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Gracilibacillus orientalis sp. nov., a novel moderately halophilic bacterium isolated from a salt lake in Inner Mongolia, China.

Three Gram-positive, moderately halophilic, spore-forming rods, designated XH-63T, XH-62 and EJ-15, were isolated from two salt lakes located near Xilin Hot and Ejinor, in Inner Mongolia, China. The strains were strictly aerobic and motile, with spherical, terminal and deforming endospores. They grew at pH 5.0-9.0 (optimal growth at pH 7.5), between 4 and 45 degrees C (optimal growth at 37 degrees C) and at salinities of 1-20% (w/v) total salts, growing optimally at 10% (w/v) salts. They had meso-diaminopimelic acid in the cell wall peptidoglycan and DNA G + C contents of 36.1-37.1 mol%. The polar lipid pattern of strain XH-63T, selected as the representative strain, consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and a phospholipid and two amino phospholipids of unknown structure. This strain possessed anteiso-C(15:0) and anteiso-C(17:0) as the major fatty acids (altogether representing 72.5% of total) and MK-7 as the major menaquinone. 16S rRNA gene analysis of the three strains showed that they were within the Gracilibacillus cluster, with highest sequence similarity (95.4-95.8%) with Gracilibacillus dipsosauri. Based on a combination of phenotypic, chemotaxonomic and phylogenetic features, it is proposed that the three isolates represent a novel species of the genus Gracilibacillus, Gracilibacillus orientalis sp. nov. The type strain is strain XH-63T (= CCM 7326T = AS 1.4250T = CECT 7097T).

Bacillaceae↗

Bacillus massiliensis sp. nov., isolated from cerebrospinal fluid.

An unidentified Gram-negative-staining, aerobic, rod-shaped, spore-forming bacterium was isolated from a sample of cerebrospinal fluid. Based on comparative analysis of 16S rRNA gene sequences and phenotypic characteristics, the novel isolate was included in the Bacillus sphaericus-like group. The isolate was closely related to Bacillus odysseyi and Bacillus silvestris, with 96.2 and 94.4 % 16S rRNA gene sequence similarity, respectively. The major fatty acid was iso-C(15 : 0) (48 %). The name Bacillus massiliensis sp. nov. is proposed for the novel isolate, with strain 4400831(T) (=CIP 108446(T)=CCUG 49529(T)) as the type strain.

Bacillaceae Infections↗

Lentibacillus halophilus sp. nov., from fish sauce in Thailand.

Fifteen strains of extremely halophilic bacteria were isolated from fish sauce (nam-pla) collected in Thailand at various stages of the fish-fermentation process. The isolates were strictly aerobic, spore-forming, Gram-positive rods. They grew optimally in the presence of 20-26 % NaCl. The cell-wall peptidoglycan contained meso-diaminopimelic acid. The predominant menaquinone was MK-7. The major cellular fatty acids were anteiso-C(15 : 0) and anteiso-C(17 : 0). Polar lipid analysis revealed the presence of phosphatidylglycerol, diphosphatidylglycerol and two unidentified glycolipids. The DNA G+C content was 42.1-43.1 mol%. On the basis of the 16S rRNA gene sequence, a representative strain, PS11-2(T), was found to be closely related to Lentibacillus juripiscarius JCM 12147(T) (97.3 % similarity). The 15 strains were included in the same species on the basis that the levels of DNA-DNA relatedness with strain PS11-2(T) were greater than 70 %. They could be distinguished from L. juripiscarius and other Lentibacillus species on the basis of several phenotypic characteristics and low levels of DNA-DNA relatedness (</=19.4 %). Therefore, the strains represent a novel species of the genus Lentibacillus, for which the name Lentibacillus halophilus sp. nov. is proposed. The type strain is PS11-2(T) (=JCM 12149(T)=TISTR 1549(T)=PCU 240(T)).

Animals↗

Exiguobacterium indicum sp. nov., a psychrophilic bacterium from the Hamta glacier of the Himalayan mountain ranges of India.

