title: Microcalorimetric measurements of the microbial activities of single- and mixed-species with trivalent iron in soil.
abstract: A microcalorimetric technique was applied to a series of experiments to follow the toxic effect caused by the trivalent iron on the single and mixed microbes in sterilized soil that was inoculated with the single Bacillus subtilis (B. subtilis) (prokaryotic bacterium), single Candida humicola (C. humicola) (eukaryotic fungus) and the mixed-species. The microbial activity was stimulated by the addition of 5.0mg glucose and 5.0mg ammonium sulfate under a 35% controlled humidity in the studied soil samples of 1.2g. The power-time curves from every experiment were analyzed, and from these analyses characteristic parameters, such as growth rate constant (k) and total thermal effect (Q) which can reflect the biochemical reactions were determined. The mixed-species have moderate tolerance to the iron overload, comparing with single species, and exhibit synergistic interaction in exponential growth phase (0-400.0 microg mL(-1)). Meanwhile, there is no much difference in the thermal effect (Q) per gram soil sample for the single and mixed culture. This also validates that the nutrient substances in natural environment determine the organisms' metabolic activities. Ultraviolet-visible spectrophotometry and dissolved oxygen sensor also were successfully applied to reflect the activities of B. subtilis and C. humicola in the pure culture. The investigation could provide insight into the microbial ecology of bacteria and fungi in ecological niches.
authors.affiliation: School of Environmental Studies and Key Laboratory of Biogeology and Environmental Geology of Chinese Ministry of Education and Sino-Hungarian Joint Laboratory of Environmental Science and Health, China University of Geosciences, 430074 Wuhan, PR China.
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.affiliation: School of Environmental Studies and Key Laboratory of Biogeology and Environmental Geology of Chinese Ministry of Education and Sino-Hungarian Joint Laboratory of Environmental Science and Health, China University of Geosciences, 430074 Wuhan, PR China. Electronic address: yaojun@cug.edu.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Yao
authors.affiliation: School of Environmental Studies and Key Laboratory of Biogeology and Environmental Geology of Chinese Ministry of Education and Sino-Hungarian Joint Laboratory of Environmental Science and Health, China University of Geosciences, 430074 Wuhan, PR China.
authors.forename: Huilun
authors.initials: H
authors.lastname: Chen
authors.affiliation: School of Environmental Studies and Key Laboratory of Biogeology and Environmental Geology of Chinese Ministry of Education and Sino-Hungarian Joint Laboratory of Environmental Science and Health, China University of Geosciences, 430074 Wuhan, PR China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: School of Environmental Studies and Key Laboratory of Biogeology and Environmental Geology of Chinese Ministry of Education and Sino-Hungarian Joint Laboratory of Environmental Science and Health, China University of Geosciences, 430074 Wuhan, PR China.
authors.forename: Yanjiao
authors.initials: Y
authors.lastname: Chen
authors.affiliation: School of Environmental Studies and Key Laboratory of Biogeology and Environmental Geology of Chinese Ministry of Education and Sino-Hungarian Joint Laboratory of Environmental Science and Health, China University of Geosciences, 430074 Wuhan, PR China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Chen
authors.affiliation: School of Environmental Studies and Key Laboratory of Biogeology and Environmental Geology of Chinese Ministry of Education and Sino-Hungarian Joint Laboratory of Environmental Science and Health, China University of Geosciences, 430074 Wuhan, PR China.
authors.forename: Nan
authors.initials: N
authors.lastname: Gai
authors.affiliation: School of Environmental Studies and Key Laboratory of Biogeology and Environmental Geology of Chinese Ministry of Education and Sino-Hungarian Joint Laboratory of Environmental Science and Health, China University of Geosciences, 430074 Wuhan, PR China.
authors.forename: Rensheng
authors.initials: R
authors.lastname: Zhuang
authors.affiliation: School of Environmental Studies and Key Laboratory of Biogeology and Environmental Geology of Chinese Ministry of Education and Sino-Hungarian Joint Laboratory of Environmental Science and Health, China University of Geosciences, 430074 Wuhan, PR China.
authors.forename: Lin
authors.initials: L
authors.lastname: Tian
authors.affiliation: UFZ Centre for Environmental Research Leipzig, 04318 Leipzig, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Maskow
authors.affiliation: Institute of Ecosystem Studies, Research Unit of Pisa, National Council of Researches, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa, Italy.
authors.forename: Brunello
authors.initials: B
authors.lastname: Ceccanti
authors.affiliation: Laboratory for Environmental Research, University of Nova Gorica, Vipavska 13, 5000 Nova Gorica, Slovenia.
authors.forename: Polonca
authors.initials: P
authors.lastname: Trebse
authors.affiliation: Department of Chemical Technology and Environmental Chemistry, Eötvös University, P.O. Box 32, H-1518 Budapest, Hungary.
authors.forename: Gyula
authors.initials: G
authors.lastname: Zaray
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects / Q000254:growth & development; D002118:Calcium / Q000032:analysis; D002151:Calorimetry / Q000379:methods; D002175:Candida / Q000187:drug effects / Q000254:growth & development; D002712:Chlorides; D005290:Ferric Compounds / Q000494:pharmacology*; D008274:Magnesium / Q000032:analysis; D008832:Microchemistry / Q000379:methods; D010100:Oxygen / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D011188:Potassium / Q000032:analysis; D012964:Sodium / Q000032:analysis; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology; D013053:Spectrophotometry
chemical_list: D002712:Chlorides; D005290:Ferric Compounds; D012987:Soil; D010758:Phosphorus; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D010100:Oxygen; D002118:Calcium; C024555:ferric chloride