Cobalamin and microbial plankton dynamics along a coastal to offshore transect in the Eastern North Atlantic Ocean

Abstract

Cobalamin (B12) is an essential cofactor that is exclusively synthesized by some prokaryotes while many prokaryotes and eukaryotes require an external supply of B12. The spatial and temporal availability of B12 is poorly understood in marine ecosystems. Field measurements of B12 along with a large set of ancillary biotic and abiotic factors were obtained during three oceanographic cruises in the NW Iberian Peninsula, covering different spatial and temporal scales. B12 concentrations were remarkably low (<1.5 pM) in all samples, being significantly higher at the subsurface Eastern North Atlantic Central Water than at shallower depths, suggesting that B12 supply in this water mass is greater than demand. Multiple regression models excluded B12 concentration as predictive variable for phytoplankton biomass or production, regardless of the presence of B12-requiring algae. Prokaryote production was the best predictor for primary production, and eukaryote community composition was better correlated with prokaryote community composition than with nutritional resources, suggesting that biotic interactions play a significant role in regulating microbial communities. Interestingly, co-occurrence network analyses based on 16S and 18S rRNA sequences allowed the identification of significant associations between potential B12 producers and consumers (e.g. Thaumarchaeota and Dynophyceae, or Amylibacter and Ostreococcus respectively), which can now be investigated using model systems in the laboratory.

Microbial and Genetic Resources for Cobalamin (Vitamin B12) Biosynthesis: From Ecosystems to Industrial Biotechnology

“…In the nature, the producers of vitamin B12 family cofactors (cobamides) are unevenly distributed across bacteria, which often metabolically coupled with algae, worms, plants and other organisms, with Actinobacteria enriched in and Bacteroidetes lacking in de novo biosynthesis (58 and 0.6%, respectively, among 11,000 publicly available genomes) [ 7 ]. Nevertheless, each of them, including possessors of the partial biosynthetic pathways, has a genomic potential for biosynthesis of cobalamins into an ecosystem [ 7 , 12 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. Meanwhile, the uptake of exogenous vitamin B12 from environmental microflora is feasible not only in auxotrophic bacteria and mammals, but also in fungi and plants, probably, due to a nonspecific transport mechanism [ 7 , 12 , 21 , 22 ].…”

High-Throughput Sequencing of Environmental DNA as a Tool for Monitoring Eukaryotic Communities and Potential Pathogens in a Coastal Upwelling Ecosystem

“…In particular, the Ría de Vigo (NW, Spain) is highly influenced by the upwelling dynamics which occurs mainly in summer periods, when oceanic currents from the depths enter in zone ( 32 ). However, high-throughput sequencing technology only has been used to study seasonal succession of small-eukaryote community in surface waters ( 31 ) and co-ocurrence networks based on eukaryotic and prokaryotic associations were performed ( 33 ).…”

Planktonic protist diversity across contrasting Subtropical and Subantarctic waters of the southwest Pacific

“…and Micromonas spp. have been recently reported during the onset of the North Atlantic spring bloom from 16S rRNA amplicon sequencing analysis (Bolaños et al 2020) and at more temperate latitudes of the Eastern North Atlantic using 18S rRNA metabarcoding (Joglar et al 2021). The deep mixing layers (>100 m) during the New Zealand STW spring bloom II voyage (TAN1212) (Chiswell et al 2019), where prasinophytes dominated, supports the idea that this picophytoplankton group thrives under high-nutrient, high-mixing conditions playing an important role in the development of spring blooms, characteristic of temperate latitudes.…”

“…reported during the onset of the North Atlantic spring bloom from 16S rRNA amplicon sequencing analysis (Bolaños et al 2020) and at more temperate latitudes of the Eastern North Atlantic using 18S rRNA metabarcoding (Joglar et al 2021). The deep mixing layers (>100 m) during the New Zealand STW to a reference sequence corresponding to Chloroparvula pacifica and included several ASVs one of which (ASV0014) was the most abundant protist ASV found in SAW (Figure 8).…”