This can be accomplished using solid media (eg agar or uncompac

This can be accomplished using solid media (e.g. agar or uncompacted soil). For soil studies, Ljungholm et al. (1979) have demonstrated that the problem can be readily solved. They closed their ampoules with a 1-mm-thick porous silicone rubber seal because the material readily transmits simple gases. This procedure was shown to allow sufficient gas exchange (O2 and CO2), without significant loss of water, between the calorimetric ampoule and the atmosphere. Similarly, addition of glucose as a powder and not as this website a solution to soil samples combined with

the use of a flow-through cell is also a simple means to achieve calorimetric measurements in soil samples (Sparling, 1983) without reaching oxygen depletion. Finally, it is also possible to calculate the amount of oxygen present in the headspace of the calorimetric ampoule and calculate the amount of substrate that can be consumed using this oxygen. Using such simple calculations, Vor et al. (2002) were able to estimate when the transition from oxic to anoxic conditions in soil samples occurred and study changes in the metabolic heat production associated with this transition. Similarly, the use of agar medium or other solid growth substrates allows microorganisms to grow on top of the medium and therefore remain in contact with oxygen anti-CTLA-4 antibody present in the headspace (Wadsöet al., 2004).

Furthermore, a closed environment can also be analytically advantageous – for mass balance calculations for example. Finally, it must be noted that the heat flow signal is a nonspecific, net signal related to the sum of all chemical and physical processes taking place in an IMC FAD ampoule. As a consequence, unknown phenomena may produce some of the heat measured, and there may be simultaneous exothermic and endothermic processes taking place (Lewis & Daniels, 2003). However, well-described phenomena can be studied

under controlled conditions with a high accuracy [see the ‘diauxie’ (Monod, 1949) example in Fig. 1, Table 2]. Careful planning of IMC experiments is of great importance. Logical experimental designs must be devised and used that ensure that the observed heat flows are directly related to the processes of interest. IMC has been used in many different fields of microbiology. Medical and environmental applications provide an indication of the possibilities. One noteworthy medical application is rapid isothermal microcalorimetric detection of bacterial infection or contamination, which is of critical importance in quickly implementing the correct treatment. Recent studies have shown that with IMC, it is possible to detect bacterial contamination of donated blood platelets within a few hours (Trampuz et al., 2007). Similarly, it is also possible to determine inhibitory effects and/or the minimal inhibitory concentration for different antimicrobial compounds and microorganisms within hours using IMC (Xi et al., 2002; Yang et al., 2008; von Ah et al., 2009).

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