ISSN:0008-4166    

DOI:10.1139/m93-066

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

There is a growing body of information on signal transduction components in microorganisms. Elements of the cyclic 3′, 5′-adenosine monophosphate signaling system and molecules similar to hormones and receptors have been identified in the majority of prokaryotes and unicellular eukaryotes that have been studied. The presence of ligand- and receptor-like molecules in parasitic microorganisms raises the possibility that these molecules may interact with host communication systems. Adrenergic control of proliferation, differentiation, and infectivity has been described in the flagellate protozoanTrypanosoma cruzi, the etiological agent of Chagas' disease. Interactions between host and parasitic systems could also be antibody mediated, with antigenic cross-reactivity between components of their cAMP-dependent systems. In this review, we discuss these possibilities and summarize the existing data in this area.Key words: cAMP, pathogenic microorganisms,Trypanosoma cruzi, signaling systems.

ISSN:0008-4166    

DOI:10.1139/m93-067

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

One mechanism by whichListeria monocytogenesis thought to obtain iron required for growth is through the extracellular reduction of a ferric iron source to the ferrous form. To better characterize this reductase activity we have developed a simple plate assay that allows detection of colonies ofListeriaspecies able to reduce ferric iron. Cells are plated on an agar base medium containing a ferric iron source and ethylenediamine dihydroxyphenylacetic acid. Colonies are then overlain with soft agarose containing NADH, flavin mononucleotide, and Ferrozine, a chelator of ferrous iron. Colonies able to reduce the ferric iron source form a red-purple color as the ferrous iron is complexed with ferrozine. Using this qualitative assay we have shown that all species ofListeriaare able to reduce ferric iron when presented as ferric ammonium citrate whereas most other species of Gram-positive and Gram-negative bacteria are not. OnlyClostridium perfringenswas able to reduce ferric iron to the same extent asListeria.Listeria monocytogeneswas further shown to be capable of reducing various ferric iron salts as well as iron bound to ferritin, transferrin, and 2,3-dihydroxybenzoic acid in the agar plate assay. The utility of this assay was demonstrated by using it to screen a bank of Tn9/6-derived mutants ofL.monocytogenesfor clones unable to reduce ferric iron. Four such mutants were identified and all were shown to have greatly decreased ferric reductase activity.Key words:Listeria, ferric reductase, reductase mutants.

ISSN:0008-4166    

DOI:10.1139/m93-068

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The biochemical reactions, carbohydrate content, and 16S-rRNA sequences ofTatlockia (Legionella) maceacherniiandTatlockia micdadeistrains were studied. Except for catalase activity,Tatlockiastrains were relatively inert in the biochemical tests commonly used in clinical laboratories. Phenotypically, the twoTatlockiaspecies could be distinguished from other legionellae by the presence of yersiniose A, by their inability to hydrolyze hippurate or starch, by the absence of colony or media fluorescence, and by the absence of distinct browning of tyrosine-containing medium. These two species differed from one another by the production of acetoin byT.micdadeibut not byT.maceachernii. Gelatinase activity, which had been reported inT.maceachernii, was observed in only one of the four strains studied. The 16S-rRNA sequences and carbohydrate profiles ofT.maceacherniiandT.micdadeiwere essentially identical. In preparing the RNA for study, it was noted that the 23S rRNA was fragmented in allT.maceacherniistrains tested, while the 23S rRNA ofT.micdadeistrains was intact. Among the legionellae studied,T.maceacherniiwas most closely related toT.micdadei.Key words: legionellae,Tatlockia, 16S rRNA, 23S rRNA, sugars, taxonomy.

