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At least 289 records · Page 16Linked to original sources
PubMed2001

Coexistence of a sulphate-reducing Desulfovibrio species and the dehalorespiring Desulfitobacterium frappieri TCE1 in defined chemostat cultures grown with various combinations of sulfate and tetrachloroethene.

A two-member co-culture consisting of the dehalorespiring Desulfitobacterium frappieri TCE1 and the sulphate-reducing Desulfovibrio sp. strain SULF1 was obtained via anaerobic enrichment from soil contaminated with tetrachloroethene (PCE). In this co-culture, PCE dechlorination to cis-dichloroethene was due to the activity of the dehalorespiring bacterium only. Chemostat experiments with lactate as the primary electron donor for both strains along with varying sulphate and PCE concentrations showed that the sulphate-reducing strain outnumbered the dehalogenating strain at relatively high ratios of sulphate/PCE. Stable co-cultures with both organisms present at similar cell densities were observed when both electron acceptors were supplied in the reservoir medium in nearly equimolar amounts. In the presence of low sulphate/PCE ratios, the Desulfitobacterium sp. became the numerically dominant strain within the chemostat co-culture. Surprisingly, in the absence of sulphate, strain SULF1 did not disappear completely from the co-culture despite the fact that there was no electron acceptor provided with the medium to be used by this sulphate reducer. Therefore, we propose a syntrophic association between the sulphate-reducing and the dehalorespiring bacteria via interspecies hydrogen transfer. The sulphate reducer was able to sustain growth in the chemostat co-culture by fermenting lactate and using the dehalogenating bacterium as a 'biological electron acceptor'. This is the first report describing growth of a sulphate-reducing bacterium in a defined two-member continuous culture by syntrophically coupling the electron and hydrogen transfer to a dehalorespiring bacterium.

Anaerobiosis↗
PubMed1997

Influence of sporulation medium and divalent ions on the heat resistance of Alicyclobacillus acidoterrestris spores.

The influence of divalent cations on the heat resistance of spores of the thermoacidophilic spoilage bacterium Alicyclobacillus acidoterrestris was studied. The heat resistance of A. acidoterrestris spores was not affected by the presence of the different divalent cations (Ca2+, Mg2+, Ba2+, Mn2+ and Sr2+) in the sporulation medium, and by the demineralization or remineralization. And the Ca and Mn contents in A. acidoterrestris spores were scarcely changed by these treatments. However, the heat resistance of Bacillus subtilis spores was affected with the changes of Ca content in the spores. The Ca contents in A. acidoterrestris spores of the different forms were greater than the DPA content. In contrast, the DPA content in the B. subtilis spores was greater than the Ca content. These findings suggest that the presence of constant amount of Ca-DPA and a stronger binding characteristic of divalent ions, especially Ca and Mn, is reflected in the specific heat resistance of A. acidoterrestris spores.

Bacillaceae↗
PubMed1997

Methods for the detection and enumeration of Alicyclobacillus acidoterrestris and investigation of growth and production of taint in fruit juice and fruit juice-containing drinks.

Methods for the detection of Alicyclobacillus acidoterrestris at a level of 1 cell per 100 ml and enumeration with a sensitivity of 5 cells ml-1 were developed. Spores of A. acidoterrestris survived pasteurization and outgrew and multiplied at a similar rate to vegetative cells in both orange juice and apple juice. Alicyclobacillus acidoterrestris grew readily in orange juice, apple juice and a non-carbonated fruit juice-containing drink at temperatures of 25-44 degrees C producing a taint and elevated levels (1-100 ppb) of guaiacol. Isolates of A. acidoterrestris can be identified using the DuPont RiboPrinter. It was isolated from apple drinks, apple juice concentrate and freshly squeezed orange juice.

Bacillaceae↗
PubMed2001

Characterization of pectin lyase produced by an endophytic strain isolated from coffee cherries.

AIMS: The effect of endophytic bacterial activity on the quality of coffee beverage was studied. METHODS AND RESULTS: A survey of the micro-organisms in coffee cherries was performed before harvesting, and their growth on the main nutrients available in coffee cherries was determined in vitro. CONCLUSION: Many endophytic bacteria were isolated from surface-sterilized coffee cherries. One of the pectinolytic strains was physiologically and phenotypically characterized, and was tentatively identified by partial 16S rDNA sequencing as Paenibacillus amylolyticus. This endophytic strain produced an extracellular pectinase with maximal activity at 40 degrees C and pH 7.9, and was thermostable up to 45 degrees C. EDTA and metal ions had little effect on pectin lyase activity. Km and Vmax values were 4.6 mg ml(-1) and 94.0 10(-8) mol min(-1) ml(-1), respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: Pectin lyases have been found in fungi but rarely in bacteria, and this isolate is a promising tool for regulation studies of these enzymes.