Strain HHS 31(T), a Gram-positive, motile, rod-shaped, non-spore-forming, alkaliphilic bacterium, was isolated from the melt water of a glacier. Phenotypic and chemotaxonomic characteristics indicate that strain HHS 31(T) is related to species of the genus Exiguobacterium. The 16S rRNA gene sequence similarities between HHS 31(T) and strains of known species confirm that it is closely related to members of the genus Exiguobacterium (93-99 %) and that it exhibits >97 % similarity with Exiguobacterium acetylicum DSM 20416(T) (98.9 %), Exiguobacterium antarcticum DSM 14480(T) (98.0 %), Exiguobacterium oxidotolerans JCM 12280(T) (97.9 %) and Exiguobacterium undae DSM 14481(T) (97.4 %). Phylogenetic analysis based on the 16S rRNA gene sequence further confirms the affiliation of HHS 31(T) with the genus Exiguobacterium. However, the levels of DNA-DNA relatedness between HHS 31(T) and E. oxidotolerans JCM 12280(T), E. acetylicum DSM 20416(T), E. undae DSM 14481(T) and E. antarcticum DSM 14480(T) are 50, 63, 67 and 28 %, respectively. Strain HHS 31(T) also differs from these four closely related species in terms of a number of phenotypic traits. The phenotypic, chemotaxonomic and phylogenetic data suggest that HHS 31(T) merits the status of a novel species, for which the name Exiguobacterium indicum sp. nov. is proposed. The type strain is HHS 31(T) (=LMG 23471(T)=IAM 15368(T)).

Bacillaceae↗

S-layer glycan-specific loci on the chromosome of Geobacillus stearothermophilus NRS 2004/3a and dTDP-L-rhamnose biosynthesis potential of G. stearothermophilus strains.

The approximately 16.5 kb surface layer (S-layer) glycan biosynthesis (slg) gene cluster of the Gram-positive thermophile Geobacillus stearothermophilus NRS 2004/3a has been sequenced. The cluster is located immediately downstream of the S-layer structural gene sgsE and consists of 13 ORFs that have been identified by database sequence comparisons. The cluster encodes dTDP-L-rhamnose biosynthesis (rml operon), required for building up the polyrhamnan S-layer glycan, as well as for assembly and export of the elongated glycan chain, and its transfer to the S-layer protein. This is the first report of a gene cluster likely to be involved in the glycosylation of an S-layer protein. There is evidence that this cluster is transcribed as a polycistronic unit, whereas sgsE is transcribed monocistronically. To get insights into the regulatory mechanisms underlying glycosylation of the S-layer protein, the influence of growth temperature on the S-layer was investigated in seven closely related G. stearothermophilus strains, of which only strain NRS 2004/3a possessed a glycosylated S-layer. Chromosomal DNA preparations of these strains were screened for the presence of the rml operon, because L-rhamnose is a frequent constituent of S-layer glycans. From rml-positive strains, flanking regions of the operon were sequenced. Comparison with the slg gene cluster of G. stearothermophilus NRS 2004/3a revealed sequence homologies between adjacent genes. The temperature inducibility of S-layer protein glycosylation was investigated in those strains by raising the growth temperature from 55 degrees C to 67 degrees C; no change of either the protein banding pattern or the glycan staining behaviour was observed on SDS-PAGE gels, although the sgsE transcript was several-fold more abundant at 67 degrees C. Cell-free extracts of the strains were capable of converting dTDP-D-glucose to dtdp-L-rhamnose. Taken together, the results indicate that the rml locus is highly conserved among G. stearothermophilus strains, and that in the investigated rml-containing strains, dTDP-L-rhamnose is actively synthesized in vitro. However, in contrast to previous reports for G. stearothermophilus wild-type strains, an increase in growth temperature did not switch an S-layer protein phenotype to an S-layer glycoprotein phenotype, via the de novo generation of a new S-layer gene sequence.

Bacillaceae↗

Biochemical characterization of different genotypes of Paenibacillus larvae subsp. larvae, a honey bee bacterial pathogen.

Paenibacillus larvae subsp. larvae (P. l. larvae) is the aetiological agent of American foulbrood (AFB), the most virulent bacterial disease of honey bee brood worldwide. In many countries AFB is a notifiable disease since it is highly contagious, in most cases incurable and able to kill affected colonies. Genotyping of field isolates of P. l. larvae revealed at least four genotypes (AB, Ab, ab and alpha B) present in Germany which are genotypically different from the reference strain DSM 7030. Therefore, based on these data, five different genotypes of P. l. larvae are now identified with genotype AB standing out with a characteristic brown-orange and circled two-coloured colony morphology. Analysing the metabolic profiles of three German genotypes (AB, Ab and ab) as well as of the reference strain using the Biolog system, a characteristic biochemical fingerprint could be obtained for each strain. Cluster analysis showed that while genotypes Ab, ab and the reference strain DSM 7030 are rather similar, genotype AB is clearly different from the others. Analysis of all isolates for plasmid DNA revealed two different plasmids present only in isolates belonging to genotype AB. Therefore, genotype AB is remarkable in all aspects analysed so far. Future analysis will show whether or not these differences will expand to differences in virulence.

