摘要:

Despite differences in disease pathologies and host range, many enteric pathogens, includingSalmonellaandShigellaspp., utilize a remarkably similar machinery to secrete proteins that promote their entry into host cells. Analogous structures are required for the export of virulence proteins in other animal and plant pathogens. While the structure and organization of the gene complexes specifying these secretory pathways are broadly conserved, their phylogenetic distribution and genomic locations suggest that these sequences arose independently in divergent pathogens.Key words: pathogenesis, protein transport, bacterial evolution,Salmonella.

ISSN:0008-4166    

DOI:10.1139/m95-074

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Yersinia enterocolitica1165 (0:8) expressed several iron-regulated proteins with molecular masses of 240, 194, 80, 79, 70, and 67 kDa. These proteins were not detected in cells grown in iron-rich conditions. Cell surface iodination indicated that the 240- and 190-kDa proteins (HMWPs) were not surface exposed, whereas the 67- and 70-kDa proteins appeared to be exposed to the cell surface. Incubation with iron protected the 67- and 70-kDa proteins from proteinase K treatment, suggesting that they may be involved in iron acquisition. Monoclonal antibodies (MAbs) were produced against the HMWPs and the 67-kDa iron-regulated protein. MAbs to the HMWPs not only recognized the 240- and 194-kDa proteins but also reacted with the 67- and 70-kDa iron-regulated proteins. Similarly, MAbs to the 67-kDa protein reacted with the 67- and 70-kDa proteins and the HMWPs, suggesting that these iron-regulated proteins are related immunologically. In addition, the MAbs recognized the 67- and 70-kDa proteins and HMWPs from otherY.enterocoliticaserotypes, suggesting that the antigenic sites recognized on these iron-regulated proteins are conserved. The MAbs examined did not inhibit iron binding or iron uptake and did not provide protection against aY.enterocolitica1165 (0:8) infection in a systemic mouse infection model. Although these MAbs were not protective in this model, these iron-regulated proteins may play a role in iron acquisition and virulence, but the MAbs examined are probably not directed against epitopes involved in iron acquisition or virulence.Key words:Yersinia enterocolitica, monoclonal antibodies, iron-regulated proteins.

ISSN:0008-4166    

DOI:10.1139/m95-075

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Listeria monocytogenesandListeria innocuadiffer markedly in virulence but are indistinguishable by classical taxonomic criteria. Both species are actively motile and produce abundant flagellin at 22 °C. We have found, however, noticeable differences betweenL.monocytogenesandL.innocuain motility and flagellin production at 37 °C. At this temperature,L.monocytogenesstrains were virtually nonmotile and produced little or no detectable flagellin, whereas strains ofL.innocuawere frequently motile and produced substantial amounts of flagellin. This flagellin was recognized by aListeriagenus-specific monoclonal antibody that also recognized flagellin produced at 22 °C. These results suggest differential regulation of flagellin production betweenL.monocytogenesandL.innocuaat 37 °C.Key words:Listeria monocytogenes,Listeria innocua, flagellin, motility, temperature, pathogenesis.

ISSN:0008-4166    

DOI:10.1139/m95-076

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Sphalerite (ZnS) oxidation was monitored inThiobacillus ferrooxidansandThiobacillus thiooxidanscultures and in abiotic controls by X-ray diffraction (XRD) analysis of solid phases and by chemical analysis of solution composition. X-ray diffraction data revealed no solid-phase reaction products in unsupplemented sphalerite media, whereas minor amounts of S0accumulated in FeSC4-amended sphalerite media with or withoutT.ferrooxidansinoculum. Jarosite ((K,Na,H3O,NH4)Fe3(SO4)2(OH)6) also precipitated in the amendedT.ferrooxidanscultures. When sphalerite media inoculated withT.thiooxidanswere amended with S0, acid production was enhanced, decreasing the pH to 1.1, but Zn dissolution was not accelerated. By comparison withT.thiooxidans,T.ferrooxidanswas more efficient in the oxidation of sphalerite.Key words: bioleaching of sphalerite, sphalerite oxidation,Thiobacillus ferrooxidans,Thiobacillus thiooxidans, zinc sulfide oxidation.

