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At least 19 recordsLinked to original sources
PubMed1997

Haloarcula argentinensis sp. nov. and Haloarcula mukohataei sp. nov., two new extremely halophilic archaea collected in Argentina.

Strains arg-1T (T = type strain) and arg-2T, two new strains of extremely halophilic archaea, were isolated from the soils of the Argentine salt flats. The taxonomic features of arg-1T were similar to, but distinct from, those of the type strain of Haloarcula vallismortis and other Haloarcula species. On the 16S rRNA phylogenetic tree, strain arg-1T formed a cluster together with Haloarcula species. Strain arg-2T differed in its glycolipid composition but still was more closely related to the genus Haloarcula than to other established genera. We propose that strain arg-1T be classified as a member of a new species, Haloarcula argentinensis, and that strain arg-2T be classified as a member of Haloarcula mukohataei sp. nov., although arg-2T may belong to a new genus or a subgenus of the genus Haloarcula. The type strain of H. argentinensis is strain arg-1 (= JCM 9737), and the type strain of H. mukohataei is strain arg-2 (= JCM 9738).

Argentina↗
PubMed1992

Transformation of members of the genus Haloarcula with shuttle vectors based on Halobacterium halobium and Haloferax volcanii plasmid replicons.

We have stably transformed both Haloarcula vallismortis and Haloarcula hispanica with the halobacterium-Escherichia coli shuttle vectors pWL102 (based on the Haloferax volcanii pHV2 replicon) and pUBP2 (based on the Halobacterium halobium pHH1 replicon). Haloferax volcanii, Halobacterium halobium, and Haloarcula vailismortis are equally distant from one another and span the phylogenetic depth of the halophilic Archaea; thus, these vectors may be generally useful for the halophiles. Both Haloarcula vallismortis and Haloarcula hispanica exhibit previously unreported complex life cycles and are therefore significant as genetically approachable models of cellular differentiation within the Archaea.

Genetic Vectors↗
PubMed1999

Haloarcula quadrata sp. nov., a square, motile archaeon isolated from a brine pool in Sinai (Egypt).

The motile, predominantly square-shaped, red archaeon strain 801030/1T, isolated from a brine pool in the Sinai peninsula (Egypt), was characterized taxonomically. On the basis of its polar lipid composition, the nucleotide sequences of its two 16S rRNA genes, the DNA G+C content (60.1 mol%) and its growth characteristics, the isolate could be assigned to the genus Haloarcula. However, phylogenetic analysis of the two 16S rRNA genes detected in this organism and low DNA-DNA hybridization values with related Haloarcula species showed that strain 801030/1T is sufficiently different from the recognized Haloarcula species to warrant its designation as a new species. A new species, Haloarcula quadrata, is therefore proposed, with strain 801030/1T (= DSM 11927T) as the type strain.

Base Composition↗
PubMed2007

Haloarcula amylolytica sp. nov., an extremely halophilic archaeon isolated from Aibi salt lake in Xin-Jiang, China.

A starch-hydrolysing and extremely halophilic archaeon (strain BD-3(T)), isolated from Aibi salt lake in Xin-Jiang, China, was characterized phenotypically and genotypically in order to determine its taxonomic status. On the basis of its polar lipid composition, nucleotide sequences of its 16S rRNA genes, genomic DNA G+C content (62.4 mol%) and growth characteristics, the organism could be assigned to the genus Haloarcula. Phenotypic differences and low DNA-DNA hybridization values to related Haloarcula species distinguished strain BD-3(T) from recognized Haloarcula species. It is therefore concluded that strain BD-3(T) represents a novel species, for which the name Haloarcula amylolytica sp. nov. is proposed. The type strain is BD-3(T) (=CGMCC 1.5335(T)=JCM 13557(T)).

Bacterial Typing Techniques↗
PubMed2004

Ureases of extreme halophiles of the genus Haloarcula with a unique structure of gene cluster.

