ISSN:0008-4166    

DOI:10.1139/m94-097

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The mitochondrial DNAs (mtDNAs) and the ribosomal repeat unit (ribosomal DNA, rDNA) of blackAspergillusisolates collected in various parts of the world were examined. Wide-ranging mtDNA variation was observed in natural populations of theAspergillus nigeraggregate. Most isolates were classifiable asA.nigerorAspergillus tubingensisaccording to their rDNA and mtDNA patterns. The mtDNA variation was distributed unevenly in the populations studied. The mtDNAs of most of the isolates collected in Australia were of theA.tubingensistype, with an unexpectedly high degree of variation, while the rDNA of these isolates exhibited the sameA.tubingensispattern as that of isolates from other locations. Some other local populations displayed very little polymorphism in their mtDNA and rDNA. Hybridization experiments in which clonedA.nigerandAspergillus nidulansmtDNA fragments were used revealed that the two main mtDNA groups corresponding toA.nigerandA.tubingensisare more distantly related than concluded earlier. Six of the 13 Brazilian isolates examined exhibited mtDNA and rDNA types different from those of all the other strains and could not be classified into the above species. Classical taxonomic examination of these strains is in progress.Key words:Aspergillus nigeraggregate, mitochondrial DNA, RFLP.

ISSN:0008-4166    

DOI:10.1139/m94-098

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

S-layers are paracrystalline protein multimers that cover the entire cell surface of many bacterial species. The presence of an S-layer inAeromonas salmonicida(also known as A-layer) predisposed this bacterium to apparently unrelated physiological consequences: inhibition of growth at 30 °C, enhanced cell filamentation at 37 °C, and enhanced uptake of the hydrophobic antibiotics streptonigrin and chloramphenicol. Growth inhibition or enhanced filamentation was not observed when the native A-layer was missing or its arrangement altered, as in Ca2+-limited or Ca2+- and Mg2+-limited cells, in A-layer-negative (A−) cells with an artificially reconstituted A-layer, or in mutants unable to correctly assemble this layer. A-layer-positive cells (A+) were far more sensitive to the intracellularly acting antibiotics streptonigrin and chloramphenicol than were A−cells, and streptonigrin-resistant mutants were predominantly A−. Hemin, a compound known to specifically bind to the A-layer, alleviated streptonigrin toxicity to A+, but not A−, cells. As well, Ca2+- and Mg2+-limited cells, or mutants harboring A-layer defects had a reduced sensitivity to streptonigrin, and A−cells with reconstituted A-layers remained resistant to streptonigrin and chloramphenicol. Thus, the presence of a native A-layer arrangement on the cell surface, and not the mere presence of A-layer protein subunits, predisposedA.salmonicidatoward the aforementioned physiological consequences. The A-layer is suggested to specifically effect these consequences, in particular the permeation of streptonigrin or chloramphenicol, by a specific interaction of A-layer subunits with the outer membrane.Key words:Aeromonas salmonicida, S-layers, physiological S-layer effects.

ISSN:0008-4166    

DOI:10.1139/m94-099

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Survival of pseudomonads during plant colonization may involve bacterial catalases to degrade the hydrogen peroxide produced by the plant. The specific activities of catalases in lysates from two saprophytic isolates ofPseudomonas putidaandPseudomonas fluorescensand three races ofPseudomonas syringaepv.glycineawere similar. To explore the location of the bacterial catalases, cells of the pathogenic and saprophytic pseudomonads were treated with chloroform, which is reported to release periplasmic proteins. Although catalase was released by chloroform treatment, the cytoplasmic enzymes isocitrate dehydrogenase, superoxide dismutase, and glucose-6-phosphate dehydrogenase were also detected. These proteins may have come from lysis of a small proportion of the cells rather than the periplasm. Water treatment of cells also released amounts of protein similar to those derived from chloroform treatment. Similar responses were found from both pathogenic and saprophytic strains. The release of catalase and proteins from the leaf pathogenP.syringaepv.glycinearace 0 and the root-associated saprophyteP.putidadecreased as the cultures aged. WithP.putidaandP.syringaepv.glycinearace 0, the single isozyme of catalase released by water and chloroform treatment also was detected in lysates. Additional catalase isozymes were present in lysates as the cultures aged.Key words: periplasmic proteins, survival.

