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PubMed1996

Buffering capacity and membrane H+ conductance of Halobacterium halobium.

Buffering capacity and membrane H+ conductance were measured in Halobacterium halobium suspensions in the light and in the dark over a wide range of external pH. The values of both variables for this archaeobacterium were significantly higher than those found for eubacteria in other reports. It appears from our results that the special chemical composition of the cell envelope and the movement of ions, mainly protons, may influence the magnitude of the buffering power and the H+ membrane conductance of these cells.

Biological Transport↗
PubMedDate not supplied

[A new description of the type strain of Halobacterium distributum].

The descriptions of strains assigned to the species Halobacterium distributum were supplemented with the results of chemo-and genotaxonomic studies. According to these data, H. distributum VKM B-1733, which was hitherto regarded as the type strain of H. distributum, cannot be assigned to this species. Instead, strain H. distributum VKM B-1739 is proposed as the type strain. It is also suggested that strain VKM B-1954 should be transferred to H. distributum.

Base Sequence↗
PubMed1977

The shape-maintaining component of halobacterium salinarium: a cell surface glycoprotein.

Halobacterium salinarium lacks the rigid peptidogylcan layer necessary for shape-maintenance in most bacteria. Instead, the major cell surface component is a high-molecular-weight glycoprotein resembling those found on the surface of eukaryotic cells. The glycoprotein is extremely acidic and has carbohydrate units attached via both N- and O-glycosidis linkages. Evidence has been obtained that demonstrates that the glycoprotein forms a rigid structural matrix at the cell surface and is responsible for maintenance of the characteristic rod-shaped morphology of these organisms.

Bacitracin↗
PubMed1997

[Plasmid DNA fragments from Halobacterium halobium active as eubacteria promoters in Escherichia coli].

In this paper; a promoter-probe plasmid pKK232-8 was used as a vector which functioned in E. coli. The plasmid pHH205 of Halobacterium halobium J7 was digested by two groups of restriction endonucleases BamHI-SalI and HindIII -SalI, recombined in vitro and transformed into E. coli. The transformants were selected on resistance plates to contain ampicillin (Am) and chloramphenicol (Cm). From random-selected 20 strains of transformants we obtained transformants T1 and T2, whose level of Cm resistance got to 110 micrograms/ml. The recombinant plasmids from T1 and T2 were named pJH and pJB, respectively. The resultes of analysis by restriction endonucleases digestion and molecular hybridization showed that recombinant plasmid pJH carried a inserted fragment with size of 800bp from plasmid pHH205. Experimental results of retransfomation proved further that the DNA fragment had promoter function in E. coli. Thus, this indicated that DNA fragments from plasmid of archaebaeteria (H halobium) may function as eubacteria (E. coil) promoters.

Escherichia coli↗
PubMed1984

Sequence analysis of the insertion element ISH1.8 and of associated structural changes in the genome of phage PhiH of the archaebacterium Halobacterium halobium.

We have sequenced the insertion element ISH1.8 which can be present in one or two copies in the genome of phage PhiH of Halobacterium halobium. ISH1.8 is 1895 bp long, has no inverted repeat at its ends, and one only of the two copies is flanked by two 5-bp duplications. An 8-bp sequence composed of 4 bp from each end of ISH1.8 is present in both sites lacking the element. This 8-bp sequence could either be a specific insertion sequence or a part of the element that is left behind upon deletion. The plasmid pPhiHL, consisting of the invertible L segment of the phage genome which is, in PhiH2 and PhiH5, flanked by two copies of ISH1.8, contains 112 bp of ISH1.8 and is released from the phage genome by recombination within a direct repeat of 9 bp. This 9-bp sequence (TCCCGCCCT) exists as an inverted repeat in ISH1.8 and therefore as two distinct repeats in phage genomes containing two copies of ISH1.8 in inverted orientation.

Journal Article↗
PubMed2004

Formation of insoluble magnesium phosphates during growth of the archaea Halorubrum distributum and Halobacterium salinarium and the bacterium Brevibacterium antiquum.

