摘要:

Microbial oxidation of inorganic sulfur compounds is governed by both chemical and enzymatic reactions. It is therefore essential to understand reactions possible in chemistry when we consider enzymatic reactions. Various oxidation states of sulfur atoms in inorganic sulfur compounds and chemical oxidation reactions as well as nucleophilic cleavage of sulfur-sulfur bonds are discussed. The scheme of enzymatic oxidation of sulfur compounds with S2-→> S0→> SO32-→> SO42-as the main oxidation pathway is discussed with thiosulfate and polythionates leading into the main pathway for complete oxidation to sulfate. Enzymatic reactions are related to chemical reactions and the use of inhibitors for S0→> SO32-and SO32-→> SO42-is discussed for analyzing and establishing reaction stoichiometries. The proposed pathway is supported by a variety of evidence in many different microorganisms including some genetic evidence if the oxidation steps include all the systems irrespective of oxidizing agents (O2, Fe3+, cytochromes etc.).Key words: sulfur, oxidation, chemical, enzymatic, reactions.

ISSN:0008-4166    

DOI:10.1139/w98-223

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Experiments have been performed to screen eight microbial commercial products that, according to the manufacturers, are able to degrade crude oil. This study compared the crude oil biodegradation activity of commercial inocula with that of natural inocula (activated sludge and tropical aquarium water). Some of the latter were previously adapted to the crude oil as the only carbon source. Nutrients and sorbents in the commercial formulations were eliminated, and each inoculum was precultured on marine yeast extract medium. Crude oil biodegradability tests were conducted with close initial substrate concentration to initial bacterial concentration ratios (S0/X0) of 0.94 g of crude oil/109CFU, which allowed a comparison of biodegradation activity. The inocula oxidized the crude oil after a short lag time of less than 3-18 days. After that time, the rate of oxidation varied between 45 and 244 mg O2/(L·day). Crude oil biodegradation after a 28-day test was effective only for 10 out of 12 inocula (from 0.1 to 25% in weight). Biodegradation mainly corresponded to the saturated fraction of the crude oil; the asphaltene fraction was never significantly biodegraded. Our results led to the conclusion that natural inocula, either adapted or not adapted to crude oil, were the most active (from 16 to 25% of loss in crude oil weight) and only one commercial inoculum was able to degrade 18% of the crude oil. Other inocula had a biodegradation activity ranging from 0.1 to 14%.Key words: biodegradability tests, microbial inoculum, crude oil, seeding.

ISSN:0008-4166    

DOI:10.1139/w98-210

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Contamination of soils with heavy metal ions is a major problem on industrial and defense-related sites worldwide. The bioavailability and mobility of these contaminants is partially determined by the microbial biomass present at these sites. In this study, we have assessed the effect of the addition of a mixture of toxic metal salts on the prokaryotic community of microcosms consisting of sandy-loam soil using direct molecular analysis of the recoverable eubacterial 16S rDNA molecules by polymerase chain reaction - denaturing gradient gel electrophoresis (PCR-DGGE) and limited phospholipid fatty acid analysis (PLFA). Addition of toxic metals (nonradioactive surrogates of Sr, Co, Cs, Cd) resulted in rapid (ca. 1 week) changes in the DGGE profile of the indigenous eubacterial community when compared with pristine controls. These changes were stable over the course of the experiment (8 weeks). No changes in the eubacterial population of control microcosms were detected. The major changes in community structure in metal-contaminated microcosms consisted of the appearance of four novel bands not detected in controls. Sequence analysis of these bands suggested that two organisms related to the genusAcinetobacterand two related to the genusBurkholderiacarried a selective advantage over other indigenous eubacteria under heavy metal induced stress. TheBurkholderiaspp. were then cultured and further characterized using lipid analysis.Key words: metals, PCR-DGGE, microbial community response.

