摘要:

An insertion sequence, designated as IST3091, was located adjacent to the putative origin of replication region of plasmid pTFI91 ofThiobacillus ferrooxidansTFI-91. The DNA sequence of the transposase gene of IST3091revealed similarity with that of IS30, IS1086, IS4351, and the integrase gene of SpV1-R8A2 B (a bacteriophage ofSpiroplasma citri). The sequence of IST3091is 1063 bp long with partially matched 30-bp terminal inverted repeats. Several restriction fragments of plasmid pTFI91 ofT.ferrooxidanscontaining the IST3091element were cloned into the vector pHSG398. The hybrid plasmids (pBTL) were transformed intoEscherichia coliNK7379 containing a miniF plasmid, which was devoid of transposable elements. The transposition function of the IST3091element was confirmed by mobilizing hybrid plasmids via conjugation from transformedE.coliNK7379 (donor) toE.coliM8820 (recipient). The presence of the transposed element in transconjugants was detected by polymerase chain reaction amplification.Key words: insertion element,Thiobacillus ferrooxidans, transformation, transposase.

ISSN:0008-4166    

DOI:10.1139/m97-072

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Soil bacteria that utilize inositol hexaphosphate (IHP) were isolated from a range of soils using defined selection media. An analysis of 200 randomly selected isolates indicated that less than 0.5% of the culturable population of soil bacteria were capable of using IHP as a sole source of C and P. From a further 238 isolates obtained from enrichment culture, four unique organisms (identified by randomly amplified polymorphic DNA – polymerase chain reaction) were selected and characterized for their ability to specifically utilize IHP. These four organisms were putatively identified as either fluorescentPseudomonasspp. (P.putidaCCAR53 and CCAR59) or nonfluorescentPseudomonasspp. (P.mendocinaCCAR31 and CCAR60) as determined by partial DNA sequence analysis of 16S rRNA genes. The fluorescentPseudomonasstrains exhibited marked phytase activity and liberated up to 81% of the phosphate from IHP either in the absence or presence of arabinose as an additional C source. The nonfluorescent strains also exhibited an ability to liberate Pifrom IHP but were effective only in the presence of added arabinose. Strains CCAR59 and CCAR60 could effectively utilize either Na-IHP or Ca-IHP at pH 7.0, whereas only strain CCAR59 could grow and utilize these substrates at pH 5.0.Key words: inositol hexaphosphate, soil phytate, phytase activity,Pseudomonasspp.

ISSN:0008-4166    

DOI:10.1139/m97-073

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Pseudomonas syringaepv.glycineaPG4180 produces coronatine (COR), a chlorosis-inducing phytotoxin that consists of the polyketide coronafacic acid (CFA) coupled via an amide bond to the ethylcyclopropyl amino acid coronamic acid (CMA). Both CFA and CMA function as intermediates in the pathway to coronatine, and genes encoding their synthesis have been localized; however, the precise factors that regulate the production of COR and its precursors remain unclear. In the present study, a λ delivery system for Tn5-gusA5was developed and used to obtain transcriptional fusions in the COR gene cluster. Selected carbon (fructose and xylose) and amino acid (isoleucine and valine) sources significantly decreased COR biosynthesis at the transcriptional level. Transcriptional activity in the COR gene cluster was temperature dependent with maximal expression at 18–24 °C and significantly less expression at 14 and 30 °C. Interestingly, changes in osmolarity and the addition of complex carbon and nitrogen sources to the growth medium did not significantly affect COR gene expression, although both factors significantly impacted the quantity of COR produced. These results indicate that multiple factors impact COR production and only some of these directly affect transcription in the COR gene cluster.Key words: transcriptional fusion, glucuronidase, gene expression, reporter gene.

