Using electron balances and molecular techniques to assess trichoroethene-induced shifts to a dechlorinating microbial community

• Published in: Biotechnology and bioengineering Vol. 109; no. 9; pp. 2230 - 2239
• Main Authors: Ziv-El, Michal, Popat, Sudeep C., Parameswaran, Prathap, Kang, Dae-Wook, Polasko, Alexandra, Halden, Rolf U., Rittmann, Bruce E., Krajmalnik-Brown, Rosa
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.09.2012; Wiley Subscription Services, Inc
• Subjects: Acetobacterium; Acetobacterium - metabolism; Bacteria; Biodegradation, Environmental; Bioreactors - microbiology; Biotechnology - methods; chlorinated ethene inhibition; Chloroflexi - metabolism; Dehalococcoides; DNA, Bacterial - chemistry; Electrons; Fermentation; fermenters; Firmicutes; Geobacter; Geobacter - metabolism; Halogenation; homoacetogens; Lactic Acid - metabolism; methanogens; Methanol; Methanol - metabolism; Microbial Consortia - genetics; Microbial Consortia - physiology; Polymerase Chain Reaction; Trichloroethylene - analysis; Trichloroethylene - chemistry; Trichloroethylene - metabolism
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.24504

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. Fill‐and‐draw reactors inoculated with a TCE‐dechlorinating consortium demonstrated a direct correlation between microbial community function and structure as the TCE‐pulsing rate was increased. An electron‐balance analysis predicted the community structure based on measured concentrations of products and constant net yields for each microorganism. The predictions corresponded to trends in the community structure based on pyrosequencing and qPCR up to the highest TCE pulsing rate, where deviations to the trend resulted from stress by the chlorinated ethenes.