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Bacterial diversity differences along an epigenic cave stream reveal evidence of community dynamics, succession, and stability.

Brannen-Donnelly K, Engel AS - Front Microbiol (2015)

Bottom Line: Community succession, specifically as predictable exogenous heterotrophic microbial community succession, was evident from decreases in community richness from the Bio-Traps®, a peak in Bio-Trap® community biomass, and from changes in the composition of Bio-Trap® communities.The planktonic community was compositionally similar to Bio-Trap® initial colonizers, but the downstream Bio-Trap® community became more similar to the sediment community at the same location.These results can help in understanding the diversity of planktonic and attached microbial communities from karst, as well as microbial community dynamics, stability, and succession during disturbance or contamination responses over time.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth and Planetary Sciences, University of Tennessee Knoxville, TN, USA.

ABSTRACT
Unchanging physicochemical conditions and nutrient sources over long periods of time in cave and karst subsurface habitats, particularly aquifers, can support stable ecosystems, termed autochthonous microbial endokarst communities (AMEC). AMEC existence is unknown for other karst settings, such as epigenic cave streams. Conceptually, AMEC should not form in streams due to faster turnover rates and seasonal disturbances that have the capacity to transport large quantities of water and sediment and to change allochthonous nutrient and organic matter sources. Our goal was to investigate whether AMEC could form and persist in hydrologically active, epigenic cave streams. We analyzed bacterial diversity from cave water, sediments, and artificial substrates (Bio-Traps®) placed in the cave at upstream and downstream locations. Distinct communities existed for the water, sediments, and Bio-Trap® samplers. Throughout the study period, a subset of community members persisted in the water, regardless of hydrological disturbances. Stable habitat conditions based on flow regimes resulted in more than one contemporaneous, stable community throughout the epigenic cave stream. However, evidence for AMEC was insufficient for the cave water or sediments. Community succession, specifically as predictable exogenous heterotrophic microbial community succession, was evident from decreases in community richness from the Bio-Traps®, a peak in Bio-Trap® community biomass, and from changes in the composition of Bio-Trap® communities. The planktonic community was compositionally similar to Bio-Trap® initial colonizers, but the downstream Bio-Trap® community became more similar to the sediment community at the same location. These results can help in understanding the diversity of planktonic and attached microbial communities from karst, as well as microbial community dynamics, stability, and succession during disturbance or contamination responses over time.

No MeSH data available.


Bio-Trap®, sediment, and water biomass estimates from qPCR results, displayed as log (number of cells) over time for each type of sample at the surface, upstream, and downstream locations.
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Figure 2: Bio-Trap®, sediment, and water biomass estimates from qPCR results, displayed as log (number of cells) over time for each type of sample at the surface, upstream, and downstream locations.

Mentions: The number of 16S rRNA gene copies qPCR reaction ranged from 1 × 105 to 1 × 102 copies/sample, which was used to calculate biomass per gram of sediment or Bio-Trap® beads, or per mL water. Bio-Trap® samples had higher biomass (up to 2.6 × 106 cells/gram) than the other sample types; water had the least biomass at only 1 × 104 cells/mL (Figure 2). Sediment biomass was greatest in August and decreased through the winter months, but biomass in the cave stream was relatively stable throughout the study period. Biomass in the Bio-Trap® samplers for both sampling locations were nearly the same, with the least biomass at the beginning of the experiment and the highest biomass in November.


Bacterial diversity differences along an epigenic cave stream reveal evidence of community dynamics, succession, and stability.

Brannen-Donnelly K, Engel AS - Front Microbiol (2015)

Bio-Trap®, sediment, and water biomass estimates from qPCR results, displayed as log (number of cells) over time for each type of sample at the surface, upstream, and downstream locations.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508600&req=5

Figure 2: Bio-Trap®, sediment, and water biomass estimates from qPCR results, displayed as log (number of cells) over time for each type of sample at the surface, upstream, and downstream locations.
Mentions: The number of 16S rRNA gene copies qPCR reaction ranged from 1 × 105 to 1 × 102 copies/sample, which was used to calculate biomass per gram of sediment or Bio-Trap® beads, or per mL water. Bio-Trap® samples had higher biomass (up to 2.6 × 106 cells/gram) than the other sample types; water had the least biomass at only 1 × 104 cells/mL (Figure 2). Sediment biomass was greatest in August and decreased through the winter months, but biomass in the cave stream was relatively stable throughout the study period. Biomass in the Bio-Trap® samplers for both sampling locations were nearly the same, with the least biomass at the beginning of the experiment and the highest biomass in November.

Bottom Line: Community succession, specifically as predictable exogenous heterotrophic microbial community succession, was evident from decreases in community richness from the Bio-Traps®, a peak in Bio-Trap® community biomass, and from changes in the composition of Bio-Trap® communities.The planktonic community was compositionally similar to Bio-Trap® initial colonizers, but the downstream Bio-Trap® community became more similar to the sediment community at the same location.These results can help in understanding the diversity of planktonic and attached microbial communities from karst, as well as microbial community dynamics, stability, and succession during disturbance or contamination responses over time.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth and Planetary Sciences, University of Tennessee Knoxville, TN, USA.

ABSTRACT
Unchanging physicochemical conditions and nutrient sources over long periods of time in cave and karst subsurface habitats, particularly aquifers, can support stable ecosystems, termed autochthonous microbial endokarst communities (AMEC). AMEC existence is unknown for other karst settings, such as epigenic cave streams. Conceptually, AMEC should not form in streams due to faster turnover rates and seasonal disturbances that have the capacity to transport large quantities of water and sediment and to change allochthonous nutrient and organic matter sources. Our goal was to investigate whether AMEC could form and persist in hydrologically active, epigenic cave streams. We analyzed bacterial diversity from cave water, sediments, and artificial substrates (Bio-Traps®) placed in the cave at upstream and downstream locations. Distinct communities existed for the water, sediments, and Bio-Trap® samplers. Throughout the study period, a subset of community members persisted in the water, regardless of hydrological disturbances. Stable habitat conditions based on flow regimes resulted in more than one contemporaneous, stable community throughout the epigenic cave stream. However, evidence for AMEC was insufficient for the cave water or sediments. Community succession, specifically as predictable exogenous heterotrophic microbial community succession, was evident from decreases in community richness from the Bio-Traps®, a peak in Bio-Trap® community biomass, and from changes in the composition of Bio-Trap® communities. The planktonic community was compositionally similar to Bio-Trap® initial colonizers, but the downstream Bio-Trap® community became more similar to the sediment community at the same location. These results can help in understanding the diversity of planktonic and attached microbial communities from karst, as well as microbial community dynamics, stability, and succession during disturbance or contamination responses over time.

No MeSH data available.