Stationary phase cells of the halophilic archaea Halobacterium salinarium and Halorubrum distributum, growing at 3-4 M NaCl, and of the halotolerant bacterium Brevibacterium antiquum, growing with and without 2.6 NaCl, took up approximately 90% of the phosphate from the culture media containing 2.3 and 11.5 mM phosphate. The uptake was blocked by the uncoupler FCCP. In B. antiquum, EDTA inhibited the phosphate uptake. The content of polyphosphates in the cells was significantly lower than the content of orthophosphate. At a high phosphate concentration, up to 80% of the phosphate taken up from the culture medium was accumulated as Mg(2)PO(4)OH x 4H(2)O in H. salinarium and H. distributum and as NH(4)MgPO(4) x 6H(2)O in B. antiquum. Consolidation of the cytoplasm and enlargement of the nucleoid zone were observed in the cells during phosphate accumulation. At phosphate surplus, part of the H. salinarium and H. distributum cell population was lysed. The cells of B. antiquum were not lysed and phosphate crystals were observed in the cytoplasm.

Archaea↗
PubMed1983

Bacterio-opsin mutants of Halobacterium halobium.

The bacterio-opsin (bop) gene of Halobacterium halobium R1 has been cloned with about 40 kilobases of flanking genomic sequence. The 40-kilobase segment is derived from the (G+C)-rich fraction of the chromosome and is not homologous to the major (pHH1) or minor endogenous covalently closed circular DNA species of H. halobium. A 5.1-kilobase Pst I fragment containing the bop gene was subcloned in pBR322 and a partial restriction map was determined. Defined restriction fragments of this clone were used as probes to analyze the defects associated with the bop gene in 12 bacterio-opsin mutants. Eleven out of 12 of the mutants examined had inserts ranging from 350 to 3,000 base pairs either in the bop gene or up to 1,400 base pairs upstream. The positions of the inserts were localized to four regions in the 5.1-kilobase genomic fragment: within the gene (one mutant), in a region that overlaps the 5' end of the gene (seven mutants), and in two different upstream regions (three mutants). Two revertants of the mutant with the most distal insert had an additional insert in the same region. The polar effects of these inserts are discussed in terms of inactivation of a regulatory gene or disruption of part of a coordinately expressed operon. Given the defined nature of the bop mRNA-i.e., it has a 5' leader sequence of three ribonucleotides-these observations indicate that the bop mRNA might be processed from a large mRNA transcript.

Journal Article↗
PubMed1984

Bacterio-opsin mRNA in wild-type and bacterio-opsin-deficient Halobacterium halobium strains.

We have examined transcripts corresponding to the Halobacterium halobium bacterio-opsin (BO) gene in wild-type and in BO-deficient mutant strains containing the insertion elements ISH1 or ISH2 in the BO gene. BO mRNA from the wild-type strain was purified by hybrid selection using single-stranded cDNA. Labeling by vaccinia virus capping enzyme and [alpha-(32)P]GTP showed that it contains the 5'-terminal nucleotide of the primary transcript. Sequence analysis showed that transcription begins only two nucleotides upstream of the initiator codon for BO. Two species of BO mRNA were found; the major species has a ragged 3' terminus approximately 45 nucleotides downstream from the terminator codon for BO, while the minor species is about 170 nucleotides longer at the 3' end. Analysis of the transcripts in several BO gene mutant strains by RNA gel-transfer hybridization showed that (i) mutants with ISH1 insertions within the NH(2)-terminal coding region of the gene contain no detectable transcripts, (ii) mutants with ISH2 near the middle of the coding region of the gene contain multiple incomplete transcripts, and (iii) a mutant that is partially BO deficient due to an insertion of ISH2 100 base pairs upstream of the site of initiation of transcription contains a decreased level of BO mRNA.

Journal Article↗
PubMed1984

An immune strain of Halobacterium halobium carries the invertible L segment of phage PhiH as a plasmid.

The structure of the circular prophage genome of PhiH varies with high frequency in single colony progeny of the defective lysogen Halobacterium halobium R(1)-3. As in linear PhiH DNA, a segment flanked by two copies of the insertion element ISH1.8 is inverted frequently. This L segment can also circularize to a plasmid of 12 kilobase pairs with simultaneous loss of the remaining phage DNA. Strain R(1)-L, which contains this plasmid, is immune to phage infection. A phage variant, PhiHL1, is able to grow on R(1)-L and carries an insertion of 1 kilobase pair in its L segment. PhiHL1 does not grow on normal lysogens. This shows that the plasmid confers to R(1)-L only part of the immunity of normal lysogens.

Journal Article↗
PubMed1988

High-frequency mutations in a plasmid-encoded gas vesicle gene in Halobacterium halobium.