ISSN:0008-4166    

DOI:10.1139/m94-100

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Eleven out of 18 sterile fungal isolates and an isolate each ofPenicilliumsp. andTrichodermasp. from the zoysiagrass rhizosphere were effective in enhancing the growth of two wheat varieties in greenhouse conditions. They enhanced the top length and top dry biomass of plants significantly and induced the plants to produce long earheads and more seeds. Notable among isolates were GS6-1, GS6-2, GS7-3, GS7-4, GS8-6, GS10-1, GS10-2, and GU23-3, which enhanced the growth by several times, resulting in a conspicuous growth promotion effect that differed depending on the variety.PenicilliumandTrichodermaspecies were less effective than sterile isolates in enhancing growth. Seven of the 11 effective sterile isolates from the zoysiagrass rhizosphere (as determined under greenhouse conditions) and a wheat rhizosphere isolate (K-17) were further tested under field conditions. Most of the isolates except K-17 enhanced the growth of one variety, whereas a few isolates enhanced the growth of the other variety. However, at least four isolates each increased yields of both varieties. Isolate GS6-1, which was very effective under greenhouse conditions in promoting overall growth, was less effective under field conditions; however, the yield components were not affected. The efficiency of the plant growth promoting isolates depended upon the wheat variety and soil nutrient conditions in addition to their inherent growth promotion abilities.Key words: plant growth promoting fungi (PGPF), sterile fungi, wheat growth promotion, yield components.

ISSN:0008-4166    

DOI:10.1139/m94-101

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The phototrophic bacteriumRhodobacter capsulatusE1F1 possesses an assimilatory, inducible nitrate reductase that is regulated by carbon and nitrogen metabolism. Nitrate reductase activity was detected in cells cultured with amino acids and nitrate as simultaneous nitrogen source but it required an additional carbon source such asD,L-malate. A significant rise in nitrate reductase activity was observed in media with increasing nitrate concentrations up to 10 mM KNO3, although higher nitrate concentrations had an inhibitory effect. Growth yield, generation time, and nitrate reductase activity were also dependent on the concentration ofD,L-malate in cells growing with 10 mM nitrate. In carbon-starved cells, nitrate reductase activity dropped even in the presence of nitrate. The intracellular concentration of keto acids such as oxaloacetate or 2-oxoglutarate fluctuated widely depending on the presence of nitrogen and carbon sources in the culture medium. The increase in the intracellular concentration of oxaloacetate or 2-oxoglutarate inR.capsulatusE1F1 correlated well with a rise in nitrate reductase activity. These results suggest that the intracellular carbon–nitrogen balance regulates nitrate uptake inR.capsulatusE1F1, thus affecting the expression of nitrate reductase.Key words: carbon–nitrogen balance, nitrate reductase,Rhodobacter capsulatus.

ISSN:0008-4166    

DOI:10.1139/m94-102

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

ThehemBgene is a member of the family of genes encoding enzymes of the porphyrin biosynthetic pathway and codes for the enzyme porphobilinogen synthase, which is responsible for the conversion of Δ-aminolevulinic acid to porphobilinogen. To clone thehemBgene ofStaphylococcus aureuswe used Tn917-mediated transposon mutagenesis. Tn917confers resistance to erythromycin and is carried by plasmid pTV1ts, which has thermosensitive replication.Hemmutants were selected by growth in the presence of kanamycin and erythromycin at 43 °C. Preliminary identification of thehemmutants was based on their dwarf colony growth, which could be restored to normal by hemin. DNA extracted from one of thehemmutants was digested with several restriction endonucleases and hybridized to a probe representing theXbaI–AvaI end of Tn917. ABglII–EcoRI fragment of 4.5 kb gave a positive signal and was cloned into pUC18. Transformants were identified by colony hybridization with the Tn917probe. The positive clones were sequenced, starting from the transposon end. The results allowed us to identify an open reading frame whose nucleotide sequence presented a homology of 63% to the sequence of thehemBgene ofBacillus subtilisand of 55% to the sequence of thehemBgene ofEscherichia coliK12. No other nucleotide sequences, except those belonging to knownhemBgenes, presented significant homologies to our sequence. The cloning of thehemBgene ofS.aureuswas confirmed by the ability of the gene to complement ahemBmutant ofE.coliK12. To our knowledge, this is the first report of the cloning of ahemgene inS.aureus.Key words: Δ-aminolevulinic acid dehydratase,hemBgene,S.aureus, heme, porphyrins.

