title: Cultivation of methanotrophic bacteria in opposing gradients of methane and oxygen.
abstract: In sediments, methane-oxidizing bacteria live in opposing gradients of methane and oxygen. In such a gradient system, the fluxes of methane and oxygen are controlled by diffusion and consumption rates, and the rate-limiting substrate is maintained at a minimum concentration at the layer of consumption. Opposing gradients of methane and oxygen were mimicked in a specific cultivation set-up in which growth of methanotrophic bacteria occurred as a sharp band at either c. 5 or 20 mm below the air-exposed end. Two new strains of methanotrophic bacteria were isolated with this system. One isolate, strain LC 1, belonged to the Methylomonas genus (type I methantroph) and contained soluble methane mono-oxygenase. Another isolate, strain LC 2, was related to the Methylobacter group (type I methantroph), as determined by 16S rRNA gene and pmoA sequence similarities. However, the partial pmoA sequence was only 86% related to cultured Methylobacter species. This strain accumulated significant amounts of formaldehyde in conventional cultivation with methane and oxygen, which may explain why it is preferentially enriched in a gradient cultivation system.
authors.affiliation: LS Mikrobielle Okologie, Fachbereich Biologie, Universität Konstanz, Konstanz, Germany. ingeborg.bussmann@uni-konstanz.de
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Bussmann
authors.forename: Monali
authors.initials: M
authors.lastname: Rahalkar
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schink
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods; D019015:Geologic Sediments / Q000382:microbiology*; D008697:Methane / Q000378:metabolism*; D008772:Methylococcaceae / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology; D010100:Oxygen / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D008697:Methane; D010100:Oxygen