ISSN:0008-4166    

DOI:10.1139/m93-069

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Polyclonal rabbit antisera raised againstVibrio ordaliiand serotype 02 strains ofVibrio anguillarumshowed extensive cross-reactivity with lipopolysaccharide from these bacterial pathogens of fish when tested in western immunoblot analysis. Results with absorbed polyclonal antisera indicated that lipopolysaccharide molecules from these strains had both common and strain-specific antigenic determinants, which allowed the antisera to be used to differentiate betweenV.ordaliiand serotype 02 strains ofV.anguillarum. Unlike rabbits, the immune response in rainbow trout to serotype 02 common antigenic epitopes was dependent on the source of the immunizing lipopolysaccharide antigens. Serum from fish immunized withV.ordaliiantigens reacted more extensively with serotype 02 common antigens. In contrast, fish anti-V.anguillarum02 serum did not interact with O antigens from theV.ordaliistrains. Lipopolysaccharide fromV.anguillarumserotype 02 and 02a strains showed identical antibody binding properties when interacted with rabbit or fish antiserum to eitherV.anguillarum02 orV.ordalii. Lipopolysaccharide fromV.anguillarum02b strains did not interact with the tested rabbit or fish polyclonal sera. The results from this study suggest that fish and rabbits recognise different antigenic determinants in lipopolysaccharide fromV.ordaliiand serotpye 02V.anguillarumstrains; thatV.ordaliiand serotype 02 strains ofV.anguillarumshould be regarded as distinct serotype 02 subgroups based on the strain-specific antigenic determinants; and finally that the serological classification ofV.anguillarumserotype 02b strains should be reexamined.Key words: antigenic heterogeneity, lipopolysaccharides, fish immune response.not available

ISSN:0008-4166    

DOI:10.1139/m93-070

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The piliof Pseudomonas aeruginosaare composed of 15-kDa pilin monomers that are synthesized in the cytoplasm and assembled in the membrane. Processing occurs between the synthesis and assembly steps. The propilin is cleaved by a unique leader peptidase encoded bypilD, which is adjacent to the pilin structural genepilA. This generates an N-terminal phenylalanine that is subsequently methylated by an as yet uncharacterized transmethylase. The pili ofP.aeruginosabelong to the type IV class of pilins, which share a highly conserved N-terminal region 35 amino acids in length, containing a short leader of 6 or 7 amino acids. Two site-specific mutants in the N-terminal region of the mature pilin were constructed. Reestablishing the fifth-position glutamate in a four amino acid deletion mutant (amino acids 4–7) restored the leader peptidase cleavage but not the methylation. A mutation of the fifth-position glutamate to alanine decreased the degree of methylation of the N-terminal phenylalanine. Pili were not assembled by these mutants as assessed by electron microscopy and sensitivity to pilus-specific bacteriophage. Methylation may be required for recognition of the pilin by the assembly machinery and is not residue specific. The fifth-position glutamate appears to play an important role in transmethylase recognition of the pilin subunit.Key words:Pseudomonas aeruginosa, pilin, transmethylase.

ISSN:0008-4166    

DOI:10.1139/m93-071

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Microbiological examinations of total bacterial population, culturable aerobic heterotrophs, photosynthetic bacteria, and particulate DNA were carried out in Palau Jellyfish Lake. A 2 m thick bacterial plate layer at 13–15 m depth consisting of various components of microbes was observed in Jellyfish Lake. Photosynthetic bacteria, as seen by flow cytometry, were concentrated at 14–15 m depths with a maximal count of 2.2 × 105cells∙mL−1and microscopic analysis confirmed that these purple bacteria wereChromatiumsp. Peaks in total bacterial counts (8.3 × 106cells∙mL−1; 13 m), in theSynechococcusspp. population (2.4 × 106cells∙mL−1; 13 m), in culturable heterotrophs (105colony-forming units∙mL−1; 15 m), and in particulate DNA (17.8 μg∙L−1; 10 m) were observed either at the bacterial plate layer that was rich in nutrients or just above this layer in the oxic zone. Bacteriochlorophyll and chlorophyllaexhibited peaks at the photosynthetic bacterial plate (14–15 m). A high concentration of particulate organic carbon was also observed at 15 m. The particulate DNA showed a high degree of correlation with the total bacterial cell number. A low ratio of particulate DNA to particulate organic carbon (0.005) in the water column was found at 15 m and suggested that the particulate materials produced by photosynthetic bacteria would have influenced the concentration of particulate organic carbon. Culturable heterotrophs, clustered into nine different groups, were dominated by species of the generaVibrio,Aeromonas, andHalomonas.Key words: Jellyfish Lake, microbiological characteristics,Chromatium, particulate DNA, het

