title: Microaerobic and anaerobic metabolism of a Methylocystis parvus strain isolated from a denitrifying bioreactor.
abstract: An obligate methanotrophic bacterium, strain MTS, was isolated from a methane-fed microaerobic denitrifying bioreactor. 16S rRNA and DNA-DNA hybridization analysis revealed that this organism was most closely related to Methylocystis parvus, a Type II methanotroph, belonging to the α-subclass of the Proteobacteria. The metabolism of the bacterium under microaerobic and anaerobic conditions was studied by (13) C-NMR. (13) C-labelled poly-β-hydroxybutyrate (PHB) formation occurred in cell suspensions incubated with (13) C-labelled methane at low (5-10%) oxygen concentration. Under these conditions low levels of succinate, acetate and 2,3-butanediol were formed and excreted into the culture medium. Intracellular PHB degradation was observed in intact cells under anaerobic conditions in the absence of an exogenous carbon source during a long-term incubation of 90 days. Multiple (13) C-labelled β-hydroxybutyrate, butyrate, acetate, acetone, isopropanol, 2,3-butanediol and succinate were identified as products in in vivo(13) C-NMR spectra and in the spectra of culture medium during the dynamic PHB degradation. The isolated obligate methanotroph clearly shows a fermentative metabolism of PHB under anaerobic conditions. The excreted products may serve as substrates for denitrifying bacteria.
authors.affiliation: Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB, Wageningen, the Netherlands. Laboratory of Biophysics, Wageningen University, Dreijenplein 3, 6703 HA, Wageningen, the Netherlands. Department of Biological Systems, Universidad Autónoma Metropolitana, 06960 Mexico City, Mexico.
authors.forename: Margarita
authors.initials: M
authors.lastname: Vecherskaya
authors.forename: Cor
authors.initials: C
authors.lastname: Dijkema
authors.forename: Hugo Ramírez
authors.initials: HR
authors.lastname: Saad
authors.forename: Alfons J M
authors.initials: AJ
authors.lastname: Stams