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Araujo, S. P.

Publications and source records attributed to Araujo, S. P..

2 recordsLinked to original sources
bioRxiv2025

Dehalobacter converts 2,3-dichloroaniline to aniline via 2-chloroaniline in a methanogenic enrichment culture

12,3-dichloroaniline (2,3-DCA) has widespread use in chemical manufacturing and remains a persistent groundwater contaminant. To better understand the pathway and kinetics of its reductive dechlorination, we conducted a laboratory kinetic experiment using an anaerobic enrichment culture dominated by Dehalobacter. At an initial field-relevant concentration of 40 mg/L, complete and stoichiometric dechlorination of 2,3-DCA to aniline via 2-CA was achieved. The intermediates, 2-chloroaniline (2-CA) and 3-chloroaniline, were transiently formed in a ratio of 8:1. The growth yields of Dehalobacter on 2,3-DCA and 2-CA were 1.2 {+/-} 0.1 x 108 and 1.3 {+/-} 0.1 x 108 16S rRNA gene copies/mol chloride, respectively. The maximum specific growth rate for 2,3-DCA, max, was 0.18 {+/-} 0.03 day-{superscript 1} with a half-saturation constant, Ks, at 45 {+/-} 16 mg /L. The first-order decay constant for Dehalobacter when starved of chlorinated electron acceptors was estimated at 0.017 {+/-} 0.001 day-{superscript 1}. Lactate fermentation, acetogenesis from ethanol, syntrophic propionate oxidation, and hydrogenotrophic methanogenesis were observed during dechlorination. This work provides insights into the organohalide respiration of 2,3-DCA to aniline and advances the understanding of microbial interactions during anaerobic dechlorination. These results offer guidance for developing stable dechlorinating microbial ecosystems and key kinetic parameters for predictive modeling of groundwater 2,3-DCA fate and transport. 3 SynopsisThis study demonstrated stoichiometric dechlorination of 2,3-dichloroaniline to aniline, characterized syntrophic interactions in a mixed anaerobic dechlorinating culture, and determined growth yield, first-order decay and Monod constants for Dehalobacter. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/639126v3_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@5d59c4org.highwire.dtl.DTLVardef@b05a3aorg.highwire.dtl.DTLVardef@1f39f6borg.highwire.dtl.DTLVardef@1676753_HPS_FORMAT_FIGEXP M_FIG C_FIG Created in BioRender. Wang, S. (2025) https://BioRender.com/f47t993

microbiology↗
bioRxiv2025

Dehalobacter dechlorinates dichloroanilines and contributes to the natural attenuation of dichloronitrobenzenes at a complex industrial site

The potential for bioremediation of dichloroanilines (2,3- and 3,4-DCA) and dichloronitrobenzenes (3,4-, 2,5- and 2,3-DCNB) was investigated using inocula from an industrial site in northeast of Brazil. Anaerobic biotransformation of these chlorinated compounds was observed in microcosms simulating site conditions, particularly when electron donor was added. To disentangle specific transformation reactions, sub-cultures from active anaerobic microcosms were enriched with individual DCA or DCNB isomers. In these single-compound enrichment cultures, DCNB isomers were reduced to the corresponding DCA. Each DCA isomer was stoichiometrically dechlorinated to the corresponding monochloroaniline (CA) isomers. Further dechlorination of CA to aniline was noted. The reduction of DCNB to DCA was sustained by known fermenters and possibly Desulfitobacterium, while Dehalobacter was clearly responsible for dechlorination of DCAs. These findings helped to attribute function to microbial community data retrieved from field samples to inform the conceptual site model and enable identification of bioactive zones and rate-limiting conditions at a complex site. More generally, these data broaden the understanding of the metabolic repertoire of Dehalobacter and provide a model for incorporating microbial community data into site remediation efforts. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=116 SRC="FIGDIR/small/638192v2_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@1667948org.highwire.dtl.DTLVardef@a4a128org.highwire.dtl.DTLVardef@507067org.highwire.dtl.DTLVardef@103a155_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG Short synopsis statementA diverse microbial community contributes to natural attenuation at a complex contaminated site. Notably, dichloroanilines produced by biologically-mediated nitroreduction of dichloronitrobenzenes were dechlorinated by Dehalobacter.

microbiology↗