We searched for urease activities in 71 strains of extreme halophiles by a urea-phenol red-agar plate method. Positive strains were further investigated by measuring the ammonia released from urea in cell-free extracts. Only 4 strains of the genus Haloarcula, Har. aidinensis, Har. hispanica, Har. japonica, and Har. marismortui were finally shown as the urease producers. A partially purified urease from Har. hispanica was a typical halophilic enzyme in that it showed maximum activity at 18-23% NaCl and lost the activity irreversibly in the absence of NaCl. Partial genes (1596 bp) of the urease encoding from upstream of the beta subunit down to the N-terminal 139 amino acids of the alpha subunit, were PCR amplified from the four strains, as well as from five urease-negative Haloarcula strains. Strains of other genera, which were urease-negative, did not yield PCR products. The deduced amino acid sequences of the beta subunit and partial alpha subunit were similar to each other (92-100% similarities) and to those from other organisms. Analysis of the draft genome sequence of Har. marismortui, however, suggested that the order of the genes encoding the three subunits (with the total number of amino acids of 834) and four accessory proteins was beta-alpha-gamma-UreG-UreD-UreE-UreF. This order is quite unique, since in other microorganisms the order is gamma-beta-alpha-UreE-UreF-UreG-UreD in most cases. No open reading frames were detected in the PCR-amplified upstream of the beta subunit, suggesting that all Haloarcula species have the same unique structure of the urease gene cluster.

Amino Acid Sequence↗
PubMed2005

Organic solvent tolerance of halophilic archaea, Haloarcula strains: effects of NaCl concentration on the tolerance and polar lipid composition.

Strains of halophilic archaea, Haloarcula vallismortis and two Haloarcula strains OHF-1 and OHF-2, showed high tolerance to organic solvents at high media NaCl concentrations. For example, the lowest log Pow of the solvent which allowed growth (log Pow is the common logarithm of the partition coefficient of a given solvent in a mixture of n-octanol and water) for H. vallismortis was 5.1 at 20% NaCl and 4.4 at 30% NaCl. The solvent tolerance of Haloarcula argentinensis, on the other hand, was not affected by the NaCl concentration. Cells of strains OHF-1 and OHF-2 were of triangular or irregular morphology but became spherical in cultures in NaCl media overlaid with cyclohexane (log Pow=3.4), but returned to the triangular shape when the organic solvent evaporated from the medium. When cells of strains OHF-1, OHF-2, and H. argentinensis were grown in NaCl media in the presence of n-decane, they contained less phosphatidylglycerol and more phosphatidylglycerosulfate and phosphatidylglycerophosphate methyl ester than when grown without added n-decane. When the solvent was removed from the media after cultivation, the levels of these compounds returned to their initial ones.

Cell Proliferation↗
PubMed1991

Halobacterial S9 operon. Three ribosomal protein genes are cotranscribed with genes encoding a tRNA(Leu), the enolase, and a putative membrane protein in the archaebacterium Haloarcula (Halobacterium) marismortui.

In the eubacterium Escherichia coli the genes for the ribosomal proteins L13 and S9 form an operon consisting of two genes. The corresponding operon of the archaebacterium Haloarcula marismortui (Halobacterium marismortui was recently reassigned to the genus Haloarcula [Oren, A., Ginzburg, M., Ginzburg, B. Z., Hochstein, L. I., and Volcani, B. E. (1990) Int. J. Syst. Bacteriol. 40, 209-210] and is now called Haloarcula marismortui) which is presented here, is much larger encoding three ribosomal proteins (HL29, HmaL13, HmaS9), a tRNA(Leu), the glycolytic enzyme enolase (HmaEno), a putative membrane protein (OrfMSG), and two not yet identified open reading frames (OrfMMV, OrfMNA). The nucleotide sequence of 3931 base pairs has been established. Northern analysis revealed the existence of a polycistronic mRNA (3.7 kilobases) demonstrating that the transcription of a gene of the glycolytic pathway is coupled to the transcription of ribosomal protein genes. Upstream of the first gene of the operon (tRNA(Leu)) a promoter structure typical for the extreme halophilic archaebacteria was detected and downstream of the last gene (OrfMSG) a terminator structure was present. As shown by S1-nuclease mapping, a tRNA-mRNA transcript as well as the mRNA alone was present in vivo. The transcriptional start point and the tRNA-mRNA cleavage point are shown to be almost identical to the 5' and 3' ends, respectively, of the putative mature tRNA. The C-terminal part of the OrfMSG protein shows a significant similarity to the vertebrate laminin receptor protein.

