title: Enrichment and detection of microorganisms involved in direct and indirect methanogenesis from methanol in an anaerobic thermophilic bioreactor.
abstract: To gain insight into the microorganisms involved in direct and indirect methane formation from methanol in a laboratory-scale thermophilic (55 degrees C) methanogenic bioreactor, reactor sludge was disrupted and serial dilutions were incubated in specific growth media containing methanol and possible intermediates of methanol degradation as substrates. With methanol, growth was observed up to a dilution of 10(8). However, when Methanothermobacter thermoautotrophicus strain Z245 was added for H2 removal, growth was observed up to a 10(10)-fold dilution. With H2/CO2 and acetate, growth was observed up to dilutions of 10(9) and 10(4), respectively. Dominant microorganisms in the different dilutions were identified by 16S rRNA-gene diversity and sequence analysis. Furthermore, dilution polymerase chain reaction (PCR) revealed a similar relative abundance of Archaea and Bacteria in all investigated samples, except in enrichment with acetate, which contained 100 times less archaeal DNA than bacterial DNA. The most abundant bacteria in the culture with methanol and strain Z245 were most closely related to Moorella glycerini. Thermodesulfovibrio relatives were found with high sequence similarity in the H2/CO2 enrichment, but also in the original laboratory-scale bioreactor sludge. Methanothermobacter thermoautotrophicus strains were the most abundant hydrogenotrophic archaea in the H2/CO2 enrichment. The dominant methanol-utilizing methanogen, which was present in the 10(8)-dilution, was most closely related to Methanomethylovorans hollandica. Compared to direct methanogenesis, results of this study indicate that syntrophic, interspecies hydrogen transfer-dependent methanol conversion is equally important in the thermophilic bioreactor, confirming previous findings with labeled substrates and specific inhibitors.
authors.affiliation: Laboratory of Microbiology, Wageningen University, Hesselink van Suchtelenweg 4, NL-6703 CT, Wageningen, The Netherlands. kees.roest@wur.nl
authors.forename: Kees
authors.initials: K
authors.lastname: Roest
authors.forename: Mahmut
authors.initials: M
authors.lastname: Altinbas
authors.forename: Paula L
authors.initials: PL
authors.lastname: Paulo
authors.forename: H G H J
authors.initials: HG
authors.lastname: Heilig
authors.forename: Antoon D L
authors.initials: AD
authors.lastname: Akkermans
authors.forename: Hauke
authors.initials: H
authors.lastname: Smidt
authors.forename: Willem M
authors.initials: WM
authors.lastname: de Vos
authors.forename: Alfons J M
authors.initials: AJ
authors.lastname: Stams
mesh_terms: D000085:Acetates; D000693:Anaerobiosis; D001105:Archaea / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology*; D002245:Carbon Dioxide; D003470:Culture Media; D006859:Hydrogen; D008697:Methane / Q000378:metabolism*; D017013:Methanobacteriaceae / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification; D000432:Methanol / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012722:Sewage; D013045:Species Specificity
chemical_list: D000085:Acetates; D003470:Culture Media; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D002245:Carbon Dioxide; D006859:Hydrogen; D008697:Methane; D000432:Methanol