Impact of estuarine gradients on reductive dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin in river sediment enrichment cultures

Targeted Cell Sorting Combined With Single Cell Genomics Captures Low Abundant Microbial Dark Matter With Higher Sensitivity Than Metagenomics

“…Obtaining genomes of rare microorganisms through culture-independent methods requires either extensive sampling over a long period of time to capture the moment when rare species become dominant or very deep sequencing, if at all possible ( Hugenholtz et al, 1998 ; Köpke et al, 2005 ). Some species with unique, important, and rate-limiting biological functions (such as nitrification, methane and methanol oxidation, or respiratory dehalogenation) are however permanently found at low abundance in the environment ( Griffiths et al, 2004 ; Dam and Häggblom, 2017 ; Pratscher et al, 2018 ). Nevertheless, those rare microorganisms play important ecological roles and contribute to biodiversity and ecological cycles more than previously known ( Jousset et al, 2017 ).…”

2,3,7,8-Tetrachlorodibenzo-p-dioxin Dechlorination is Differentially Enhanced by Dichlorobenzene Amendment in Passaic River, NJ Sediments

“…This was expected, since previous work demonstrated microbial dechlorination of 1,2,3,4-TeCDD in both the Passaic 21 and Hackensack rivers. 33 The fact that set 4, created with the original river sediment, showed the least amount of dechlorination supports the notion that cultures enriched on the alternate, more soluble organohalides would be able to more rapidly dechlorinate PCDDs than unenriched cultures. This same pathway of 1,2,3,4-TeCDD dechlorination (Figure S3) was proposed by Bunge et al, 41 Ahn et al, 23 and Dam et al, 33 but not Fennell et al, 14 TrCDD by strain 195.…”

“…In the current study, it is unclear if slightly different sets of dehalogenases are operating in the different treatment sets (e.g., set 7 has a high ratio of 2,3-to 1,3-DiCDD, while set 10 and 13 have more 1,3-than 2,3-DiCDD) since they are all at vastly different dechlorination stages. We also do not know if 1,3-DiCDD is a product of both 1,2,3-and 1,2,4-TrCDD dechlorination as is the case for strain CBDB1, 15 or if it comes exclusively from one of the TrCDD congeners as observed with the H1 Hackensack River enrichment culture described by Dam et al 33 Interestingly, Ahn et al 23 reported that the ratio of 1,3-DiCDD: 2,3-DiCDD in 1,2,3,4-TeCDD-amended microcosms was greater with the hydrophobic tetrachlorobenzene cosubstrate rather than the hydrophilic chlorophenol cosubstrate. 23 We also saw a greater ratio of 1,3-DiCDD: The fact that set 13, the culture enriched with DCB, proved most capable of 1,2,3,4-TeCDD dechlorination indicates that DCB was a more suitable substrate for growing PCDDdechlorinating OHRB than TCE in this system.…”

“…21,32 Dam et al recently observed rapid dechlorination of the model PCDD congener 1,2,3,4-TeCDD in sediments from the adjacent Hackensack River, NJ and identified Dehalococcoides strains in their enrichments. 33 We investigated methods to stimulate OHRB capable of 2,3,7,8-TeCDD dechlorination in Passaic River sediments. We first enriched the sediment on two organohalides, trichloroethene (TCE) and 1,2-dichlorobenzene (DCB) to increase OHRB and/or dehalogenase expression.…”

“…Access to the river’s natural resources are limited because of this bioaccumulative pollutant. − 2,3,7,8-TeCDD was a byproduct of production of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), a component of the defoliant Agent Orange. , The majority of 2,3,7,8-TeCDD present in the river is due to discharge and site runoff from an adjacent chemical manufacturing company, which produced 2,4,5-T. , The 2,3,7,8-TeCDD has been tidally distributed throughout the estuary and detected 26 miles upstream in the Hudson River . The work by the Adriaens group in the 1990s indicated that 2,3,7,8-TeCDD is dechlorinated by bacteria native to the Passaic River, but the responsible bacteria and genes involved were not identified at the time. , Dam et al recently observed rapid dechlorination of the model PCDD congener 1,2,3,4-TeCDD in sediments from the adjacent Hackensack River, NJ and identified Dehalococcoides strains in their enrichments …”