ISSN:0008-4166    

DOI:10.1139/w98-221

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The role of catalase in hydrogen peroxide resistance inSchizosaccharomyces pombewas investigated. A catalase gene disruptant completely lacking catalase activity is more sensitive to hydrogen peroxide than the parent strain. The mutant does not acquire hydrogen peroxide resistance by osmotic stress, a treatment that induces catalase activity in the wild-type cells. The growth rate of the disruptant is not different from that of the parent strain. Additionally, transformed cells that overexpress the catalase activity are more resistant to hydrogen peroxide than wild-type cells with normal catalase activity. These results indicate that the catalase ofS. pombeplays an important role in resistance to high concentrations of hydrogen peroxide but offers little in the way of protection from the hydrogen peroxide generated in small amounts under normal growth conditions.Key words: catalase, gene disruption, induced hydrogen peroxide resistance, overexpression,Schizosaccharomyces pombe.

ISSN:0008-4166    

DOI:10.1139/w98-216

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The effects of surfactant physicochemical properties, such as the hydrophile-lipophile balance (HLB) and molecular structure, on the biodegradation of 2% w/v Bow River crude oil by a mixed-bacterial culture were examined. Viable counts increased 4.6-fold and total petroleum hydrocarbon (TPH) biodegradation increased 57% in the presence of Igepal CO-630, a nonylphenol ethoxylate (HLB 13, 0.625 g/L). Only the nonylphenol ethoxylate with an HLB value of 13 substantially enhanced biodegradation. The surfactants from other chemical classes with HLB values of 13 (0.625 g/L) had no effect or were inhibitory. TPH biodegradation enhancement by Igepal CO-630 occurred at concentrations above the critical micelle concentration. When the effect of surfactant on individual oil fractions was examined, the biodegradation enhancement for the saturate and aromatic fractions was the same. In all cases, biodegradation resulted in increased resin and asphaltene concentrations. Optimal surfactant concentrations for TPH biodegradation reduced resin and asphaltene formation. Chemical surfactants have the potential to improve crude oil biodegradation in complex microbial systems, and surfactant selection should consider factors such as molecular structure, HLB, and surfactant concentration.Key words: mixed culture, crude oil, surfactant, hydrophile-lipophile balance, biodegradation.

ISSN:0008-4166    

DOI:10.1139/w98-209

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Colonization of the spermosphere and rhizosphere by plant-beneficial bacteria is limited by competition with indigenous soil microbes for resources such as reduced carbon compounds. A study of the soil microbial community around germinating seeds was undertaken as a necessary first step in understanding the competition between the introduced plant-beneficial bacteria and the indigenous microbial community. Two soil types, Galestown gravely loamy sand soil, with pH 5.8 and 0.6% humic material, and Hatborough loamy sand soil, with pH 4.5 and 3.2% humic material, were compared. Five seed types, corn, cucumber, radish, soybean, and sunflower were used. Microbial communities were characterized functionally, using a substrate utilization assay, and structurally, using fatty acid methyl ester analysis, over a 96-h period after the onset of germination. Soil type affected the microbial communities far more than seed type. The communities in Hatborough soil had greater functional and structural changes compared with the control than Galestown soil. The communities changed more functionally than structurally, with increased substrate utilization compared with the soil controls.Key words: spermosphere, microbial community, Biolog, substrate utilization, fatty acid.

ISSN:0008-4166    

DOI:10.1139/w98-227

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

A Gram-negative, anaerobic sulfate-reducing bacterium was isolated from hindgut contents of the lower termiteMastotermes darwiniensisFroggatt (strain KMS2). Strain KMS2 is motile by a single polar flagellum. The isolate possesses desulfoviridin and catalase activity. The G+C content of its DNA is in the range of 54.5-55.5 mol% (strain KMS2). It respires hydrogen and different low molecular weight organic compounds in the presence of sulfate, thiosulfate, and sulfite, and also oxygen. The isolated strain ferments pyruvate. Fastest growth with a doubling time of 12.5 h was obtained at 37°C and not at 28°C, the temperature at which the termites were grown. The isolate showed a 16S rDNA sequence homology of 95.9% toDesulfovibrio desulfuricansATCC 27774 and a DNA-DNA homology of 44.6% toD. desulfuricansEssex 6 (type strain). Based on its biochemical properties and 16S rDNA sequence, the isolate was assigned to a new species namedDesulfovibrio intestinalis.Key words:Desulfovibrio, termite, intestinal flor