Bacillaceae↗
PubMed2003

Enhanced secretion and low temperature stabilization of a hyperthermostable and Ca2+-independent alpha-amylase of Geobacillus thermoleovorans by surfactants.

AIMS: Selection of suitable surfactants for enhancing and stabilizing alpha-amylase of Geobacillus thermoleovorans. METHODS AND RESULTS: Geobacillus thermoleovorans was cultivated in shake flasks containing 50 ml of starch-yeast extract-tryptone (SYT) medium with/without surfactants. Titres of the enzyme in media were monitored. The enzyme was also preserved at 4 degrees C with/without surfactants and enzyme activities were determined. Among polyethylene glycol (PEGs) of different molecular weights, PEG 8000 (0.5%, w/v) caused a slight increase in the enzyme titre, while Tween-20, Tween-40 and Tween-60 (0.03%, w/v) exerted a significant stimulatory effect on enzyme secretion. In the presence of SDS, Tween-80 and cholic acid (0.03%, w/v), the enzyme production was nearly twofold higher than that in the control. The anionic (SDS, cholic acid) and non-ionic (Tweens) detergents increased the cell membrane permeability, and thus, enhanced alpha-amylase secretion. Furthermore, anionic surfactants exhibited stabilizing effect on the enzyme during preservation at 4 degrees C. CONCLUSIONS: PEG 8000 and the ionic detergents (SDS, cholic acid and Tween-80) were more effective in the solubilization of cell membrane components, and enhancing enzyme yields than the cationic detergents such as CTAB (N,Cetyl-N,N,N-trimethyl ammonium bromide). Further, these surfactants were found to stabilize the enzyme at 4 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: The secretion of Ca2+-independent hyperthermostable alpha-amylase was enhanced in the presence of certain anionic and non-ionic detergents in the medium. Furthermore, the surfactants stabilized the enzyme during preservation at 4 degrees C. The use of this enzyme in starch hydrolysis eliminates the addition of Ca2+ in starch liquefaction and its subsequent removal by ion exchange from sugar syrups.

Bacillaceae↗
PubMed2001

Bacillus sphaericus bacteraemia in children with cancer: case reports and literature review.

In the period 1989-1999, Bacillus sphaericus was demonstrated to cause 12 out of 469 (2%) episodes of bacteraemia in children with cancer or receiving bone marrow transplant at G. Gaslini Children's Hospital, Genoa, Italy. Neutropenia was present in five episodes, six episodes, (all without neutropenia) were related to the presence of a central venous catheter, and one episode occurred in a patient with intestinal graft vs. host disease and gut colonization. All patients survived. Ciprofloxacin was the only drug active against all the isolated strains.Bacillus sphaericus represents a new cause of infection in the immunocompromised host, with low aggressiveness, but a peculiar pattern of antibiotic susceptibility.

Bacillaceae Infections↗
PubMed1997

Ventricular shunt infection and meningitis due to Bacillus cereus.

Non-anthrax Bacillus species are usually considered to be contaminants if found in clinical specimens. Only a few patients with systemic infections due to Bacillus cereus are reported. We present the case of a 18-month old boy with a primitive neuroectodermal tumor (PNET) in the brainstem and obstructive hydrocephalus that required an outlying and subsequently a ventriculoperitoneal drain. Following contamination at the site of entry of the external drain, shunt infection and meningitis with Bacillus cereus developed. Antibiotic treatment with vancomycin failed to eliminate the bacterium from the cerebrospinal fluid, so the shunt system had to be removed. Explantation of the shunt and addition of fosfomycin to the antibiotic regimen resulted in a complete cure of the infection.

Bacillaceae Infections↗
PubMed1997

[Bacillus cereus pneumonia after thoracic trauma. Case report and review of the literature].

