Niche differentiation among annually recurrent coastal Marine Group II Euryarchaeota

Abstract

Since the discovery of archaeoplankton in 1992, the euryarchaeotal Marine Group II (MGII) remains uncultured and less understood than other planktonic archaea. We characterized the seasonal dynamics of MGII populations in the southern North Sea on a genomic and microscopic level over the course of four years. We recovered 34 metagenome-assembled genomes (MAGs) of MGIIa and MGIIb that corroborated proteorhodopsin-based photoheterotrophic lifestyles. However, MGIIa and MGIIb MAG genome sizes differed considerably (~1.9 vs. ~1.4 Mbp), as did their transporter, peptidase, flagella and sulfate assimilation gene repertoires. MGIIb populations were characteristic of winter samples, whereas MGIIa accounted for up to 23% of the community at the beginning of summer. Both clades consisted of annually recurring, sequence-discrete populations with low intra-population sequence diversity. Oligotyping of filtered cell-size fractions and microscopy consistently suggested that MGII cells were predominantly free-living. Cells were coccoid and ~0.7 µm in diameter, likely resulting in grazing avoidance. Based on multiple lines of evidence, we propose distinct niche adaptations of MGIIa and MGIIb Euryarchaeota populations that are characteristic of summer and winter conditions in the coastal North Sea.

Marine Group-II archaea dominate particle-attached as well as free-living archaeal assemblages in the surface waters of Kongsfjorden, Svalbard, Arctic Ocean

“…The relative abundance of differentially abundant MGIIa OTU001 in the PA fraction showed a strong negative correlation (R = − 0.7008) with the C: N ratio, suggesting their preference for fresh and highly liable organic matter. Metagenomic analyses of the MGII group showed the presence of protein (Iverson et al 2012 ; Orsi et al 2015 ; Orellana et al 2019 ; Rinke et al 2019 ), lipids, and carbohydrates degradation pathways (Orsi et al 2016 ; Xie et al 2018 ) indicating their role in the transformation of dissolved (Orsi et al 2016 ) as well as particulate (Orsi et al 2015 ) organic matter in the marine ecosystem. distLM and db-RDA analysis of the ASV-level data also showed that PON and C: N ratio were the most significant variables explaining the variation in FL and PA communities, respectively (Supplementary figure S.3), which is similar to our observations from the OTU-level data.…”

Mesozooplankton taurine production and prokaryotic uptake in the northern Adriatic Sea

“…Thaumarchaeota MG I and Euryarchaeota MGIIb in the winter and Euryarchaeota MGIIa in the summer exist in various ecotypes in the coastal surface waters of the western Mediterranean Sea, characterized by different activity patterns (Hugoni et al 2013). Furthermore, several recent studies on the Euryarchaeota MGII group in coastal and open ocean systems identified diverse subclades with different ecological niches and lifestyles including members able to utilize taurine (Orellana et al 2019; Pereira et al 2019). Alteromonas phylo‐ and ecotypes also drastically differ in their utilization efficiencies of specific C‐compounds (Gómez‐Consarnau et al 2012; Sarmento and Gasol 2012).…”

The Evolutionary Success of the Marine Bacterium SAR11 Analyzed through a Metagenomic Perspective

“…In addition, intrapopulation microdiversity has also been proposed as a measure of evolutionary success. High diversity corresponds to populations with high temporal persistence and therefore greater adaptive success in their environment (17,27). In contrast, less diversity is associated with populations that have undergone a recent clonal sweep (18,27).…”