Gas vesicle-deficient mutants of Halobacterium halobium arise spontaneously at high frequency (about 1%). The mutants are readily detected, forming translucent colonies on agar plates in contrast to opaque wild-type colonies. To investigate the mechanism of this mutation, we recently cloned a plasmid-encoded gas vesicle protein gene, gvpA, from H. halobium. In the wild-type NRC-1 strain the gvpA gene is encoded by a multicopy plasmid of approximately 150 kilobase pairs (kb). We have now characterized 18 gas vesicle-deficient mutants and 4 revertants by phenotypic and Southern hybridization analyses. Our results indicate that the mutants fall into three major classes. Class I mutants are partially gas vesicle-deficient (Vac(delta-)) and unstable, giving rise to completely gas vesicle-deficient (Vac(-)) derivatives and Vac(+) revertants at frequencies of 1-5%. The restriction map of the gvpA gene region in class I mutants is unchanged but the gene copy number is reduced compared to the Vac(+) strains. Class II mutants can be either Vac(delta-) or completely Vac(-) but are relatively stable. They contain insertion sequences within or upstream of the gvpA gene. A Vac(-) class II mutant, R1, contains the 1.3-kb insertion sequence, ISH3, within the gvpA gene, whereas four Vac(delta-) class II mutants contain other insertion sequences upstream of the gene. Class III mutants are stable Vac(-) derivatives of either the wild-type or class I mutants and have no detectable copies of the gvpA gene. Based on these results, we discuss the mechanisms of gas vesicle mutations in H. halobium.

Journal Article↗
PubMed1990

Transformation of Halobacterium halobium: development of vectors and investigation of gas vesicle synthesis.

We developed vector plasmids for the transformation of Halobacterium halobium, using the replicon region from the halobacterial phage H or from the plasmid pHH1 together with a DNA fragment conferring resistance to mevinolin. H. halobium P03, a strain lacking pHH1 as well as the restriction endonuclease activity found in wild-type H. halobium, was used as the recipient strain. All H. halobium fragments tested for autonomous replication as well as the Haloferax volcanii vector pWL102 enabled stable plasmid maintenance in this strain. A frequent loss of all vectors (including pWL102) was observed in Hf. volcanii, where >90% of the mevinolin-resistant colonies obtained after transformation had lost the vector, presumably because of restriction endonuclease activity and concomitant recombination of the mevinolin resistance marker with the chromosome. The expression of gas vesicle-encoding genes (vac) was analyzed by using a 4.5-kilobase-pair (kbp) fragment containing the plasmid-encoded p-vac gene from H. halobium or an 11-kbp fragment containing the mc-vac chromosomal gene from Haloferax mediterranei for transformation experiments with H. halobium and Hf. volcanii. These experiments indicated that the mc-vac fragment contains all information necessary to synthesize gas vesicles, whereas in the case of the smaller p-vac fragment, complementation by other genes was required for a Vac+ phenotype.

Journal Article↗
PubMed1989

Sequence analysis of the peptide-elongation factor EF-2 gene, downstream from those of ribosomal proteins H-S12 and H-S7, from the archaebacterial extreme halophile, Halobacterium halobium.

The gene for the peptide-elongation factor 2 (EF-2) was cloned from the archaebacterial extreme halophile Halobacterium halobium and sequenced. The 1013 nucleotides upstream from this gene was two open reading frames similar to ribosomal proteins S12 and S7 from Escherichia coli. Sequence alignment studies showed the halobacterial elongation factor 2 to be equivalent to eukaryotic EF-2 and eubacterial EF-G. Sequence similarity to the eukaryotic elongation factor was much higher than to the eubacterial factor. Conserved sequence regions were present within the factor and are likely to constitute functionally important domains. These include the sites of GTP binding and ADP ribosylation by diphtheria toxin.

Animals↗
PubMed1990

Ecophysiology of Bacteriophage S5100 Infecting Halobacterium cutirubrum.

Increasing salinity reduces burst size and increases the latent period of infection of Halobacterium cutirubrum by lytic bacteriophage S5100. Cells become reversibly and persistently infected at saturation-level concentrations of NaCl. We propose that high salinity provides a natural refuge for sensitive host bacteria and that phage S5100 acts as a scavenger, proliferating when host viability is threatened by dilution of the environment.

Journal Article↗
PubMed2005

Ca(2+)-dependent cell aggregation of halophilic archaeon, Halobacterium salinarum.

Halobacterium salinarum CCM 2090 exhibits a Ca(2+)-dependent cellular aggregation system. This process is caused by the interaction between Ca(2+) and aggregation factor(s). Although the aggregates formed are encased in matrix-like substances, such as bacterial biofilms, they are not attached to the abiotic substratum. Therefore, these substances may be distinguished from typical biofilms.

Biofilms↗