Bacterial Proteins↗
PubMed2000

A novel bacteriorhodopsin-like protein from Haloarcula japonica strain TR-1: gene cloning, sequencing, and transcript analysis.

The gene encoding a novel bacteriorhodopsin (bR)-like protein from Haloarcula japonica strain TR-1 was cloned and sequenced. The nucleotide sequence of the gene contained an open reading frame that corresponded to a protein of 250 amino acids. The deduced amino acid sequence of Ha. japonica bR-like protein exhibited the highest homology to those of cruxrhodopsins (cRs) produced by members of the genus Haloarcula, suggesting that the bR-like protein of Ha. japonica belonged to the cR subfamily. The hydropathy analysis of Ha. japonica bR-like protein (cR) revealed that the Ha. japonica cR had a transmembrane heptahelical structure similar to that of bR. Furthermore, transcription of the cR gene in Ha. japonica was confirmed by the reverse transcription-polymerase chain reaction method.

Amino Acid Sequence↗
PubMed2005

AMP-forming acetyl-CoA synthetase from the extremely halophilic archaeon Haloarcula marismortui: purification, identification and expression of the encoding gene, and phylogenetic affiliation.

Halophilic archaea activate acetate via an (acetate)-inducible AMP-forming acetyl-CoA synthetase (ACS), (Acetate+ATP+CoA --> Acetyl-CoA+AMP+PP(i)). The enzyme from Haloarcula marismortui was purified to homogeneity. It constitutes a 72-kDa monomer and exhibited a temperature optimum of 41 degrees C and a pH optimum of 7.5. For optimal activity, concentrations between 1 M and 1.5 M KCl were required, whereas NaCl had no effect. The enzyme was specific for acetate (100%) additionally accepting only propionate (30%) as substrate. The kinetic constants were determined in both directions of the reaction at 37 degrees C. Using the N-terminal amino acid sequence an open reading frame - coding for a 74 kDa protein - was identified in the partially sequenced genome of H. marismortui. The function of the ORF as acs gene was proven by functional overexpression in Escherichia coli. The recombinant enzyme was reactivated from inclusion bodies, following solubilization in urea and refolding in the presence of salts, reduced and oxidized glutathione and substrates. Refolding was dependent on salt concentrations of at least 2 M KCl. The recombinant enzyme showed almost identical molecular and catalytic properties as the native enzyme. Sequence comparison of the Haloarcula ACS indicate high similarity to characterized ACSs from bacteria and eukarya and the archaeon Methanosaeta. Phylogenetic analysis of ACS sequences from all three domains revealed a distinct archaeal cluster suggesting monophyletic origin of archaeal ACS.

Acetate-CoA Ligase↗
PubMed1994

The novel ion pump rhodopsins from Haloarcula form a family independent from both the bacteriorhodopsin and archaerhodopsin families/tribes.

Extreme halophiles newly collected from Argentine salt flats were characterized, in one of which, Haloarcula (sp. arg-1), light-driven retinal protein ion pumps were found. The proton pump, cruxrhodopsin-1, shows amino acid sequence homologies of 52% to bacteriorhodopsin and 48% to archaerhodopsin-1. The anion pump, cruxhalorhodopsin-1, identified partially as a 394bp polymerase chain reaction product, shows homologies of 70% to halorhodopsin, and 72% to pharaonis halorhodopsin. The ion pumps (and possibly sensors still to be found) in Haloarcula sp. arg-1, which constitute the cruxrhodopsin-1 family, are distinct from the bacteriorhodopsin and the archaerhodopsin families/tribes.

Amino Acid Sequence↗
PubMed1990

Haloarcula marismortui (Volcani) sp. nov., nom. rev., an extremely halophilic bacterium from the Dead Sea.

An extremely halophilic red archaebacterium isolated from the Dead Sea (Ginzburg et al., J. Gen. Physiol. 55: 187-207, 1970) belongs to the genus Haloarcula and differs sufficiently from the previously described species of the genus to be designated a new species; we propose the name Haloarcula marismortui (Volcani) sp. nov., nom. rev. because of the close resemblance of this organism to "Halobacterium marismortui," which was first described by Volcani in 1940. The type strain is strain ATCC 43049.

Archaea↗
PubMed2001

Direct localization by cryo-electron microscopy of secondary structural elements in Escherichia coli 23 S rRNA which differ from the corresponding regions in Haloarcula marismortui.

