摘要:

Unrooted phylogenetic dendrograms were calculated by two independent methods, parsimony and distance matrix analysis, from an alignment of the derived amino acid sequences of the A and C subunits of the DNA-dependent RNA polymerases of the archaebacteriaSulfolobus acidocaldariusandHalobacterium halobiumwith 12 corresponding sequences including a further set of archaebacterial A + C subunits, eukaryotic nuclear RNA polymerases, pol I, pol II, and pol III, eubacterial β′ and chloroplast β′ and β″ subunits. They show the archaebacteria as a coherent group in close neighborhood of and sharing a bifurcation with eukaryotic pol II and (or) pol IIIA components. The most probable trees show pol IA branching off from the tree separately at a bifurcation with the eubacterial β′ lineage. The implications of these results, especially for understanding the possibly chimeric origin of the eukaryotic nuclear genome, are discussed.Key words: transcription, evolution, taxonomy, subunits, gene organization.

ISSN:0008-4166    

DOI:10.1139/m89-011

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The primary structure of the glyceraldehyde-3-phosphate dehydrogenase from the archaebacteria shows striking deviation from the known sequences of eubacterial and eukaryotic sequences, despite unequivocal homologies in functionally important regions. Thus, the structural similarity between the eubacterial and eukaryotic enzymes is significantly higher than that between the archaebacterial enzymes and the eubacterial and eukarytic enzymes. This preferred similarity of eubacterial and eukaryotic glyceraldehyde-3-phosphate dehydrogenase structures does not correspond to the phylogenetic distances among the three urkingdoms as deduced from comparisons of ribosomal ribonucleic acid sequences. Indications will be presented that the closer relationship of the eubacterial and eukaryotic glyceraldehyde-3-phosphate dehydrogenase resulted from a gene transfer from eubacteria to eukaryotes after the segregation of the three urkingdoms.Key words: glyceraldehyde-3-phosphate dehydrogenase, archaebacteria, protein evolution.

ISSN:0008-4166    

DOI:10.1139/m89-012

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

To study the molecular biology of the halophilic archaebacteriumHalobacterium halobium, the introduction of DNA engineeredin vitrois desirable. As a first step in developing a cloning vector, the complete 1736 base pair nucleotide sequence of the natural, high copy number,Halobacteriumplasmid pHSB1 has been determined. The plasmid was found to show homology to the small plasmids ofHalobacteriumstrains GRB and GN101. Plasmid pHSB1 encodes a 317 amino acid protein of unknown function. The related halophile,H.halobium, could be transformed by pHSB1, demonstrating its utility as the basis of a cloning vector.Key words: archaebacteria,Halobacterium, plasmid.

ISSN:0008-4166    

DOI:10.1139/m89-013

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Three new isolates ofHalobacterium volcaniiwere screened for the presence of plasmids. Each of the different isolates was found to contain one plasmid. These plasmids do not show any homology to each other, nor to the previously isolated plasmid pHV2. Partial restriction maps of these plasmids were determined. One of the plasmids contains chromosomal repetitive sequences as judged by the existence of homologous sequences in the chromosomal DNA of the three isolates. Using the protoplast fusion technique, we showed that at least one of the newly isolated plasmids is compatible with pHV2.Key words:Halobacterium volcanii, archaebacterium, plasmids.

ISSN:0008-4166    

DOI:10.1139/m89-014

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Halobacterium halobiumcontains two gas vacuole protein genes that are located in plasmid pHH1 (p-vac) and in the chromosomal DNA (c-vac). The mutation frequency for these genes is different: the constitutively expressedp-vacgene is mutated with a frequency of 10−2, while the chromosomal gene expressed in the stationary phase of growth is mutated with a frequency of 10−5. The difference in the mutation susceptibility is due to the dynamics of plasmid pHH1.p-vacgene mutations are caused (i) by the integration of an insertion element or (ii) by a deletion event encompassing thep-vacgene region. In contrast,c-vacmutants analyzed to date incurred neither insertion elements nor deletions. Deletion events within pHH1 occur at high frequencies during the development of aH.halobiumculture. The investigation of the fusion regions resulting from deletion events indicates that insertion elements are involved. The analysis of pHH1 deletion variants led to a 4 kilobase pair DNA region containing the origin of replication of the pHH1 plasmid.Key words: gas vacuole protein gene, plasmid dynamics, deletions, insertion elements.

ISSN:0008-4166    

DOI:10.1139/m89-015

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The DNA sequences encoding component C of methyl coenzyme M reductase (mcrgenes) inMethanothermus fervidus,Methanobacterium thermoautotrophicum,Methanococcus vannielii, andMethanosarcina barkerihave been published. Comparisons of transcription initiation and termination sites and of the amino acid sequences of themcrgene products are presented. Structural features conserved within the amino acid sequences are identified and a comparison of methyl reductase with other disulfide bond synthesizing enzymes is presented.Key words: archaebacterium, methanogen, methyl reductases, gene cloning, heterodisulfide synthesis.

