How do thermoacidophiles use sulfur in their metabolism?

What is a Sulfolobales?

The Sulfolobales are a group of very small (1-2 m diameter) anaerobic bacteria that require reduced sulfur compounds for growth. The Sulfolobales have a single membrane-bound ribosome which is surrounded by a membrane-coated nucleoid. They differ from other bacteria in that their cytoplasm contains a crystalline protein storage granule. Sulfolobales bacteria have small genomes (about 1.5 million bp in length), and grow chemoorganotrophically using small organic molecules, such as monosaccharides, amino acids, and carbon monoxide.

Discovery and History. The first Sulfolobales were discovered in a deep-sea vent in 1977, named Thermus aquaticus by Martin Klug in 1984. The group was not formally recognized until 1991, when Peter R. Lang, David H. Nelson, Bruce G. Stock, and colleagues published an important paper in the journal FEMS Microbiology Reviews, describing the discovery and classification of new Archaea, the group that includes the Sulfolobales. Prior to this paper, which we now recognize as a ground-breaking work on Archaea, little was known about Archaea.

Structure and Classification. Genome Structure and Genome Size. The Sulfolobales are characterized by a single membrane-bound ribosome surrounded by a membrane-coated nucleoid, in addition to small amounts of ribosomes inside the cell, and an RNA-containing storage granule. The Sulfolobales have small genomes, 1.5-2.0 Mb in length, with a GC content around 60%.

Phylogenetic Analysis of 16S rRNA Sequences. Below is a phylogenetic tree based on 16S rRNA sequences from the Sulfolobales and other representative species. (Note that the internal nodes (the dots between the two groups) represent inferred common ancestors.) The topology of the tree shows that the Sulfolobales fall into the Thermoplasma genus of the Thermoproteales phylum within the Euryarchaeota.

How do thermoacidophiles use sulfur in their metabolism?

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The thermophiles are the best example for the application of metagenomics in the analysis of natural communities since these organisms represent a high diversity of metabolic capacities. The latter group can be either anaerobic or facultatively anaerobic depending on oxygen availability in the environment. Thus, the authors propose that this type of thermophile represents one of the oldest metabolically active microorganisms surviving in extreme habitats. These studies have opened the door to the study of thermoacidophiles by metagenomic approaches, mainly those that use S-oxidizing strains as a model. By incubating the samples in media amended with 5 mM of molybdate, they isolated bacteria that were able to use sulfate as a substrate to grow.