ISSN:0008-4166    

DOI:10.1139/m93-072

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The structural gene and regulatory element for a cytolytic enterotoxin of a diarrheal isolate, SSU, ofAeromonas hydrophilawas cloned and its DNA sequence was determined. A complementary, mixed synthetic oligonucleotide based on the first 10 NH2-terminal amino acid residues of theAeromonascytolytic enterotoxin was used as a probe to screen a genomic library constructed in bacteriophage EMBL3. Cell lysates ofEscherichia coli(λCH4), containing the cytolytic enterotoxin gene, lysed rabbit red blood cells and destroyed Chinese hamster ovary cells, caused fluid secretion in rat ileal loops, and were lethal to mice when injected intravenously. All biological activities associated with the cytolytic enterotoxin were neutralized by rabbit homologous polyclonal antibodies. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and subsequent Western blot analysis of the cell lysate ofE.coli(λCH4) revealed a protein band of approximately 52 kDa, using antisera to the cytolytic enterotoxin or antibodies generated against a synthetic peptide to the toxin. DNA sequence analysis of a 2.8-kbSalI-BamHI fragment revealed the presence of one large open reading frame (1479 bp) that would encode a protein of 54.5 kDa, a precursor form of the cytolytic enterotoxin, with a 23 amino acid leader peptide. Despite a significant amount of homology at the DNA and amino acid levels between our cytolytic enterotoxin and two aerolysins ofAeromonasspecies, variation in the restriction maps of these three toxin genes was prominent. Likewise, considerable divergence in DNA sequence was observed upstream of the structural genes for the reported aerolysins and our cytolytic enterotoxin, suggesting that these structurally similar toxin molecules may be regulated differently. Finally, our data showed that the cytolytic enterotoxin from a diarrheal isolate, SSU, ofA.hydrophilaexhibited characteristics that were unique compared with those of the reported aerolysins.Key words:Aeromonas hydrophila, cytolytic enterotoxin, aerolysin, cholera toxin.

ISSN:0008-4166    

DOI:10.1139/m93-073

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Mutants ofBrevibacteriumsp. R312 were isolated for the production of adipic acid from adiponitrile. One mutant (Ad) with a modified cell wall showed activity against adipamide 3 times greater than the wild type. Another mutant (ACV2) derived from the Ad strain had 30 times more activity on cyano-5-valeric acid, and 7 times more on adipamide, than the wild type. The presence of an amidase acting on amide intermediates in the hydrolysis of dinitriles to organic acids was demonstrated in these mutants.Key words:Brevibacteriumsp., adiponitrile, cyano-5-valeric acid, adipamide, adipic acid, mutant.

ISSN:0008-4166    

DOI:10.1139/m93-074

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Four strains of an ectomycorrhizal fungus,Pisolithus tinctorius, were investigated for carbon nutrition, and for production of hydrolytic and cellulolytic enzymes. Glucose, mannose, and cellobiose supported rapid mycelial growth of all four strains. Fructose was utilized by two strains, SMF and S359. Of the 10 hydrolytic enzymes examined, acid phosphatase, acid α-galactosidase, acid esterase, and acid β-glucosidase were found in all four strains. β-Galactosidase was only observed in strain S359. α-Mannosidase, β-mannosidase, α-glucosidase, β-xylosidase, and proteinase were not detected in any of the four strains. Isozyme patterns of β-glucosidase and esterase in the four strains were compared by activity staining after native gradient gel electrophoresis. The isozyme pattern of β-glucosidase showed three major forms in all four strains. In addition, two more isoforms were found in strain S370. All strains shared two esterase bands, while strain S370 had three more isoforms. Study on strain SMF indicated that acid β-glucosidase was expressed constitutively, with increased activity in cellobiose-containing media. Under nitrogen-limiting conditions, a low level of endoglucanase and exoglucanase activity was observed in strains SMF and S359. Further study on S359 showed that high concentrations of nitrogen repressed the cellulolytic activity. When cellobiose served as carbon source, higher cellulolytic activity was observed. Cellulose did not induce higher activity.Key words:Pisolithus, ectomycorrhizal, β-glucosidase, hydrolytic enzymes, cellulolytic enzymes.

ISSN:0008-4166    

DOI:10.1139/m93-075

出版商:NRC Research Press    

年代:1993

数据来源: NRC