Microorganisms in radioactive thermal springs

The hypothesis of the presence of deep hot biosphere by Thomas Gold predicts that all life inside the Earth, if it were brought to the surface from as much as 5 km down, might form a layer 1.5 m thick, covering all land surfaces, and weighing more than all flora and fauna together. This biomass would consist of microorganisms, mainly bacteria and archaea. Numerous recent findings have indeed confirmed the presence of subterranean microbial communities in deep drilling bore cores, in seafloor sediments, in oil reservoirs and in ultradeep gold and uranium mines. Thermal springs, which are delivering their water from reservoirs in the rocks, are in contact with the subterranean biosphere and can transport members from these environments to the surface, thus providing a link between surface and subsurface. Bad Gastein, a village in the Central Alps near Salzburg, Austria, is known for its thermal mineral springs, which contain slightly radioactive waters. A cluster of 17 major springs with temperatures up to 47C provide about 4 to 5 million liters of water per day. Microscopic studies have shown a vast diversity of cells, some of very small sizes (nanobacteria) in biofilms on the rock surfaces of the springs and in the water, following deposition of biomass on glass slides. Analysis of amplified16S rRNA genes revealed the presence of numerous archaeal and bacterial phylotypes, which showed similarities or, in some cases, only low relatedness to known prokaryotes. Questions about the energy and carbon sources for this life without sunlight are unanswered and will be explored in this study. Specifically, non-thermophilic crenarchaeota, which have become a focal point of interest due to their wide occurrence (also in the thermal springs) and possible involvement in the global nitrogen cycle will be investigated. Other groups are potentially hydrogen- or methaneconsuming, ammonia- or metal-oxidizing microorganisms, which are probably present by evidence of signature-like sequences. Culturing of prokaryotes will be carried out, but also culture-independent techniques will be used, such as stable isotope probing and a metagenomic search for functional genes. To be expected are the identification of genes for ammonia monooxygenase (amo), nitrate reductase/s (nir), particulate methane monooxygenase (pmo), and others. In addition, fluorescent in-situ hybridisation (FISH) and EDX (energy dispersive X-ray) electron microscopy will be applied to samples, in order to correlate morphology with specific genes and chemical element composition. The results are expected to provide information about the impact of microorganisms on geological processes and possibly global elemental cycles. In addition, the occurrence of viable microorganisms deep in crystalline rocks should provide a testing ground for development of identification methods, which will be needed for the exploration of other planets and moons with solid rock surfaces; life forms, if present there, will likely occur below the surface, where they are sheltered from radiation and harsh space conditions.

The hypothesis of the presence of "deep hot biosphere" by Thomas Gold predicts that all life inside the Earth, if it were brought to the surface from as much as 5 km down, might form a layer 1.5 m thick, covering all land surfaces, and weighing more than all flora and fauna together. This biomass would consist of microorganisms, mainly bacteria and archaea. Numerous recent findings have indeed confirmed the presence of subterranean microbial communities in deep drilling bore cores, in seafloor sediments, in oil reservoirs and in ultradeep gold and uranium mines. Thermal springs, which are delivering their water from reservoirs in the rocks, are in contact with the subterranean biosphere and can transport members from these environments to the surface, thus providing a link between surface and subsurface. Bad Gastein, a village in the Central Alps near Salzburg, Austria, is known for its thermal mineral springs, which contain slightly radioactive waters. A cluster of 17 major springs with temperatures up to 47 C provide about 4 to 5 million liters of water per day. Microscopic studies have shown a vast diversity of cells, some of very small sizes ("nanobacteria") in biofilms on the rock surfaces of the springs and in the water, following deposition of biomass on glass slides. Analysis of amplified16S rRNA genes revealed the presence of numerous archaeal and bacterial phylotypes, which showed similarities or, in some cases, only low relatedness to known prokaryotes. Questions about the energy and carbon sources for this life without sunlight are unanswered and will be explored in this study. Specifically, non-thermophilic crenarchaeota, which have become a focal point of interest due to their wide occurrence (also in the thermal springs) and possible involvement in the global nitrogen cycle will be investigated. Other groups are potentially hydrogen- or methaneconsuming, ammonia- or metal-oxidizing microorganisms, which are probably present by evidence of signature-like sequences. Culturing of prokaryotes will be carried out, but also culture-independent techniques will be used, such as stable isotope probing and a metagenomic search for functional genes. To be expected are the identification of genes for ammonia monooxygenase (amo), nitrate reductase/s (nir), particulate methane monooxygenase (pmo), and others. In addition, fluorescent in-situ hybridisation (FISH) and EDX (energy dispersive X-ray) electron microscopy will be applied to samples, in order to correlate morphology with specific genes and chemical element composition. The results are expected to provide information about the impact of microorganisms on geological processes and possibly global elemental cycles. In addition, the occurrence of viable microorganisms deep in crystalline rocks should provide a testing ground for development of identification methods, which will be needed for the exploration of other planets and moons with solid rock surfaces; life forms, if present there, will likely occur below the surface, where they are sheltered from radiation and harsh space conditions.