ISSN:0008-4166    

DOI:10.1139/m95-077

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Production and consumption of nitric oxide (NO) byFlexibacter canadensiscells under anaerobic conditions was investigated using a chemiluminescence NO analyzer. Net NO production from nitrite in the presence of carbonyl cyanidem-chlorophenylhydrazone (CCCP) was pH dependent, increased in the pH range from 4.5 to 6.5, and sharply decreased at pH >6.5. CCCP inhibited NO consumption but only at pH values ≤6.5. This can explain why CCCP stimulation of NO production depends on the pH. Denitrification of nitrite at high concentrations (≥5 mM) also resulted in net NO accumulation. Diethyldithiocarbamate, a copper chelating agent, prevented not only net production of NO during the reduction of nitrite in the presence of CCCP, but also production of nitrous oxide (N2O) from nitrite in the presence of C2H2. This suggests thatF.canadensismay possess a copper-type nitrite reductase. However, cytochromecd1- and copper-containing nitrite reductase DNA probes fromPseudomonasspecies did not hybridize with the total DNA ofF.canadensis, indicating that the nitrite reductase ofF.canadensismay possess unique properties. In addition to diethyldithiocarbamate, sulfide, carbon monoxide, azide, cyanide, hydroxylamine and Triton X-100 prevented net NO production from nitrite in the presence of CCCP, and also inhibited NO consumption. C2H2, an inhibitor of N2O reductase, did not affect NO production or consumption.Key words: nitrite reductase, nitric oxide (NO), carbonyl cyanide m-chlorophenylhydrazone (CCCP),Flexibacter canadensis.

ISSN:0008-4166    

DOI:10.1139/m95-078

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Forty-one morphologically distinct bacterial isolates were developed from six lignin-containing environments. Each isolate was initially screened for potential lignin-degrading activity using relative growth on a lignocellulosic substrate and relative decolorization of a polymeric dye. Screened isolates were then tested for the ability to oxidize various lignin-related monomers, and the dimers anisoin and veratrylglycerol-β-guaiacyl ether. Although most of the isolates oxidized the monomers, only two successfully oxidized the dimers. The dimer-degrading isolates were tested for extracellular activity against the β-O-4 dimer veratryl-glycerol-β-guaiacyl ether. No activity was detected for the isolates.Phanerochaete chrysosporiumBurds used as a positive control demonstrated a high degree of activity in each assay. Extensive ultrastructural studies of lignocellulose alteration by the dimer-degrading isolates were conducted via light and transmission electron microscopy. These studies indicate that one of the isolates, identified asSerratia marcescens, is capable of degrading highly lignified secondary cell wall components. This activity is localized, apparently requiring direct contact between cells and substrate, which could be facilitated by an associated glycocalix. The results of the dimer degradation assays concur with the characterization of the responsible enzyme system as being membrane associated.Key words: lignin, β-O-4 dimer, bacteria,Serratia, ultrastructure.

ISSN:0008-4166    

DOI:10.1139/m95-079

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The effects of altered leader sequences on the secretion and localization of restrictocin expression inAspergillus nidulansandAspergillus nigerwere investigated. The region encoding the leader sequence of theAspergillus resirictusrestrictocin (res) gene was altered and variants were expressed under the glucoamylase (glaA) promoter inA.nidulansandA.niger. The entire restrictocin leader sequence was replaced by the glaA leader sequence in one variant. In another, the signal sequence of restrictocin was replaced with the glaA signal, leaving a hybrid with the putative restrictocin pro region in place of the glaA pro region. The putative pro region was deleted from the restrictocin leader of a third variant. Toxic effects, such as reduced transcript levels and cellular lysis, were minimal when restrictocin was expressed with the native leader sequence, but became more pronounced as the leader sequence was varied. These toxic effects were inversely proportional to the level of restrictocin secreted. In all transformed strains, restrictocin secretion appeared at the periphery of colonies and was observed to occur at the tips of hyphae. Localization of restrictocin to differentiated structures (conidiophores), as occurs inA.resirictus, was observed only in transformed strains containing the complete restrictocin leader sequence.Key words: localization, secretion, targeting, translocation, development.

