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Particle-Associated Differ from Free-Living Bacteria in Surface Waters of the Baltic Sea.

Rieck A, Herlemann DP, Jürgens K, Grossart HP - Front Microbiol (2015)

Bottom Line: Although temporal and spatial gradients in environmental variables are known to shape BCC, it remains unclear how and to what extent PA and FL bacterial diversity responds to such environmental changes.To elucidate the BCC of both bacterial fractions related to different environmental settings, we studied surface samples of three Baltic Sea stations (marine, mesohaline, and oligohaline) in two different seasons (summer and fall/winter).In general, a high fraction of bacterial OTUs was found exclusively in the PA fraction (52% of total OTUs).

View Article: PubMed Central - PubMed

Affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries Stechlin, Germany.

ABSTRACT
Many studies on bacterial community composition (BCC) do not distinguish between particle-associated (PA) and free-living (FL) bacteria or neglect the PA fraction by pre-filtration removing most particles. Although temporal and spatial gradients in environmental variables are known to shape BCC, it remains unclear how and to what extent PA and FL bacterial diversity responds to such environmental changes. To elucidate the BCC of both bacterial fractions related to different environmental settings, we studied surface samples of three Baltic Sea stations (marine, mesohaline, and oligohaline) in two different seasons (summer and fall/winter). Amplicon sequencing of the 16 S rRNA gene revealed significant differences in BCC of both bacterial fractions among stations and seasons, with a particularly high number of PA operational taxonomic units (OTUs at genus-level) at the marine station in both seasons. "Shannon and Simpson indices" showed a higher diversity of PA than FL bacteria at the marine station in both seasons and at the oligohaline station in fall/winter. In general, a high fraction of bacterial OTUs was found exclusively in the PA fraction (52% of total OTUs). These findings indicate that PA bacteria significantly contribute to overall bacterial richness and that they differ from FL bacteria. Therefore, to gain a deeper understanding on diversity and dynamics of aquatic bacteria, PA and FL bacteria should be generally studied independently.

No MeSH data available.


Unweighted-pair group method with arithmetic mean (UPGMA) dendrograms based on Bray–Curtis dissimilarities of total bacteria in summer (A) and winter samples (B) of the three stations (marine, mesohaline, oligohaline). And non-metric multidimensional scaling (NMDS) for particle-associated (PA) and free-living (FL) bacteria in summer (C) and winter samples (D) of the three stations, with light gray: stations considered as “marine” (mar), dark gray: stations considered as “mesohaline” (meso) and black: stations considered as “oligohaline” (oligo). So, summer; Wi, winter; squares, PA; and dots, FL.
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Figure 5: Unweighted-pair group method with arithmetic mean (UPGMA) dendrograms based on Bray–Curtis dissimilarities of total bacteria in summer (A) and winter samples (B) of the three stations (marine, mesohaline, oligohaline). And non-metric multidimensional scaling (NMDS) for particle-associated (PA) and free-living (FL) bacteria in summer (C) and winter samples (D) of the three stations, with light gray: stations considered as “marine” (mar), dark gray: stations considered as “mesohaline” (meso) and black: stations considered as “oligohaline” (oligo). So, summer; Wi, winter; squares, PA; and dots, FL.

Mentions: The total BCC revealed significant differences between marine, mesohaline and oligohaline stations for both studied seasons (Table 2) even though this shift was less clear in fall/winter. In summer, BCC of the mesohaline station was more similar to the marine station, whereas in fall/winter it was more similar to the oligohaline station (Figures 5A,B). BCC varied with stations, fractions, and sampling time, except BCC of the oligohaline station did not significantly differ between both seasons (Table 2). Supplemental Figure S1C shows that this pattern was mainly explained by FL bacteria being highly similar in summer and fall/winter. Changes in BCC with stations revealed a stronger significance in summer (R = 1.00, p = 0.002) than in fall/winter (R = 0.78, p = 0.003), and differences in BCC between stations were lower when comparing the neighboring stations (mesohaline vs. marine or mesohaline vs. oligohaline) (Table 2). Differences in BCC were mainly explained by the higher overall bacterial α-diversity in fall/winter compared to the summer samples and changes in the dominant phyla (Figure 3). Differences between PA and FL BCC were more significant in fall/winter than in summer (Table 2). Thereby, the mesohaline station showed, together with the oligohaline station, the lowest differences between FL and PA fractions in summer (Supplemental Figures S1A–D). At all stations there were differences in PA vs. FL BCC in summer as well as in fall/winter (Figures 5C,D). The high BCC similarity of meso- and oligohaline samples in fall/winter is based on both fractions (PA and FL). Generally, there was a significant difference between PA and FL BCC within stations or seasons (Table 2, Supplemental Figure S2). Comparing each sample within season and station with a Wilcoxon rank sum test revealed a significant difference between both fractions at the marine station in both seasons as well as at the oligohaline station in fall/winter. Differences between bacteria fractions at the mesohaline station, however, remained non-significant (Supplemental Table S1).


