Microbial Ecology

, Volume 75, Issue 1, pp 38–51 | Cite as

Microbial Composition and Diversity Patterns in Deep Hyperthermal Aquifers from the Western Plain of Romania

  • Cecilia M. Chiriac
  • Andreea Baricz
  • Edina Szekeres
  • Knut Rudi
  • Nicolae Dragoș
  • Cristian ComanEmail author
Microbiology of Aquatic Systems


A limited number of studies have investigated the biodiversity in deep continental hyperthermal aquifers and its influencing factors. Here, we present the first description of microbial communities inhabiting the Pannonian and Triassic hyperthermal aquifers from the Western Plain of Romania, the first one being considered a deposit of “fossilized waters,” while the latter is embedded in the hydrological cycle due to natural refilling. The 11 investigated drillings have an open interval between 952 and 3432 m below the surface, with collected water temperatures ranging between 47 and 104 °C, these being the first microbial communities characterized in deep continental water deposits with outflow temperatures exceeding 80 °C. The abundances of bacterial 16S rRNA genes varied from approximately 105–106 mL−1 in the Pannonian to about 102–104 mL−1 in the Triassic aquifer. A 16S rRNA gene metabarcoding analysis revealed distinct microbial communities in the two water deposits, especially in the rare taxa composition. The Pannonian aquifer was dominated by the bacterial genera Hydrogenophilus and Thermodesulfobacterium, together with archaeal methanogens from the Methanosaeta and Methanothermobacter groups. Firmicutes was prevalent in the Triassic deposit with a large number of OTUs affiliated to Thermoanaerobacteriaceae, Thermacetogenium, and Desulfotomaculum. Species richness, evenness, and phylogenetic diversity increased alongside with the abundance of mesophiles, their presence in the Triassic aquifer being most probably caused by the refilling with large quantities of meteoric water in the Carpathian Mountains. Altogether, our results show that the particular physico-cheminal characteristics of each aquifer, together with the water refilling possibilities, seem to determine the microbial community structure.


Deep biosphere Continental aquifer Microbial composition Hyperthermal water 16S rRNA gene Diversity patterns 



This work was partially supported by the EnviroAMR project (grant no. 3499/20.05.2015, financed through the EEA 2009-2014 Financial Mechanism) through the EnviroBioInfo bioinformatic center. CMC and ES were also supported by the POSDRU/187/1.5/S/155383 research scholarship programme. All the samples were collected with the approval of S.C. TRANSGEX S.A. company. The authors wish to thank Dr. Codruta Bendea (University of Oradea) and Sanda Sferle (TRANSGEX) for their valuable support towards obtaining the water samples.

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Copyright information

© Springer Science+Business Media, LLC 2017

Authors and Affiliations

  • Cecilia M. Chiriac
    • 1
    • 2
  • Andreea Baricz
    • 1
    • 2
  • Edina Szekeres
    • 1
    • 2
  • Knut Rudi
    • 3
  • Nicolae Dragoș
    • 1
    • 2
  • Cristian Coman
    • 1
    Email author
  1. 1.NIRDBS, Institute of Biological ResearchCluj-NapocaRomania
  2. 2.Molecular Biology and Biotechnology Department, Faculty of Biology and GeologyBabeş-Bolyai UniversityCluj-NapocaRomania
  3. 3.Chemistry, Biotechnology and Food Science DepartmentNorwegian University of Life SciencesAasNorway

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