We report on the case of a pneumonia caused by Bacillus cereus in a patient who sustained severe thoracic trauma, fractures of ribs 3-12, left lung contusion and haematopneumothorax. Bronchoscopic alveolar lavage (BAL) performed on ICU day four helped identifying the underlying cause of pneumonia. Inspite of early diagnosis and antibiotic treatment with clindamycin, cefotaxim and tobramycin, which rapidly eliminated the bacteria from the patient's lungs, the patient eventually died from the severe underlying injuries. However, this case emphasises that early performed BAL and rapid microbiological staining techniques can help diagnose pneumonia in critically ill patients. We also review the literature on pulmonary infections caused by Bacillus cereus.

Adult↗
PubMed2001

Paenibacillus macerans pseudobacteremia resulting from contaminated blood culture bottles in a neonatal intensive care unit.

Paenibacillus species are gram-positive, rod-shaped, spore-forming aerobes that are abundant in nature and closely related to Bacillus. Between June 24 and June 30, 1999, 8 neonates in our neonatal intensive care unit had positive blood cultures for Paenibacillus macerans. This cluster of positive blood cultures with an unusual pathogen suggested a pseudoepidemic. Investigation revealed that the most likely etiology of the pseudobacteremia was environmental contamination of the rubber stoppers in blood culture bottles. This was confirmed by environmental sampling and simulated inoculation studies. This pseudobacteremia outbreak highlights the importance of adhering to well-established methods for blood culture collection and ongoing infection control surveillance.

Bacillaceae Infections↗
PubMed2006

Domain architecture and structure of the bacterial cell division protein DivIB.

Bacterial cytokinesis requires the coordinated assembly of a complex of proteins, collectively known as the divisome, at the incipient division site. DivIB/FtsQ is a conserved component of the divisome in bacteria with cell walls, suggesting that it plays a role in synthesis and/or remodeling of septal peptidoglycan. We demonstrate that the extracytoplasmic region of DivIB comprises three discrete domains that we designate alpha, beta, and gamma from the N to C terminus. The alpha-domain is proximal to the cytoplasmic membrane and coincident with the polypeptide transport-associated domain that was proposed previously to function as a molecular chaperone. The beta-domain has a unique 3D fold, with no eukaryotic counterpart, and we show that it interconverts between two discrete conformations via cis-trans isomerization of a Tyr-Pro peptide bond. We propose that this isomerization might modulate protein-protein interactions of the flanking alpha- and gamma-domains. The C-terminal gamma-domain is unstructured in the absence of other divisomal proteins, but we show that it is critical for DivIB function.

Amino Acid Sequence↗
PubMed2000

Identification of two GDP-6-deoxy-D-lyxo-4-hexulose reductases synthesizing GDP-D-rhamnose in Aneurinibacillus thermoaerophilus L420-91T.

The glycan repeats of the surface layer glycoprotein of Aneurinibacillus thermoaerophilus L420-91T contain d-rhamnose and 3-acetamido-3,6-dideoxy-d-galactose, both of which are also constituents of lipopolysaccharides of Gram-negative plant and human pathogenic bacteria. The two genes required for biosynthesis of the nucleotide-activated precursor GDP-d-rhamnose, gmd and rmd, were cloned, sequenced, and overexpressed in Escherichia coli. The corresponding enzymes Gmd and Rmd were purified to homogeneity, and functional studies were performed. GDP-d-mannose dehydratase (Gmd) converted GDP-d-mannose to GDP-6-deoxy-d-lyxo-4-hexulose, with NADP+ as cofactor. The reductase Rmd catalyzed the second step in the pathway, namely the reduction of the keto-intermediate to the final product GDP-d-rhamnose using both NADH and NADPH as hydride donor. The elution behavior of the intermediate and end product was analyzed by high performance liquid chromatography. Nuclear magnetic resonance spectroscopy was used to identify the structure of the final product of the reaction sequence as GDP-alpha-d-rhamnose. This is the first characterization of a GDP-6-deoxy-d-lyxo-4-hexulose reductase. In addition, Gmd has been shown to be a bifunctional enzyme with both dehydratase and reductase activities. So far, no enzyme catalyzing these two types of reactions has been identified. Both Gmd and Rmd are members of the SDR (short chain dehydrogenase/reductase) protein family.

Amino Acid Sequence↗
PubMed2001

Biosynthesis of nucleotide-activated D-glycero-D-manno-heptose.