Animals↗

Identification of a gene cluster encoding an arginine ATP-binding-cassette transporter in the genome of the thermophilic Gram-positive bacterium Geobacillus stearothermophilus strain DSMZ 13240.

A single gene cluster encoding components of a putative ATP-binding cassette (ABC) transporter for basic amino acids was identified in the incomplete genome sequence of the thermophilic Gram-positive bacterium Geobacillus stearothermophilus by blast searches. The cluster comprises three genes, and these were amplified from chromosomal DNA of G. stearothermophilus, ligated into plasmid vectors and expressed in Escherichia coli. The purified solute-binding protein (designated ArtJ) was demonstrated to bind L-arginine with high affinity (Kd=0.39+/-0.06 microM). Competition experiments revealed only partial inhibition by excess L-lysine (38 %) and L-ornithine (46 %), while no inhibition was observed with L-histidine or other amino acids tested. The membrane-associated transport complex, composed of a permease (designated ArtM) and an ATPase component (designated ArtP), was solubilized from E. coli membranes by decanoylsucrose and purified by metal-affinity chromatography. The ArtMP complex, when incorporated into liposomes formed from a crude extract of G. stearothermophilus lipids, displayed ATPase activity in the presence of ArtJ only. Addition of L-arginine further stimulated the activity twofold. ATP hydrolysis was optimal at 60 degrees C and sensitive to the specific inhibitor vanadate. Analysis of kinetic parameters revealed a maximal velocity of ATP hydrolysis of 0.71 micromol Pi min(-1) (mg protein)(-1) and a Km(ATP) of 1.59 mM. Together, these results identify the ArtJMP complex as a high-affinity arginine ABC transporter.

ATP-Binding Cassette Transporters↗

The structure of secondary cell wall polymers: how Gram-positive bacteria stick their cell walls together.

The cell wall of Gram-positive bacteria has been a subject of detailed chemical study over the past five decades. Outside the cytoplasmic membrane of these organisms the fundamental polymer is peptidoglycan (PG), which is responsible for the maintenance of cell shape and osmotic stability. In addition, typical essential cell wall polymers such as teichoic or teichuronic acids are linked to some of the peptidoglycan chains. In this review these compounds are considered as 'classical' cell wall polymers. In the course of recent investigations of bacterial cell surface layers (S-layers) a different class of 'non-classical' secondary cell wall polymers (SCWPs) has been identified, which is involved in anchoring of S-layers to the bacterial cell surface. Comparative analyses have shown considerable differences in chemical composition, overall structure and charge behaviour of these SCWPs. This review discusses the progress that has been made in understanding the structural principles of SCWPs, which may have useful applications in S-layer-based 'supramolecular construction kits' in nanobiotechnology.

Bacillaceae↗

A complete sequence of the T. tengcongensis genome.

Thermoanaerobacter tengcongensis is a rod-shaped, gram-negative, anaerobic eubacterium that was isolated from a freshwater hot spring in Tengchong, China. Using a whole-genome-shotgun method, we sequenced its 2,689,445-bp genome from an isolate, MB4(T) (Genbank accession no. AE008691). The genome encodes 2588 predicted coding sequences (CDS). Among them, 1764 (68.2%) are classified according to homology to other documented proteins, and the rest, 824 CDS (31.8%), are functionally unknown. One of the interesting features of the T. tengcongensis genome is that 86.7% of its genes are encoded on the leading strand of DNA replication. Based on protein sequence similarity, the T. tengcongensis genome is most similar to that of Bacillus halodurans, a mesophilic eubacterium, among all fully sequenced prokaryotic genomes up to date. Computational analysis on genes involved in basic metabolic pathways supports the experimental discovery that T. tengcongensis metabolizes sugars as principal energy and carbon source and utilizes thiosulfate and element sulfur, but not sulfate, as electron acceptors. T. tengcongensis, as a gram-negative rod by empirical definitions (such as staining), shares many genes that are characteristics of gram-positive bacteria whereas it is missing molecular components unique to gram-negative bacteria. A strong correlation between the G + C content of tDNA and rDNA genes and the optimal growth temperature is found among the sequenced thermophiles. It is concluded that thermophiles are a biologically and phylogenetically divergent group of prokaryotes that have converged to sustain extreme environmental conditions over evolutionary timescale.

