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PubMed1997

Epidemic Bacillus endophthalmitis after cataract surgery I: acute presentation and outcome.

OBJECTIVE: The purpose of the study is to report the clinical outcome of acute Bacillus endophthalmitis after cataract surgery. DESIGN: The study design is a cohort study. PARTICIPANTS: Fourteen eyes of 14 patients with epidemic acute postoperative inflammation after exposure to bacteria-contaminated viscoelastic material were studied. INTERVENTION: Three patients with milder clinical presentations were treated without vitrectomy or antibiotics. Eleven patients with more severe infection were treated with vitrectomy as well as intravitreous and topical fortified antibiotics. MAIN OUTCOME MEASURES: Final visual acuities were obtained in all 14 study patients. Results of microbiologic studies of aqueous and vitreous specimens from 11 vitrectomized eyes also were analyzed. RESULTS: One patient with late presentation had severe inflammation and had phthisis bulbi develop with no light perception. The remaining 13 patients had successful resolution of inflammation after treatment by 1 month of follow-up. Twelve of these 13 patients, including 1 nonvitrectomized patient, had final visual acuities of 20/100 or better at 6 months' follow-up. Six patients, including two patients with nonvitrectomized eyes, had outcomes of 20/40 or better visual acuity. Bacillus species were grown from all 11 (100%) vitreous and 7 (88%) of 8 aqueous specimens obtained from vitrectomized patients, as well as from the contaminated viscoelastic material remaining in the operating room. CONCLUSIONS: Postoperative Bacillus endophthalmitis need not result in poor outcome. Results depend on factors including bacterial load, specific bacterial species, timing of treatment, and immune status of the patient.

Acute Disease↗
PubMed2003

Production of amylase by newly isolated moderate halophile, Halobacillus sp. strain MA-2.

Production of extracellular amylase was demonstrated under stress conditions of high temperature and high salinity in aerobically cultivated culture of a newly isolated moderately halophilic bacterium of spore-forming Halobacillus sp. strain MA-2 in medium containing starch, peptone, beef extract, and NaCl. The maximum amylase production was secreted in the presence of 15% (w/v) Na(2)SO(4) (3.2 U ml(-1)). The isolate was capable of producing amylase in the presence of NaCl, NaCH(3)COOH, or KCl, with the results NaCl>NaCH(3)COOH>KCl. Maximum amylase activity was exhibited in the medium containing 5% (w/v) NaCl (2.4 U ml(-1)). Various carbon sources induced enzyme production. The potential of different carbohydrates in the amylase production was in the order: dextrin>starch>maltose>lactose>glucose>sucrose. In the presence of sodium arsenate (100 mM), maximum production of the enzyme was observed at 3.0 U ml(-1). Copper sulfate (0.1 mM) decreased the amylase production considerately, while lead nitrate had no significant enhancement on amylase production (p<0.05). The pH, temperature, and aeration optima for enzyme production were 7.8, 30 degrees C, and 200 rpm, respectively, while the optimum pH and temperature for enzyme activity was 7.5-8.5 and 50 degrees C, respectively.

Amylases↗
PubMed2000

Distinctness of spore and vegetative cellular fatty acid profiles of some aerobic endospore-forming bacilli.

A gas chromatographic analysis method was employed to determine the cellular fatty acid (CFA) profiles of spores and vegetative cells of some aerobic endospore-forming bacilli. The harvests of experimental strains were processed to obtain pure spores and acquire whole cell fatty acid methyl esters for the subsequent gas chromatographic analysis, and the corresponding vegetative cells were set as control. Evaluation of reproducibility of spore CFA components revealed that, provided under standardized experimental procedure, spore CFA composition was stable enough for research purposes. Fatty acids recovered in spores in greater quantities were saturated branched-chain acids containing 15 and 17 carbon atoms, similar to the vegetative cells. Commonly, the proportions of saturated branched-chain acids in spores were greater than in vegetative cells. The dendrograms obtained by cluster analysis provided some meaningful taxonomic information of the experimental strains. The fatty acids analysis of spores seems to be a promising supplementary tool for the chemotaxonomic research of aerobic endospore-forming bacilli.

Bacillaceae↗
PubMed1999

Modeling the inhibitory effects of organic acids on bacteria.

