Microcalorimetric performance of the growth in culture of Escherichia coli, Proteus mirabilis and their mixtures in different proportions
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Microcalorimetry is a technique that determines the heat flow produced as a result of microbial activities. The heat variations resulting from chemical reactions, which take place during metabolism, can be used to monitor bacterial growth in a culture medium. However, there are very few studies using calorimetry to investigate the relationships between two bacteria. In this work, we studied the interaction between E. coli and P. mirabilis, two bacteria belonging to the family Enterobacteriaceae. We have prepared three samples, mixing both enterobacteria at a concentration of 103 CFU mL−1 but in different proportions. Experimental equipment used was a Calvet microcalorimeter, where a constant temperature of 309.65 K was maintained. Then, we compared the shape of the heat flow–time curves of single microorganisms and their mixtures. Also, we calculated the thermokinetic parameters such as growth constant (k), generation time (G), detection time (t d) and the amount of heat released (Q). The results obtained showed that when E. coli and P. mirabilis were put together in the culture medium, the growth profile of P. mirabilis seemed to dominate, even at low proportions in the sample.
KeywordsMicrocalorimetry Bacteria Metabolism Escherichia coli Proteus mirabilis
We thank María Perfecta Salgado Gonzalez and Sofia Baz Rodríguez for their collaboration with the technical measures. We are also thankful for the financial support provided by the projects EM 2012/141, CN 2012/285, and ‘Agrupación Estratégica de Biomedicina (INBIOMED)’ by ‘Xunta de Galicia’ and the project FIS 2011-23322 funded by Ministry of Science and Innovation of Spain. All these projects are co-financed with FEDER funds.
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