Bacillaceae↗

The fate of laterally transferred genes: life in the fast lane to adaptation or death.

Large-scale genome arrangement plays an important role in bacterial genome evolution. A substantial number of genes can be inserted into, deleted from, or rearranged within genomes during evolution. Detecting or inferring gene insertions/deletions is of interest because such information provides insights into bacterial genome evolution and speciation. However, efficient inference of genome events is difficult because genome comparisons alone do not generally supply enough information to distinguish insertions, deletions, and other rearrangements. In this study, homologous genes from the complete genomes of 13 closely related bacteria were examined. The presence or absence of genes from each genome was cataloged, and a maximum likelihood method was used to infer insertion/deletion rates according to the phylogenetic history of the taxa. It was found that whole gene insertions/deletions in genomes occur at rates comparable to or greater than the rate of nucleotide substitution and that higher insertion/deletion rates are often inferred to be present at the tips of the phylogeny with lower rates on more ancient interior branches. Recently transferred genes are under faster and relaxed evolution compared with more ancient genes. Together, this implies that many of the lineage-specific insertions are lost quickly during evolution and that perhaps a few of the genes inserted by lateral transfer are niche specific.

Adaptation, Physiological↗

Crystallization and preliminary X-ray study of alpha-glucosidase from Geobacillus sp strain HTA-462, one of the deepest sea bacteria.

An alpha-glucosidase (EC 3.2.1.20) was purified from Geobacillus sp. strain HTA-462 cells and crystallized using the hanging-drop vapour-diffusion technique. The Geobacillus strain is a thermophilic and high-pressure-resistant bacterium found at the bottom of the Challenger Deep in the Mariana Trench. The crystal was characterized by X-ray diffraction and belongs to space group C2, with unit-cell parameters a = 104.0, b = 91.5, c = 72.9 A, beta = 109.4 degrees. Diffraction data to 2.5 A resolution were collected and processed.

Bacillaceae↗

Protein preparation, crystallization and preliminary X-ray crystallographic studies of a thermostable hypoxanthine-guanine phosphoribosyltransferase from Thermoanaerobacter tengcongensis.

Native and His-tagged mutant (L160I) hypoxanthine-guanine phosphoribosyltransferase (HGPRT) from Thermoanaerobacter tengcongensis were cloned, expressed in Escherichia coli and purified. Both proteins were crystallized with polyethylene glycol as the main precipitant at 293 K using the hanging-drop vapour-diffusion method. The crystal of native HGPRT belongs to space group C222(1), with unit-cell parameters a = 65.77, b = 137.73, c = 95.27 A, and diffracted to 2.2 A resolution on an in-house X-ray generator. The crystal of the His-tagged mutant (L160I) HGPRT belongs to the space group I222, with unit-cell parameters a = 52.21, b = 88.36, c = 93.03 A, and diffracted to 1.7 A resolution in-house.

Bacillaceae↗

Structure determination of the extracellular xylanase from Geobacillus stearothermophilus by selenomethionyl MAD phasing.

Xylanases are hemicellulases that hydrolyze the internal beta-1,4-glycoside bonds of xylan. The extracellular thermostable endo-1,4-beta-xylanase (EC 3.2.1.8; XT6) produced by the thermophilic bacterium Geobacillus stearothermophilus T-6 was shown to bleach pulp optimally at pH 9 and 338 K and was successfully used in a large-scale biobleaching mill trial. The xylanase gene was cloned and sequenced. The mature enzyme consists of 379 amino acids, with a calculated molecular weight of 43 808 Da and a pI of 9.0. Crystallographic studies of XT6 were performed in order to study the mechanism of catalysis and to provide a structural basis for the rational introduction of enhanced thermostability by site-specific mutagenesis. XT6 was crystallized in the primitive trigonal space group P3(2)21, with unit-cell parameters a = b = 112.9, c = 122.7 A. A full diffraction data set for wild-type XT6 has been measured to 2.4 A resolution on flash-frozen crystals using synchrotron radiation. A fully exchanged selenomethionyl XT6 derivative (containing eight Se atoms per XT6 molecule) was also prepared and crystallized in an isomorphous crystal form, providing full selenium MAD data at three wavelengths and enabling phase solution and structure determination. The structure of wild-type XT6 was refined at 2.4 A resolution to a final R factor of 15.6% and an R(free) of 18.6%. The structure demonstrates that XT6 is made up of an eightfold TIM-barrel containing a deep active-site groove, consistent with its 'endo' mode of action. The two essential catalytic carboxylic residues (Glu159 and Glu265) are located at the active site within 5.5 A of each other, as expected for 'retaining' glycoside hydrolases. A unique subdomain was identified in the carboxy-terminal part of the enzyme and was suggested to have a role in xylan binding. The three-dimensional structure of XT6 is of great interest since it provides a favourable starting point for the rational improvement of its already high thermal and pH stabilities, which are required for a number of biotechnological and industrial applications.

