ISSN:0008-4166    

DOI:10.1139/m93-165

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

A recombinant plasmid, pBMR5, carrying arecA-like gene ofHerbaspirillum seropedicae, was isolated from aH.seropedicaegenomic library by intergeneric complementation ofEscherichia coli recAmutant strain HB101. Quantitative survival experiments showed that pBMR5 restored the ultraviolet radiation and methyl methanesulfonate resistances and recombinational proficiency of this strain. Hybridization studies showed that there is DNA sequence homology between therecAgene ofE.coliK12 and that ofH.seropedicae. Restriction sites forEcoRI,HindIII,BamHI, andBglII were found in the DNA insert derived fromH.seropedicaein pBMR5. A Tn5 insertional mutant of pBMR5, called pBMR26.2, failed to restore recombination proficiency and methyl methanesulfonate and ultraviolet resistance torecAmutants ofE.coli.Key words:Herbaspirillum seropedicae, nitrogen fixation,recA-like gene, Tn5 mutagenesis.

ISSN:0008-4166    

DOI:10.1139/m93-166

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The infectivity ofBorrelia burgdorferidepends on the number of passages in Barbour–Stoenner–Kelly (BSK-II) medium in ambient air. In this study the parameters of medium formulation or O2–CO2atmosphere were altered to define conditions that would retain borrelial infectivity upon serial passage. The infective strain Sh-2-82 was passaged 20 times in BSK-II and BSK-A (a modified BSK-II medium) in ambient O2–CO2and BSK-II in 4% O2– 5% CO2– 91% N2. Spirochetes of every fifth passage were inoculated intraperitoneally into neonatal Lewis rats. Infectivity was lost after 15 passages in media in ambient O2–CO2. However, infectivity was maintained through all 20 passages in BSK-II in 4% O2– 5% CO2– 91% N2. There were no pH differences, but the dissolved O2concentration in ambient O2–CO2was approximately twice that in 4% O2– 5% CO2– 91% N2. Therefore, differences in infectivity were due to culturing under a constant environment of decreased O2and increased CO2. This environment may place a selective pressure on the borreliae for retention of the infective phenotype. The results suggest that the levels of O2and CO2in the environment influence infectivity by preventing the loss of genetic information or inducing the expression of virulence determinants inB.burgdorferi.Key words:Borrelia burgdorferi; Lyme disease, infectivity, serial passage.

ISSN:0008-4166    

DOI:10.1139/m93-167

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Pseudomonas putidaGR12-2R3 is a rifampicin-resistant derivative of a cold-tolerant, nitrogen-fixing bacterium isolated from the roots of grasses growing in the Canadian high arctic. It colonizes canola (Brassica campestris) roots and promotes canola root and shoot growth under gnotobiotic conditions and in the field. TnphoAinsertion mutagenesis was used to isolate derivatives of strain GR12-2R3 that had reduced abilities to promote canola root elongation (PRE−mutants). Within a pool of 10 290 TnphoAinsertion mutants, 1.4% expressed active PhoA fusion proteins (PhoA+). Among 20 PhoA+mutants, 6 were PRE−and 4 of those strains secreted PhoA activity into the culture medium. PhoA+strain PG269 showed PhoA activity, 25% cell associated, that was induced by canola seed exudate. The ability of this strain to promote canola root elongation was similar to that of the parent strain. Like other pseudomonads, strain GR12-2R3 utilizes a wide range of sugars, amino acids, and other compounds as carbon and nitrogen sources. Twenty-one TnphoAinsertion mutants, all PhoA−, were unable to utilize a specific nutrient. That group included strains that could not utilize arabinose (Ara−, three mutants) or glycerol and other compounds (Csu−, three mutants) as carbon source and strains that could not utilize glycine (Gut−, eight mutants), histidine (Hut−, three mutants), or proline (Put−, four mutants) as nitrogen source. One Ara−mutant, three Gut−mutants, and one Csu−mutant were PRE−. Five of the mutant strains examined in detail (two PhoA−PRE−, one PhoA−PRE+, one PhoA+PRE−, and one PhoA+PRE+) grew less well than strain GR12-2R3 in LB and (or) seed exudate medium. Further characterization of the TnphoAtarget genes in selected PRE−strains is expected to yield additional insight regarding the molecular basis for the interaction betweenP.putidaGR12-2R3 and canola.Key words:Pseudomonas putida, plant growth promoting rhizobacterium, TnphoA.