The inhibitory effect of acids on microbial growth has long been used to preserve foods from spoilage. While much of the effect can be accounted for by pH, it is well known that different organic acids vary considerably in their inhibitory effects. Because organic acids are not members of a homologous series, but vary in the numbers of carboxy groups, hydroxy groups and carbon-carbon double bonds in the molecule, it has typically not been possible to predict the magnitude, or in some cases even the direction, of the change in inhibitory effect upon substituting one acid for another or to predict the net result in food systems containing more than one acid. The objective of this investigation was to attempt to construct a mathematical model that would enable such prediction as a function of the physical and chemical properties of organic acids. Principal Components Analysis (PCA) was applied to 11 properties for each of 17 acids commonly found in food systems; this resulted in four significant principal components (PCs), presumably representing fundamental properties of the acids and indicating each acid's location along each of these four scales. These properties correspond to polar groups, the number of double bonds, molecular size, and solubility in non-polar solvents. Minimum inhibitory concentrations (MICs) for each of eight acids for six test microorganisms were determined at pH 5.25. The MICs for each organism were modeled as a function of the four PCs using partial least squares (PLS) regression. This produced models with high correlations for five of the bacteria (R2 = 0.856, 0.941, 0.968, 0.968 and 0.970) and one with a slightly lower value (R2 = 0.785). Acid susceptible organisms (Bacillus cereus, Bacillus subtilis, and Alicyclobacillus) exhibited a similar response pattern. There appeared to be two separate response patterns for acid resistant organisms; one was exhibited by the two lactobacilli studied and the other by E. coli. Predicting the inhibitory effects of the organic acids as a function of their chemical and physical properties is clearly possible.

Bacillaceae↗
PubMed1999

Thermal inactivation of Alicyclobacillus acidoterrestris spores under different temperature, soluble solids and pH conditions for the design of fruit processes.

Alicyclobacillus acidoterrestris, a thermoacidophilic, non-pathogenic and spore-forming bacterium has been detected in several spoiled commercial pasteurised fruit juices. A. acidoterrestris spores, besides being resistant to the pasteurisation treatment conditions normally applied to acidic fruit products, can germinate and grow causing spoilage. Therefore, this microorganism was suggested as the target to be used in the design of adequate pasteurisation processes. The objectives of this work were to investigate the influence of temperature (T: 85-97 degrees C), total soluble solids (SS: 5-60 degrees Brix or % by weight) and pH (2.5-6.0) on D-values (decimal reduction time) of Alicyclobacillus acidoterrestris (type strain, NCIMB 13137) spores, and to fit a model using response surface methodology. A central composite face-centred experimental design was used, and the response, D-value determined in malt extract broth, ranged between 0.498+/-0.045 and 94.9+/-6.7 min. Within the factor ranges studied, temperature was the parameter that most affected the D-value. Following this was the SS and, lastly, the pH value. A linear decrease in D-value was observed with decreasing SS and pH, and a non-linear decrease in D-value was noticed with increasing temperature. A second order polynomial was successfully fitted to the data (R2 = 0.98). In general, D-values measured in real fruit systems, such as orange, apple and grape juices, blackcurrant concentrates, cupuaçu (exotic fruit) extract and orange juice drink, were higher than those predicted by the malt extract broth model. This result emphasises the importance of experimental validation of any model-derived process.

Bacillaceae↗
PubMed1999

Thermal inactivation of Bacillus cereus spores formed at different temperatures.

The effects of the sporulation temperature in the range 20-45 degrees C on the D and z values of three isolates of Bacillus cereus (ATCC 4342, 7004 and 9818) were investigated. The strains were found to differ in their response. Higher D100 values (around 10-fold) were obtained with isolates 4342 and 9818 when the sporulation temperature increased from 20 to 45 degrees C. With isolate 7004 (the least heat resistant of the three strains), however, the most thermal tolerant spores were obtained at 35 degrees C. The z values were not significantly modified (P > 0.05) by the sporulation temperature. Mean z values of 7.46+/-0.22 degrees C for isolate 4342, 7.80+/-0.40 degrees C for 7004 and 8.09+/-0.33 degrees C for 9818 were obtained.

Bacillaceae Infections↗
PubMed1999

An outbreak of Bacillus cereus respiratory tract infections on a neonatal unit due to contaminated ventilator circuits.

An outbreak of Bacillus cereus respiratory tract infections affecting six ventilated preterm neonates over a two-week period is described. Reusable ventilator circuits were identified as the cause of the outbreak. Ordinarily these were reprocessed on the Neonatal Unit (NNU), first through a washing machine and then through a low-temperature steam (LTS) disinfector. The onset of the outbreak coincided with a breakdown of the LTS facility, which necessitated sending the washed circuits off site for LTS disinfection. The washing machine was shown to be contaminated with the same serovars of B. cereus as those isolated from patients. Two critical steps in the off site LTS disinfection process allowed exsporulation and multiplication of B. cereus: the circuits were inadequately dried after processing, whilst return of the moist circuits to the NNU was often delayed. The outbreak was terminated by withdrawal of the heat-disinfected ventilator circuits. This outbreak emphasizes the need for high standards where medical equipment is reprocessed, especially for use in vulnerable patients.