Insertions were introduced by a two-step mutagenesis procedure into each of five double-helical regions of Escherichia coli 23 S rRNA, so as to extend the helix concerned by 17 bp. The helices chosen were at sites within the 23 S molecule (h9, h25, h45, h63 and h98) where significant length variations between different species are known to occur. At each of these positions, with the exception of h45, there are also significant differences between the 23 S rRNAs of E. coli and Haloarcula marismortui. Plasmids carrying the insertions were introduced into an E. coli strain lacking all seven rrn operons. In four of the five cases the cells were viable and 50 S subunits could be isolated; only the insertion in h63 was lethal. The modified subunits were examined by cryo-electron microscopy (cryo-EM), with a view to locating extra electron density corresponding to the insertion elements. The results were compared both with the recently determined atomic structure of H. marismortui 23 S rRNA in the 50 S subunit, and with previous 23 S rRNA modelling studies based on cryo-EM reconstructions of E. coli ribosomes. The insertion element in h45 was located by cryo-EM at a position corresponding precisely to that of the equivalent helix in H. marismortui. The insertion in h98 (which is entirely absent in H. marismortui) was similarly located at a position corresponding precisely to that predicted from the E. coli modelling studies. In the region of h9, the difference between the E. coli and H. marismortui secondary structures is ambiguous, and the extra electron density corresponding to the insertion was seen at a location intermediate between the position of the nearest helix in the atomic structure and that in the modelled structure. In the case of h25 (which is about 50 nucleotides longer in H. marismortui), no clear extra cryo-EM density corresponding to the insertion could be observed.

Base Sequence↗
PubMed1999

Haloarcula marismortui 50S subunit-complementarity of electron microscopy and X-Ray crystallographic information.

The large 50S subunit of the Haloarcula marismortui 70S ribosome was solved to 19 A using cryo-electron microscopy and single particle reconstruction techniques and to 9 A using X-ray crystallography. In the latter case, phases were determined by multiple isomorphous replacement and anomalous scattering from three heavy atom derivatives. The availability of X-ray and electron microscopy (EM) data has made it possible to compare the results of the two experimental methods. In the flexible regions of the 50S subunit, small differences in the mass distribution were detected. These differences can be attributed to the influence of packing in the crystal cell. The rotationally averaged power spectra of X-ray and EM were compared in an overlapping spatial frequency range from 60 to 13 A. The resulting ratio of X-ray to EM power ranges from 1 to 15, reflecting a progressively larger underestimation of the Fourier amplitudes by the electron microscope.

Archaeal Proteins↗
PubMed2004

Unusual ADP-forming acetyl-coenzyme A synthetases from the mesophilic halophilic euryarchaeon Haloarcula marismortui and from the hyperthermophilic crenarchaeon Pyrobaculum aerophilum.

ADP-forming acetyl-CoA synthetase (ACD), the novel enzyme of acetate formation and energy conservation in archaea Acety - CoA + ADP + Pi<==>acetate + ATP CoA), has been studied only in few hyperthermophilic euryarchaea. Here, we report the characterization of two ACDs with unique molecular and catalytic features, from the mesophilic euryarchaeon Haloarcula marismortui and from the hyperthermophilic crenarchaeon Pyrobaculum aerophilum. ACD from H. marismortui was purified and characterized as a salt-dependent, mesophilic ACD of homodimeric structure (166 kDa). The encoding gene was identified in the partially sequenced genome of H. marismortui and functionally expressed in Escherichia coli. The recombinant enzyme was reactivated from inclusion bodies following solubilization and refolding in the presence of salts. The ACD catalyzed the reversible ADP- and Pi-dependent conversion of acetyl-CoA to acetate. In addition to acetate, propionate, butyrate, and branched-chain acids (isobutyrate, isovalerate) were accepted as substrates, rather than the aromatic acids, phenylacetate and indol-3-acetate. In the genome of P. aerophilum, the ORFs PAE3250 and PAE 3249, which code for alpha and beta subunits of an ACD, overlap each other by 1 bp, indicating a novel gene organization among identified ACDs. The two ORFs were separately expressed in E. coli and the recombinant subunits alpha (50 kDa) and beta (28 kDa) were in-vitro reconstituted to an active heterooligomeric protein of high thermostability. The first crenarchaeal ACD showed the broadest substrate spectrum of all known ACDs, catalyzing the conversion of acetyl-CoA, isobutyryl-CoA, and phenylacetyl-CoA at high rates. In contrast, the conversion of phenylacetyl-CoA in euryarchaeota is catalyzed by specific ACD isoenzymes.

