title: Use of an isothermal microcalorimetry assay to characterize microbial oxalotrophic activity.
abstract: Isothermal microcalorimetry (IMC) has been used in the past to monitor metabolic activities in living systems. A few studies have used it on ecological research. In this study, IMC was used to monitor oxalotrophic activity, a widespread bacterial metabolism found in the environment, and particularly in soils. Six model strains were inoculated in solid angle media with K-oxalate as the sole carbon source. Cupriavidus oxalaticus, Cupriavidus necator, and Streptomyces violaceoruber presented the highest activity (91, 40, and 55 μW, respectively) and a maximum growth rate (μmax h(-1) ) of 0.264, 0.185, and 0.199, respectively, among the strains tested. These three strains were selected to test the incidence of different oxalate sources (Ca, Cu, and Fe-oxalate salts) in the metabolic activity. The highest activity was obtained in Ca-oxalate for C. oxalaticus. Similar experiments were carried out with a model soil to test whether this approach can be used to measure oxalotrophic activity in field samples. Although measuring oxalotrophic activity in a soil was challenging, there was a clear effect of the amendment with oxalate on the metabolic activity measured in soil. The correlation between heat flow and growth suggests that IMC analysis is a powerful method to monitor bacterial oxalotrophic activity.
authors.affiliation: Laboratory of Microbiology, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bravo
authors.forename: Olivier
authors.initials: O
authors.lastname: Braissant
authors.forename: Anna
authors.initials: A
authors.lastname: Solokhina
authors.forename: Martin
authors.initials: M
authors.lastname: Clerc
authors.forename: Alma U
authors.initials: AU
authors.lastname: Daniels
authors.forename: Eric
authors.initials: E
authors.lastname: Verrecchia
authors.forename: Pilar
authors.initials: P
authors.lastname: Junier
mesh_terms: D001419:Bacteria / Q000254:growth & development / Q000378:metabolism*; D002151:Calorimetry / Q000379:methods*; D020118:Cupriavidus necator / Q000378:metabolism; D010070:Oxalates / Q000032:analysis / Q000378:metabolism*; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*; D013302:Streptomyces / Q000254:growth & development / Q000378:metabolism
chemical_list: D010070:Oxalates; D012987:Soil; D012989:Soil Pollutants