The Misten bog is located on the Hautes Fagnes plateau (eastern Belgium). It includes thick peat deposit with more than 7 m of peat accumulation in ombrotrophic situation. Several palaeoclimatic and/or palaeohydrological proxies such as pollen grains, Sphagnum remains and testate amoebae have been fossilized under anoxic conditions. Several peat cores were retrieved from the bog during a study conducted by the University of Liege and the field laboratory of the Hautes Fagnes (DE VLEESCHOUWER et al., 2010). The peat was cored using a Wardenaar corer (for the top first meter) and a Belarus corer for the layers below. The Belarus sections of cores reached about 7.5 m in depth. The distance between cores 01 and 07, which are considered in this paper, is 1.5 m. The Belarus sections of cores 01 and 07 were correlated thanks to palynology and the analysis of the degree of humification.
The Mbuji-Mayi Supergroup, deposited between 1170 ± 22 Ma and ca. 800 Ma [1], outcrops in the eastern Oriental Kasai Province and western Katanga Province of the Democratic Republic of Congo. It is the youngest Precambrian unit of the Kasai block and was deposited in the SE–NW trending failed-rift Sankuru-Mbuji-MayiLomami-Lovoy basin filled with siliciclastic and carbonate sediments. In the northern part of this basin (Oriental Kasai Province), the Mbuji-Mayi Supergroup rests unconformably upon the Archean Dibaya Granite Complex, but in the southern part (northeastern Katanga Province), it overlies the Mesoproterozoic Kibaran Supergroup. The Supergroup is divided into two groups: the lower, ∼ 500-m thick siliciclastics-rich BI Group and the upper, ∼ 1000-m thick carbonate-rich BII Group. Our own and previous sedimentological observations [2] indicate facies ranging from subtidal, low-energy stromatolitic environments to overlying intertidal to supratidal evaporitic settings of lagoon and sabkha.
Abstract Cyanobacteria form one of the most diversified phylum of Bacteria. They are important ecologically as primary producers, for Earth evolution and biotechnological applications. Yet, Cyanobacteria are notably difficult to purify and grow axenically, and most strains in culture collections contain heterotrophic bacteria that were likely associated to Cyanobacteria in the environment. Obtaining cyanobacterial DNA without contaminant sequences is thus a challenging and time-consuming task. Here, we deploy a metagenomic pipeline that enables the easy recovery of high-quality genomes from non-axenic cultures. We tested this pipeline on 17 cyanobacterial cultures from the BCCM/ULC public collection and generated novel genome sequences for 15 arctic or subarctic strains, of which 14 early-branching organisms that will be useful for cyanobacterial phylogenomics. In parallel, we managed to assemble 31 co-cultivated bacteria from the same cultures and showed that they mostly belong to Bacteroidetes and Proteobacteria, some of them being very closely related in spite of geographically distant sampling sites. Importance Complete genomes of cold-adapted Cyanobacteria are underrepresented in databases, due to the difficulty to grow them axenically. In this work, we report the genome sequencing of 12 (sub)arctic and 3 temperate Cyanobacteria, along with 21 Proteobacteria and 5 Bacteroidetes recovered from their microbiome. Following the use of a state-of-the-art metagenomic pipeline, 12 of our new cyanobacterial genome assemblies are of high-quality, which indicates that even non-axenic cultures can yield complete genomes suitable for phylogenomics and comparative genomics. From a methodological point of view, we investigate the fate of SSU rRNA (16S) genes during metagenomic binning and observe that multi-copy rRNA operons are lost because of higher sequencing coverage and divergent tetranucleotide frequencies. Moreover, we devised a measure of genomic identity to compare metagenomic bins of different completeness, which allowed us to show that Cyanobacteria-associated bacteria can be highly related in spite of considerable distance between collection points.