Acetate-CoA Ligase↗
PubMed2004

Organic solvent tolerance of halophilic alpha-amylase from a Haloarchaeon, Haloarcula sp. strain S-1.

A halophilic archaeon, Haloarcula sp. strain S-1, produced extracellular organic solvent-tolerant alpha-amylase. Molecular mass of the enzyme was estimated to be 70 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This amylase exhibited maximal activity at 50 degrees C in buffer containing 4.3 M NaCl, pH 7.0. Moreover, the enzyme was active and stable in various organic solvents (benzene, toluene, and chloroform, etc.). Activity was not detected at low ionic strengths, but it was detected in the presence of chloroform at low salt concentrations. On the other hand, no activity was detected in the presence of ethyl alcohol and acetone.

Acetone↗
PubMed2005

Gene cloning, expression and partial characterization of cell division protein FtsZ1 from extremely halophilic archaeon Haloarcula japonica strain TR-1.

The gene encoding a cell division protein FtsZ1 was cloned from an extremely halophilic archaeon, Haloarcula japonica strain TR-1. Nucleotide sequencing analysis of the ftsZ1 gene revealed that the structural gene consisted of an open reading frame of 1,158 nucleotides encoding 386 amino acids. Transcription of the ftsZ1 gene in Ha. japonica was confirmed by RT-PCR. A modified ftsZ1 gene was inserted into the shuttle vector pWL102 and used to transform Ha. japonica. The recombinant FtsZ1 was produced as a fusion with hexahistidine-tag in Ha. japonica host cells and purified. Purified recombinant FtsZ1 exhibited GTP-dependent polymerization activity and GTP-hydrolyzing activity in the presence of high concentrations of KCl.

Amino Acid Sequence↗
PubMed2005

Gene replacement in Haloarcula marismortui: construction of a strain with two of its three chromosomal rRNA operons deleted.

Site-directed mutagenesis were done in Haloarcula marismortui using the strategy that Khorana and coworkers devised for deleting the bacteriorhodopsin gene from Halobacterium halobium [Krebs et al. Proc Natl Acad Sci USA 90:1987-1991 (1993)]. Strains have been prepared from H. marsimortui, which normally has three rRNA operons, that are missing either its rrnB operon or both its rrnB and rrnC operons. In rich media, both strains grow at about the same rate as wild type. The G2099 in the 23S rRNA gene of the single operon strain was changed to A, and a three amino acid deletion was introduced into the gene for ribosomal protein L22 of the wild-type organism. The structural consequences of these and other such mutations can be determined with unusual accuracy because crystals of the large ribosomal subunit of H. marismortui diffract to atomic resolution.

Base Sequence↗
PubMed2005

Characterisation of a highly stable alpha-amylase from the halophilic archaeon Haloarcula hispanica.

Intracellular and extracellular proteins from halophilic archaea face very saline conditions and must be able to maintain stability and functionality at nearly saturated salt concentrations. Haloarchaeal proteins contain specific adaptations to prevent aggregation and loss of activity in such conditions, but these adaptations usually result in a lack of stability in the absence of salt. Here, we present the characterisation of a secreted alpha-amylase (AmyH) from the halophilic archaeon Haloarcula hispanica. AmyH was shown to be very halophilic but, unusually for a halophilic protein, it retained activity in the absence of salt. Intrinsic fluorescence measurements and activity assays showed that AmyH was very stable in high-salt buffer and even maintained stability upon the addition of urea. Urea-induced denaturation was only achieved in the absence of NaCl, demonstrating clearly that the stability of the protein was salt-dependent. Sequencing of the amyH gene showed an amino acid composition typical of halophilic proteins and, moreover, the presence of a signal peptide containing diagnostic features characteristic of export via the Twin-arginine translocase (Tat). Analysis of the export of AmyH showed that it was translocated post-translationally, most likely in a folded and active conformation, confirming that AmyH is a substrate of the Tat pathway.

Amino Acid Sequence↗