Bacillaceae Infections↗
PubMed1997

Acidostable and acidophilic proteins: the example of the alpha-amylase from Alicyclobacillus acidocaldarius.

Acidophilic microorganisms grow optimally at pH values between 1-4. They have adapted to the acid condition by maintaining their cytoplasmic pH at a value close to neutrality. Hence, only those (macro)-molecules, which face the acid medium, have had to adapt to this extreme condition. Literature data show that several exoproteins from thermoacidophilic prokaryotes are characterized by a low charge density. It is proposed that this property contributes to the stability of these proteins both below and above the pKa-values of their glutamate and aspartate residues. As an example of an acidophilic protein, the alpha-amylase from the Gram-positive Alicyclobacillus acidocaldarius ATCC27009 was studied. The enzyme is thermoacidophilic, with optima of temperature and pH of 75 degrees C and pH 3, respectively. The nucleotide sequence of the cloned gene (8) indicates that the alpha-amylase belongs to a large family of starch-degrading enzymes with a characteristic catalytic (beta alpha)8-domain. Three essential and probably catalytic acidic residues have been conserved, suggesting that the acidophilic alpha-amylase degrades starch with essentially the same mechanism as do its neutrophilic relatives. Still, the acidophilic protein contains three exchanges in residues uniformally or almost uniformally conserved among all members of the enzyme family. In order to test whether these exchanges contribute to the acidic pH optimum, the alpha-amylase gene was expressed in Escherichia coli. Sonication of the enzyme-producing cells released alpha-amylase activity associated with a 140 kDa protein. The optima of temperature and pH for the protein produced in E. coli were similar to those of the native enzyme. Experiments are underway in which it is tested which residues contribute to the acid pH optimum of the alpha-amylase.

Amino Acid Sequence↗
PubMed2003

Novel pyrazine metabolites found in polymyxin biosynthesis by Paenibacillus polymyxa.

A complex mixture of methyl-branched alkyl-substituted pyrazines was found in the growth medium of the polymyxin-producing bacterium Paenibacillus polymyxa, and of these, seven are new natural compounds. A total of 19 pyrazine metabolites were identified. The dominant metabolite was 2,5-diisopropylpyrazine as identified using a combination of high-resolution mass spectrometry, (1)H- and (13)C-nuclear magnetic resonance, gas chromatography-mass spectrometry as well as co-elution with an authentic standard. Its biosynthesis was correlated with growth and production was strongly stimulated by valine supplementation. The other pyrazine metabolites, all related pyrazines with either one, two or three alkyl substituents, were identified by means of their mass spectral data and/or co-elution with authentic standards.

Bacillaceae↗
PubMed1996

Larvicidal activity of Bacillus thuringiensis natural isolates; indigenous to Japan, against two nematoceran insect pests occurring in urban sewage environments.

A total of 1449 Bacillus thuringiensis strains, indigenous to Japan, were screened for larvicidal activity against two nematoceran insect pests, the mosquito, Culex pipiens molestus (Culicidae), and the moth-fly, Telmatoscopus albipunctatus (Psychodidae). Mosquito specific strains were abundant in H serotypes 3abc (serovar kurstaki), 3ade (fukuokaensis), 4ac (kenyae), 7 (aizawai), 11ac (kyushuensis) and 29 (amagiensis), while moth-fly specific strains were predominantly found in H serotype 17 (tohokuensis). Strains toxic to both insects were most frequently detected in H serotypes 10 (darmstadiensis) and 17/27. Seven selected B. thuringiensis strains were highly toxic to Culex and/or Telmatoscopus. There was a diversity in SDS-PAGE profiles of inclusion proteins of these strains.

Animals↗
PubMed2002

Crystal structure of a squalene cyclase in complex with the potential anticholesteremic drug Ro48-8071.

Squalene-hopene cyclase (SHC) catalyzes the conversion of squalene into pentacyclic compounds. It is the prokaryotic counterpart of the eukaryotic oxidosqualene cyclase (OSC) that catalyzes the steroid scaffold formation. Because of clear sequence homology, SHC can serve as a model for OSC, which is an attractive target for anticholesteremic drugs. We have established the crystal structure of SHC complexed with Ro48-8071, a potent inhibitor of OSC and therefore of cholesterol biosynthesis. Ro48-8071 is bound in the active-center cavity of SHC and extends into the channel that connects the cavity with the membrane. The binding site of Ro48-8071 is largely identical with the expected site of squalene; it differs from a previous model based on photoaffinity labeling. The knowledge of the inhibitor binding mode in SHC is likely to help develop more potent inhibitors for OSC.

