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

Abstract

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.

Kinetic modeling of Shewanella baltica KB30 growth on different substrates through respirometry

“…The ability of strain KB30 to use a wide array of substrates (95) had been tested by Pesciaroli et al [ 22 ] using the Biolog Microarray System together with those of many other Arctic bacteria. However, the KB30 specific metabolic competences had never been discussed in details and no further investigations, indicating which metabolic choices are favored by the strain, were done.…”

“…Bacteria with very high proteolytic capacity, accompanied by extremely scarce ability to degrade sugars and related compounds, are known, as shown by Juárez-Jiménez et al for Delftia tsuruhatensis BM90, which is practically unable to degrade carbohydrates [ 30 ]. Strain KB30 is known for its ability to use a complex pattern of carbon sources including various sugars, amino acids, lipids and organic acids, showing a marked composite metabolism [ 22 ], but the respirometry results suggest that its proteolytic pathways could be favored. On the other hand, the faster metabolism on peptone could be justified by the higher bioavailability of its nitrogen sources, if compared with that contained in M9 (NH 4 Cl).…”

“…Stock solutions of sodium acetate (5.0 g L −1 ), glucose (2.5 g L −1 ), tween 80 (0.2 g L −1 ) and peptone (1.0 g L −1 ) were prepared in order to establish the same gradient of substrate concentration (S). Since S. baltica KB30 can use for its growth a very differentiated pattern of carbon sources, including organic acids, sugars, lipids and amino acids [ 22 ], the substrates for respirometric investigations had been chosen as prototypic compounds of principal cell metabolism (glucidic, proteolytic and lipolytic). As required by the kinetic method, the concentration of the different organic substrates was expressed as the chemical oxygen demand (COD) (mg O 2 L −1 ), determined in accordance with standard methods [ 25 ].…”

“…Shewanella baltica KB30, isolated from seawater collected at the Arctic Circle (Kandalaksha Bay, White Sea, Russia) has been previously investigated for some physiological and metabolic competences [ 8 , 22 ]. The strain showed an uncommon adaptation to temperature variations, growing from 0 to over 35 °C, but above all, revealing optimal or sub-optimal growth in a very wide range of temperatures (15–30 °C), reflecting adaptation to the environmental peculiarities of that sub-extreme region [ 8 ].…”

“…The strain showed an uncommon adaptation to temperature variations, growing from 0 to over 35 °C, but above all, revealing optimal or sub-optimal growth in a very wide range of temperatures (15–30 °C), reflecting adaptation to the environmental peculiarities of that sub-extreme region [ 8 ]. In view of potential applications, together with those of other bacteria from same area, its substrate utilization pattern was profiled using the Biolog Microarray System [ 22 ].…”