title: Cultivation of Aquincola tertiaricarbonis L108 on the fuel oxygenate intermediate tert-butyl alcohol induces aerobic anoxygenic photosynthesis at extremely low feeding rates.
abstract: Aerobic anoxygenic photosynthesis (AAP) is found in an increasing number of proteobacterial strains thriving in ecosystems ranging from extremely oligotrophic to eutrophic. Here, we have investigated whether the fuel oxygenate-degrading betaproteobacterium Aquincola tertiaricarbonis L108 can use AAP to compensate kinetic limitations at low heterotrophic substrate fluxes. In a fermenter experiment with complete biomass retention and also during chemostat cultivation, strain L108 was challenged with extremely low substrate feeding rates of tert-butyl alcohol (TBA), an intermediate of methyl tert-butyl ether (MTBE). Interestingly, formation of photosynthetic pigments, identified as bacteriochlorophyll a and spirilloxanthin, was only induced in growing cells at TBA feeding rates less than or equal to maintenance requirements observed under energy excess conditions. Growth continued at rates between 0.001 and 0.002 h(-1) even when the TBA feed was decreased to values close to 30 % of this maintenance rate. Partial sequencing of genomic DNA of strain L108 revealed a bacteriochlorophyll synthesis gene cluster (bchFNBHL) and photosynthesis regulator genes (ppsR and ppaA) typically found in AAP and other photosynthetic proteobacteria. The usage of light as auxiliary energy source enabling evolution of efficient degradation pathways for kinetically limited heterotrophic substrates and for lowering the threshold substrate concentration Smin at which growth becomes zero is discussed.
authors.affiliation: Helmholtz Centre for Environmental Research - UFZ, Department of Environmental Microbiology, Permoserstr. 15, D-04318 Leipzig, Germany.
authors.forename: Thore
authors.initials: T
authors.lastname: Rohwerder
authors.affiliation: Helmholtz Centre for Environmental Research - UFZ, Department of Environmental Microbiology, Permoserstr. 15, D-04318 Leipzig, Germany.
authors.forename: Roland H
authors.initials: RH
authors.lastname: Müller
authors.affiliation: Helmholtz Centre for Environmental Research - UFZ, Department of Environmental Microbiology, Permoserstr. 15, D-04318 Leipzig, Germany.
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Weichler
authors.affiliation: Helmholtz Centre for Environmental Research - UFZ, Department of Environmental Microbiology, Permoserstr. 15, D-04318 Leipzig, Germany.
authors.forename: Judith
authors.initials: J
authors.lastname: Schuster
authors.affiliation: Helmholtz Centre for Environmental Research - UFZ, Department of Environmental Microbiology, Permoserstr. 15, D-04318 Leipzig, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hübschmann
authors.affiliation: Helmholtz Centre for Environmental Research - UFZ, Department of Environmental Microbiology, Permoserstr. 15, D-04318 Leipzig, Germany.
authors.forename: Susann
authors.initials: S
authors.lastname: Müller
authors.affiliation: Helmholtz Centre for Environmental Research - UFZ, Department of Environmental Microbiology, Permoserstr. 15, D-04318 Leipzig, Germany.
authors.forename: Hauke
authors.initials: H
authors.lastname: Harms
mesh_terms: D000693:Anaerobiosis; D025541:Bacteriochlorophyll A / Q000032:analysis; D020562:Betaproteobacteria / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism* / Q000502:physiology; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004734:Energy Metabolism; D008969:Molecular Sequence Data; D010788:Photosynthesis; D017422:Sequence Analysis, DNA; D024341:Xanthophylls / Q000032:analysis; D020002:tert-Butyl Alcohol / Q000378:metabolism*
chemical_list: D025541:Bacteriochlorophyll A; D004269:DNA, Bacterial; D024341:Xanthophylls; D020002:tert-Butyl Alcohol; C055255:spirilloxanthin