Marie-Laure Fardeau

Bioremediation of chromate: thermodynamic analysis of the effects of Cr(VI) on sulfate-reducing bacteria.

Abstract. Developing new bioremediation processes for soils and effluents polluted by Cr(VI) requires the selection of the most efficient and the most heavy-metal-resistant bacteria. The effects of Cr(VI) on bioenergetic metabolism in two sulfate-reducing bacteria (SRB), Desulfovibrio vulgaris Hildenborough and Desulfomicrobium norvegicum, were monitored using isothermal microcalorimetry. The complete reduction of Cr(VI) to Cr(III) was studied by spectrophotometry and by speciation using a combination of high-performance liquid chromatography and inductively coupled plasma-mass spectrometry. Results revealed that Cr(VI) induces an inhibition of growth with concomitant production of energy, which can be compared to the reaction of the bacteria to a stress such as oxidative stress. Moreover, the sensitivity of bacteria towards this metal is as a characteristic of the strain, which leads to differences in the kinetics of Cr(VI) reduction. The study by microcalorimetry of heavy metal effects on SRB bioenergetic metabolism thus appears an appropriate tool to identify better strains to be used for industrial bioremediation process development.

Desulfovibrio aminophilus sp. nov., a novel amino acid degrading and sulfate reducing bacterium from an anaerobic dairy wastewater lagoon

A mesophilic strain of sulfate-reducing bacterium, designated ALA-3T (T = type strain), was isolated from an anaerobic lagoon of a dairy wastewater treatment plant. The curved, Gram-negative, non-sporeforming cells (0.2 x 3.0-4.0 microns) existed singly or in chains, and were motile by single polar flagella. Optimum growth occurred at 35 degrees C and pH 7.5 on a medium containing lactate and sulfate. Thiosulfate or sulfite but not elemental sulfur, nitrate, or fumarate could also replace sulfate as an electron acceptor. Formate, alanine, aspartate, leucine, isoleucine, valine, and methionine, H2/CO2 and ethanol also served as electron donors with sulfate as an electron acceptor. Pyruvate, casamino acids, peptone, serine, glycine, cysteine and threonine were fermented. Sulfite and thiosulfate were disproportionated to sulfate and sulfide. The G + C content of the DNA was 66 mol % G + C. Phylogenetic analysis revealed that Desulfovibrio africanus was the nearest relative (similarity of 89%). Strain ALA-3T is physiologically and phylogenetically different from other Desulfovibrio species, and is designated Desulfovibrio aminophilus sp. nov. (DSM 12254).

Energetics of the growth of Methanococcus thermolithotrophicus

Methanococcus thermolithotrophicus was grown in a mineral salts medium at 65° C in a fermenter gassed with H2 and CO2, which were the sole carbon and energy sources. Evolution of growth parameters during batch culture experiments showed the existence of an uncoupling phenomenon. The growth was then studied using a continuous technique and steady states for various gas flow rates were obtained. YCH4and the maintenance coefficient varied with the gas input. The maximum YCH4 determined for Methanococcus thermolithotrophicus was 3.33 g·mol-1 CH4. An excess of energy and carbon sources induced uncoupling of growth.

Energetics of the growth of Methanobacterium thermoautotrophicum and Methanococcus thermolithotrophicus on ammonium chloride and dinitrogen

AbstractMethanobacterium thermoautotrophicum was grown in continuous culture in a fermenter gassed with H2 and CO2 as sole carbon and energy sources, and in a medium which contained either NH4Cl or gaseous N2 as nitrogen source. Growth was possible with N2. Steady states were obtained at various gas flow rates with NH4Cl and with

Anaerobic degradation of landfill leachate using an upflow anaerobic fixed-bed reactor with microbial sulfate reduction

N2{\text{ }} \cdot {\text{ Y}}_{{\text{CH}}{}_{\text{4}}}

Microcalorimetric evaluation of the efficacy of the alkaline treatment on the fermentation of straw

and the maintenance coefficient varied with the gas input and with the nitrogen source. Growth of Methanococcus thermolithotrophicus in continuous culture in a fermenter gassed with H2, CO2 as nitrogen, carbon and energy sources was also examined.

Microcalorimetry: A tool for the study of the biodegradability of straw by mixed bacterial cultures

Thermoanaerobacter brockii, T. ethanolicus, T. thermohydrosulfuricus, T. finnii, and Thermoanaerobacter strain SEBR 5268 (an isolate from an oil-producing well) were studied for their ability to oxidize proteinaceous compounds that included gelatin, peptides, and casamino acids. All bacteria tested used peptides and amino acids, but only slightly. However, in the presence of thiosulfate all the Thermoanaerobacter species showed a substantial improvement in growth and/or the production of acetate, isovalerate, isobutyrate, and sulfide. Propionate was a minor product of peptide or amino acid oxidation. The reduction of thiosulfate during growth on peptides by members of the Thermoanaerobacter species is a trait that closely resembles that of archaeal hyperthermophiles during growth on peptides and amino acids with elemental sulfur as electron acceptor.

Determination of the G + C Content of Two Syntrophus buswellii Strains by Ultracentrifugation Techniques

This study evaluated the anaerobic degradation of landfill leachate and sulfate reduction as a function of COD/(SO(4)(2-)) ratio in an upflow anaerobic fixed-bed reactor. The reactor, which was inoculated with a mixed consortium, was operated under a constant hydraulic retention time (HRT) of 5 days. We investigated the effect of COD/(SO(4)(2-)) ratio variation on the sulfate reduction efficiency, hydrogen sulfide production, chemical oxygen demand (COD) removal, conductivity, and pH variation. The best reactor performance, with significant sulfate reduction efficiency and COD removal efficiency of 91% and 87%, respectively, was reached under a COD/(SO(4)(2-)) ratio of 1.17. Under these conditions, microscopic analysis showed the abundance of vibrios and rod-shaped bacterial cells. Two anaerobic bacteria were isolated from the reactor sludge. Phylogenetic studies performed on these strains identified strain A1 as affiliated to Clostridium genus and strain H1 as a new species of sulfate-reducing bacteria affiliated to the Desulfovibrio genus. The closest phylogenetic relative of strain H1 was Desulfovibrio desulfuricans, at 96% similarity for partial 16S RNA gene sequence data. Physiological and metabolic characterization was performed for this strain.