Amino Acid Sequence↗

Crystallization and preliminary crystallographic analysis of a thermostable family 52 beta-D-xylosidase from Geobacillus stearothermophilus T-6.

Beta-D-xylosidases (EC 3.2.1.37) are hemicellulases that hydrolyze short xylooligosaccharides into single xylose units. In this study, the first crystallization and preliminary X-ray analysis of a family 52 glycoside hydrolase, the beta-D-xylosidase (XynB2) from Geobacillus stearothermophilus T-6, is described. XynB2 is a dimeric protein consisting of two identical subunits of 705 amino acids with a calculated molecular weight of 79 894 Da. XynB2 was crystallized by the hanging-drop vapour-diffusion method and the crystals were found to belong to space group P1, with unit-cell parameters a = 80.6, b = 97.5, c = 107.2 A, alpha = 107.4, beta = 98.2, gamma = 106.6 degrees. The native crystals diffracted X-rays to a resolution of 2.0 A.

Bacillaceae↗

Crystallization and preliminary X-ray diffraction studies of the carboxylesterase EST2 from Alicyclobacillus acidocaldarius.

EST2, a thermophilic carboxylesterase from Alicyclobacillus acidocaldarius, belonging to the HSL group of the esterase/lipase superfamily, has been crystallized for the first time. Ammonium sulfate was used as a precipitant and the crystallization proceeded at pH 7.8. The crystals belong to space group P41212 or its enantiomorph P43212, with unit-cell parameters a = b = 78.8, c = 106. 4 A. A complete data set has been collected at the synchrotron source Elettra in Trieste to 2.4 A resolution, using a single frozen crystal.

Bacillaceae↗

Crystallization and preliminary X-ray diffraction studies of two thermostable alpha-galactosidases from glycoside hydrolase family 36.

alpha-Galactosidases from thermophilic organisms have gained interest owing to their applications in the sugar industry. The alpha-galactosidases AgaA, AgaB and AgaA A355E mutant from Geobacillus stearothermophilus have been overexpressed in Escherichia coli. Crystals of AgaB and AgaA A355E have been obtained by the vapour-diffusion method and synchrotron data have been collected to 2.0 and 2.8 A resolution, respectively. Crystals of AgaB belong to space group I222 or I2(1)2(1)2(1), with unit-cell parameters a = 87.5, b = 113.3, c = 161.6 A. Crystals of AgaA A355E belong to space group P3(1)21 or P3(2)21, with unit-cell parameters a = b = 150.1, c = 233.2 A.

Bacillaceae↗

The quaternary structure of the amidase from Geobacillus pallidus RAPc8 is revealed by its crystal packing.

The amidase from Geobacillus pallidus RAPc8, a moderate thermophile, is a member of the nitrilase enzyme superfamily. It converts amides to the corresponding acids and ammonia and has application as an industrial catalyst. RAPc8 amidase has been cloned and functionally expressed in Escherichia coli and has been purified by heat treatment and a number of chromatographic steps. The enzyme was crystallized using the hanging-drop vapour-diffusion method. Crystals produced in the presence of 1.2 M sodium citrate, 400 mM NaCl, 100 mM sodium acetate pH 5.6 were selected for X-ray diffraction studies. A data set having acceptable statistics to 1.96 A resolution was collected under cryoconditions using an in-house X-ray source. The space group was determined to be primitive cubic P4(2)32, with unit-cell parameter a = 130.49 (+/-0.05) A. The structure was solved by molecular replacement using the backbone of the hypothetical protein PH0642 from Pyrococcus horikoshii (PDB code 1j31) with all non-identical side chains substituted with alanine as a probe. There is one subunit per asymmetric unit. The subunits are packed as trimers of dimers with D3 point-group symmetry around the threefold axis in such a way that the dimer interface seen in the homologues is preserved.

Amidohydrolases↗