ISSN:0008-4166    

DOI:10.1139/m95-080

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

In this study, we isolated and characterized biphenyl (BP) and polychlorinated biphenyl (PCB) degrading bacterial strains found in PCB-contaminated soil from an auto manufacturing plant located in Syracuse, New York. Twenty-one BP and PCB-degrading bacteria were randomly selected to form a representative sample of the bacterial population present at the site. Of the 21 bacteria, 13 were identified asComamonas testosteroni, constituting about 60% of the bacterial population examined. Other PCB degraders identified wereAcidovorax facilis,Alcaligenes xylosoxydans,Bacillus sphericus,Hydrogenophaga pseudoflava,Pseudomonas avanae, andRhodococcus fascians. Owing to the abundance ofC.testosteroniat this site, only these isolates were further characterized for their PCB congener degradation profile, 2,3-dihydroxybiphenyl 1,2-dioxygenase activity, and genetic relatedness by polymerase chain reaction (PCR) analysis. The PCB congener degradation pattern revealed a high degree of variability among theC.testosteroniisolates. The majority of theC.testosteroniisolates tested could degrade more than 95% of the PCB congeners up to pentachiorinated biphenyl. Only four isolates could degrade more than 80% of hexachlorobiphenyl. All 12 isolates ofC.testosteronitested were able to attack 2,3,4,5,6,3′,4′-heptachlorobiphenyl, indicating involvement of biphenyl 2,3-dioxygenase, while 2,3,5,6,2′,3′,6′-heptach!orobiphenyl was attacked by 6 strains, suggesting an oxidation reaction mediated by 3,4-dioxygenase. 2,3-Dihydroxybiphenyl 1,2-dioxygenase activity was also found to vary among the C. testosteroni isolates tested in this study. Eleven strains showed 2,3-dihydroxybiphenyl 1,2-dioxygenase activity specific for 2,3-dihydroxybiphenyl, whereas isolate BW169 could metabolize both 2,3-dihydroxybiphenyl and 4-methylcatechol, and isolate BW74 had the ability to metabolize all three substrates (2,3-dihydroxybiphenyl, 4-chlorocatechol, and 4-methylcatechol). Further molecular characterization of these isolates was done by a PCR-based assay, random amplified polymorphic DNA (RAPD) analysis. Amplifications of common DNA fragments of 450 dp using primer OPJ6 and 650 bp using primer OPJ14 were identified in theC.testosteroniisolates, although a distinct RAPD pattern was obtained for all of the isolates using primer OPJ14, and a combination of the two primers. Therefore, the results presented in this study demonstrate that RAPD can be used to fingerprint theC.testosteroniisolates.Key words:comamonas testosteroni, polychlorinated biphenyl, arbitrary primer-PCR.

ISSN:0008-4166    

DOI:10.1139/m95-081

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Replication of measles virus (MV) in populations of peripheral blood mononuclear cells enriched for T cells and monocytes was studied using a temperature-sensitive mutant, MV ts38, and the parent counterpart, MV Lee. Stimulation of the cells was required for a full cycle of virus replication in both cell types. More infectious virus was released after stimulation from MV-infected populations enriched for T cells, T cell-enriched than from monocyte-enriched populations. However, similar amounts of viral mRNA, genomic RNA, and viral proteins of the expected size were found in both cell populations. The results indicate that MV-specific macromolecular synthesis is similar in both T cells and monocytes, but the assembly and (or) release of infectious virus is greatly reduced in monocytes as compared with T cells.Key words: Measles virus replication.

ISSN:0008-4166    

DOI:10.1139/m95-082

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

When the broad host range plasmid vector pGSS15 was used to genetically transform the plant growth promoting rhizobacteriumPseudomonas putidaGR12-2, the transformants were physiologically debilitated. It was postulated that the expression of the β-lactamase gene of pGSS15 caused a metabolic load resulting in the impaired functioning of the bacterium. To test this hypothesis, derivatives of pGSS15 that either lack the β-lactamase gene (pYH122) or in which a β-glucosidase gene was substituted for the β-lactamase gene (pYH124) were constructed and examined to see whether their presence also impaired the functioning ofP.putidaGR12-2. On the basis of growth rates, siderophore production, and the ability to stimulate canola root elongation in sterile growth pouches, neither of the newly constructed plasmids debilitatedP.putidaGR12-2. In addition,P.putidaGR12-2 transformed with pYH124 facilitated the proliferation of the bacterium in minimal medium containing cellobiose at low temperature. This latter trait may enableP.putidaGR12-2 to persist in the soil in competition with other microorganisms.Key words: plant growth promoting rhizobacteria, PGPR, bacterial fertilizer, soil bacteria, metabolic load, β-glucosidase

ISSN:0008-4166    

DOI:10.1139/m95-083

出版商:NRC Research Press    

年代:1995

数据来源: NRC