title: Calcite biomineralization by bacterial isolates from the recently discovered pristine karstic herrenberg cave.
abstract: Karstic caves represent one of the most important subterranean carbon storages on Earth and provide windows into the subsurface. The recent discovery of the Herrenberg Cave, Germany, gave us the opportunity to investigate the diversity and potential role of bacteria in carbonate mineral formation. Calcite was the only mineral observed by Raman spectroscopy to precipitate as stalactites from seepage water. Bacterial cells were found on the surface and interior of stalactites by confocal laser scanning microscopy. Proteobacteria dominated the microbial communities inhabiting stalactites, representing more than 70% of total 16S rRNA gene clones. Proteobacteria formed 22 to 34% of the detected communities in fluvial sediments, and a large fraction of these bacteria were also metabolically active. A total of 9 isolates, belonging to the genera Arthrobacter, Flavobacterium, Pseudomonas, Rhodococcus, Serratia, and Stenotrophomonas, grew on alkaline carbonate-precipitating medium. Two cultures with the most intense precipitate formation, Arthrobacter sulfonivorans and Rhodococcus globerulus, grew as aggregates, produced extracellular polymeric substances (EPS), and formed mixtures of calcite, vaterite, and monohydrocalcite. R. globerulus formed idiomorphous crystals with rhombohedral morphology, whereas A. sulfonivorans formed xenomorphous globular crystals, evidence for taxon-specific crystal morphologies. The results of this study highlighted the importance of combining various techniques in order to understand the geomicrobiology of karstic caves, but further studies are needed to determine whether the mineralogical biosignatures found in nutrient-rich media can also be found in oligotrophic caves.
authors.affiliation: Aquatic Geomicrobiology Group, Institute of Ecology, Friedrich Schiller University Jena, Jena, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Rusznyák
authors.forename: Denise M
authors.initials: DM
authors.lastname: Akob
authors.forename: Sándor
authors.initials: S
authors.lastname: Nietzsche
authors.forename: Karin
authors.initials: K
authors.lastname: Eusterhues
authors.forename: Kai Uwe
authors.initials: KU
authors.lastname: Totsche
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Neu
authors.forename: Torsten
authors.initials: T
authors.lastname: Frosch
authors.forename: Jürgen
authors.initials: J
authors.lastname: Popp
authors.forename: Robert
authors.initials: R
authors.lastname: Keiner
authors.forename: Jörn
authors.initials: J
authors.lastname: Geletneky
authors.forename: Lutz
authors.initials: L
authors.lastname: Katzschmann
authors.forename: Ernst-Detlef
authors.initials: ED
authors.lastname: Schulze
authors.forename: Kirsten
authors.initials: K
authors.lastname: Küsel
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D044822:Biodiversity; D001711:Biotransformation; D002119:Calcium Carbonate / Q000378:metabolism*; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D005858:Germany; D060587:Groundwater / Q000382:microbiology*; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D013059:Spectrum Analysis, Raman
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D002119:Calcium Carbonate