t he culture system from some of the external oscillations (i.e., electromagn etic radiation) with aluminum foil. Growth in the presence of carbon materi al was strongly increased at culture temperatures between 43.0 and 43.5 deg rees C. Temperatures lower than 42 degrees C were not lethal, while those a bove 44 degrees C were usually lethal even in the presence of carbon materi al (0.75% agar plate). Growth of bacteria in the presence of graphite under these standard conditions was close to 100% of the inoculum on 2% agar but less than 20% on 0.6% agar. Thus, the promotion/sustenance of the growth o f B, carboniphilus on stress-agar plates containing carbon material was inf luenced by temperature and the concentrations of KCl and agar, as well as e xternal energies such as some oscillations. The results indicate that the m echanism of the growth-promoting/sustaining effect of carbon in the agar pl ate is similar, at least in part, to that of the remote effect of the carbo n material located distantly, as reported previously.