MICRO-ECOLOGY OF PEAT - MINIMALLY INVASIVE ANALYSIS USING CONFOCAL LASER-SCANNING MICROSCOPY, MEMBRANE INLET MASS-SPECTROMETRY AND PCR AMPLIFICATION OF METHANOGEN-SPECIFIC GENE-SEQUENCES

A peat monolith (15 cm diameter, 35 cm length) from Ellergower Moss (N ew Galloway, Scotland), kept outdoors and maintained water-saturated, was investigated for the distributions of gases (O-2, CO2, CH4), micro -organisms, total archaeal DNA and methanogen DNA. From the water tabl e (at the surface of the Sphagnum), a steep oxycline gave < 0.25 mu M O-2 at ? cm depth (as shown by membrane inlet mass spectrometry and ox ygen electrode methods) and < 10 nM O-2 at 6 cm depth (photobacterium gas diffusion probe). Redox potential measurements indicated a steep d ecline between 6 cm and 13 cm to a value of -90 mV. At the oxic surfac e of the peat, CO2 measured 0.5 mM and CH4 < 1 mu M. Below 7 cm both g ases increased to plateaux at 2 mM and 550 mu M respectively; CH4 conc entrations also indicated two distinct zones (7 mu M to 2.5 cm depth, then to 28 mu M at between 3 and 6 cm). Confocal laser scanning micros copy using the fluorophores 5-cyano-2,3-ditolyl tetrazolium chloride o r 3,3-dihexyloxacarbocyanine iodide was used to image micro-organisms with redox active electron transport activities or transmembrane elect rochemical potentials, respectively. Samples from 1-5 cm depth showed the presence of active aerobic organisms, whereas those from 10 and 20 cm depth were more active anaerobically, and especially so under H-2. Archaeal DNA was present throughout the core; strongest hybridisation was below 9 cm. Two methanogen-specific primers, ME1 and ME2 (which a mplify a region of the alpha-subunit of methyl coenzyme M reductase), hybridised with DNA extracted from below 9 cm depth. Here we describe the concerted application of a number of techniques providing direct i nformation on the precise location and activities of microbes involved in the flux of gases from peatlands. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V.