bDehalococcoides mccartyi 195 (strain 195) and Syntrophomonas wolfei were grown in a sustainable syntrophic coculture using butyrate as an electron donor and carbon source and trichloroethene (TCE) as an electron acceptor. The maximum dechlorination rate (9.9 ؎ 0.1 mol day ؊1 ) and cell yield [(1.1 ؎ 0.3) ؋ 10 8 cells mol ؊1 Cl ؊ ] of strain 195 maintained in coculture were, respectively, 2.6 and 1.6 times higher than those measured in the pure culture. The strain 195 cell concentration was about 16 times higher than that of S. wolfei in the coculture. Aqueous H 2 concentrations ranged from 24 to 180 nM during dechlorination and increased to 350 ؎ 20 nM when TCE was depleted, resulting in cessation of butyrate fermentation by S. wolfei with a theoretical Gibbs free energy of ؊13.7 ؎ 0.2 kJ mol ؊1 . Carbon monoxide in the coculture was around 0.06 mol per bottle, which was lower than that observed for strain 195 in isolation. The minimum H 2 threshold value for TCE dechlorination by strain 195 in the coculture was 0.6 ؎ 0.1 nM. Cell aggregates during syntrophic growth were observed by scanning electron microscopy. The interspecies distances to achieve H 2 fluxes required to support the measured dechlorination rates were predicted using Fick's law and demonstrated the need for aggregation. Filamentous appendages and extracellular polymeric substance (EPS)-like structures were present in the intercellular spaces. The transcriptome of strain 195 during exponential growth in the coculture indicated increased ATP-binding cassette transporter activities compared to the pure culture, while the membrane-bound energy metabolism related genes were expressed at stable levels. Groundwater contamination by trichloroethene (TCE), a potential human carcinogen, poses a serious threat to human health and can lead to the generation of vinyl chloride (VC), which is a known human carcinogen (1). Strains of Dehalococcoides mccartyi are the only known bacteria that can completely degrade TCE to the benign end product ethene. Biostimulation of indigenous Dehalococcoides spp. and bioaugmentation using Dehalococcoides-containing cultures are recognized as the most reliable in situ bioremediation technologies resulting in the complete dechlorination of TCE to ethene (2). However, the mechanisms that regulate the activity of D. mccartyi within natural ecosystems and shape its functional robustness in disturbed environments are poorly understood due to multiscale microbial community complexity and heterogeneity of biogeochemical processes involved in the sequential degradation (3, 4). D. mccartyi exhibits specific restrictive metabolic requirements for a variety of exogenous compounds, such as hydrogen, acetate, corrinoids, biotin, and thiamine, which can be supplied by other microbial genera through a complex metabolic network (1,(5)(6)(7)(8). Therefore, the growth of D. mccartyi is more robust within functionally diverse microbial communities that are deterministically assembled than in pure cultures (5,8,9). Previous studies have shown t...

In order to elucidate interactions between sulfate reduction and dechlorination, we systematically evaluated the effects of different concentrations of sulfate and sulfide on reductive dechlorination by isolates, constructed consortia, and enrichments containing Dehalococcoides sp. Sulfate (up to 5 mM) did not inhibit the growth or metabolism of pure cultures of the dechlorinator Dehalococcoides mccartyi 195, the sulfate reducer Desulfovibrio vulgaris Hildenborough, or the syntroph Syntrophomonas wolfei. In contrast, sulfide at 5 mM exhibited inhibitory effects on growth of the sulfate reducer and the syntroph, as well as on both dechlorination and growth rates of D. mccartyi. Transcriptomic analysis of D. mccartyi 195 revealed that genes encoding ATP synthase, biosynthesis, and Hym hydrogenase were downregulated during sulfide inhibition, whereas genes encoding metal-containing enzymes involved in energy metabolism were upregulated even though the activity of those enzymes (hydrogenases) was inhibited. When the electron acceptor (trichloroethene) was limiting and an electron donor (lactate) was provided in excess to cocultures and enrichments, high sulfate concentrations (5 mM) inhibited reductive dechlorination due to the toxicity of generated sulfide. The initial cell ratio of sulfate reducers to D. mccartyi (1:3, 1:1, or 3:1) did not affect the dechlorination performance in the presence of sulfate (2 and 5 mM). In contrast, under electron donor limitation, dechlorination was not affected by sulfate amendments due to low sulfide production, demonstrating that D. mccartyi can function effectively in anaerobic microbial communities containing moderate sulfate concentrations (5 mM), likely due to its ability to outcompete other hydrogen-consuming bacteria and archaea.IMPORTANCE Sulfate is common in subsurface environments and has been reported as a cocontaminant with chlorinated solvents at various concentrations. Inconsistent results for the effects of sulfate inhibition on the performance of dechlorination enrichment cultures have been reported in the literature. These inconsistent findings make it difficult to understand potential mechanisms of sulfate inhibition and complicate the interpretation of bioremediation field data. In order to elucidate interactions between sulfate reduction and reductive dechlorination, this study systematically evaluated the effects of different concentrations of sulfate and sulfide on reductive dechlorination by isolates, constructed consortia, and enrichments containing Dehalococcoides sp. This study provides a more fundamental understanding of the competition mechanisms between reductive dechlorination by Dehalococcoides mccartyi and sulfate reduction during the bioremediation process. It also provides insights on the significance of sulfate concentrations on reductive dechlorination under electron donor/acceptor-limiting conditions during in situ bioremediation applications. For example, at a trichloroethene-contaminated site with a high sulfate concentration, proper...

