Limits...
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.


Venn diagram of OTU distribution of the normalized data between marine (mar), mesohaline (meso) and oligohaline (oligo) samples in summer (A) and winter (B) (areas are proportional to OTU number). Relative abundances of all exclusive and shared OTUs in either particle-associated fraction, free-living fraction or both fractions are shown.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4664634&req=5

Figure 2: Venn diagram of OTU distribution of the normalized data between marine (mar), mesohaline (meso) and oligohaline (oligo) samples in summer (A) and winter (B) (areas are proportional to OTU number). Relative abundances of all exclusive and shared OTUs in either particle-associated fraction, free-living fraction or both fractions are shown.

Mentions: The α-diversity measures the OTU diversity of individual samples. The OTU distribution (Figure 2) showed a higher overall bacterial diversity in fall/winter than in summer. Out of the total 348 bacterial OTUs in summer, 184 OTUs were found at the marine, 158 OTUs at the mesohaline and 213 OTUs at the oligohaline stations. In summer, the oligohaline station with the lowest water temperature had the highest total bacterial α-diversity and the mesohaline station the lowest. In fall/winter, the total number of OTUs was higher (547), with 340 OTUs at the marine, 251 OTUs at the mesohaline, and 281 OTUs at the oligohaline station. The majority of OTUs at the mesohaline station was shared with those found at the other stations. Only a small proportion exclusively occurred at the mesohaline station, with a higher proportion in fall/winter. At the mesohaline station, there was a high number of shared OTUs with either the marine or oligohaline stations. Interestingly, when comparing all bacterial fractions, high numbers of both PA and FL OTUs were related to those OTUs, which occurred at all three stations. A high number of exclusively PA OTUs occurred in almost all samples (52% of total OTUs and 59% of the OTUs in winter), with a particularly high number of exclusively PA OTUs at the marine station in both seasons (71% in winter and 53% in summer). A high number of both PA and FL OTUs were shared between oligohaline and mesohaline stations and surprisingly also between the marine and oligohaline stations. Comparison of α-diversity indices (Figure 3) showed that richness was significantly higher in the PA fraction (Wilcoxon rank sum test: W = 268, p = 0.0008), but a pairwise comparison of each station showed no significant difference for the mesohaline station in both seasons and the oligohaline station in summer (Supplemental Table S1). The “Simpson index” [1-D] indicated that PA and FL fractions were in general evenly distributed at the marine station, but not at the meso- and oligohaline stations, where single taxa dominated the system. “Shannon and Simpson indices” showed higher diversity of PA bacteria at the marine station in both seasons and at the oligohaline station in fall/winter. Evenness was higher in the FL fraction at the mesohaline station in both seasons and the oligohaline station in summer. Generally, samples with a low evenness showed also a low diversity in the Shannon and Simpson indices (raw data shown in Supplemental Table S2).


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)

Venn diagram of OTU distribution of the normalized data between marine (mar), mesohaline (meso) and oligohaline (oligo) samples in summer (A) and winter (B) (areas are proportional to OTU number). Relative abundances of all exclusive and shared OTUs in either particle-associated fraction, free-living fraction or both fractions are shown.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Venn diagram of OTU distribution of the normalized data between marine (mar), mesohaline (meso) and oligohaline (oligo) samples in summer (A) and winter (B) (areas are proportional to OTU number). Relative abundances of all exclusive and shared OTUs in either particle-associated fraction, free-living fraction or both fractions are shown.
Mentions: The α-diversity measures the OTU diversity of individual samples. The OTU distribution (Figure 2) showed a higher overall bacterial diversity in fall/winter than in summer. Out of the total 348 bacterial OTUs in summer, 184 OTUs were found at the marine, 158 OTUs at the mesohaline and 213 OTUs at the oligohaline stations. In summer, the oligohaline station with the lowest water temperature had the highest total bacterial α-diversity and the mesohaline station the lowest. In fall/winter, the total number of OTUs was higher (547), with 340 OTUs at the marine, 251 OTUs at the mesohaline, and 281 OTUs at the oligohaline station. The majority of OTUs at the mesohaline station was shared with those found at the other stations. Only a small proportion exclusively occurred at the mesohaline station, with a higher proportion in fall/winter. At the mesohaline station, there was a high number of shared OTUs with either the marine or oligohaline stations. Interestingly, when comparing all bacterial fractions, high numbers of both PA and FL OTUs were related to those OTUs, which occurred at all three stations. A high number of exclusively PA OTUs occurred in almost all samples (52% of total OTUs and 59% of the OTUs in winter), with a particularly high number of exclusively PA OTUs at the marine station in both seasons (71% in winter and 53% in summer). A high number of both PA and FL OTUs were shared between oligohaline and mesohaline stations and surprisingly also between the marine and oligohaline stations. Comparison of α-diversity indices (Figure 3) showed that richness was significantly higher in the PA fraction (Wilcoxon rank sum test: W = 268, p = 0.0008), but a pairwise comparison of each station showed no significant difference for the mesohaline station in both seasons and the oligohaline station in summer (Supplemental Table S1). The “Simpson index” [1-D] indicated that PA and FL fractions were in general evenly distributed at the marine station, but not at the meso- and oligohaline stations, where single taxa dominated the system. “Shannon and Simpson indices” showed higher diversity of PA bacteria at the marine station in both seasons and at the oligohaline station in fall/winter. Evenness was higher in the FL fraction at the mesohaline station in both seasons and the oligohaline station in summer. Generally, samples with a low evenness showed also a low diversity in the Shannon and Simpson indices (raw data shown in Supplemental Table S2).

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.