Detection and phylogenetic analysis of the membrane-bound nitrate reductase (Nar) in pure cultures and microbial communities from deep-sea hydrothermal vents.

Over the past few years the relevance of nitrate respiration in microorganisms from deep-sea hydrothermal vents has become evident. In this study, we surveyed the membrane-bound nitrate reductase (Nar) encoding gene in three different deep-sea vent microbial communities from the East Pacific Rise and the Mid-Atlantic Ridge. Additionally, we tested pure cultures of vent strains for their ability to reduce nitrate and for the presence of the NarG-encoding gene in their genomes.

Isolation and characterization of arsenic resistant Geobacillus kaustophilus strain from geothermal soils.

A thermophilic, arsenate resistant bacterial strain was isolated from a geothermal field located in the area surrounding Monterotondo (Tuscany, Italy). Based on 16S rRNA gene analysis and recN comparisons the strain was identified as Geobacillus kaustophilus. Cells of the strain, designated A1, were rod-shaped, 2-3 μm long and reacted negatively to Gram staining, despite its taxonomic classification as a Gram positive microorganism.

Arsenate reduction and expression of multiple chromosomal ars operons in Geobacillus kaustophilus A1.

Geobacillus kaustophilus strain A1 was previously isolated from a geothermal environment for its ability to grow in the presence of high arsenate levels. In this study, the molecular mechanisms of arsenate resistance of the strain were investigated. As(V) was reduced to As(III), as shown by HPLC analysis.

Response to excess copper in the hyperthermophile Sulfolobus solfataricus strain 98/2.

Copper is an essential micronutrient, but toxic in excess. Sulfolobus solfataricus cells have the ability to adapt to fluctuations of copper levels in their external environment. To better understand the molecular mechanism behind the organismal response to copper, the expression of the cluster of genes copRTA, which encodes the copper-responsive transcriptional regulator CopR, the copper-binding protein CopT, and CopA, has been investigated and the whole operon has been shown to be cotranscribed at low levels from the copR promoter under all conditions, whereas increased transcription from the copTA promoter occurs in the presence of excess copper.