Abstract
Terrestrial sulfidic springs support diverse microbial communities by serving as stable conduits for geochemically diverse and nutrient-rich subsurface waters. Microorganisms that colonize terrestrial springs likely originate from groundwater, but may also be sourced from the surface. As such, the biogeographic distribution of microbial communities inhabiting sulfidic springs should be controlled by a combination of spring geochemistry and surface and subsurface transport mechanisms, and not necessarily geographic proximity to other springs. We examined the bacterial diversity of seven springs to test the hypothesis that occurrence of taxonomically similar microbes, important to the sulfur cycle, at each spring is controlled by geochemistry. Complementary Sanger sequencing and 454 pyrosequencing of 16S rRNA genes retrieved five proteobacterial classes, and Bacteroidetes, Chlorobi, Chloroflexi, and Firmicutes phyla from all springs, which suggested the potential for a core sulfidic spring microbiome. Among the putative sulfide-oxidizing groups (Epsilonproteobacteria and Gammaproteobacteria), up to 83% of the sequences from geochemically similar springs clustered together. Abundant populations of Hydrogenimonas-like or Sulfurovum-like spp. (Epsilonproteobacteria) occurred with abundant Thiothrix and Thiofaba spp. (Gammaproteobacteria), but Arcobacter-like and Sulfurimonas spp. (Epsilonproteobacteria) occurred with less abundant gammaproteobacterial populations. These distribution patterns confirmed that geochemistry rather than biogeography regulates bacterial dominance at each spring. Potential biogeographic controls were related to paleogeologic sedimentation patterns that could control long-term microbial transport mechanisms that link surface and subsurface environments. Knowing the composition of a core sulfidic spring microbial community could provide a way to monitor diversity changes if a system is threatened by anthropogenic processes or climate change.
Highlights
Dispersion (Martiny et al, 2006; Ramette and Tiedje, 2006; Telford et al, 2006) and transport due to wind (Smith et al, 2013), water (Sinton et al, 1997; Crump et al, 2012), and biology (Grossart et al, 2010) distribute microbes into different environments
Spring water temperature ranged from 7.5◦C at Richfield Springs to 45.3◦C at South Canyon Hot Spring (SCHS). pH ranged from 7.07 at Richfield Springs to 9.75 at Tully Valley 2* (TV2), and conductivity ranged from 647 μS/cm at Palmetto Springs to 32,800 μS/cm at TV2
This study examined the distribution of 16S rRNA genes across geochemically diverse, terrestrial sulfidic springs to identify common microbial communities to test the hypothesis that a core microbiome for sulfidic springs would be linked to similar geochemical conditions and not geographic distance
Summary
Dispersion (Martiny et al, 2006; Ramette and Tiedje, 2006; Telford et al, 2006) and transport due to wind (Smith et al, 2013), water (Sinton et al, 1997; Crump et al, 2012), and biology (Grossart et al, 2010) distribute microbes into different environments. Rock type (e.g., sandstone, limestone) and properties (e.g., fractured, karstified), as well as hydrostatic pressure and flow dynamics, influence where a spring discharges at the surface (Manga, 2001; Pitts and Alfaro, 2001; Cantonati et al, 2012), the position of a spring and its water composition can be nearly constant over time due to stable aquifer hydrogeochemical conditions (Prescott and Habermehl, 2008). A few studies attempt to correlate microbial genes (Zhang et al, 2008) and populations across multiple springs separated by varying geographic distances (Rudolph et al, 2004; Porter and Engel, 2008). There has been limited work to correlate presentday microbial communities separated by large geographic distances and differing in geologic processes (and geologic time) that may be affected by spring geochemistry (e.g., Bahl et al, 2011)
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