John G. Holt

Phylum BVI. Chloroflexi phy. nov.

The phylum Chloroflexi is a deep branching lineage of Bacteria The single class within Chloroflexi subdivides into two orders: the “Chloroflexales” and the “Herpetosiphonales”. Gram-negative, filamentous Bacteria. exhibiting gliding motility. Peptidoglycan contains L-ornithine as the diamino acid. Lipopolysaccharide-containing outer membrane not present.

Phylum All. Euryarchaeota phy. nov.

The phylum currently consists of seven classes: the Methanobacteria, the Methanococci, the Halobacteria, the Thermoplasmata, the Thermococci, the Archaeoglobi, and the Methanopyri. With the sole exception of the Methanococci, which is subdivided into three orders, each class contains a single order. The Euryarchaeota are morphologically diverse and occur as rods, cocci, irregular cocci, lancet-shaped, spiral-shaped, disk-shaped, triangular, or square cells. Cells stain Gram-positive or Gram-negative based on the presence or absence of pseudomurein in cell walls. In some classes, cell walls consist entirely of protein or may be completely absent (Thermoplasmata). Five major physiological groups have been described previously: the methanogenic Archaea, the extremely halophilic Archaea, Archaea lacking a cell wall, sulfate reducing Archaea, and the extremely thermophilic S0 metabolizers.

Phylum BXI. Chlorobi phy. nov.

The Chlorobi share a common root with Bacteroidetes in both of the major reference trees. At present, the phylum contains a single class, order, and family. Gram-negative, spherical, ovoid, straight, or curved rod-shaped Bacteria. Strictly anaerobic, obligately phototrophic. Cells grow preferentially by photoassimilation of simple organic compounds. Some species may utilize sulfide or thiosulfate as an electron donor for CO2 accumulation. Sulfur globules accumulate on the outside of the cells when grown in the presence of sulfide and light, and sulfur is rarely oxidized further to sulfate. Ammonia and dinitrogen used as the nitrogen source. Most genera require one or more growth factors; the most common are biotin, thiamine, niacin, and p-aminobenzoic acid.

Phylum BVIII. Nitrospirae phy. nov.

The phylum Nitrospirae is based mainly on phylogenetic grounds. At present, it consists of a single class, order, and family of Bacteria and environtaxa that branch deeply in the major reference trees; member taxa consistently group together. Gram-negative, curved, vibrioid or spiral-shaped cells. Metabolically diverse, most genera are aerobic chemolithotrophs including nitrifiers, dissimilatory sulfate reducers, and magnetotactic forms. One genus (Thermodesulfovibrio) is thermophilic, and obligately acidophilic and anaerobic.

Phylum Al. Crenarchaeota phy. nov.

The phylum consists of a single class, the Thermoprotei, which is well supported by 16S rDNA sequence data. It is subdivided into three orders: the Thermoproteales, the Desulfurococcales, and the Sulfolobales. Morphologically diverse, including rods, cocci, filamentous forms, and disk-shaped cells. Stain Gram-negative. Motility observed in some genera. Obligately thermophilic, with growth occurring at temperatures ranging from 70 to 113°C. Acidophilic. Aerobic, facultatively anaerobic, or strictly anaerobic-chemolithoautotrophs or chemoheterotrophs. Most metabolize S0. Chemoheterotrophs, may grow by sulfur respiration. RNA polymerase of the BAC type.

Phylum BVII. Thermomicrobia phy. nov.

The phylum Thermomicrobia consists of a single known representative that branches deeply in the major reference trees and is distantly related to the Chloroflexi. Gram negative, short, irregularly shaped nonmotile rods. Nonsporulating. No diamino acid present in peptidoglycan in significant amount. Hyperthermophilic, optimum growth temperature 70–75°C. Obligately aerobic and chemoorganotrophic.

Phylum BIII. Thermodesulfobacteria phy. nov.

The phylum Thermodesulfobacteria is currently represented by a single genus which branches deeply in the major reference trees. Gram-negative, rod-shaped cells possessing an outer membrane layer which forms protrusions. Thermophilic, strictly anaerobic, chemoheterotrophs exhibiting a dissimilatory sulfatereducing metabolism.

Phylum BV. Chrysiogenetes phy. nov.

The phylum Chrysiogenetes is currently represented by a single species, which was reportedly distinct from members of other phyla. Exact placement is currently uncertain, but a distant relationship to Deferribacteres is likely. Gram-negative, motile, curved, rod-shaped cells. Mesophilic, exhibiting anaerobic respiration in which arsenate serves as the electron acceptor.