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| Titel |
Iron encrustations on filamentous algae colonized by Gallionella-related bacteria in a metal-polluted freshwater stream |
| VerfasserIn |
J. F. Mori, T. R. Neu, S. Lu, M. Händel, K. U. Totsche, K. Küsel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 18 ; Nr. 12, no. 18 (2015-09-16), S.5277-5289 |
| Datensatznummer |
250118089
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| Publikation (Nr.) |
 copernicus.org/bg-12-5277-2015.pdf |
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| Zusammenfassung |
| Filamentous macroscopic algae were observed in slightly acidic to
circumneutral (pH 5.9–6.5), metal-rich stream water that
leaked out from a former uranium mining district (Ronneburg, Germany). These
algae differed in color and morphology and were encrusted with Fe-deposits. To
elucidate their potential interaction with Fe(II)-oxidizing bacteria (FeOB),
we collected algal samples at three time points during summer 2013 and
studied the algae-bacteria-mineral compositions via confocal laser scanning
microscopy (CLSM), scanning electron microscopy (SEM), Fourier transform
infrared (FTIR) spectra, and a 16S and 18S rRNA gene-based bacterial and
algae community analysis. Surprisingly, sequencing analysis of 18S rRNA gene
regions of green and brown algae revealed high homologies with the
freshwater algae Tribonema (99.9–100 %). CLSM imaging indicated a
loss of active chloroplasts in the algae cells, which may be responsible for
the change in color in . Fe(III)-precipitates on algal cells identified as
ferrihydrite and schwertmannite by FTIR were associated with microbes and
extracellular polymeric substances (EPS)-like glycoconjugates. SEM imaging
revealed that while the green algae were fully encrusted with
Fe-precipitates, the brown algae often exhibited discontinuous series of
precipitates. This pattern was likely due to the intercalary growth of algal
filaments which allowed them to avoid detrimental encrustation. 16S rRNA
gene-targeted studies revealed that Gallionella-related FeOB dominated the bacterial
RNA and DNA communities (70–97 and 63–96 %, respectively), suggesting
their capacity to compete with the abiotic Fe-oxidation under the putative
oxygen-saturated conditions that occur in association with photosynthetic
algae. Quantitative PCR (polymerase chain reaction) revealed even higher Gallionella-related 16S rRNA gene copy
numbers on the surface of green algae compared to the brown algae. The
latter harbored a higher microbial diversity, including some putative
predators of algae. A loss of chloroplasts in the brown algae could have led
to lower photosynthetic activities and reduced EPS production, which is known
to affect predator colonization. Collectively, our results suggest the
coexistence of oxygen-generating algae Tribonema sp. and strictly microaerophilic
neutrophilic FeOB in a heavy metal-rich environment. |
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