ISSN:0008-4166    

DOI:10.1139/m94-103

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The genes encoding the lysis proteins ofLactococcus lactisbacteriophagewere cloned, sequenced, and expressed inEscherichia coli. Thelysis genes,lysAandlysB, encode a membrane-disrupting protein (LysA) of 88 amino acids, and a cell wall degrading protein (LysB) of 429 amino acids, which shares significant sequence similarity with lysins from theStreptococcus pneumoniaephages Cp-1, Cp-7, and Cp-9, andLactobacillus delbrueckiiphage mv 1. Both LysA and LysB function inE.coli, as judged by lysis of theE.colihost cells and by lytic activity against lactococcal cells when the clonedlysAandlysBgenes are expressed. The LysA protein possesses two putative transmembrane helices and highly charged N- and C-termini, and is structurally similar to phage holins that are known to induce lesions in the inner membrane through which phage endolysin can be released to its cell wall substrate. The C-terminal end of LysB contains two highly homologous sequence repeats of 43 amino acids. The LysB repeats show strong sequence similarity to repeats found in lytic enzymes from other Gram-positive bacteria and fromBacillus subtilisphageand PZA, as well as in some functionally unrelated proteins, and they are possibly involved in binding of the enzyme to the cell wall substrate. The organization of the duallysis system supports earlier suggestions that exchange of modular units is an important principle in protein evolution.Key words: amino acid sequence repeats, bacteriophage, holin,Lactococcus lactis, lysin, lytic enzyme.

ISSN:0008-4166    

DOI:10.1139/m94-104

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The chemical composition of lipopolysaccharides fromLegionella erythraandLegionella oakridgensiswas analysed. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed both lipopolysaccharides to have a smooth-type character. The polysaccharide part of both lipopolysaccharides containedD-mannose,D-glucose,D-glycero-D-mannoheptose,L-glycero-D-manno-heptose, 2-keto-3-deoxyoctonic acid,L-fucosamine,D-glucosamine, and glucosamine phosphate. In addition,L-rhamnose, glycerol phosphate, and glucose phosphate were identified in the polysaccharide part ofL.erythralipopolysaccharide. The main sugar identified in the lipid A part of both lipopolysaccharides, 2,3-diamino-2,3-dideoxy-D-glucose, was found to be substituted with a complex fatty acid composition including at least 16 different amide-linked 3-hydroxy fatty acids. Both lipopolysaccharides contained nonhydroxy fatty acids and the uncommon 27-oxo-octacosanoic acid, 29-oxotriacontanoic acid, and 27-hydroxyoctacosanoic acid. The lipopolysaccharide ofL.oakridgensisalso contained 29-hydroxytriacontanoic acid. The dioic long-chain acids heptacosane-1,27-dioic acid and nonacosane-1,29-dioic acid were only present in the lipopolysaccharide ofL.erythra.Key words: taxonomy, long-chain fatty acids, chemical analysis, 2,3-diamino-2,3-dideoxy-D-glucose.

ISSN:0008-4166    

DOI:10.1139/m94-105

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Spiramycin biosynthesis inStreptomyces ambofacienswas stimulated in the presence of valine or by sequential addition of some short-chain fatty acids to a culture medium containing an ammonium salt as source of nitrogen. Acetate kinase and acetyl-CoA carboxylase, enzymes that catalysed the formation of precursors of spiramycin biosynthesis (acetyl-CoA and malonyl-CoA), were detected during the active growth and antibiotic production phases. In this latter phase a higher level of acetyl-CoA carboxylase activity was observed with valine (1.02 μmol∙min−1∙mg protein−1) than with ammonium (0.05 μmol∙min−1∙mg protein−1) as nitrogen source, while the evolution and the level of acetate kinase activity were the same in both media. Successive addition of acetate and isobutyrate stimulated highly and weakly the acetyl-CoA carboxylase and acetate kinase activity, respectively.Key words: spiramycin,Streptomyces ambofaciens,

ISSN:0008-4166    

DOI:10.1139/m94-106

出版商:NRC Research Press    

年代:1994

数据来源: NRC