The glycan chain repeats of the S-layer glycoprotein of Aneurinibacillus thermoaerophilus DSM 10155 contain d-glycero-d-manno-heptose, which has also been described as constituent of lipopolysaccharide cores of Gram-negative bacteria. The four genes required for biosynthesis of the nucleotide-activated form GDP-d-glycero-d-manno-heptose were cloned, sequenced, and overexpressed in Escherichia coli, and the corresponding enzymes GmhA, GmhB, GmhC, and GmhD were purified to homogeneity. The isomerase GmhA catalyzed the conversion of d-sedoheptulose 7-phosphate to d-glycero-d-manno-heptose 7-phosphate, and the phosphokinase GmhB added a phosphate group to form d-glycero-d-manno-heptose 1,7-bisphosphate. The phosphatase GmhC removed the phosphate in the C-7 position, and the intermediate d-glycero-alpha-d-manno-heptose 1-phosphate was eventually activated with GTP by the pyrophosphorylase GmhD to yield the final product GDP-d-glycero-alpha-d-manno-heptose. The intermediate and end products were analyzed by high performance liquid chromatography. Nuclear magnetic resonance spectroscopy was used to confirm the structure of these substances. This is the first report of the biosynthesis of GDP-d-glycero-alpha-d-manno-heptose in Gram-positive organisms. In addition, we propose a pathway for biosynthesis of the nucleotide-activated form of l-glycero-d-manno-heptose.

Amino Acid Sequence↗
PubMed2001

The surface layer (S-layer) glycoprotein of Geobacillus stearothermophilus NRS 2004/3a. Analysis of its glycosylation.

Geobacillus stearothermophilus NRS 2004/3a possesses an oblique surface layer (S-layer) composed of glycoprotein subunits as the outermost component of its cell wall. In addition to the elucidation of the complete S-layer glycan primary structure and the determination of the glycosylation sites, the structural gene sgsE encoding the S-layer protein was isolated by polymerase chain reaction-based techniques. The open reading frame codes for a protein of 903 amino acids, including a leader sequence of 30 amino acids. The mature S-layer protein has a calculated molecular mass of 93,684 Da and an isoelectric point of 6.1. Glycosylation of SgsE was investigated by means of chemical analyses, 600-MHz nuclear magnetic resonance spectroscopy, and matrix-assisted laser desorption ionization-time of flight mass spectrometry. Glycopeptides obtained after Pronase digestion revealed the glycan structure [-->2)-alpha-L-Rhap-(1-->3)-beta-L-Rhap-(1-->2)-alpha-L-Rhap-(1-->](n = 13-18), with a 2-O-methyl group capping the terminal trisaccharide repeating unit at the non-reducing end of the glycan chains. The glycan chains are bound via the disaccharide core -->3)-alpha-l-Rhap-(1-->3)-alpha-L-Rhap-(L--> and the linkage glycose beta-D-Galp in O-glycosidic linkages to the S-layer protein SgsE at positions threonine 620 and serine 794. This S-layer glycoprotein contains novel linkage regions and is the first one among eubacteria whose glycosylation sites have been characterized.

Amino Acid Sequence↗
PubMed2002

Detailed kinetic analysis and identification of the nucleophile in alpha-L-arabinofuranosidase from Geobacillus stearothermophilus T-6, a family 51 glycoside hydrolase.

alpha-l-Arabinofuranosidases cleave the l-arabinofuranoside side chains of different hemicelluloses and are key enzymes in the complete degradation of the plant cell wall. The alpha-l-arabinofuranosidase from Geobacillus stearothermophilus T-6, a family 51 glycoside hydrolase, was subjected to a detailed mechanistic study. Aryl-alpha-l-arabinofuranosides with various leaving groups were synthesized and used to verify the catalytic mechanism and catalytic residues of the enzyme. The steady-state constants and the resulting Brønsted plots for the E175A mutant are consistent with the role of Glu-175 as the acid-base catalytic residue. The proposed nucleophile residue, Glu-294, was replaced to Ala by a double-base pairs substitution. The resulting E294A mutant, with 4-nitrophenyl alpha-l-arabinofuranoside as the substrate, exhibited eight orders of magnitude lower activity and a 10-fold higher K(m) value compared with the wild type enzyme. Sodium azide accelerated by more than 40-fold the rate of the hydrolysis of 2',4',6'-trichlorophenyl alpha-l-arabinofuranoside by the E294A mutant. The glycosyl-azide product formed during this reaction was isolated and characterized as beta-l-arabinofuranosyl-azide by (1)H NMR, (13)C NMR, mass spectrometry, and Fourier transform infrared analysis. The anomeric configuration of this product supports the assignment of Glu-294 as the catalytic nucleophile residue of the alpha-l-arabinofuranosidase T-6 and allows for the first time the unequivocal identification of this residue in glycoside hydrolases family 51.

