Introduction 1992 4 2 2 2 1994 1977 2002 2 K s μ max 1985 1988 1994 2 1986 2 2 2002 2005 \documentclass[12pt]{minimal}
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\begin{document}$${\text{SO}}_{\text{4}} ^{2 - } $$\end{document} 1993 \documentclass[12pt]{minimal}
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\begin{document}$${{{\text{COD}}} \mathord{\left/ {\vphantom {{{\text{COD}}} {{\text{SO}}_{\text{4}} ^{2 - } }}} \right. \kern-\nulldelimiterspace} {{\text{SO}}_{\text{4}} ^{2 - } }}$$\end{document} 1998 \documentclass[12pt]{minimal}
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\begin{document}$${{{\text{COD}}} \mathord{\left/ {\vphantom {{{\text{COD}}} {{\text{SO}}_{\text{4}} ^{2 - } }}} \right. \kern-\nulldelimiterspace} {{\text{SO}}_{\text{4}} ^{2 - } }}$$\end{document} 2001 1991 1994 1993 1993 1995 2007a 1995 In the present study, the structure and function of anaerobic communities maintained in lab-scale continuously stirred tank reactors (CSTR) under sulfidogenic and nonsulfidogenic conditions was investigated. An integrated approach of molecular techniques including DGGE and FISH together with chemical analysis was used to link the microbial population dynamics with changes in the lactate (electron donor) concentration and sulfate availability. The focus of our study was the competition and interaction between the dominant microbial communities of SRB, acetogens and methane-producing Archaea. Materials and methods Reactor operation 1 −1 r −1 r 2 4 2 4 4 4 2 2 2 4 3 3 2 2 2 2 2 2 2 2 2 2 4 2 2 3 2 2 4 2 12 p 2 2 D −1 Fig. 1 −1  Chemical analysis 1995 1969 Nucleic acid extraction, reverse transcription of RNA, and PCR amplification 2007b 1995 2005 w v DGGE of 16S rRNA gene fragments and phylogenetic analysis 2001 http://www.ncbi.nlm.nih.gov/BLAST 2004 2004 Design of oligonucleotide probes 2004 2007a 1 Table 1 Oligonucleotides used in this study Probe name Target organism Probe sequence (5′–3′) Reference EUB338I Most bacteria GCT GCC TCC CGT AGG AGT 1990 EUB338II Phylum Planctomycetes GCA GCC ACC CGT AGG TGT 1999 EUB338III Phylum Verrucomicrobia GCT GCC ACC CGT AGG TGT 1999 ARCH915 Archaea GTG CTC CCC CGC CAA TTC 1991 SPS770 Sporomusa ATC CCG TTC ACT CCC CTG This study SRB385 Most Deltaproteobacteria CGC GTC GCT GCG TCA GG 1990 SRB385Db Some Deltaproteobacteria CGG CGT TGC TGC GTC AGG 1996 DSR660 Desulfobulbus GAA TTC CAC TTT CCC CTC TG 1992 DSM1265 Desulfomicrobium AGA TTC GCT CGA CCT CGC This study DSV139 Desulfovibrio CGC TGT TAT CCC GAT CAC 2007a DSCOC814 Desulfococcus ACC TAG TGA TCA ACG TTT 1992 Fluorescence in situ hybridization 2007b 1992 v v 1996 1992 Sequence accession numbers The sequences determined in this study were submitted to GenBank under accession numbers EU276620–EU276626. Results Microbial community dynamics at different lactate/sulfate ratio 2 r −1 2 2 r 2 2 r −1 2 2 r Fig. 2 2  Table 2 Stoichiometry of anaerobic degradation reactions relevant to this study No. Reaction G 01 −1 1 \documentclass[12pt]{minimal}
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\begin{document}$${\text{C}}_3 {\text{H}}_5 {\text{O}}_{\text{3}} ^{ - 1}  + 1.5 \cdot {\text{SO}}_{\text{4}} ^{ - 2}  \to 3 \cdot {\text{HCO}}_{\text{3}} ^{ - 1}  + 1.5 \cdot {\text{HS}}^{ - 1}  + 0.5 \cdot {\text{H}}^{{\text{ + 1}}} $$\end{document} −128.5 2 \documentclass[12pt]{minimal}
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\begin{document}$${\text{C}}_3 {\text{H}}_5 {\text{O}}_{\text{3}} ^{ - 1} + 0.5 \cdot {\text{SO}}_{\text{4}} ^{ - 2} \to {\text{C}}_2 {\text{H}}_3 {\text{O}}_{\text{2}} ^{ - 1} + {\text{HCO}}_{\text{3}} ^{ - 1} + 0.5 \cdot {\text{HS}}^{ - {\text{1}}} + 0.5 \cdot {\text{H}}^{ + 1} $$\end{document} −80.8 3 \documentclass[12pt]{minimal}
