Felix Gropp

Desulfurolobus ambivalens, gen. nov., sp. nov., an autotrophic Archaebacterium facultatively oxidizing or reducing sulfur

Summary The archaebacterium Desulfurolobus ambivalens gen. nov. sp. nov., family Sulfolobaceae , is an obligate chemolitho-autotroph, facultatively growing by the oxidation with O 2 or the reduction with H 2 of elemental sulfur with CO 2 as sole carbon source. D. ambivalens contains several plasmids, one of which, pSL10, is amplified during anaerobic growth. This amplification is accompanied by the appearance of virus-like particles resembling those described for Sulfolobus spec. B12. A subclone of D. ambivalens not containing the plasmid pSL10 is still able to grow by both sulfur oxidation and sulfur reduction indicating that the plasmid does not harbor genes for chemolithoautotrophic growth. The phylogenetic position of this organism within the Sulfolobaceae and the taxonomy of this group are discussed in the light of molecular evidence.

Viruses of Archaebacteria

The archaebacteria constitute the third distinct urkingdom of life, beside eubacteria and eucytes (eukaryotic nucleus and cytoplasm) (Woese and Fox, 1977; Woese et al., 1978; Fox et al., 1980). They exhibit a characteristic mosaic of features, some of them—e.g., their lipids—unique to the group (for review see Langworthy, 1985); others—e.g., the organization of genes in operons (Konheiser et al., 1984; Hamilton and Reeve, 1985; Reeve et al., 1986; Reiter et al., 1987a) and the existence of ribosome-binding sites in mRNAs (Reiter et al., 1987a, and literature cited therein)—of eubacterial quality; and a third type—e.g., the ADP ribosylatability of their EFIIs by diphtheria toxin (Kessel and Klink, 1982)—of eukaryotic quality. Most interestingly, features of a fourth group—e.g., the structures of 5S rRNAs, initiator tRNAs, and DNA-dependent RNA polymerases and the occurrence of introns in tRNA genes—are highly divergent in different archaebacteria (Zillig et al., 1985a). Phylogenetically, the archaebacterial kingdom is deeply divided into three major branches (Woese and Olsen, 1986; Klenk et al., 1986): (1) the methanogens (Methanococcales, Methanobacteriales, and Methanomicrobiales) (for review see Whitman, 1985) plus extreme halophiles (Halobacteriales and Thermoplasmales) (for review see Kushner, 1985); (2) the sulfur-dependent extremely thermophilic Thermococcales (Woese and Olsen, 1986; Zillig et al., 1987); and (3) the sulfur-dependent, extremely thermophilic Thermoproteales plus Sulfolobales (for review see Stetter and Zillig, 1985) (Fig. 1).

Homologies of components of DNA-dependent RNA polymerases of archaebacteria, eukaryotes and eubacteria

Summary Using an immunochemical approach homologies between single components of DNA-dependent RNA polymerases from eubacteria, archaebacteria and eukaryotes were investigated. The largest components of all RNA polymerases included in this study are homologous to one another indicating a monophyletic origin of these proteins. Immunological crossreactions show that one of the large subunits present in the enzymes of sulfur-dependent archaebacteria is split into two smaller components in methanogens and halophiles. One of these smaller components roughly corresponds to the second largest subunit of the three eukaryotic enzymes whereas the other one shares antigenic determinants with subunit s of eubacterial RNA polymerases. Semi-quantitative evaluation of the data suggests that the three nuclear RNA polymerases of eukaryotes have evolved from an ancestral enzyme of the type that is found in sulfur-dependent archaebacteria.

The immunity-conferring plasmid pφHL from the Halobacterium salinarium phage φH: Nucleotide sequence and transcription

Abstract The complete nucleotide sequence of the plasmid pφHL, composing the central 12,041-bp L-region from the temperate phage φH of Halobacterium salinarium is presented. Transcripts mapped to the pφHL and the L-region produced under immune conditions, under lytic growth or constitutively, are described. The sequences upstream of the transcription start points show homology to the consensus sequence for archaeal (formerly archaebacterial) promoters. Lytic transcription is shown to be strictly time-dependent, with an early gene product required for the expression of late genes.

Archaebacterial virus host systems

Summary Within a review on archaebacterial virus host systems particular emphasis is laid on the description of the novel virus-like particle SSV1 (formerly SAV1) of Sulfolobus solfataricus strain B12, and of the novel viruses TTV1, 2, 3 and 4 of Thermoproteus tenax . Structure, virus host relationships, gene sequence and expression, genome organization and phylogenetic aspects are discussed.

Phylogeny of DNA-Dependent RNA Polymerases: Testimony for the Origin of Eukaryotes

The organization of the genes for the large components of DNA-dependent RNA polymerase in archaebacteria resembles that in eubacteria.