ISSN:0008-4166    

DOI:10.1139/m89-016

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The origin of the eukaryotic nucleus is difficult to reconstruct. While eukaryotic organelles (chloroplast, mitochondrion) are eubacterial endosymbionts, the source of nuclear genes has been obscured by multiple nucleotide substitutions. Using evolutionary parsimony, a newly developed rate-invariant treeing algorithm, the eukaryotic rRNA genes are shown to have evolved from the eocytes, a group of extremely thermophilic, sulfur-metabolizing, anucleate cells. The deepest bifurcation yet found separates the reconstructed tree into two taxonomic divisions. These are a proto-eukaryotic group (karyotes) and an essentially bacterial one (parkaryotes). Within the precision of the rooting procedure, the tree is not consistent with either the prokaryotic–eukaryotic or the archaebacterial–eubacterial–eukaryotic groupings. It implies that the last common ancestor of extant life, and the early ancestors of eukaryotes, very likely lacked nuclei, metabolized sulfur, and lived at near boiling temperatures.Key words: rRNA, evolution, phylogeny, sulfur metabolism.

ISSN:0008-4166    

DOI:10.1139/m89-017

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Critical analysis of the recently proposed alternative to the normal archaebacterial tree, the new eocyte tree, shows that the latter's central topology, in which the eubacteria branch from an entirely different section of the unrooted archaebacterial tree than the eukaryotes, is consistent with an artifact. The effects of the alignment used and the particular composition of the sequence quartets analyzed to infer this tree are discussed in detail.Key words: archaebacteria, molecular phylogeny, 16S ribosomal RNA, evolution, eocyte tree.

ISSN:0008-4166    

DOI:10.1139/m89-018

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The complete nucleotide sequence of the 16S rRNA gene fromThermoplasma acidophilum, as well as its 5′ and 3′ flanking regions, were determined by the dideoxynucleotide chain termination method. The 16S rRNA gene encodes 1471 nucleotides. The primary and secondary structures ofT.acidophilum16S rRNA both exhibit typical archaebacterial features. The sequence appears to be more closely related to 16S rRNAs of the methanogen–halophile group than to those of the thermoacidophile group. Secondary-structure comparisons generally support this relationship, although there are several examples in which the single-stranded loops in particular helices ofT.acidophilum16S rRNA more strongly resemble their counterparts in the 16S rRNA ofSulfolobus solfataricus, a member of the thermoacidophile group. In contrast to the polycistronic rRNA operons found in most organisms, the three rRNA genes fromT.acidophilumoccur in only a single copy per genome and appear to be physically unlinked. Consistent with this, the 16S rRNA gene is flanked by putative promoter and terminator sequences that are comparable to the transcription control signals from other archaebacterial genes. The sequence TATATATA, which is very similar to the archaebacterial promoter consensus TTTAT/AATA, is located 18 bases before the probable site of transcription initiation, TGCACAT. There is a potential transcription termination site immediately downstream from the gene that consists of a relatively stable stem and loop structure followed by stretches of Tresidues.Key words: archaebacteria, thermoacidophile, rRNA sequence, rRNA secondary structure, promoter.

ISSN:0008-4166    

DOI:10.1139/m89-019

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The protein bacterio-opsin, complexed with retinal, functions as a light-driven proton pump in the purple membrane of the halophilic archaebacterium,Halobacterium halobium. Bacterio-opsin deficient mutants have been characterized in attempts to elucidate regulation of the gene encoding bacterio-opsin (bop). Analysis of the mutational defect in Bop mutants has revealed the existence of at least two genes that affectbopgene expression and (or) purple membrane formation: (i) thebrpgene, located 526 base pairs upstream of thebopgene, is transcribed in the opposite orientation, and (ii) thebatgene, located 1602 base pairs upstream of thebopgene, is transcribed in the same orientation as thebrpgene. Thebatgene start codon overlaps the stop codon of thebrpgene. Thebatgene could encode an acidic protein of 73 000 Da (674 amino acids) with a predicted secondary structure typical of a soluble alpha–beta type protein. This type of secondary structure is in contrast to the hydrophobic structure predicted for the putativebrpprotein. Transcriptional analyses of the wild type, 11 Bop mutants, and a Bop revenant suggest that thebatgene has a more direct role than thebrpgene inbopgene expression and is involved in activatingbopandbrpgene expression.Key words: purple membrane, bacterio-opsin,bopgene cluster, transcripts, activator.

ISSN:0008-4166    

DOI:10.1139/m89-020

出版商:NRC Research Press    

年代:1989

数据来源: NRC