Netsu Sokutei, 31 (3), p. 117, (2004)



Evaluation of the Growth Activity of Microbial Colonies on Solid Medium using Calorimetry

In many cases, microbes exist on solid phase. Microbes on solid phase multiply as colonial growth. It is known that the growth on solid phase is different from the growth in liquid state. Comparing with microbes in liquid state, microbes on solid phase are hard to take nutrients. And the environment of microbes varies from place to place in the colony and affects the metabolism of microbes. Information of colonial growth of microbes on solid phase is required for prevention of putrefaction of solid food, utilization of soil microbes or investigation of a infection mechanism of pathogenic bacteria to an organism. However, the information regarding colonial growth of microbes on solid phase is not enough compared with that of microbes in liquid state by the reason of the absence of suitable and quantitative methods of estimating the colonial growth curve. In this article, microbial calorimetry is introduced to be the method suitable for non-destructive measurement of microbial colonial growth on solid phase. Changes in the metabolic heats of colonial growth with time (the growth thermogram) are obtained with good reproducibility. The actual heat evolution curves (f(t) curves) obtained from the thermograms of growing colonies give good agreement with the changes in viable cell numbers in colonies under the same conditions. Using microbial calorimetry, the colonial growth of microbes can be evaluated quantitatively. And still, the method is useful for evaluation of the complicated phenomenon by microbes such as putrefaction, and development of novel natural substances which suppress the colonial growth microbes.