title: Comparisons of the composition and biogeographic distribution of the bacterial communities occupying South African thermal springs with those inhabiting deep subsurface fracture water.
abstract: South Africa has numerous thermal springs that represent topographically driven meteoric water migrating along major fracture zones. The temperature (40-70°C) and pH (8-9) of the thermal springs in the Limpopo Province are very similar to those of the low salinity fracture water encountered in the South African mines at depths ranging from 1.0 to 3.1 km. The major cation and anion composition of these thermal springs are very similar to that of the deep fracture water with the exception of the dissolved inorganic carbon and dissolved O2, both of which are typically higher in the springs than in the deep fracture water. The in situ biological relatedness of such thermal springs and the subsurface fracture fluids that feed them has not previously been evaluated. In this study, we evaluated the microbial diversity of six thermal spring and six subsurface sites in South Africa using high-throughput sequencing of 16S rRNA gene hypervariable regions. Proteobacteria were identified as the dominant phylum within both subsurface and thermal spring environments, but only one genera, Rheinheimera, was identified among all samples. Using Morisita similarity indices as a metric for pairwise comparisons between sites, we found that the communities of thermal springs are highly distinct from subsurface datasets. Although the Limpopo thermal springs do not appear to provide a new window for viewing subsurface bacterial communities, we report that the taxonomic compositions of the subsurface sites studied are more similar than previous results would indicate and provide evidence that the microbial communities sampled at depth are more correlated to subsurface conditions than geographical distance.
authors.affiliation: Department of Geosciences, Princeton University Princeton, NJ, USA.
authors.forename: Cara
authors.initials: C
authors.lastname: Magnabosco
authors.affiliation: Department of Environmental Sciences, School of Agriculture and Environmental Sciences, University of South Africa Florida, South Africa.
authors.forename: Memory
authors.initials: M
authors.lastname: Tekere
authors.affiliation: Department of Geosciences, Princeton University Princeton, NJ, USA.
authors.forename: Maggie C Y
authors.initials: MC
authors.lastname: Lau
authors.affiliation: Department of Microbial, Biochemical and Food Biotechnology, University of the Free State Bloemfontein, South Africa.
authors.forename: Borja
authors.initials: B
authors.lastname: Linage
authors.affiliation: Department of Microbial, Biochemical and Food Biotechnology, University of the Free State Bloemfontein, South Africa.
authors.forename: Olukayode
authors.initials: O
authors.lastname: Kuloyo
authors.affiliation: Department of Microbial, Biochemical and Food Biotechnology, University of the Free State Bloemfontein, South Africa.
authors.forename: Mariana
authors.initials: M
authors.lastname: Erasmus
authors.affiliation: Department of Microbial, Biochemical and Food Biotechnology, University of the Free State Bloemfontein, South Africa.
authors.forename: Errol
authors.initials: E
authors.lastname: Cason
authors.affiliation: Department of Microbial, Biochemical and Food Biotechnology, University of the Free State Bloemfontein, South Africa.
authors.forename: Esta
authors.initials: E
authors.lastname: van Heerden
authors.affiliation: Extreme Life Isyensya Gentbrugge, Belgium.
authors.forename: Gaetan
authors.initials: G
authors.lastname: Borgonie
authors.affiliation: Biology Department, New Mexico Institute of Mining and Technology Socorro, NM, USA.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Kieft
authors.affiliation: Department of Environmental Sciences, School of Agriculture and Environmental Sciences, University of South Africa Florida, South Africa.
authors.forename: Jana
authors.initials: J
authors.lastname: Olivier
authors.affiliation: Department of Geosciences, Princeton University Princeton, NJ, USA.
authors.forename: Tullis C
authors.initials: TC
authors.lastname: Onstott
keywords: 16S rRNA gene; V6 hypervariable region; diversity; subsurface; thermal springs