Vertical Distribution of Ammonia-Oxidizing Crenarchaeota and Methanogens in the Epipelagic Waters of Lake Kivu (Rwanda-Democratic Republic of the Congo)

• DOI: 10.1128/aem.02864-09
• Publication Date: 2010-08-28T02:30:37Z
• Authors: Marc Llirós; Frederic Gich; Anna Plasencia; Jean-Christophe A...; François Darchambeau; Emilio O. Casamayor; Jean-Pierre Descy; Carles Borrego
• Keywords: Crenarchaeota; Euryarchaeota; Ammonia monooxygenase

Four stratified basins in Lake Kivu (Rwanda-Democratic Republic of the Congo) were sampled March 2007 to investigate abundance, distribution, and potential biogeochemical role planktonic archaea. We used fluorescence situ hybridization with catalyzed-reported deposition microscopic counts (CARD-FISH), denaturing gradient gel electrophoresis (DGGE) fingerprinting, quantitative PCR (qPCR) signature genes for ammonia-oxidizing archaea (16S rRNA marine Crenarchaeota group 1.1a [MCG1] ammonia monooxygenase subunit A [amoA]). Abundance ranged from 1 4.5% total DAPI (4',6-diamidino-2-phenylindole) maximal concentrations at oxic-anoxic transition zone (∼50-m depth). Phylogenetic analysis archaeal community revealed a higher level richness crenarchaeal 16S gene sequences (21 28 operational taxonomic units [OTUs] identified [75%]) over euryarchaeotal ones (7 OTUs). Sequences affiliated kingdom Euryarchaeota mainly recovered anoxic water compartment mostly grouped into methanogenic lineages (Methanosarcinales Methanocellales). In turn, phylotypes throughout epipelagic waters (0- 100-m depth), clear phylogenetic segregation along oxic masses. Thus, whereas hypolimnion crenarchaeotal OTUs assigned miscellaneous crenarchaeotic group, above belonged groups 1.1b, two containing most representatives known so far. The concomitant vertical distribution both nitrite nitrate maxima copy numbers MCG1 amoA suggest implication nitrification processes occurring epilimnetic lake.