ISSN:0008-4166    

DOI:10.1139/m93-168

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

An antibody reacting with extracellular polysaccharide fromXanthomonas oryzaepv.oryzaewas used to detect the extracellular polysaccharide in infected leaf tissues of rice plants (Oryzae sativacv. IR24) by immunofluorescence and immunoelectron microscopy. Using extracellular polysaccharide as a hapten and bovine serum albumin as a carrier, an extracellular polysaccharide – bovine serum albumin conjugate was prepared. After a rabbit was immunized against the conjugate, an antibody reacting with extracellular polysaccharide fromX.oryzaepv.oryzaewas isolated and purified. Using ELISA, the antibody was capable of detecting extracellular polysaccharide at concentrations above 0.1 μg/mL. Immunofluorescent antibody staining of infected rice leaves showed that extracellular polysaccharide produced byX.oryzaepv.oryzaewas distributed in both xylem vessels and transverse veins but not in either sieve tubes or mesophyll tissues. This demonstrates that the distribution of extracellular polysaccharide coincided with that of bacteria in the infected leaf tissues. Immunoelectron microscopy showed that localization of extracellular polysaccharide was restricted to the area close to bacterial cells. The amount of extracellular polysaccharide may not be enough to plug xylem vessels of rice leaves infected withX.oryzaepv.oryzae.Key words: anti extracellular polysaccharide antibody,Xanthomonas oryzaepv.oryzae, immunofluorescent microscopy, immunoelectron microscopy, rice plant.

ISSN:0008-4166    

DOI:10.1139/m93-169

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The effect of recombinant human urokinase (rh-UK) in a rat model of chronicPseudomonas aeruginosapulmonary infection was studied. Efficacy was assessed by lung histology and quantitative bacteriology. Male Sprague–Dawley rats received 1 × 104or 1 × 105P.aeruginosaencapsulated in agar beads via the intratracheal route on day 1. Intratracheal administration of up to 12 500 units of rh-UK on day 21 led to a dose-dependent disappearance of viable organisms from the lungs by day 24 in rats receiving 104organisms. In slightly longer term infections (30 days), rh-UK was still effective in facilitating the disappearance of the organisms from the lungs of most of the treated animals. rh-UK was effective in eliminating organisms when animals were infected with 104, but not 105bacteria. In vitro analysis revealed that rh-UK was not directly toxic for the organisms. Histologically, lungs from short-term infected control animals exhibited acute inflammation, inflammatory cell infiltrates, and fibrin deposition. Histology of lungs from UK-treated, short-term infected rats revealed decreased airway inflammation and cellular infiltration compared with infected controls. Lungs from infected animals treated with 12 500 units of rh-UK were histologically indistinguishable from the lungs of uninfected control animals, except for the foreign body reaction. These results indicate that exogenous rh-UK may be efficacious in the treatment of pulmonary inflammation accompanying exposure to Gram-negative bacteria such asP.aeruginosa.Key words: chronic pulmonary infection,Pseudomonas aeruginosainfection, fibrinolysis, urokinase.

ISSN:0008-4166    

DOI:10.1139/m93-170

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Three strains,Rhodotorula rubra,Rhodotorula glutinis, andCandida zeylanoides, isolated from fish, were tested for the expression of putative tissue colonization factors. All strains were able to bind collagen type I, fibronectin, and laminin to various degrees after growing on various solid and broth media, while the binding to collagen type IV was sparse under all conditions tested. For the three strains tested, a very low cell surface hydrophobicity was shown for growth on various solid and broth media. Mostly, the strains also expressed a negatively charged surface. Extracellular protease activity using different substrates was shown for all three strains. Furthermore, two properties related to iron scavenging, i.e., binding of lactoferrin and production of siderophores, were also tested. For the three strains a capacity to bind lactoferrin as well as a capacity to excrete siderophores were demonstrated. Since these different properties have been correlated to virulence and to the capacity of colonization in other organisms, we address the question of whether the expression of these properties in yeasts could contribute to colonization in fish.Key words: marine yeasts, fish colonization.