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\begin{document}$${\text{C}}_3 {\text{H}}_5 {\text{O}}_{\text{3}} ^{ - 1} \to 0.33 \cdot {\text{C}}_2 {\text{H}}_3 {\text{O}}_{\text{2}} ^{ - 1} + 0.67 \cdot {\text{C}}_3 {\text{H}}_5 {\text{O}}_{\text{2}} ^{ - 1} + 0.33 \cdot {\text{HCO}}_{\text{3}} ^{ - 1} + 0.33 \cdot {\text{H}}^{ + 1} $$\end{document} −55.7 4 \documentclass[12pt]{minimal}
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\begin{document}$${\text{C}}_3 {\text{H}}_5 {\text{O}}_{\text{2}} ^{ - 1} + 0.75 \cdot {\text{SO}}_{\text{4}} ^{ - 2} \to {\text{C}}_2 {\text{H}}_3 {\text{O}}_{\text{2}} ^{ - 1} + {\text{HCO}}_{\text{3}} ^{ - 1} + 0.75 \cdot {\text{HS}}^{ - 1} + 0.25 \cdot {\text{H}}^{ + 1} $$\end{document} −37.7 5 \documentclass[12pt]{minimal}
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\begin{document}$${\text{C}}_3 {\text{H}}_5 {\text{O}}_{\text{2}} ^{ - 1} + 1.75 \cdot {\text{SO}}_{\text{4}} ^{ - 2} \to 3 \cdot {\text{HCO}}_{\text{3}} ^{ - 1} + 1.75 \cdot {\text{HS}}^{ - 1} + 0.25 \cdot {\text{H}}^{ + 1} $$\end{document} −85.4 6 \documentclass[12pt]{minimal}
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\begin{document}$${\text{C}}_2 {\text{H}}_3 {\text{O}}_{\text{2}} ^{ - 1} + {\text{H}}_2 {\text{O}} \to {\text{CH}}_4 + {\text{HCO}}_{\text{3}} ^{ - 1} $$\end{document} −31.1 3 r 4 Sporomusa Pectinatus Selenomonas Dendrosporobacter quercicolus r Desulfovibrio Desulfovibrio mexicoense Desulfobulbus Desulfobulbus rhabdoformis r −1 Desulfomicrobium apsheronum Cytophaga Spirochetes Desulfococcus biacutus Fig. 3 Lanes 1 2 lanes 3 4 lanes 5 6 lanes 7 8 dot  Fig. 4 3 boldface Black dots scale bar  r Methanosaeta Microbial community dynamics using FISH 5 D. quercicolus 5 6 5 6 5 6 5 6 1 Desulfomicrobium r −1 5 r r Desulfovibrio 5 Fig. 5 a b Desulfomicrobium Desulfovibrio Desulfobulbus Dendrosporobacter  Fig. 6 blue green red a b c d  Desulfobulbus 5 r Desulfobulbus 5 5 Discussion This study evaluates the shift in microbial structure in lab-scale CSTR reactors as affected by changing lactate to sulfate ratios using a combined approach of molecular methods (PCR–DGGE and FISH) and chemical analysis. The combination of different methods allowed the establishment of a link between the population structure and function of the anaerobic communities in the reactors under sulfidogenic and nonsulfidogenic conditions. 1989 1997 2 2 2 2 2 2 −1 2 −1 2 Desulfomicrobium Desulfovibrio 2 5 6 1988 2 1993 1988 μ max K s Given the fact that the nested amplification suggested that the numbers of the complete oxidizers were very low in the inoculum, a long period of time would have been required before such SRB would have grown to a significant number. Therefore, we cannot rule out that eventually the complete oxidizers might have become dominant under lactate-limiting conditions in R1. 2 Dendrosporobacter 5 6 D. quercicolus Sporomusa Pectinatus Selenomonas 2000 2 2000 D. quercicolus 2 2 2 5 −1 −1 −1 2 2 D. quercicolus 5 6 1993 1989 1988 1986 1993 3 −1 D. rhabdoformis 5 2 D. rhabdoformis −1 −1 2 −1 −1 Methanoseata −1 2 Archaeoglobales 1987 In conclusion, this study points to different metabolic routes being followed by a mixed anaerobic community, even in the mineralization of simple substrates like lactate. We could establish a link in microbial population dynamics to major perturbations caused by changing influent lactate to sulfate ratios. This study demonstrated that at low lactate to sulfate molar ratios in the influent, SRB had a competitive advantage over acetogens and methanogens and that, in the near absence of sulfate, heteroacetogens formed a syntropic association with methanogens. Higher lactate to sulfate ratio resulted in a pathway that had propionate and acetate as products, and the majority of sulfidogenesis and methanogenesis was dependent on the fermentation products. All these results were substantiated by corresponding shifts in relative abundance of the microbial communities present as analyzed by DGGE and FISH.