Bacterial diversity and ecosystem function of filamentous microbial mats from aphotic (cave) sulfidic springs dominated by chemolithoautotrophic 'Epsilonproteobacteria', 2004,
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Engel As, Porter Ml, Stern La, Quinlan S, Bennett Pc,

Filamentous microbial mats from three aphotic sulfidic springs in Lower Kane Cave. Wyoming. were assessed with regard to bacterial diversity, community structure, and ecosystem function using a 16S rDNA-based phylogenetic approach combined with elemental content and stable carbon isotope ratio analyses. The most prevalent mat morphotype consisted of while filament bundles, with low C:N ratios (3.5-5.4) and high sulfur content (16.1-51.2%). White filament bundles and two other mat morphotypes organic carbon isotope values (mean delta(13)C = -34.7parts per thousand: 1sigma = 3.6) consistent with chemolithoautotrophic carbon fixation from a dissolved inorganic carbon reservoir (cave water, mean delta(13)C = -7.47parts per thousand for two springs, n = 8). Bacterial diversity was as low overall in the clone libraries, and the most abundant taxonomic group was affiliated with the 'Epsilonproteobacteria' (68%) with other bacterial sequences affiliated with Gammaproteobacteria (12.2%), Betaproteobacteria (11.7%), Deltaproteobacteria (0.8%), and the Acidobacterium (5.6%) and Bacteriodetes/Chlorobi (1.7%) divisions. Six distinct epsilonproteobacterial taxonomic groups were identified from the microbial mats. Epsilonproteobacterial and bacterial group abundances and community structure shifted front the spring orifices downstream. corresponding to changes in dissolved sulfide and oxygen concentrations and metabolic requirements of certain bacterial groups. Most of the clone sequences for epsilonproteobacterial groups were retrieved from areas with high sulfide and low oxygen concentrations, whereas Thiothrix spp. and Thiobacillus spp. had higher retrieved clone abundances where conditions of low sulfide and high oxygen concentrations were measured. Genetic and metabolic diversity among the 'Epsilonproteobacteria' maximizes overall cave ecosystem function, and these organisms play a significant role in providing chemolithoautotrophic energy to the otherwise nutrient-poor cave habitat. Our results demonstrate that sulfur cycling supports subsurface ecosystem through chemolithoautotrophy and expand the evolutionary and ecological views of 'Epsilonproteobacteria' in terrestrial habitats. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier BY. All rights reserved

Productivity-Diversity Relationships from Chemolithoautotrophically Based Sulfidic Karst Systems, 2009,
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Porter M. L. , Summers Engel A. , Kane T. C. And Kinkle B. K.

Although ecosystems thriving in the absence of photosynthetic processes are no longer considered unique phenomena, we have yet to understand how these ecosystems are energetically sustained via chemosynthesis. Ecosystem energetics were measured in microbial mats from active sulfidic caves (Movile Cave, Romania; Frasassi Caves, Italy; Lower Kane Cave, Wyoming, USA; and Cesspool Cave, Virginia, USA) using radiotracer techniques. We also estimated bacterial diversity using 16S rRNA sequences to relate the productivity measurements to the composition of the microbial communities. All of the microbial communities investigated were dominated by chemolithoautotrophic productivity, with the highest rates from Movile Cave at 281 g C/m2/yr. Heterotrophic productivities were at least one order of magnitude less than autotrophy from all of the caves. We generated 414 new 16S rRNA gene sequences that represented 173 operational taxonomic units (OTUs) with 99% sequence similarity. Although 13% of these OTUs were found in more than one cave, the compositions of each community were significantly different from each other (P?0.001). Autotrophic productivity was positively correlated with overall species richness and with the number of bacterial OTUs affiliated with the Epsilonproteobacteria, a group known for sulfur cycling and chemolithoautotrophy. Higher rates of autotrophy were also strongly positively correlated to available metabolic energy sources, and specifically to dissolved sulfide concentrations. The relationship of autotrophic productivity and heterotrophic cycling rates to bacterial species richness can significantly impact the diversity of higher trophic levels in chemolithoautotrophically-based cave ecosystems, with the systems possessing the highest productivity supporting abundant and diverse macro-invertebrate communities.

Productivity-Diversity Relationships from Chemolithoautotrophically Based Sulfidic Karst Systems, 2009,
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Porter M. L. , Summers Engel A. , Kane T. C. , Kinkle B. K.

Although ecosystems thriving in the absence of photosynthetic processes are no longer considered unique phenomena, we have yet to understand how these ecosystems are energetically sustained via chemosynthesis. Ecosystem energetics were measured in microbial mats from active sulfidic caves (Movile Cave, Romania; Frasassi Caves, Italy; Lower Kane Cave, Wyoming, USA; and Cesspool Cave, Virginia, USA) using radiotracer techniques. We also estimated bacterial diversity using 16S rRNA sequences to relate the productivity measurements to the composition of the microbial communities. All of the microbial communities investigated were dominated by chemolithoautotrophic productivity, with the highest rates from Movile Cave at 281 g C/m2/yr. Heterotrophic productivities were at least one order of magnitude less than autotrophy from all of the caves. We generated 414 new 16S rRNA gene sequences that represented 173 operational taxonomic units (OTUs) with 99% sequence similarity. Although 13% of these OTUs were found in more than one cave, the compositions of each community were significantly different from each other (P≤0.001). Autotrophic productivity was positively correlated with overall species richness and with the number of bacterial OTUs affiliated with the Epsilonproteobacteria, a group known for sulfur cycling and chemolithoautotrophy. Higher rates of autotrophy were also strongly positively correlated to available metabolic energy sources, and specifically to dissolved sulfide concentrations. The relationship of autotrophic productivity and heterotrophic cycling rates to bacterial species richness can significantly impact the diversity of higher trophic levels in chemolithoautotrophically-based cave ecosystems, with the systems possessing the highest productivity supporting abundant and diverse macro-invertebrate communities.