title: The roles of methanogens and acetogens in dechlorination of trichloroethene using different electron donors.
abstract: We evaluated the effects of methanogens and acetogens on the function and structure of microbial communities doing reductive dechlorination of trichloroethene (TCE) by adding four distinct electron donors: lactate, a fermentable organic; acetate, a non-fermentable organic; methanol, a fermentable 1-C (carbon) organic; and hydrogen gas (H2), the direct electron donor for reductive dechlorination by Dehalococcoides. The fermentable electron donors had faster dechlorination rates, more complete dechlorination, and higher bacterial abundances than the non-fermentable electron donors during short-term tests. Phylotypes of Dehalococcoides were relatively abundant (≥9%) for the cultures fed with fermentable electron donors but accounted for only ~1-2% of the reads for the cultures fed by the non-fermentable electron donors. Routing electrons to methanogenesis and a low ratio of Dehalococcoides/methanogenesis (Dhc/mcrA) were associated with slow and incomplete reductive dechlorination with methanol and H2. When fermentable substrates were applied as electron donors, a Dhc/mcrA ratio ≥6.4 was essential to achieve fast and complete dechlorination of TCE to ethene. When methanogenesis was suppressed using 2-bromoethanesulfonate (BES), achieving complete dechlorination of TCE to ethane required a minimum abundance of the mcrA gene. Methanobacterium appeared to be important for maintaining a high dechlorination rate, probably by providing Dehalococcoides with cofactors other than vitamin B12. Furthermore, the presence of homoacetogens also was important to maintain a high dechlorination rate, because they provided acetate as Dehalococcoides's obligatory carbon source and possibly cofactors.
authors.affiliation: MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Li-Lian
authors.initials: LL
authors.lastname: Wen
authors.affiliation: MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Ya-Wei
authors.initials: YW
authors.lastname: Pan
authors.affiliation: MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Wen-Qi
authors.initials: WQ
authors.lastname: Wu
authors.affiliation: MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Shao-Hua
authors.initials: SH
authors.lastname: Meng
authors.affiliation: Department of Civil and Environmental Engineering, FAMU-FSU College of Engineering, Florida State University, Tallahassee, FL, 32310-6046, USA.
authors.forename: Chen
authors.initials: C
authors.lastname: Zhou
authors.affiliation: Department of Civil and Environmental Engineering, FAMU-FSU College of Engineering, Florida State University, Tallahassee, FL, 32310-6046, USA.
authors.forename: Youneng
authors.initials: Y
authors.lastname: Tang
authors.affiliation: MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zheng
authors.affiliation: MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China. zhaohp@zju.edu.cn.
authors.forename: He-Ping
authors.initials: HP
authors.lastname: Zhao
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D017738:Alkanesulfonic Acids; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology; D041862:Chloroflexi / Q000378:metabolism*; D004583:Electrons; D005285:Fermentation; D054879:Halogenation; D006859:Hydrogen / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D000432:Methanol / Q000378:metabolism; D059013:Microbial Consortia; D014241:Trichloroethylene / Q000378:metabolism*
chemical_list: D017738:Alkanesulfonic Acids; C018853:2-bromoethanesulfonic acid; D014241:Trichloroethylene; D019344:Lactic Acid; D006859:Hydrogen; D019342:Acetic Acid; D000432:Methanol
keywords: Dehalococcoides; Homoacetogens; Methanogens; Reductive dechlorination; TCE