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Open Access Research article

Measurement of soil bacterial colony temperatures and isolation of a high heat-producing bacterium

Kenji Tabata1*, Fuminori Hida2, Tomoyuki Kiriyama2, Noriaki Ishizaki2, Toshiaki Kamachi2 and Ichiro Okura2

Author affiliations

1 Frontier Research Center, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan

2 Department of Bioengineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan

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Citation and License

BMC Microbiology 2013, 13:56  doi:10.1186/1471-2180-13-56

Published: 11 March 2013

Abstract

Background

The cellular temperatures of microorganisms are considered to be the same as those of their surroundings because the cellular volume is too small to maintain a cellular temperature that is different from the ambient temperature. However, by forming a colony or a biofilm, microorganisms may be able to maintain a cellular temperature that is different from the ambient temperature. In this study, we measured the temperatures of bacterial colonies isolated from soils using an infrared imager and investigated the thermogenesis by a bacterium that increases its colony temperature.

Results

The temperatures of some colonies were higher or lower than that of the surrounding medium. A bacterial isolate with the highest colony temperature was identified as Pseudomonas putida. This bacterial isolate had an increased colony temperature when it grew at a temperature suboptimal for its growth. Measurements of heat production using a microcalorimeter showed that the temperature of this extraordinary, microcalorimetrically determined thermogenesis corresponded with the thermographically observed increase in bacterial colony temperature. When investigating the effects of the energy source on this thermal behavior, we found that heat production by this bacterium increased without additional biomass production at a temperature suboptimal for its growth.

Conclusions

We found that heat production by bacteria affected the bacterial colony temperature and that a bacterium identified as Pseudomonas putida could maintain a cellular temperature different from the ambient temperature, particularly at a sub-optimal growth temperature. The bacterial isolate P. putida KT1401 increased its colony temperature by an energy-spilling reaction when the incubation temperature limited its growth.

Keywords:
Heat production; Thermogenesis; Thermograph; Growth-independent reaction; Energy-spilling reaction