Abstract. The reaction of iron sulfide (FeS) with H2S in water, in presence of CO2 under anaerobic conditions was found to yield H2 and a variety of organic sulfur compounds, mainly thiols and small amounts of CS2 and dimethyldisulfide. The same compounds were produced when H2S was replaced by HC1, in the H2S-generating system FeS/HCl/COí. The identification of the products was confirmed by GC-MS analyses and the incorporation of H2 in the organic sulfur compounds was demonstrated by experiments in which all hydrogen compounds were replaced by deuterium compounds. Generation of H2 and the synthesis of thiols were both dependent upon the relative abundance of FeS and HC1 or H2S, i.e. the FeS/HCl-or FeS/I-hS-proportions. Whether thiols or CS2 were formed as the main products depended also on the FeS/HCl-ratio: All conditions which create a H2 deficiency were found to initiate a proportional increase in the amount of CS2 . The quantities of H2 and thiols generated depended on temperature: the production of H2 was significantly accelerated from 50 °C onward and thiol synthesis above 75 °C. The yield of thiols increased with the amount of FeS and HC1 (H2S), given a certain FeS/HCl-ratio and a surplus of CO2, A deficiency of CO2 results in lower thiol systhesis. The end product, pyrite (FeSa), was found to appear as a silvery granular layer floating on the aqueous surface. The identity of the thiols was confirmed by mass spectrometry, and the reduction of CO2 demonstrated by the determination of deuterium incorporation with DC1 and D2O. The described reactions can principally proceed under the conditions comparable to those obtaining around submarine hydrothermal vents, or the global situation about 4 billion years ago, before the dawn of life, and could replace the need for a reducing atmosphere on the primitive earth.

Scanning electron microscopy revealed great morphological diversity in biofilms from several largely unexplored subterranean thermal Alpine springs, which contain radium 226 and radon 222. A culture-independent molecular analysis of microbial communities on rocks and in the water of one spring, the "Franz-Josef-Quelle" in Bad Gastein, Austria, was performed. Four hundred fifteen clones were analyzed. One hundred thirty-two sequences were affiliated with 14 bacterial operational taxonomic units (OTUs) and 283 with four archaeal OTUs. Rarefaction analysis indicated a high diversity of bacterial sequences, while archaeal sequences were less diverse. The majority of the cloned archaeal 16S rRNA gene sequences belonged to the soil-freshwatersubsurface (1.1b) crenarchaeotic group; other representatives belonged to the freshwater-wastewater-soil (1.3b) group, except one clone, which was related to a group of uncultivated Euryarchaeota. These findings support recent reports that Crenarchaeota are not restricted to high-temperature environments. Most of the bacterial sequences were related to the Proteobacteria (␣, ␤, ␥, and ␦), Bacteroidetes, and Planctomycetes. One OTU was allied with Nitrospina sp. (␦-Proteobacteria) and three others grouped with Nitrospira. Statistical analyses suggested high diversity based on 16S rRNA gene analyses; the rarefaction plot of archaeal clones showed a plateau. Since Crenarchaeota have been implicated recently in the nitrogen cycle, the spring environment was probed for the presence of the ammonia monooxygenase subunit A (amoA) gene. Sequences were obtained which were related to crenarchaeotic amoA genes from marine and soil habitats. The data suggested that nitrification processes are occurring in the subterranean environment and that ammonia may possibly be an energy source for the resident communities.

A sample from a hot spring on the northern island of New Zealand contained five different thermophilic bacterial strains. One strain with peculiar properties, i.e. the formation of dark yellow colonies at 30 degrees C as well as at 70 degrees C, was further characterized. It was found to be a gram-positive, facultatively aerobic, motile Bacillus species, with terminal endospores. According to the physiologic properties the strain closely resembled B. coagulans. However, two typical characteristics were contradictory to this conclusion, namely the intense yellow pigmentation of the colonies and the range of growth temperature. The latter was found to reach from 40 to 70 degrees C, with an optimum at 60 degrees C under aerobic and at 65 degrees C under anaerobic conditions. Growth at moderate temperatures was slower than at 60 degrees C, but the final cell yields were almost equal. The strain can therefore be considered as facultatively thermophilic. The pigment, which was found to be located in the cytoplasmic membrane, was spectroscopically identified as a carotenoid. Because the characteristics of this strain did not correspond with any of the Bacillus species described thus far, we concluded, that we had isolated a novel strain, for which the name Bacillus flavothermus is proposed.

No abstract

Summary. A mesophilic bacterium, Proteus mirabilis, which was known to be able to accumulate monomer silicate ions, a thermophilic bacterium, Bacillus caldolyticus, originating from a habitat with high silica concentrations, and a silicautilizing plant, Equisetum arvense, were all found to produce monomer silica from its polymer. The monomer silica, resulting from the mineralysis of either experimentally polymerized silica, or from quartz, is taken up by P. mirabilis cells, and also by Equisetum, which then deposits the silica again as a polymer in its stem and leaves. With B. caldolyticus, which does not utilize the depolymerized product under the given cor/ditions, we found that the intensity of the minerMysis depends on the growth rate of the organism.Many investigators have demonstrated in recent years that various plants and microorganisms, including molds, diatoms and bacteria, are able to incorporate silicate ions from a silica-containing medium (Okuda and Takahashi, 1964;Yoshida et al., 1959Yoshida et al., , 1962a tIolzapfel and Engel, 1959;Lewin, 1955Lewin, , 1957Lewin et al., 1966). Most of these studies have been conducted under laboratory conditions, the silica being supplied in its monomer state. This was also the ease in our experiments on bacterial silicon metabolism (Heinen, 1962(Heinen, , 1963a(Heinen, , 1965a. In nature, however, silica scarcely occurs as a monomer, but is in the contrary mostly present in a more or less polymerized form. In most experiments on bacterial silicon metabolism this fact has so far been neglected, so that there remains a gap between the laboratory conditions and the true state given in a natural environment.There are, however, many reports that naturally occurring silica can be depolymerized and solubilized by biological action. Okuda and Takahashi (1964) for instance have shown that the concentration of monomer soluble silica in the bleeding sap exuded from cut rice stems vastly exceeds the concentration of the environment, where only high amounts of polymer silica were available. This can only be interpreted as a depolymerization process, leading to the release of monomer silica from the polymerized material. Holzapfel and Engel (1954) used quartz suspension for their experiments with molds, and reported the incorporation of monomer silica. That bacteria are also able to depolymerize crystalline silicates has been shown by Webley et al. (1960) and the release of A1, Mg, and SiO~ by fungal action from rocks has been described (Henderson and Duff, 1963). The destruction 5*