Particle-Associated Differ from Free-Living Bacteria in Surface Waters of the Baltic Sea.

Rieck A, Herlemann DP, Jürgens K, Grossart HP - Front Microbiol (2015)

Unweighted-pair group method with arithmetic mean (UPGMA) dendrograms based on Bray–Curtis dissimilarities of total bacteria in summer (A) and winter samples (B) of the three stations (marine, mesohaline, oligohaline). And non-metric multidimensional scaling (NMDS) for particle-associated (PA) and free-living (FL) bacteria in summer (C) and winter samples (D) of the three stations, with light gray: stations considered as “marine” (mar), dark gray: stations considered as “mesohaline” (meso) and black: stations considered as “oligohaline” (oligo). So, summer; Wi, winter; squares, PA; and dots, FL.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664634&req=5

Figure 5: Unweighted-pair group method with arithmetic mean (UPGMA) dendrograms based on Bray–Curtis dissimilarities of total bacteria in summer (A) and winter samples (B) of the three stations (marine, mesohaline, oligohaline). And non-metric multidimensional scaling (NMDS) for particle-associated (PA) and free-living (FL) bacteria in summer (C) and winter samples (D) of the three stations, with light gray: stations considered as “marine” (mar), dark gray: stations considered as “mesohaline” (meso) and black: stations considered as “oligohaline” (oligo). So, summer; Wi, winter; squares, PA; and dots, FL.
Mentions: The total BCC revealed significant differences between marine, mesohaline and oligohaline stations for both studied seasons (Table 2) even though this shift was less clear in fall/winter. In summer, BCC of the mesohaline station was more similar to the marine station, whereas in fall/winter it was more similar to the oligohaline station (Figures 5A,B). BCC varied with stations, fractions, and sampling time, except BCC of the oligohaline station did not significantly differ between both seasons (Table 2). Supplemental Figure S1C shows that this pattern was mainly explained by FL bacteria being highly similar in summer and fall/winter. Changes in BCC with stations revealed a stronger significance in summer (R = 1.00, p = 0.002) than in fall/winter (R = 0.78, p = 0.003), and differences in BCC between stations were lower when comparing the neighboring stations (mesohaline vs. marine or mesohaline vs. oligohaline) (Table 2). Differences in BCC were mainly explained by the higher overall bacterial α-diversity in fall/winter compared to the summer samples and changes in the dominant phyla (Figure 3). Differences between PA and FL BCC were more significant in fall/winter than in summer (Table 2). Thereby, the mesohaline station showed, together with the oligohaline station, the lowest differences between FL and PA fractions in summer (Supplemental Figures S1A–D). At all stations there were differences in PA vs. FL BCC in summer as well as in fall/winter (Figures 5C,D). The high BCC similarity of meso- and oligohaline samples in fall/winter is based on both fractions (PA and FL). Generally, there was a significant difference between PA and FL BCC within stations or seasons (Table 2, Supplemental Figure S2). Comparing each sample within season and station with a Wilcoxon rank sum test revealed a significant difference between both fractions at the marine station in both seasons as well as at the oligohaline station in fall/winter. Differences between bacteria fractions at the mesohaline station, however, remained non-significant (Supplemental Table S1).

Bottom Line: Although temporal and spatial gradients in environmental variables are known to shape BCC, it remains unclear how and to what extent PA and FL bacterial diversity responds to such environmental changes.To elucidate the BCC of both bacterial fractions related to different environmental settings, we studied surface samples of three Baltic Sea stations (marine, mesohaline, and oligohaline) in two different seasons (summer and fall/winter).In general, a high fraction of bacterial OTUs was found exclusively in the PA fraction (52% of total OTUs).

View Article: PubMed Central - PubMed

Affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries Stechlin, Germany.

ABSTRACT
Many studies on bacterial community composition (BCC) do not distinguish between particle-associated (PA) and free-living (FL) bacteria or neglect the PA fraction by pre-filtration removing most particles. Although temporal and spatial gradients in environmental variables are known to shape BCC, it remains unclear how and to what extent PA and FL bacterial diversity responds to such environmental changes. To elucidate the BCC of both bacterial fractions related to different environmental settings, we studied surface samples of three Baltic Sea stations (marine, mesohaline, and oligohaline) in two different seasons (summer and fall/winter). Amplicon sequencing of the 16 S rRNA gene revealed significant differences in BCC of both bacterial fractions among stations and seasons, with a particularly high number of PA operational taxonomic units (OTUs at genus-level) at the marine station in both seasons. "Shannon and Simpson indices" showed a higher diversity of PA than FL bacteria at the marine station in both seasons and at the oligohaline station in fall/winter. In general, a high fraction of bacterial OTUs was found exclusively in the PA fraction (52% of total OTUs). These findings indicate that PA bacteria significantly contribute to overall bacterial richness and that they differ from FL bacteria. Therefore, to gain a deeper understanding on diversity and dynamics of aquatic bacteria, PA and FL bacteria should be generally studied independently.

No MeSH data available.