Alanine↗
PubMed2003

Biosynthesis of dTDP-3-acetamido-3,6-dideoxy-alpha-D-galactose in Aneurinibacillus thermoaerophilus L420-91T.

The glycan chain of the S-layer protein of Aneurinibacillus thermoaerophilus L420-91T (DSM 10154) consists of d-rhamnose and 3-acetamido-3,6-dideoxy-d-galactose (d-Fucp3NAc). Thymidine diphosphate-activated d-Fucp3NAc serves as precursor for the assembly of structural polysaccharides in Gram-positive and Gram-negative organisms. The biosynthesis of dTDP-3-acetamido-3,6-dideoxy-alpha-d-galactose (dTDP-d-Fucp3NAc) involves five enzymes. The first two steps of the reaction are catalyzed by enzymes that are part of the well studied dTDP-l-rhamnose biosynthetic pathway, namely d-glucose-1-phosphate thymidyltransferase (RmlA) and dTDP-d-glucose-4,6-dehydratase (RmlB). The enzymes catalyzing the last three synthesis reactions have not been characterized biochemically so far. These steps include an isomerase, a transaminase, and a transacetylase. We identified all five genes involved by chromosome walking in the Gram-positive organism A. thermoaerophilus L420-91T and overexpressed the three new enzymes heterologously in Escherichia coli. The activities of these enzymes were monitored by reverse phase high performance liquid chromatography, and the intermediate products formed were characterized by 1H and 13C nuclear magnetic resonance spectroscopy analysis. Alignment of the newly identified proteins with known sequences revealed that the elucidated pathway in this Gram-positive organism may also be valid in the biosynthesis of the O-antigen of lipopolysaccharides of Gram-negative organisms. The key enzyme in the biosynthesis of dTDP-d-Fucp3NAc has been identified as an isomerase, which converts the 4-keto educt into the 3-keto product, with concomitant epimerization at C-4 to produce a 6-deoxy-d-xylo configuration. This is the first report of the functional characterization of the biosynthesis of dTDP-d-Fucp3NAc and description of a novel type of isomerase capable of synthesizing dTDP-6-deoxy-d-xylohex-3-ulose from dTDP-6-deoxy-d-xylohex-4-ulose.

Acetylgalactosamine↗
PubMed2003

Identification of the catalytic residues in family 52 glycoside hydrolase, a beta-xylosidase from Geobacillus stearothermophilus T-6.

beta-d-Xylosidases (EC 3.2.1.37) are exo-type glycoside hydrolases that hydrolyze short xylooligosaccharides to xylose units. The enzymatic hydrolysis of the glycosidic bond involves two carboxylic acid residues, and their identification, together with the stereochemistry of the reaction, provides crucial information on the catalytic mechanism. Two catalytic mutants of a beta-xylosidase from Geobacillus stearothermophilus T-6 were subjected to detailed kinetic analysis to verify their role in catalysis. The activity of the E335G mutant decreased approximately 106-fold, and this activity was enhanced 103-fold in the presence of external nucleophiles such as formate and azide, resulting in a xylosyl-azide product with an opposite anomeric configuration. These results are consistent with Glu335 as the nucleophile in this retaining enzyme. The D495G mutant was subjected to detailed kinetic analysis using substrates bearing different leaving groups (pKa). The mutant exhibited 103-fold reduction in activity, and the Brønsted plot of log(kcat) versus pKa revealed that deglycosylation is the rate-limiting step, indicating that this step was reduced by 103-fold. The rates of the glycosylation step, as reflected by the specificity constant (kcat/Km), were similar to those of the wild type enzyme for hydrolysis of substrates requiring little protonic assistance (low pKa) but decreased 102-fold for those that require strong acid catalysis (high pKa). Furthermore, the pH dependence profile of the mutant enzyme revealed that acid catalysis is absent. Finally, the presence of azide significantly enhanced the mutant activity accompanied with the generation of a xylosyl-azide product with retained anomeric configuration. These results are consistent with Asp495 acting as the acid-base in XynB2.

Amino Acid Substitution↗