Thermochimica Acta 471 (2008) 86–89 Contents lists available at ScienceDirect Thermochimica Acta journal homepage: www.elsevier.com/locate/tca Calorimetric investigation of m-methoxyphenol effect on Chromobacterium violaceum activity in soil Denise A. Oliveira a , Nieves Barros b , Claudio Airoldi a,∗ a Instituto de Qu´ımica, Universidade Estadual de Campinas, Caixa Postal 6154, 13084-971 Campinas, S˜ao Paulo, Brazil b Department of Applied Physics, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain article info Article history: Received 6 November 2007 Received in revised form 6 March 2008 Accepted 10 March 2008 Available online 18 March 2008 Keywords: Microcalorimetry Soil microorganisms Chromobacterium violaceum m-Alkoxyphenol abstract The microbial activity of Chromobacterium violaceum inoculated in sterile and natural red latosol soil samples was monitored by calorimetry to investigate metabolism of the native organic matter, easily degradable substrates (glucose) and the bacterial inhibitor m-alkoxyphenol. The results show that C. violaceum in sterile soil grows for a few hours, or, if easily degradable nutrients are available in soil, for 80 h. Inoculation of C. violaceum in unsterilized soil affected the metabolism of the native microflora in the presence of m-methoxyphenol with increases in the dissipation of heat per unit of growth. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Chromobacterium violaceum, a Gram-negative rod-shaped bac- terium, is a saprophyte of soil and water in tropical and subtropical areas and although it is generally considered to be non-pathogenic [1], some cases of fatal septicemia caused by this bacterium have been reported [2,3]. High numbers of this bacterium can be found in water and in soil on the banks of the Negro river [4], one of the largest tributaries of the Amazon river in Brazil. The metabolites synthesized by C. violaceum have potential application in several biotechnological and pharmacological research areas, and for this reason its genome sequencing has been promoted by a Brazilian Laboratories Consortium [5–7]. It can hydrolyze plastic films, pro- ducing cyanide, and this process could be useful in the extraction of gold, avoiding the use of mercury and the consequent environ- mental contamination [2,5]. There are no reports on the metabolism of C. violaceum in soil. The activity of this bacteria was measured previously by calorimetry in pure cultures to determine the effects of anionic surfactants [8,9] and uncouplers of oxidative phosphorylation [10,11]. Calorimetry can be applied to monitor the activity of C. violaceum in soil, and addition of nutrients can be used to stimulate microbial activity to obtain information on microbial degradation of soil substrates [12–17]. The present investigation ∗ Corresponding author. E-mail address: airoldi@iqm.unicamp.br (C. Airoldi). measured the thermal effects of C. violaceum metabolism in soil to obtain information on bacterial production of CO 2 from soil organic carbon. A second objective of this study is to explore the toxicity of m-methoxyphenol on C. violaceum in soil and on soil microflora. m-Alkoxyphenol is commonly employed in bio- transformation reactions [18] due to the high lipophilic activity with irreversible damage to cell walls and membranes [11]. The effect of these compounds on microbial respiration by flow-through calorimetry [10,18] has previously been used as an indicator of their toxicity. A second objective of this study is to explore the toxicity of m-methoxyphenol on C. violaceum in soil and on soil microflora. 2. Experimental 2.1. Maintenance and storage A C. violaceum suspension (1 ml) was inoculated into a 1500 ml reactor flask (B. Braun Biotech, Biostat B2) containing the sterilized culture medium whose composition (g l −1 ) was: 3.0 of yeast extract, 7.5 of glucose and 7.5 bacteriologic peptone in distilled water. This culture medium was maintained at 298 K under shaking (200 rpm) with an air flow of 2.0 l min −1 , for 14 h. The cells were separated from the culture medium by centrifu- gation at 4000 rpm for 20 min, washed three times and suspended in sterilized phosphate buffered solution (PBS), whose composi- tion (g l −1 ) was: 8.0 NaCl, 0.20 KCl, 1.15 Na 2 HPO 4 and 0.20 KH 2 PO 4 ; then the mixture was centrifuged and the cells suspended again in 100ml sterile PBS solution containing 10% of dimethylsulfoxide. 0040-6031/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.tca.2008.03.002