ISSN:0008-4166    

DOI:10.1139/w98-222

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

This study investigated the involvement of RNA folding in the synthesis of a fusion protein with beta-galactosidase activity. The coding gap region of thePrevotella loescheiiadhesin geneplaAwas fused in-frame with theEscherichia colilacZgene on plasmid pSK105. N-Terminal sequencing of the expressedplaA-lacZprotein indicated that it resulted from translational initiation at a fortuitous ribosomal-binding site within theplaAsequence at nt 570. Specific mutations were introduced in the stem-loop region that precedes the gap sequence. Analysis of stem-loop mutants, together with the introduction of compensatory mutations that restored activity, supports a requirement for stem-loop formation within theplaAsequence preceding the translational initiation site. A mutation reducing the predicted size of the loop, but preserving the stem structure, inactivated fusion protein synthesis. A suppressor mutation predicted to restore the size of the loop restored efficient fusion protein synthesis. In addition, the sequence preceding the translational start site of theplaA-lacZfusion has several similarities to sequences that function as translational enhancers in prokaryotes. These include a stem-loop structure, an A-U rich region preceding the initiation codon, and a region of homology to 16S rRNA.Key words: site-directed mutagenesis, stem-loop formation, fusion protein, translational initiation, translational enhancer.

ISSN:0008-4166    

DOI:10.1139/w98-232

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Although phenol catabolism is described for many different microorganisms, there is no example for such a pathway in an enterobacterial strain. Here we characterize aKlebsiella oxytocastrain that grows on phenol as the only source of carbon and energy. As the key enzyme of phenol degradation, phenol hydroxylase was purified to apparent homogeneity. Compared with other phenol hydroxylases, theKlebsiellaenzyme differs with respect to several properties: (i) SDS-PAGE and gel-filtration analysis of the purified protein revealed that the enzyme is a monomer with a molecular mass of 156 kDa; (ii) steady-state kinetic measurements resulted in aKmvalue of 0.22 mM for phenol; and (iii) the enzyme is both dependent on NADPH/FAD and sensitive to EDTA. Further degradation of catechol, the reaction product of phenol hydroxylase, may occur via the effectivemeta-fission pathway often located on TOL or TOL-like plasmids. Such a plasmid was prepared from theKlebsiellastrain and further characterized. The given data demonstrate that the isolated strain exhibits all characteristics of an efficient phenol-degrading microorganism.Key words: phenol metabolism,Klebsiella oxytoca,phenol hydroxylase, TOL plasmids.

ISSN:0008-4166    

DOI:10.1139/w98-218

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Two new yeast species were isolated from flowers ofHibiscusspecies in Eastern and Northern Australia.Kodamaea kakaduensisis heterothallic, haploid, and similar to otherKodamaeaspecies and toCandida restingae. Buds are often produced on short protuberances, and a true mycelium is formed. The new species differs from others by the assimilation of trehalose, melezitose, and xylitol, and is reproductively isolated. The cells ofCandida toleransare small and a pseudomycelium is formed. The carbon and nitrogen assimilation pattern is reminiscent of that ofZygosaccharomyces rouxiibut the two are not closely related. Sequences of the D1/D2 domain of large subunit ribosomal DNA confirm the membership ofK. kakaduensisin the genusKodamaeaand indicate thatC. toleransbelongs to theClavispora-Metschnikowiaclade, with a moderate relatedness toCandida mogii. The type strains are:K. kakaduensis, UWO(PS)98-119.2 (h+, holotype, CBS 8611) and UWO(PS)98-117.1 (h-, isotype, CBS 8612); andC. tolerans, UWO(PS)98-115.5 (CBS 8613).Key words:Kodamaea, Candida, new yeast species, ribosomal DNA, whole-cell PCR.

ISSN:0008-4166    

DOI:10.1139/w98-225

出版商:NRC Research Press    

年代:1999

数据来源: NRC