摘要:

FC3-11, a bacteriophage specific for theKlebsiella pneumoniaeporin OmpK36, was isolated by its ability to infectEscherichia colistrains expressing the cloned OmpK36 porin. Porin OmpK36 was shown to be the receptor for phage FC3-11 by the observations thatK.pneumoniaeandE.colistrains that do not express OmpK36 were resistant to phage FC3-11, the purified porin inactivated the phage, and mutants selected for FC3-11 resistance had lost OmpK36. The outer membrane protein OmpK35 was isolated from aK.pneumoniaephage-resistant mutant by using porin isolation methods and was shown to contain an N-terminal sequence typical of enterobacterial porins. Bacteriophage FC3-11, alone or in combination with previously described lipopolysaccharide-specific phages, is a valuable tool to obtain OmpK36-porinless mutants.Key words:Klebsiella pneumoniae, porins, bacteriophage.

ISSN:0008-4166    

DOI:10.1139/m95-053

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The adjacent genesstrR–strA–strB1lie within the large cluster of genes of streptomycin biosynthesis and resistance inStreptomyces griseus.sirRencodes a pathway-specific activator StrR, suggested by previous work to be either an antiterminator or a conventional activator, binding to its DNA target via a helix-turn-helix motif.strB1is transcribed in an StrR-dependent fashion from a promoter (PstrB1) that lies downstream fromstrA; betweenPstrB1andsirB1there is a 300-bp leader region containing numerous inverted repeats that could represent modulatable transcription termination sites. Hybrid plasmids were constructed in vitro with transcriptional fusions in which fragments containingPstrB1and either the entire leader region ("long" fragments) or a small part of it (the "short" fragment) were cloned upstream of (i)aphas reporter gene, in a high copy number plasmid background, or (ii)xylEas reporter gene, in a low copy number plasmid background. The short fragment directed high levels of APH (aminoglycoside 3′-phosphotransferase) whether StrR was present or not, while the long fragments did not do so in the absence of StrR; one long fragment directed high levels in wild-typeS.griseus, in which StrR would be present. Insertion of an extraneous fragment intoPstrB1in the short fragment construct led to loss of APH activity, demonstrating that no adventitious promoter had been formed in the short construct. In vitro deletion of part of the leader region in a long fragment construct led to high APH expression with or without StrR present. Although these results are consistent with the target of StrR being within the leader region, and thus with an antiterminator role, it was found that both long and short fragments in the low copy number background failed to direct high expression of catechol oxygenase (the product ofxylE) unlessstrRwas also present on a compatible plasmid. Transfer ofPstrB1-xylEfragments to the high copy number vector did not increase catechol oxygenase expression. We interpret these results in terms of an effect, in the hybrid constructs, of one of the reporter genes on promoter function, possibly by affecting local DNA topology.Key words: gene fusions, reporter genes,Streptomyces, streptomycin, regulation of secondary metabolism.

ISSN:0008-4166    

DOI:10.1139/m95-054

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Sediment samples from Japanese coasts were screened for microorganisms able to degrade resin components of crude oil, and a mixed population that could degrade 35% of 5000 ppm resin in 15 days was obtained. This population also metabolized 50% of saturates and aromatics present in crude oil (5000 ppm) in 7 days. APseudomonassp. isolated from the mixed population emulsified and degraded 30% of resins. This strain also degraded saturates and aromatics (30%) present in crude oil (5000 ppm). This is the first report describing organisms that are able to grow on the resin fraction of crude oil as a sole source of carbon and energy.Key words: resin, crude oil, biodegradation, Iatroscan.

ISSN:0008-4166    

DOI:10.1139/m95-055

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The macro-restriction map ofMycoplasma fermentans(incognitusstrain) was constructed and its rRNA genes were located on the map. It was found that this organism contains two sets of rRNA genes. The 16S and 23S rRNA genes were closely linked as two clusters. However, both 5S rRNA genes were separated from the 16S and 23S genes. The two 16S–23S rRNA gene clusters were arranged in an unusual tail to tail orientation.Key words: physical map, rRNA,Mycoplasma fermentans, genome, gene organization.

ISSN:0008-4166    

DOI:10.1139/m95-056

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Stable mutants ofCryptococcus neoformans(strain CSF-1) induced by treatment with ultraviolet light and nitrosoguanidine were isolated that demonstrated reduced adherence to glial cells in culture. Adherence of the mutants, as measured by a radiometric assay, was reduced by 50–70% of that attained for the parent CSF-1 strain. The adherence mutants appeared to be phenotypically similar to the CSF-1 strain. However, all but one mutant (designated as CSF-23) demonstrated slightly slower growth rates than the wild-type strain. The CSF-1 and CSF-23 strains were injected intravenously and intratracheally into normal rats and rats immunosuppressed by cyclophosphamide treatment, and the organ distribution and recovery of viable yeasts determined over 2–96 h. During this relatively short period of observation the majority of the yeasts were localized in the lungs. By either route of injection, the recovery of the CSF-23 adherence mutant was reduced by as much as 90% of that obtained for the wild-type strain. The results indicated that host cell adherence may be important for the persistence of cryptococci in tissue and that further studies with the adherence mutants are warranted.Key words:Cryptococcus, adherence, cryptococcosis, yeast.

ISSN:0008-4166    

DOI:10.1139/m95-057

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Environmental scanning electron microscopic observations ofPostia placentagrown on a defined medium and on red spruce wood allowed for the examination of the hydrated sheath ofP.placenta. In the wood environment, mature hyphae that were not adhering to the substrate were observed to have a mycofibrillar morphology whereas hyphal tips and branch points had a smooth sheath morphology. A mycofibrillar adhesive matrix was observed on the hyphae growing on glass slides in the defined medium. These morphologies for hyphal sheaths inP.placentaare similar to those previously described by investigators from other laboratories who have used traditional electron microscopic preparative protocols that include dehydration steps. The potential future usefulness of environmental scanning electron microscopic technology in the study of the fine details of extracellular matrices is briefly discussed.Key words: mycofibrils, hyphal sheath, environmental scanning electron microscopy, extracellular matrix.

ISSN:0008-4166    

DOI:10.1139/m95-058

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Enzyme activities involved inL-threonine bioconversions present in cells ofPseudomonassp. strain NCIB 11097 were separated by phenyl-Sepharose hydrophobic chromatography. The separation of the two main activity components was monitored by discontinuous polyacrylamide gel electrophoresis. Threonine aldolase catalyzed the conversion of glycine and acetaldehyde to a mixture of isomers,L-threonine andL-allothreonine, in a biotransformation reaction having pH and temperature optima of 7.5 and 25–30 °C, respectively. The fraction containing serine hydroxymethyltransferase converted acetaldehyde and glycine specifically toL-allothreonine in a biotransformation reaction having pH and temperature optima of 7.4 and 37 °C, respectively.Key words:L-threonine aldolase, serine hydroxymethyltransferase,Pseudomonas,L-allothreonine, biotransformation.

ISSN:0008-4166    

DOI:10.1139/m95-059

出版商:NRC Research Press    

年代:1995

数据来源: NRC