Relationship between phylogenetic and nutritional diversity in Arctic (Kandalaksha Bay) seawater planktonic bacteria

Due to huge yearly variations of environmental stressing conditions, Kandalaksha Bay (Arctic Circle, White Sea, Russia) could represent a model to study microbial adaptation in extreme environments. This peculiar estuarine system has been scarcely investigated for its microbial diversity. In this work, to gather information on their nutritional competencies, seawater planktonic bacteria were studied for their ability to use different carbon sources by the Biolog phenotype microarray assays. Nestedness, a useful statistical tool used in ecology, was employed to underline nutritional differences among microbial groups. In particular, nestedness was used to understand the complex relationship that is established when many nutrients are available for various microorganisms, and to highlight presence of specialists and generalists. Among the studied bacteria, which showed very diverse nutritional abilities, 47% belonged to Pseudomonas, 21% to Serratia and 32% to other Genera. Within Pseudomonas, both highly generalist and highly specialist strains were discovered. However, most of them used organic and/or amino acids as principal carbon sources. In contrast, Serratia strains typically preferred sugars and appeared to be more generalist. On the whole, important differences in specialization levels and nutritional competencies were recorded in strains belonging to the same species. Correlations between phylogenetic and nutritional data were validated by Procrustes analysis.