ISSN:0008-4166    

DOI:10.1139/m97-074

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

A hypervariable region ofRhizobium23S rDNA was amplified by polymerase chain reaction and phylogenetic relationships of several strains were determined by comparing nucleotide sequences of the amplified product. Variation in the 23S rDNA nucleotide sequences was consistent with phylogenetic relationships determined by host nodulation specificity and (or) 16S rDNA sequence analysis. Six strains representing threeRhizobiumspecies (R.leguminosarumbv.trifolii,R.meliloti, andR.etli), and two strains each ofBradyrhizobiumandAgrobacteriumwere clustered into five rDNA groups. Unique features identified by secondary structure analysis of the 23S rRNA sequenced region were consistent with the hypothesis that 23S rDNA could be used to design species- or strain-specificRhizobiumprobes.Key words:Rhizobium, rDNA, strain identification, phylogeny.

ISSN:0008-4166    

DOI:10.1139/m97-075

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Transfer by mobilization of a pBR derivative recombinant plasmid lacking transfer functions (oriT+,tra−,mob−) from oneE.coliK12 strain to another was investigated in seven sterile microcosms corresponding to different environments. These microcosms were chosen as representative of environments that genetically engineered microorganisms (GEMOs) encounter after accidental release, namely attached biomass in aquatic environments (biofilm), soil, seawater, freshwater, wastewater, mouse gut, and mussel gut. GEMOs survived in the same way as the host strains in all microcosms. Recombinant DNA mobilization occurred in the mouse gut, in sterile soil, and in biofilm. The plasmid transfer rates principally reflected the environmental conditions encountered in each microcosm.Key words: recombinant DNA, plasmid transfer, mobilization, conjugation, microcosm.

ISSN:0008-4166    

DOI:10.1139/m97-076

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The potential pathogenicity of a microorganism is a major concern for Health Canada evaluators, who will be processing new biotechnology products under the Canadian Environmental Protection Act. Potential pathogenicity is generally predicted by the results of animal pathogenicity studies. In an attempt to define surrogate data for an animal model, this study was initiated.Pseudomonas aeruginosaisolates from clinical and environmental sources were screened for their pilus type, serotype, lipopolysaccharide type, ability to evade host responses, and production of toxin A, exoenzyme S, elastase, phospholipase C, and total protease. The 50% lethal dose (LD50) of the same isolates was determined in the neutropenic mouse model of infection. An attempted correlation was drawn between each (or combinations) of the virulence determinants and the LD50. Stepwise linear regression showed that the presence of high levels of exoenzyme S in association with elastase or phospholipase C, or to a minor extent toxin A, was correlated with low numbers of bacteria required to elicit an LD50. No correlation between any of the other factors examined and virulence was detected. The data suggest that an in vitro high level of exoenzyme S production could be used as surrogate information for neutropenic mouse modelling; however, the levels of all of the extracellular enzymes should be considered when making such an assessment.Key words: virulence, exotoxins, exoenzyme S, clinical strains, environmental strains.

ISSN:0008-4166    

DOI:10.1139/m97-077

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Treatment of actively growingBotrytis cinereahyphae with micromolar concentrations of the dicarboximide fungicide vinclozolin resulted in significant alterations in the growth rate, morphology, and chemical composition of the cells. The addition of vinclozolin resulted in an immediate and severe reduction in the hyphal growth rate and a retardation in the emergence of the second germ tube. Cells treated with vinclozolin had a lower content of pool metabolites than control cells, and this difference increased with time of exposure to the fungicide. In contrast, vinclozolin-treated cells had a higher chitin concentration than control cells. These biochemical alterations were followed by the disorganization and clearing of cells, and by the appearance of dense and dark masses outside the hyphae, presumably composed of cell debris. Hyphae exposed to vinclozolin were more curved and branched and had shorter cells than the controls. The results indicate that vinclozolin causes a slow but generalized leakage of pool metabolites; this release precedes cell lysis and is not the result of a rapid and gross damage to the cytoplasmic membrane.Key words: vinclozolin,Botrytis cinerea, pool metabolites, membrane damage.

