摘要:

A new medium, mX-Gal, has been developed for the membrane filter enumeration of β-galactosidase-positive bacteria in municipal water supplies. mX-Gal medium contains the chromogenic β-galactosidase substrate 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside (X-Gal). AllAeromonas,Citrobacter, andEnterobacterstrains isolated from raw water on mX-Gal medium were β-galactosidase positive. In contrast, only 10 to 20% of these strains produced a red colony with a metallic sheen on m-Endo agar LES medium. Of 674 chlorinated water samples analyzed for total coliforms on m-Endo agar LES medium and for β-galactosidase-positive bacteria on mX-Gal medium, 18 that were negative for coliforms on m-Endo agar LES showed β-galactosidase-positive bacteria on mX-Gal. Of a total of 50 β-galactosidase-positive bacteria isolated from these samples, 76% were identified asAeromonas hydrophila.Key words: β-galactosidase, 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside, total coliforms,Aeromonas.

ISSN:0008-4166    

DOI:10.1139/m93-122

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

NADH dehydrogenase ofBacillus megateriumwas isolated from the sonicate soluble fraction. The enzyme was purified approximately 61-fold by a combination of ammonium sulfate fractionation and column chromatography on DEAE-Sephadex and hydroxyapatite. The purified enzyme has an apparent molecular weight of 42 000 as determined by SDS-polyacrylamide gel electrophoresis and activity staining for NADH-MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) oxidoreductase. The enzyme is specific for NADH and has a pH optimum of 7.5–7.8. The apparentKmvalues for NADH are 15.7, 34.8, and 69.2 μM as determined for NADH-DCIP (dichlorophenol–indophenol), NADH-ferricyanide, and NADH-MTT oxidoreductases. FAD is the prosthetic group of the enzyme. NAD+acts as a competitive inhibitor. The inhibition studies suggest that NADH dehydrogenase is the primary electron donor of the NADH oxidase system. Localization studies and inhibition studies together indicate that the NADH oxidase is a complex of membrane-bound enzymes and coenzymes.Key words: NADH dehydrogenase, NADH oxidase,Bacillus megaterium, purification, characterization.

ISSN:0008-4166    

DOI:10.1139/m93-123

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Water and sediment samples collected monthly from six aquaculture ponds in east-central Alabama were analyzed for the presence of actinomycetes and cyanobacteria capable of producing geosmin and (or) 2-methylisoborneol, which cause earthy–musty off-flavors in fish. Six actinomycetous isolates were identified as geosmin producers, five of which were capable of producing 2-methylisoborneol. The one actinomycetous isolate producing geosmin but not 2-methylisoborneol was identified asStreptomyces halstedii. Only one of several cyanobacterial isolates was found to produce geosmin. This isolate was identified asLyngbyacf.subtilisand was prevalent throughout the sampling period in a pond with a history of off-flavor problems. None of the cyanobacterial isolates produced 2-methylisoborneol in laboratory culture.Key words: geosmin,Streptomyces,Lyngbya, off-flavor, aquaculture.

ISSN:0008-4166    

DOI:10.1139/m93-124

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The extent to which lactic acid bacteria, intestinal bacteria, and yeast from the gastrointestinal tract of rats suppress the absorption of 3-amino-1,4-dimethyl-5H-pyrido(4,3-b)indole (Trp-P-1) was investigated. Trp-P-1 was absorbed from the small intestine very rapidly, but in the stomach it was slowly absorbed, requiring 1 or 2 h after administration. When mixtures of Trp-P-1 and freeze-dried microorganisms were administered to rats for 1 h, the amounts of Trp-P-1 absorbed from the small intestine were significantly reduced, and the levels of Trp-P-1 in blood decreased by 40.4–64.7% compared with a control in which only Trp-P-1 was administered. There were no significant differences between the organisms used. In vitro, freeze-dried cells of the strains tested bound 51-97% of Trp-P-1. The Trp-P-1 bound to cells was effectively extracted by aqueous methanol, ethanol, ammonia (50 g/L), and solutions of MgCl2and CaCl2(100 mM/mL), but little was extracted by water and solutions of KCl, NaCl, and buffers at various pH values.Key words: Trp-P-1, gastrointestinal absorption, binding, intestinal bacteria, mutagen–carcinogen.

ISSN:0008-4166    

DOI:10.1139/m93-125

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Humicola griseavar.thermoideamycelium grown on maltose as the main source of carbon produced at least two amylases. The major amylolytic component was purified to homogeneity and classified as a glucoamylase. The apparent molecular mass of the purified enzyme was estimated to be 63 000 Da by SDS-PAGE and 65 000 Da by Bio-Gel P-100 filtration. The purified enzyme was a glycoprotein with 1.8% carbohydrate content and pH and temperature optima of 5.0 and 55 °C, respectively. The purified glucoamylase was thermostable at 60 °C with a half-life of 16 min at 65 °C. In the presence of starch the purified enzyme retained 75% of its thermostability at 65 °C, while the addition of maltose failed to protect the activity. The purified enzyme hydrolyzed branched substrates more efficiently than linear substrates. Starch and amylopectin were the best substrates utilized and amylose was hydrolyzed faster than maltopentaose, maltotetraose, and maltotriose. Kinetic experiments suggested that maltose and starch were hydrolyzed at the same catalytic site.Key words: glucoamylase, amylase,Humicola grisea.

