Spatial Dominance and Inorganic Carbon Assimilation by Conspicuous Autotrophic Biofilms in a Physical and Chemical Gradient of a Cold Sulfurous Spring: The Role of Differential Ecological Strategies |
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Authors: | Antonio Camacho Carlos Rochera Juan José Silvestre Eduardo Vicente Martin W Hahn |
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Institution: | (1) Department of Microbiology and Ecology and Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, E-46100 Burjassot, Spain;(2) Institute for Limnology, Austrian Academy of Sciences, Mondseestrasse 9, A-5310 Mondsee, Austria |
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Abstract: | The community composition and ecophysiological features of microbial autotrophic biofilms were studied in Fuente Podrida,
a cold sulfur spring located in East Spain. We demonstrated how different ecophysiological strategies, such as resistance
and/or utilization of sulfide and oxygen, light adaptation, or resistance to high water flow, allow each of the microorganisms
described to efficiently colonize several areas within the environmental gradient. In the zone of the spring constantly influenced
by sulfide-rich waters, biofilms were formed by purple bacteria, cyanobacteria, and filamentous colorless sulfur bacteria.
Purple bacteria showed higher photosynthetic efficiency per pigment unit than cyanobacteria, although they were dominant only
in anoxic areas. Two filamentous cyanobacteria, strain UVFP1 and strain UVFP2, were also abundant in the sulfide-rich area.
Whereas the cyanobacterial strain UVFP2 shows a strategy based on the resistance to sulfide of oxygenic photosynthesis, strain
UVFP1, additionally, has the capacity for sulfide-driven anoxygenic photosynthesis. Molecular phylogenetic analyses cluster
the benthic strain UVFP1 with genus Planktothrix, but with no particular species, whereas UVFP2 does not closely cluster with any known cyanobacterial species. The colorless
sulfur bacterium Thiothrix sp. extended throughout the zone in which both sulfide and oxygen were present, exhibiting its capacity for chemolithoautotrophic
dark carbon fixation. Downstream from the source, where springwater mixes with well-oxygenated stream water and sulfide disappears,
autotrophic biofilms were dominated by diatoms showing higher photosynthetic rates than cyanobacteria and, by a lesser extent,
by a sulfide-sensitive cyanobacterium (strain UVFP3) well adapted to low light availability, although in the areas of higher
water velocity far from the river shore, the dominance shifted to crust-forming cyanobacteria. Both types of microorganisms
were highly sensitive to sulfide impeding them from occupying sulfide-rich areas of the spring. Sulfide, oxygen, light availability,
and water velocity appear as the main factors structuring the autotrophic community of Fuente Podrida spring.
An erratum to this article is availbale at . |
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