ISSN:0008-4166    

DOI:10.1139/m93-171

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

A procedure based upon DNA hybridization was developed for the specific detection ofRhizobium leguminosarumand its different biovars among bacteria isolated from soil. DNA colony hybridization and restriction fragment length polymorphism analysis with aR.leguminosarumchromosomal probe were found to be species specific forR.leguminosarumandRhizobium etli. By usingR.leguminosarum nodgene probes, biovar specificity was obtained. Of 302 soil isolates screened for their inability to grow on Luria-Bertani agar medium, 13 strains could be assigned to theR.leguminosarumspecies on the basis of DNA homology to the chromosomal probe and antibiotic resistance tests. Of these strains, three and two were assigned by colony hybridization and subsequent plant host specificity tests, respectively, toR.leguminosarumbiovarsviciaeandtrifolii. The eight otherR.leguminosarumsoil isolates lacked symbiotic information but were able to gain nodulation capacity with the acquisition of a conjugative symbiotic plasmid. They were thus considered as nonsymbioticR.leguminosarum.Key words:Rhizobium leguminosarum, DNA hybridization, soil, symbiotic genes.

ISSN:0008-4166    

DOI:10.1139/m93-172

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

In greenhouse trials, root growth ofAsparagus officinalisL. increased up to 30% when roots of 3-week-old seedlings were dipped in the culture filtrate ofPseudomonas putidaRSA9, a strain isolated from rhizosphere soil of asparagus and antagonistic to the crown rot pathogenFusarium moniliforme. The culture filtrate was extracted with ethyl acetate at pH 3, and the extracts were fractionated on a column of octadesylsilica gel. The active fraction was found to be a 45:55 mixture of succinic and lactic acids. Root mass increased 40% when the roots of the seedlings were treated with a 1:1 mixture of the acids at 10 ppm. The results provide an explanation for the plant growth promoting effects of some rhizobacteria; the bacteria may secrete organic acids, such as succinic and lactic acids, and these acids may increase plant growth under conditions in which the populations of pathogens are reduced.Key words: succinic acid, lactic acid,Pseudomonas putida, plant growth promotion, rhizobacteria, PGPR.

ISSN:0008-4166    

DOI:10.1139/m93-173

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

ThehemGgene ofEscherichia coliK12 is involved in the activity of protoporphyrinogen oxidase, the enzyme responsible for the conversion of protoporphyrinogen IX into protoporphyrin IX during heme and chlorophyll biosynthesis. The gene is located at min 87 on the genetic map ofE.coliK12. ThehemGgene was isolated by a mini-Mu in vivo cloning procedure. As expected, thehemGgene is able to restore normal growth to thehemGmutant, and the transformed cells display strong protoporphyrinogen oxidase activity. Sequencing of thehemGgene allowed us to identify an open reading frame of 546 nucleotides (181 amino acids), within the minimal fragment able to complement the mutant. The presumed molecular mass of the HemG protein is 21 202 Da, in agreement with values found by SDS-PAGE, in a DNA-directed coupled transcription–translation system. The identity of the first 18 amino acids at the amino-terminal end of the protein was confirmed by microsequencing. To our knowledge, this is the first cloning of a gene involved in the protoporphyrinogen oxidase activity ofE.coli.Key words: protoporphyrinogen oxidase (PROTOX),hemGgene,Escherichia coli, DPE herbicides, heme.

ISSN:0008-4166    

DOI:10.1139/m93-174

出版商:NRC Research Press    

年代:1993

数据来源: NRC