ISSN:0008-4166    

DOI:10.1139/m93-126

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Xylanase production from aBacillus subtilisgene cloned into a strain ofEscherichia coliwas monitored. Although this gene was expressed inE.coliat several temperatures, efficient xylanase secretion did not occur; the observed protein release apparently depended on cell leakage or lysis. Screening for a better microbial protein secretor free of cellulase selectedBacillus cereusNo. 518. A bidirectional vector plasmid (pMK3) was employed to carry the cloned gene into thisB.cereusstrain. Transformation was carried out by electroporation. Total xylanase production by the new pMK3-borne gene inB.cereuswas similar to that fromE.colibut the xylanase was shown to be normally secreted. The xylanase gene products from theE.coliandB.cereushosts were shown to function identically. Both xylanases improved the delignification of unbleached softwood and hardwood kraft pulps, thus reducing the Cl2required to achieve a given degree of bleaching, without altering the physical properties of the fibers. Using a target kappa number (lignin content) of 5, xylanase pretreatment of aspen kraft (chemical) pulp led to a 22% savings of chlorine. Adsorbable organic halogens in the bleachery effluent were also lowered by more than 50%.Key words:Bacillus subtilis, endoxylanase gene, bleaching, kraft pulp properties.

ISSN:0008-4166    

DOI:10.1139/m93-127

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The mycotoxin patulin is a toxic, carcinogenic, unsaturated lactone produced by a number of molds. Polyclonal antibodies against patulin hemiglutarate were produced. Specific antibodies against patulin alone, however, were not clearly demonstrated. Because of its low molecular weight, patulin required conjugation to bovine serum albumin (BSA) to increase its immunogenicity. Anti-patulin-hemiglutarate-BSA antibody titer and specificity were determined using indirect and indirect competitive ELISA, respectively. Immunoassays would facilitate detection and quantitation of patulin.Key words: patulin, mycotoxin, antibodies.

ISSN:0008-4166    

DOI:10.1139/m93-128

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

SomeCandidaspecies that were similar in phenotypic characteristics were studied by molecular taxonomic comparisons including electrophoretic karyotypes, DNA base composition, and DNA relatedness. Among the species studied,Candida terebra,Candida entomaea, andCandida veronaeshowed similar electrophoretic karyotypes and a G + C range from 39.7 to 40.2 mol% in DNA base composition, and demonstrated 85–104% DNA similarity on the basis of flourometric hybridization in microdilution wells. AsC.terebrahas priority, we suggest thatC.entomaeaandC.veronaeshould be synonyms ofC.terebra. Other species in this study,Candida dendronema,Candida diddensiae,Candida naeodendra, andCandida atmospherica, had low DNA relatedness. Thus, these species should be maintained in their original separate taxa.Key words: DNA reassociation, electrokaryotype,Candidaspecies, synonym.

ISSN:0008-4166    

DOI:10.1139/m93-129

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The growth and intracellular accumulation of polyhydroxy alcohols (polyols) were studied in 10 yeastlike fungi of the generaGeotrichumandEndomycesin media with and without the addition of NaCl. The specific growth rate of all strains decreased when the NaCl concentration in the medium was higher than 0.25 M, and no growth occurred at concentrations higher than 1.50 M. High-performance liquid chromatography showed that mannitol was the main polyol accumulated during the late exponential and stationary phases of growth in media without added NaCl. In the presence of 0.75 or 1.0 M NaCl these organisms, with the exception ofGeotrichum penicillatumIGC 3460, accumulated high levels of arabinitol (arabitol) as a compatible solute; mannitol was detected in trace amounts only in the late stationary phase of some strains.Geotrichum penicillatumIGC 3460, however, accumulated mannitol instead of arabinitol in response to an increase of NaCl in the growth medium. In this organism, the substitution of arabinitol for glucose in the growth medium did not affect the accumulation of mannitol.Key words: polyol, osmoregulation,Geotrichum,Endomyces.

ISSN:0008-4166    

DOI:10.1139/m93-130

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

This report deals with the qualitative and quantitative distributions of bacterial populations in the rhizosphere of two date-palm cultivars, one sensitive and one resistant to fusariosis, and with the antagonistic capacity of these bacteria against the pathogenFusarium oxysporumf.sp.albedinis. In the external zones of young roots, bacterial growth was stimulated more by the sensitive cultivar than by the resistant one. A survey of 665 isolates permitted the bacteria to be grouped in two main genera,PseudomonasandBacillus, and in a coryneform group composed ofArthrobacter,Brevibacterium, andPimelobacter. The generic and specific composition differed between the two cultivars and varied with root age (young or old) and the root zones considered (internal or external). In external zones,Pseudomonas caryophylliandPseudomonas gladioliwere the most abundant for the sensitive cultivar. In the endorhizosphere,Bacillus firmuswas more abundant in the resistant cultivar, andPseudomonas fluorescensbiovar II in the sensitive one. Difference were also noted in the percentages of antagonistic bacteria againstF.o.albedinis. The present study confirms the findings of several authors that plants are capable of controlling their own rhizosphere bacterial populations.Key words: bacteria, rhizosphere, systematics, fusariosis, date palm.[Journal translation]

ISSN:0008-4166    

DOI:10.1139/m93-131

出版商:NRC Research Press    

年代:1993

数据来源: NRC