ISSN:0008-4166    

DOI:10.1139/m97-078

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

In a laboratory-scale system, denitrification activity of a heterotrophic microbial starter culture changed when different lots of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (P(HB-co-HV)) were used as the solid carbon source in the heterotrophic denitrification reactor. In this study, possible influences of physical and chemical properties of commercially produced P(HB-co-HV) (Biopol®) on biofilm formation and metabolic activity of a denitrifying starter culture were investigated. These parameters indicate the polymers' suitability for the application as the matrix substance in the bioreactor. No differences in microstructure were detected between the different lots of polymers. Growth inhibitory effects by chemical additives were found in the case of triacetine, which was included as a plasticizer in seven of eight tested lots. The amount of hydroxyvaleric acid in the polymer was not assumed to affect denitrification activity. Relevant differences could be detected regarding primary adhesion of the starter culturePseudomonassp. strain 2nIII. It showed good adsorption properties to hydrophobic substances with a dependence on precultivation conditions.Pseudomonassp. strain 2nIII degraded poly-3-hydroxybutyrate acid homopolymer and P(HB-co-HV) copolymers but was unable to break up poly-3-hydroxyvaleric acid. A possible reason for these findings is the substrate specifity of the polyhydroxyalkanoate depolymerase.Key words: poly-3-hydroxybutyrate-co-3-hydroxyvalerate, drinking water denitrification, biofilm, microbial adsorption.

ISSN:0008-4166    

DOI:10.1139/m97-079

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

An increase of the unsaturation level of the cellular fatty acids was observed at sublethal or superoptimal temperatures inSaccharomyces cerevisiae. The hypothesis of this paper is that a high unsaturated fatty acids relative content "per se" is not a prerequisite for withstanding sublethal temperature stress in yeast but is the result of oxygen-consuming desaturase activation, with consequent reduction of oxygen and the oxygen free radicals as they form during thermal stress. In the thermotolerant strains, no increase of cellular thiobarbituric acid reactive substances (TBARSs) was observed when temperature approached the maximal growth temperature, suggesting prevention of oxidative damage. On the other hand, the values of TBARSs tripled at 42 °C in nonthermotolerant strains. When a sublethal hydrogen peroxide treatment preceded a rapid temperature rise, a selected thermotolerant strain responded with a relative increase of saturated fatty acids. This response, associated with an insignificant viability loss due to the double stress, suggests the induction an alternative oxygen consumption mechanism preventing excessive fatty acid unsaturation, which could be detrimental to the cells in the presence of hydrogen peroxide at sublethal temperatures.Key words:Saccharomyces cerevisiae, fatty acid composition, desaturase, thermotolerance, oxidative stress.

ISSN:0008-4166    

DOI:10.1139/m97-080

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Investigations were conducted to determine how a systemic plant-colonizing bacteriumEnterobacter asburiaeJM22 enters cotton plant tissues. Passive uptake was excluded for JM22 by experimentation with glutaraldehyde-fixed (killed) bacterial cells applied to seeds and leaves; no bacteria were found internally or externally on roots or leaves. In contrast, application of live JM22 cells led to colonization of external and internal root and leaf tissues. Active penetration of JM22 in the absence of external wounding was demonstrated for cotton seedlings germinated on water agar and inoculated with the bacterial suspension. The mean internal bacterial population density for seedlings was 3.8 × 103 CFU/g surface-disinfected radicle tissue. Studies of in planta enzymatic activity demonstrated hydrolysis of wall-bound cellulose in the vicinity of JM22 bacterial cells. The same phenomenon was observed for a cortical root colonizing bacterium,Pseudomonas fluorescens89B-61, a plant growth-promoting strain with biocontrol potential against various pathogens.Key words: endophytic bacteria, cotton, cell wall hydrolysis.

ISSN:0008-4166    

DOI:10.1139/m97-081

出版商:NRC Research Press    

年代:1997

数据来源: NRC