Anticholesteremic Agents↗
PubMed1999

The binding site for an inhibitor of squalene:hopene cyclase determined using photoaffinity labeling and molecular modeling.

BACKGROUND: The squalene:hopene cyclases (SHCs) are bacterial enzymes that convert squalene into hopanoids, a function analogous to the action of oxidosqualene cyclases (OSCs) in eukaryotic steroid and triterpenoid biosynthesis. We have identified the binding site for a selective, potent, photoactivatable inhibitor of an SHC. RESULTS: SHC from Alicyclobacillus acidocaldarius was specifically labeled by [3H]Ro48-8071, a benzophenone-containing hypocholesteremic drug. Edman degradation of a peptide fragment of covalently modified SHC confirmed that Ala44 was specifically modified. Molecular modeling, using X-ray-derived protein coordinates and a single point constraint for the inhibitor, suggested several geometries by which Ro48-8071 could occupy the active site. CONCLUSIONS: A covalent complex of a potent inhibitor with a squalene cyclase has been characterized. The amino acid modification and molecular modeling suggest that Ro48-8071 binds at the junction between the central cavity and substrate entry channel, therefore inhibiting access of the substrate to the active site.

Affinity Labels↗
PubMed2000

Epidemiology and pathogenesis of Bacillus cereus infections.

Bacillus cereus is a causative agent in both gastrointestinal and in nongastrointestinal infections. Enterotoxins, emetic toxin (cereulide), hemolysins, and phoshpolipase C as well as many enzymes such as beta-lactamases, proteases and collagenases are known as potential virulence factors of B. cereus. A special surface structure of B. cereus cells, the S-layer, has a significant role in the adhesion to host cells, in phagocytosis and in increased radiation resistance. Interest in B. cereus has been growing lately because it seems that B. cereus-related diseases, in particular food poisonings, are growing in number.

Animals↗
PubMed2005

pHluorin-based in vivo assay for hydrolase screening.

pHluorin, a pH-sensitive mutant of green fluorescent protein (GFP), acts as a sensor for intracellular pH shifts, triggered by hydrolytic enzymes. This principle was used to develop a pHluorin-based in vivo assay for hydrolase screening. The presented assay was evaluated for Escherichia coli (E. coli) cells, producing heterologous pHluorin and an esterase from Geobacillus stearothermophilus which is considered as a model hydrolase. Subsequently, the utility of this detection system was also demonstrated with recombinantly expressed hydantoinase and amidase in E. coli. This in vivo assay also shows capability for readout with flow cytometric devices. Population shifts of pHluorin-expressing E. coli cells were easily recognized due to pH changes caused by substrate hydrolysis.

Bacillaceae↗
PubMed2003

Detailed kinetic analysis of a family 52 glycoside hydrolase: a beta-xylosidase from Geobacillus stearothermophilus.

Geobacillus stearothermophilus T-6 encodes for a beta-xylosidase (XynB2) from family 52 of glycoside hydrolases that was previously shown to hydrolyze its substrate with net retention of the anomeric configuration. XynB2 significantly prefers substrates with xylose as the glycone moiety and exhibits a typical bell-shaped pH dependence curve. Binding properties of xylobiose and xylotriose to the active site were measured using isothermal titration calorimetry (ITC). Binding reactions were enthalpy driven with xylobiose binding more tightly than xylotriose to the active site. The kinetic constants of XynB2 were measured for the hydrolysis of a variety of aryl beta-D-xylopyranoside substrates bearing different leaving groups. The Brønsted plot of log k(cat) versus the pK(a) value of the aglycon leaving group reveals a biphasic relationship, consistent with a double-displacement mechanism as expected for retaining glycoside hydrolases. Hydrolysis rates for substrates with poor leaving groups (pK(a) > 8) vary widely with the aglycon reactivity, indicating that, for these substrates, the bond cleavage is rate limiting. However, no such dependence is observed for more reactive substrates (pK(a) < 8), indicating that in this case hydrolysis of the xylosyl-enzyme intermediate is rate limiting. Secondary kinetic isotope effects suggest that the intermediate breakdown proceeds with modest oxocarbenium ion character at the transition state, and bond cleavage proceeds with even lower oxocarbenium ion character. Inhibition studies with several gluco analogue inhibitors could be measured since XynB2 has low, yet sufficient, activity toward 4-nitrophenyl beta-D-glucopyranose. As expected, inhibitors mimicking the proposed transition state structure, such as 1-deoxynojirimycin, bind with much higher affinity to XynB2 than ground state inhibitors.

Bacillaceae↗