To evaluate the microbial populations involved in the reduction of Fe(III) in an acidic, iron-rich sediment, the anaerobic flow of supplemental carbon and reductant was evaluated in sediment microcosms at the in situ temperature of 12°C. Supplemental glucose and cellobiose stimulated the formation of Fe(II); 42 and 21% of the reducing equivalents that were theoretically obtained from glucose and cellobiose, respectively, were recovered in Fe(II). Likewise, supplemental H2 was consumed by acidic sediments and yielded additional amounts of Fe(II) in a ratio of approximately 1:2. In contrast, supplemental lactate did not stimulate the formation of Fe(II). Supplemental acetate was not consumed and inhibited the formation of Fe(II). Most-probable-number estimates demonstrated that glucose-utilizing acidophilic Fe(III)-reducing bacteria approximated to 1% of the total direct counts of 4′,6-diamidino-2-phenylindole-stained bacteria. From the highest growth-positive dilution of the most-probable-number series at pH 2.3 supplemented with glucose, an isolate, JF-5, that could dissimilate Fe(III) was obtained. JF-5 was an acidophilic, gram-negative, facultative anaerobe that completely oxidized the following substrates via the dissimilation of Fe(III): glucose, fructose, xylose, ethanol, glycerol, malate, glutamate, fumarate, citrate, succinate, and H2. Growth and the reduction of Fe(III) did not occur in the presence of acetate. Cells of JF-5 grown under Fe(III)-reducing conditions formed blebs, i.e., protrusions that were still in contact with the cytoplasmic membrane. Analysis of the 16S rRNA gene sequence of JF-5 demonstrated that it was closely related to an Australian isolate of Acidiphilium cryptum (99.6% sequence similarity), an organism not previously shown to couple the complete oxidation of sugars to the reduction of Fe(III). These collective results indicate that the in situ reduction of Fe(III) in acidic sediments can be mediated by heterotrophicAcidiphilium species that are capable of coupling the reduction of Fe(III) to the complete oxidation of a large variety of substrates including glucose and H2.

A strictly anaerobic, H 2 -utilizing bacterium, strain SL1, was isolated from the sediment of an acidic coal mine pond. Cells of strain SL1 were sporulating, motile, long rods with a multilayer cell wall. . These results indicate that (i) sediments of acidic coal mine ponds harbour acetogens and (ii) C. scatologenes is an acetogen that tends to lose its capacity to grow acetogenically under H 2 /CO 2 or CO/CO 2 after prolonged laboratory cultivation.

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Stabilität gelöster organischer (DON) und mineralischer Stickstoffverbindungen in Freilandniederschlägen und Kronentraufe Freilandniederschläge und Kronentraufe unter Fichte wurden an 4 Terminen von Mai bis August 1996 für jeweils 4 Wochen im Freiland in Standardregensammlern inkubiert, um die Stabilität der mineralischen und organischen Stickstoffverbindungen zu untersuchen. Eine Zunahme der mineralischen Stickstoffkomponenten, v.a. von NH4+, erfolgte mit der Zeit und war besonders in Kronentrauflösungen ausgeprägt. Dies wird auf die wahrscheinliche Mineralisation von partikulärem organischem Stickstoff zurückgeführt. Die Konzentrationen an gelöstem (< 0.45 μm) organischem Stickstoff (DON) erwiesen sich hingegen als relativ stabil. Um eine Überschätzung der NH4+‐Einträge zu vermeiden, sollte der Probenahmezeitraum so kurz wie möglich sein und die Regensammler mit Feinporenfiltern bzw. chemischen Inhibitoren versehen werden.