title: Investigation of the toxic effect of cadmium on Candida humicola and Bacillus subtilis using a microcalorimetric method.
abstract: In this study, the technique of microcalorimetry based on heat-output by aerobic bacterial respiration was explored to evaluate the toxic effect of cadmium on Candida humicola, Bacillus subtilis, singularly or in a mixture of both. Power-time curves of the growth metabolism of C. humicola and B. subtilis and the effect of Cd(2+) were studied using the TAM III (the third generation thermal activity monitor) multi-channel microcalorimetric system, isothermal mode, at 28 degrees C. The differences in shape of the power-time curves and the thermodynamic and kinetic characteristics of microorganisms growth were compared. The effect of cadmium added into microorganism would significantly reduce the life cycle and change the thermal effect of microbial metabolic process with different concentrations of Cd(2+). The experimental results revealed that at the same concentration, the sequence of inhibitory ratio (I) and maximum thermal power (P(max)) of the Cd(2+) was: mixed microorganisms>C. humicola>B. subtilis. The sequence of total thermal effect (Q(total)) and growth rate constant (k) is mixed microorganisms>B. subtilis>C. humicola. These results are important to further studies of the physiology and pharmacology of C. humicola and B. subtilis and may support the theory of restoring contaminated soil.
authors.affiliation: School of Environmental Studies & Key Laboratory of Biogeology and Environmental Geology of Chinese Ministry of Education & Sino-Hungarian Joint Laboratory of Environmental Science and Health, China University of Geosciences, 430074 Wuhan, PR China.
authors.forename: Hai-Yan
authors.initials: HY
authors.lastname: Chen
authors.forename: Jun
authors.initials: J
authors.lastname: Yao
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhou
authors.forename: Hui-Lun
authors.initials: HL
authors.lastname: Chen
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.forename: Nan
authors.initials: N
authors.lastname: Gai
authors.forename: Ren-Sheng
authors.initials: RS
authors.lastname: Zhuang
authors.forename: Brunello
authors.initials: B
authors.lastname: Ceccanti
authors.forename: Thomas
authors.initials: T
authors.lastname: Maskow
authors.forename: Gyula
authors.initials: G
authors.lastname: Zaray
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects*; D019187:Cadmium Compounds / Q000633:toxicity*; D002151:Calorimetry; D002175:Candida / Q000187:drug effects*; D003470:Culture Media; D012988:Soil Microbiology; D013816:Thermodynamics
chemical_list: D019187:Cadmium Compounds; D003470:Culture Media