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conditions to maintain the scale of medical device manufacturing; and 4) the treatment must not incorporate antibiotics to maintain global antimicrobial stewardship efforts. The zwitterionic polymer polysulfobetaine (PSB) was selected as the antifouling component of the surface modification to benefit from its biocompatibility, ultralow-fouling properties, and oxidative stability. By adsorbing water electrostatically, PSB coatings form a thin hydration barrier that prevents organic materials from adhering to surfaces. [22] Commonly used approaches to attach PSB coatings to surfaces, such as radical-initiated graft polymerizations of PSB-methacrylate necessitate the use of oxygen-free conditions, [23] preconditioning steps, [24] or long reaction times [25] that do not meet scalability requirements. To circumvent the use of air-free graft polymerizations, we employ perfluorophenylazide (PFPA) chemistry as a molecular anchor to link the PSB coatings onto the surfaces of polymeric materials under ambient conditions. When triggered with UV-light, PFPA moieties generate a highly reactive nitrene that forms covalent bonds with materials containing amines, CC double bonds, and CH bonds. [26,27] With this method, PSB is rapidly coated onto a broad range of substrates using UV light under ambient conditions with no preconditioning steps. Thus, many different medical devices may be quickly and conveniently treated on the manufacturing level.We first demonstrate the effect of the treatment on polydimethylsiloxane (PDMS) as an exemplary, extremely difficultto-modify model for a common elastomer used in implantable medical devices. [28] Commonly known as silicone, PDMS is widely used for its biocompatibility, good chemical stability, ease of fabrication using injection molding or extrusion, and low cost. [29][30][31] Many implantable device makers have moved away from classical medical elastomers and plastics such as latex and polyvinyl chloride due to allergens [32] or plasticizers [33] in these materials that leach out and often lead to irritation or complications. PDMS-based devices do not require plasticizers and have been shown to lead to fewer complications than latex and polyurethane-based devices. [34] Despite its ideal properties, the nonpolar nature of PDMS facilitates the adhesion of organic materials. Bacteria, platelets, proteins, and other biomolecules bind strongly to the hydrophobic surfaces of PDMS elastomers, leading to the colonization and proliferation of biofilms. [22] When common hydrophilic surface treatments are performed on PDMS, such as plasma oxidation, [35] UV-ozone, [36] or corona discharge, [37] the effects are short-term due to rapid hydrophobic recovery. The highly mobile chains of PDMS (glass transition temperature ≈ −120 °C) can reorient themselves to "hide" the surface modified elastomers, when exposed to air, within hours. [38] Other methods seeking long-lasting hydrophilic PDMS surfaces typically require preconditioning steps with silane [39][40][41] chemistry or radical polymerization. [...

This study demonstrated the utility in correlating performance and community structure of a trichloroethene (TCE)‐dechlorinating microbial consortium; specifically dechlorinators, fermenters, homoacetogens, and methanogens. Two complementary approaches were applied: predicting trends in the microbial community structure based on an electron balance analysis and experimentally assessing the community structure via pyrosequencing and quantitative polymerase chain reaction (qPCR). Fill‐and‐draw reactors inoculated with the DehaloR⁁2 consortium were operated at five TCE‐pulsing rates between 14 and 168 µmol/10‐day‐SRT, amended with TCE every 2 days to give peak concentrations between 0.047 and 0.56 mM (6–74 ppm) and supplied lactate and methanol as sources of e‐ donor and carbon. The complementary approaches demonstrated the same trends: increasing abundance of Dehalococcoides and Geobacter and decreasing abundance of Firmicutes with increasing TCE pulsing rate, except for the highest pulsing rate. Based on qPCR, the abundance of Geobacter and Dehalococcoides decreased for the highest TCE pulsing rate, and pyrosequencing showed this same trend for the latter. This deviation suggested decoupling of Dehalococcoides growth from dechlorination. At pseudo steady‐state, methanogenesis was minimal for all TCE pulsing rates. Pyrosequencing and qPCR showed suppression of the homoacetogenic genera Acetobacterium at the two highest pulsing rates, and it was corroborated by a decreased production of acetate from lactate fermentation and increased propionate production. Suppression of Acetobacterium, which can provide growth factors to Dehalococcoides, may have contributed to the decoupling for the highest TCE‐pulsing rate. Biotechnol. Bioeng. 2012;109: 2230–2239. © 2012 Wiley Periodicals, Inc.