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Link to original content: https://pubmed.ncbi.nlm.nih.gov/22286998
Abundance and single-cell activity of heterotrophic bacterial groups in the western Arctic Ocean in summer and winter - PubMed Skip to main page content
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. 2012 Apr;78(7):2402-9.
doi: 10.1128/AEM.07130-11. Epub 2012 Jan 27.

Abundance and single-cell activity of heterotrophic bacterial groups in the western Arctic Ocean in summer and winter

Mrinalini P Nikrad  1 , M T Cottrell, D L Kirchman
Affiliations

Abundance and single-cell activity of heterotrophic bacterial groups in the western Arctic Ocean in summer and winter

Mrinalini P Nikrad et al. Appl Environ Microbiol. 2012 Apr.

Abstract

Environmental conditions in the western Arctic Ocean range from constant light and nutrient depletion in summer to complete darkness and sea ice cover in winter. This seasonal environmental variation is likely to have an effect on the use of dissolved organic matter (DOM) by heterotrophic bacteria in surface water. However, this effect is not well studied and we know little about the activity of specific bacterial clades in the surface oceans. The use of DOM by three bacterial subgroups in both winter and summer was examined by microautoradiography combined with fluorescence in situ hybridization. We found selective use of substrates by these groups, although the abundances of Ant4D3 (Antarctic Gammaproteobacteria), Polaribacter (Bacteroidetes), and SAR11 (Alphaproteobacteria) were not different between summer and winter in the Beaufort and Chukchi Seas. The number of cells taking up glucose within all three bacterial groups decreased significantly from summer to winter, while the percentage of cells using leucine did not show a clear pattern between seasons. The uptake of the amino acid mix increased substantially from summer to winter by the Ant4D3 group, although such a large increase in uptake was not seen for the other two groups. Use of glucose by bacteria, but not use of leucine or the amino acid mix, related strongly to inorganic nutrients, chlorophyll a, and other environmental factors. Our results suggest a switch in use of dissolved organic substrates from summer to winter and that the three phylogenetic subgroups examined fill different niches in DOM use in the two seasons.

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Figures

Fig 1
Fig 1
Relative abundance of bacterial groups in the Beaufort Sea (top) and Chukchi Sea (bottom). Each bar is the abundance in one sample. There were nine samples from the Beaufort Sea (six summer and three winter samples) and eight samples from the Chukchi Sea (four summer and four winter samples). Error bars are ±standard errors (SE) of probe-positive cells from 10 fields of view. Probe-positive cells are expressed as a percentage of all cells.
Fig 2
Fig 2
Percentage of total prokaryotes active in using leucine (top), glucose (middle), and amino acids (bottom). Bars are averages based on six summer and three winter samples from the Beaufort Sea and four summer and four winter samples from the Chukchi Sea. Error bars are 1 SE.
Fig 3
Fig 3
Percentage of cells within each bacterial group active in using leucine, glucose, and amino acids in the Beaufort Sea. Error bars are ±SE of probe-positive cells from 10 fields of view. Each bar represents one sampling site (six in summer and three in winter). No bar means that there were no active cells for that sample. Note the differences in scale for each graph.
Fig 4
Fig 4
Percentage of cells within each bacterial group active in using leucine, glucose, and amino acids in the Chukchi Sea. Error bars are ±SE of probe-positive cells from 10 fields of view. Each bar represents one sampling site (four in summer and four in winter). No bar means that there were no active cells for that sample. Note the differences in scale for each graph.
Fig 5
Fig 5
Relationship between abundance and activity of each phylogenetic subgroup for leucine, glucose, and amino acid uptake in the Beaufort Sea. The line represents the 1:1 line. Closed and open symbols are summer and winter samples, respectively, with ±SE.
Fig 6
Fig 6
Frequency distribution of silver grain area for all active cells using leucine in Beaufort (Beau) and Chukchi (Chuk) Seas. Silver grain area of active cells was sorted into 0.50-μm2 increments, and the relative number of cells per bin is plotted. Symbols represent the lower limit of a bin. For example, symbols at 0.5 represent cells with silver grain area from 0.50 to 0.99 μm2. Symbols at the 0 point represent cells with silver grain area from just above 0 to 0.49 μm2. S, summer; W, winter.
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